Title of Invention	SYNTHESIS OF A NOVEL N-DOPED TIV MIXED OXIDE FOR OVERALL WATER SPLITTING
Abstract	Synthesis of N-doped TiV mixed oxide by solid state reaction method using vanadyl (IV) sulfate, titanium (IV) oxysulfate sulfuric acid complex and N-precursors (hexamine, pyridine, urea, glycine) in the molar ratio 1:1:1, was performed in a muffle furnace by varying the temperature from 300-800°C. The samples were characterized by PXRD, optical absorption studies. Photocatalytic hydrogen production over various N-doped TiV mixed photocatalysts were investigated under UV and visible light irradiation. XRD confirmed the formation of mixed oxide. Optical absorption spectra clearly showed that all the photocatalysts are active under visible light irradiation. N-doped TiV mixed oxide prepared at 500°C using hexamine as nitrogen precursor exhibited highest activity towards photodecomposition of water to hydrogen under visible light irradiation.

Title of Invention

SYNTHESIS OF A NOVEL N-DOPED TIV MIXED OXIDE FOR OVERALL WATER SPLITTING

Abstract

Synthesis of N-doped TiV mixed oxide by solid state reaction method using vanadyl (IV) sulfate, titanium (IV) oxysulfate sulfuric acid complex and N-precursors (hexamine, pyridine, urea, glycine) in the molar ratio 1:1:1, was performed in a muffle furnace by varying the temperature from 300-800°C. The samples were characterized by PXRD, optical absorption studies. Photocatalytic hydrogen production over various N-doped TiV mixed photocatalysts were investigated under UV and visible light irradiation. XRD confirmed the formation of mixed oxide. Optical absorption spectra clearly showed that all the photocatalysts are active under visible light irradiation. N-doped TiV mixed oxide prepared at 500°C using hexamine as nitrogen precursor exhibited highest activity towards photodecomposition of water to hydrogen under visible light irradiation.

Full Text	FIELD OF THE INVENTION The present invention relates to N-doped TiV mixed oxide and the process for the preparation thereof. More particularly, the present invention relates to N-doped TiV mixed oxide, an effective semiconducting photocatalytic material for overall water splitting to liberate hydrogen. BACKGROUND OF THE INVENTION In 1971, Fujishima and Honda reported that a TiO2 (rutile) photoanode photochemically split water into H2 and O2 in UV light under a small applied electrochemical potential [A. Fujishima, K. Honda, Bull. Chem. Soc. Jpn. 44 (1971) 1148; A. Fujishima, K. Honda, Nature 238 (1972) 37]. Since then, more than 130 semiconductors have been identified as catalysts for photochemical splitting of water [P.V. Kamat, J. Phys. Chem. C 111 (2007) 2834; F.E. Osterloh, Chem. Mater. 20 (2008) 35; K. Maeda, K. Domen, J. Phys. Chem. C 111 (2007) 7851; A. Kudo, Int. J. Hydr. Ener. 31 (2006) 197; Z.G. Zou, J.H. Ye, K. Sayama, H. Arakawa, Nature 414 (2001) 625; A.J. Bard, M.A. Fox, Acc. Chem. Res. 28 (1995)141]. The efficient conversion of solar energy into chemical fuels has great economic and environmental significance [N.S. Lewis, D.G. Nocera, Proc. Natl. Acad. Sci. USA 103 (2003) 15729]. Catalytic splitting of pure water into hydrogen and oxygen in presence of semiconductor powders using visible light is a promising approach for storing solar energy as chemical energy [A. Fujishima, K. Honda, Nature 238 (1972) 37; J.S. Lee, Catal. Surv. Asia 9 (2005) 217; K. Maeda, K. Teramura, N. Saito, Y. Inoue, H. Kobayashi, K. Domen, J. Phys. Chem. C 111 (2007) 7851; A. Kudo, Y. Miseki, Chem. Soc. Rev. 38 (2009) 253]. The reaction is a typical "uphill reaction", having a large positive change in the Gibb's free energy (ΔGo = 238 kJ/mol). It is necessary for water splitting by semiconductor photocatalysts that their conduction band levels are more negative than the reduction potential of water to produce H2 and their valence band levels are more positive than the oxidation potential of H2O to produce O2. However, such a term of band potentials is just one of the requirements concerned with thermodynamics. Other important factors are also concerned with photocatalytic water splitting. Efficient charge separation and suppression of recombination between photogenerated electrons and holes are important factors for efficient photocatalytic water splitting. Moreover, creation and separation of active sites for H2 and O2 evolution are also important. A great amount of work on TiO2 [R. Abe, K. Sayama, K. Domen, H. Arakawa, Chem. Phys. Lett. 344 (3-4) (2001) 339], N-doped TiO2 [H.G. Kim, D.W. Hwang, J.S. Lee, J. Am. Chem. Soc. 126 (29) (2004) 8912], modified pervoskites [K. Sayama, K. Mukasa, R. Abe, Y. Abe, H. Arakawa, Chem. Commun. (23) (2001) 2416; H. Song, P. Cai, Y. Huabing, C. Yan, Catal. Lett. 113 (1-2) (2007) 54; D.W. Hwang, H.G. Kirn, J.S. Lee, J. Kim, W.Li, S.H. Oh, J. Phys. Chem. B 109 (6) (2005) 2093], GaN:ZnO [K. Maeda, K. Teramura, D.L. Lu, T. Takata, N. Saito, Y. Inoue, K. Domen, J. Phys. Chem. B 110 (28) (2006) 13753; K. Maeda, K. Teramura, D.L. Lu, T. Takata, N. Saito, Y. Inoue, K. Domen, Nature 440 (7082) (2006) 295], metal sulfides [E.N. Savinov, Y.A. Gruzdkov, V.N. Parmon, Int. J. Hydr. Energy 14 (1) (1989) 1; S. Yanagida, T. Azuma, H. Sakurai, Chem. Lett. (7) (1982) 1069; I. Tsuji, H. Kobayashi, A. Kudo, J. Am. Chem. Soc. 126 (41) (2004) 13406], layered zirconium titanium phosphate [M.P. Kapoor, S. Inagaki, H. Yoshida, J. Phys. Chem. B 109 (2005) 9231], CdS/mesoporous zirconium titanium phosphate [D. Jing, L. Guo, J. Phys. Chem. C 111 (2007) 13437] have been reported by esteem investigators. The water splitting over porphyrin nanotube [John A. Shelnutt, James E. Miller, Z. Wang, C.J. Medforth, US patent 7,338,590 (2008)], supramolecular complexes [K.J. Brewer, M. Elvington, US patent 7,582,584 (2009)], electron conducting membranes [U. Balachandran, S. Wang, S.E. Dorris, T.H. Lee, US patent 7,087,211 (2006)], tantalum nitride [K. Domen, M. Hara, T. Takata, G. Hitoki, US patent 6,864,211 (2005)], oxysulfide [K. Domen, M. Hara, T. Takata, A. Ishikawa, US patent 6,838,413 (2005)], graphite intercalation compounds [B.W. McQuillan, J.H. Norman, US patent 4,663,144 (1987)] have been patented. Till date neither any report has been published nor patented on N-doped TiV mixed oxides for overall water splitting. In this invention, we report herein a solid state reaction route for the synthesis of N-doped TiV mixed oxide which is used here for water splitting without using any co-catalyst and which is all together different material and superior to the literature reported inventions [J. Yuan, M. Chen, J. Shi, W. Shangguan, Inter. J. Hydro. Ener. 31 (2006) 1326; P. Charvin, S. Abanades, E. Beche, F. Lemont, G. Flamant, Solid State Ionics 180 (2009) 1003] and our own work [K.M. Parida, N. Biswal, D.P. Das, S. Martha, Inter. J. Hydro. Ener. 35 (2010) 5262]. The draw back and demerits of the existing photocatalytic materials such as TiO2, TiO2/ZrO2 (J. Andrews, US patent 7,261,942 (2007)) and Fe (III)-HY (M. Subrahmanyam et al., US patent 7,407,908 (2008)) are that they are active and effective under UV light. The semiconducting materials such as tantalum nitride, oxynitrides of La, Ta, Nb, Ti, Zr are also very much active for H2 production under UV-illumination. CdS and ZnS are the first studied visible light responsive catalyst for water splitting and photocatalytic degradation of pollutants in water. But both are prone to dissociation under light illumination, thus chemical unstable under reaction conditions. In order to utilize the free solar light, there is a need for the development of visible light responsive and chemically stable photocatalytic materials. CdS-ZTP samples were prepared by ionexchange and subsequent sulfurisation by taking sodium sulfide as the reagent. The preparation of photocatalysts takes very long time. All the photocatalysts absorb light at wavelength less than 450nm (Int journal of Hydrogen Energy, Vol 35, 11(2010) 5262-5269). Synthesis of Nitrogen (N)-doped TiO2 from TiCL; as precursor by heating urea and TiO2 was carried out at 350-700 °C in air and tested towards water splitting reaction for production of hydrogen gas. (Int journal of Hydrogen Energy, 31, 10, (2006), 1326-1331). OBJECTIVES OF THE INVENTION The main object of the present invention is to provide N-doped TiV mixed oxide. Another objective of the present invention is to provide the process for the preparation of a N-doped TiV mixed oxide for overall water splitting to liberate hydrogen which obviates the drawbacks of the hitherto known prior art as detailed above. Another objective of the present invention is to provide use of different N- doped TiV- mixed oxides with some physical/chemical pretreatment. Still another objective of the present invention is to provide easily controllable experimental conditions. The process for the synthesis of N-doped TiV mixed oxides by varying N-precursors is not available in the literature and it has been processed for the first time. The conditions prescribed in this invention are not specified by any other invention so far. SUMMARY OF THE INVENTION Accordingly, present invention relates to N-doped TiV mixed oxide and process for the preparation of thereof. The present invention provides synthesis of N-doped TiV mixed oxides for water splitting to liberate hydrogen. The process for the synthesis of N-doped TiV mixed oxides comprised, (a) making of a solid-solid mixture of 1-2 g of vanadyl (IV) sulfate, 2-3 g of titanium (IV) oxysulfate sulfuric acid complex and 1-2 g of N-precursors (hexamine, pyridine, urea, glycine), (b) pretreatment of the mixture at 110 °C, (c) physical and chemical treatment of 1-2 g N-doped TiV mixed oxide, (e) calcination of the residue at 300-800 °C for 2-3 h and grinding. In an embodiment of the present invention, N-doped Ti V mixed oxide catalyst comprising: a) Ti oxide in the range of 66-67%. b) V oxide in the range of 33-34% and N-precursor in the range of 0.04 to 0.1%. In another embodiment of the present invention, a process for the preparation of N-doped TiV mixed oxide, which comprises (a) mixing of salt of vanadyl (IV), salt of Ti (IV) and N-precursors in the ratio ranging between 1:1:1 -2:2:2 (b) pretreating mixture as obtained in step (a) at temperature in the range of 300-800 °C for a time period in the range of 2-3 h to obtain residue, (c) activating the residue as obtained in step (b) at temperature in the range of 300-800 °C for a period in the range of 2-3 hrs followed by grinding to obtain N-doped Ti V mixed oxide. In another embodiment of the present invention, wherein salts of Vanadyl (IV) used is Vanadyl (IV) sulphate. In another embodiment of the present invention, wherein salts of Ti (IV) used is Titanium (IV) oxysulphate. In another embodiment of the present invention, wherein N-precursor used in step (a) is selected from the group consisting of hexamine, pyridine, urea and glycine. In another embodiment of the present invention, a process for water splitting to liberate hydrogen using N-doped Ti (V) mixed oxide catalyst, wherein said method comprising a. charging N-doped Ti (V) mixed oxide catalyst and aqueous solution of sacrificial agent in molecular ratio ranging between 20-22 mmol in quartz batch reactor. , b. exposing the reaction mixture as obtained in step (a) to the light source of 125 W UV (low) and Visible ( medium) pressure mercury for a period ranging between 2-3 h minutes to obtain liberated hydrogen. In another embodiment of the present invention, wherein sacrificial agent used in step (a) is selected from the group consisting of Na2S and Na2( SO4)2. In another embodiment of the present invention, wherein source light used in step (b) is selected from the group consisting of a Mercury visible lamp and Mercury UV lamp. In another embodiment of the present invention, wherein hydrogen liberated in step (b) is in the range of 2679 to 8482 micro mol. BRIEF DESCRIPTION OF THE FIGURES Fig. 1. Optical absorption spectra of the material prepared in Example 1 (NTiV-300), Example 3 (NTiV-600), used in Example 6, 9 (NTiV-400), Example 7, 10 (NTiV-500), Example 8 (NTiV-800). Fig. 2. Optical absorption spectra of the material prepared in Example 2 (NTiV- Pyridine), Example 4 (NTiV-Urea) and Example 5 (NTiV-glycine). Fig. 3. XRD patterns of the material prepared in Example 1 (NTiV-300), Example 3 (NTiV-600), used in Example 6, 9 (NTiV-400), Example 7, 10 (NTiV-500), Example 8 (NTiV-800). Fig. 4. XRD patterns of the material prepared in Example 2 (NTiV-Pyridine), Example 4 (NTiV-Urea) and Example 5 (NTiV-glycine). DETAILED DESCRIPTION OF THE INVENTION The PXRD pattern of all the samples was recorded on a X'pert PRO PANanalytica diffractometer with automatic control. The patterns were run with monochromatic CuKa radiation from 28 = 10-70 ° with a scan rate of 2 °/min. Diffused reflectance UV-vis (DRUV-vis) spectra of the catalyst samples were taken with a Varian Cary 100 spectrophotometer equipped with a diffuse reflectance accessory in the region 200-800 nm, with boric acid as reference. The reflectance spectra were converted into Kubelka- Munk function (F (R)) which is proportional to the absorption co-efficient for low values of F(R). EXAMPLES The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention. Example 1: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (TV) sulphate = 1.63 g, Titanium (IV) oxysulphate = 2.762 g, Hexamine = 1.4014 g) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 300 °C for 2 hrs in a muffle furnace. The product was found to be 1.71 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.2 %, 33.5 %, 0.06%, respectively. Example 2: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 3.26 g, Titanium (IV) oxysulphate = 5.524 g, Pyridine = 1.64 ml) A silica crucible is charged with 3.26 g of vanadyl (IV) sulfate, 5.524 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.64 ml pyridine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 400 °C for 2 hrs in a muffle furnace. The product was found to be 3.44 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.3 %, 33.2 %, 0.05 %, respectively. Example 3: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 3.26 g, Titanium (IV) oxysulphate = 5.524 g, Hexamine = 2.8028 g) A silica crucible is charged with 3.26 g of vanadyl (IV) sulfate, 5.524 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 2.8028 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 600 °C for 2 hrs in a muffle furnace. The product was found to be 3.42 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.3%, 33.3 %, 0.08 %, respectively. Example 4: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 1.63 g, Titanium (IV) oxysulphate = 2.762 g, Urea = 0.6g) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 0.6 g urea. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 500 °C for 2 hrs in a muffle furnace. The product was found to be 1.72 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.6%, 33.1 %, 0.07 %, respectively. Example 5: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 3.26 g, Titanium (IV) oxysulphate = 5.524 g, Glycine = 1.5164 8) A silica crucible is charged with 3.26 g of vanadyl (IV) sulfate, 5.524 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.5164 g glycine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 700 °C for 2 hrs in a muffle furnace. The product was found to be 3.43 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.1%, 33.4 %, 0.08 %, respectively. Example 6: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) (Reactants: N-TiV(activation temperature 400 °C) = 1 g/L, Light source = 125 W UVlamp) (The catalyst was prepared in the procedure similar to that of Example 1, but it was activated at 400 °C instead of 300 °C) Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W UV mercury lamp. The photon flux in the quartz flask was found to be 7 x 1019 photons/s for the 254 nm spectral region,as determined with ferrioxalate chemical actinometry. For catalytic measurements, the quartz flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 4911 umol using 0.02 g of catalyst in 120 min of light illumination Example 7: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) {Reactants: N-TiV (activation temperature 500 °C) = 1 g/L, Light source = 125 W UVlamp) (The catalyst was prepared in the procedure similar to that of Example 1, but it was activated at 500 °C instead of 300 °C) Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury lamp. The photon flux in the quartz flask was found to be 7 x 1019 photons/s for the 254 nm spectral region,as determined with ferrioxalate chemical actinometry. For catalytic measurements, the quartz flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 7143 umol using 0.02 g of catalyst in 120 min of light illumination. Example 8: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) {Reactants: N-TiV (activation temperature 800 °C) = 1 g/L, Light source = 125 W UVlamp) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 800 °C for 2 hrs in a muffle furnace. Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury lamp. The photon flux in the quartz flask was found to be 7 x 1019 photons/s for the 254 nm spectral region,as determined with ferrioxalate chemical actinometry. For catalytic measurements, the quartz flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 2679 µmol using 0.02 g of catalyst in 120 min of light illumination. Example 9: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) (Reactants: N-TiV (activation temperature 400 °C) = 1 g/L, Light source = 125 W visible lamp) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 400 °C for 2 hrs in a muffle furnace. Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury visible lamp. The photon flux in the quartz flask was found to be 0.748475 x 1019 photons/m2s for the > 420 nm spectral region, as determined with LUX meter with inbuilt Si-diode. For catalytic measurements, the glass flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 7143 µmol using 0.02 g of catalyst in 120 min of light illumination. Example 10: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) (Reactants: N-TiV (activation temperature 500 °C) = 1 g/L, Light source = 125 W visible lamp) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 500 °C for 2 hrs in a muffle furnace. Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury visible lamp. The photon flux in the quartz flask was found to be 0.748475 x 1019 photons/m2s for the > 420 nm spectral region, as determined with LUX meter with inbuilt Si-diode. For catalytic measurements, the glass flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 8482 umol using 0.02 g of catalyst in 120 min of light illumination. Example 11: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) (Reactants: N-TiV (activation temperature 600 °C) = 1 g/L, Light source = 125 W visible lamp) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 600 °C for 2 hrs in a muffle furnace. Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury visible lamp. The photon flux in the quartz flask was found to be 0.748475 x 10 photons/m s for the > 420 nm spectral region, as determined with LUX meter with inbuilt Si-diode. For catalytic measurements, the glass flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 6250 µmol using 0.02 g of catalyst in 120 min of light illumination. ADVANTAGES OF THE INVENTION 1. The above mentioned inventions are novel and cost effective process of preparation of N-doped TiV mixed oxide. 2. The preparation of N-doped TiV mixed oxides includes the use of very cheap and easily available chemicals. 3. These N-doped TiV mixed oxides can be use in UV-light as well as visible light for production of hydrogen gas. 5% of solar spectrum accounts for UV whereas visible light accounts for 43% which has not yet been exploited. Therefore, the development of visible light responsive semiconducting materials has become one of the most challenging topics today to efficiently utilize the solar radiation. So, the present invention might be useful for efficient H2 production from water under solar light illumination. 4. The preparation of N-doped mixed TiV oxide includes easy steps. We claim 1. N-doped Ti V mixed oxide catalyst comprising: Ti oxide in the range of 66-67%, V oxide in the range of 33-34% and N-precursor in the range of 0.04 to 0.1%. 2. A process for the preparation of N-doped TiV mixed oxide as claimed in claim 1, which comprises (a) mixing of salt of vanadyl (IV), salt of Ti (IV) and N-precursors in the ratio ranging between 1:1:1-2:2:2 (b) pretreating mixture as obtained in step (a) at temperature in the range of 100- 110°C for a time period in the range of 10- 12h to obtain residue, (c) activating the residue as obtained in step (b) at temperature in the range of 300-800 °C for a period in the range of 2-3 hrs followed by grinding to obtain N-doped Ti V mixed oxide. 3. A process as claimed in claim 2, wherein salts of Vanadyl (IV) used in step (a) is Vanadyl (IV) sulphate. 4. A process as claimed in claim 2, wherein salts of Ti (IV) used in step (a) is Titanium (IV) oxysulphate. 5. A process as claimed in claim 2, wherein N-precursor used in step (a) is selected from the group consisting of hexamine, pyridine, urea and glycine. 6. A process for water splitting to liberate hydrogen using N-doped Ti (V) mixed oxide catalyst as claimed in claim 1, wherein said method comprising a. charging N-doped Ti (V) mixed oxide catalyst and aqueous solution of sacrificial agent in molecular ratio ranging between 20-22 mmol in quartz batch reactor; b. exposing the reaction mixture as obtained in step (a) to the light source of 125 W UV (low) and Visible ( medium) pressure mercury for a period ranging between 2-3 h to obtain liberated hydrogen. 7. A process as claimed in claim 6, wherein sacrificial agent used in step (a) is selected from the group consisting of Na2S and Na2( SO4)2. 8. A process as claimed in claim 6, wherein source light used in step (b) is selected from the group consisting of g Mercury visible lamp and Mercury UV lamp. 9. A process as claimed in claim 6, wherein hydrogen liberated in step (b) is in the range of 2679 to 8482 micro mol. 10. N-doped Ti V mixed oxide catalyst, process for the preparation thereof and process for liberation of hydrogen substantially as herein described with reference to the examples accompanying this specification.

Full Text

FIELD OF THE INVENTION
The present invention relates to N-doped TiV mixed oxide and the process for the preparation thereof. More particularly, the present invention relates to N-doped TiV mixed oxide, an effective semiconducting photocatalytic material for overall water splitting to liberate hydrogen.
BACKGROUND OF THE INVENTION
In 1971, Fujishima and Honda reported that a TiO2 (rutile) photoanode photochemically split water into H2 and O2 in UV light under a small applied electrochemical potential [A. Fujishima, K. Honda, Bull. Chem. Soc. Jpn. 44 (1971) 1148; A. Fujishima, K. Honda, Nature 238 (1972) 37]. Since then, more than 130 semiconductors have been identified as catalysts for photochemical splitting of water [P.V. Kamat, J. Phys. Chem. C 111 (2007) 2834; F.E. Osterloh, Chem. Mater. 20 (2008) 35; K. Maeda, K. Domen, J. Phys. Chem. C 111 (2007) 7851; A. Kudo, Int. J. Hydr. Ener. 31 (2006) 197; Z.G. Zou, J.H. Ye, K. Sayama, H. Arakawa, Nature 414 (2001) 625; A.J. Bard, M.A. Fox, Acc. Chem. Res. 28 (1995)141]. The efficient conversion of solar energy into chemical fuels has great economic and environmental significance [N.S. Lewis, D.G. Nocera, Proc. Natl. Acad. Sci. USA 103 (2003) 15729]. Catalytic splitting of pure water into hydrogen and oxygen in presence of semiconductor powders using visible light is a promising approach for storing solar energy as chemical energy [A. Fujishima, K. Honda, Nature 238 (1972) 37; J.S. Lee, Catal. Surv. Asia 9 (2005) 217; K. Maeda, K. Teramura, N. Saito, Y. Inoue, H. Kobayashi, K. Domen, J. Phys. Chem. C 111 (2007) 7851; A. Kudo, Y. Miseki, Chem. Soc. Rev. 38 (2009) 253]. The reaction is a typical "uphill reaction", having a large positive change in the Gibb's free energy (ΔGo = 238 kJ/mol). It is necessary for water splitting by semiconductor photocatalysts that their conduction band levels are more negative than the reduction potential of water to produce H2 and their valence band levels are more positive than the oxidation potential of H2O to produce O2. However, such a term of band potentials is just one of the requirements concerned with thermodynamics. Other important factors are also concerned with photocatalytic water splitting. Efficient charge separation and suppression of recombination between photogenerated electrons and holes are important factors for efficient photocatalytic water splitting. Moreover,

creation and separation of active sites for H2 and O2 evolution are also important. A great amount of work on TiO2 [R. Abe, K. Sayama, K. Domen, H. Arakawa, Chem. Phys. Lett. 344 (3-4) (2001) 339], N-doped TiO2 [H.G. Kim, D.W. Hwang, J.S. Lee, J. Am. Chem. Soc. 126 (29) (2004) 8912], modified pervoskites [K. Sayama, K. Mukasa, R. Abe, Y. Abe, H. Arakawa, Chem. Commun. (23) (2001) 2416; H. Song, P. Cai, Y. Huabing, C. Yan, Catal. Lett. 113 (1-2) (2007) 54; D.W. Hwang, H.G. Kirn, J.S. Lee, J. Kim, W.Li, S.H. Oh, J. Phys. Chem. B 109 (6) (2005) 2093], GaN:ZnO [K. Maeda, K. Teramura, D.L. Lu, T. Takata, N. Saito, Y. Inoue, K. Domen, J. Phys. Chem. B 110 (28) (2006) 13753; K. Maeda, K. Teramura, D.L. Lu, T. Takata, N. Saito, Y. Inoue, K. Domen, Nature 440 (7082) (2006) 295], metal sulfides [E.N. Savinov, Y.A. Gruzdkov, V.N. Parmon, Int. J. Hydr. Energy 14 (1) (1989) 1; S. Yanagida, T. Azuma, H. Sakurai, Chem. Lett. (7) (1982) 1069; I. Tsuji, H. Kobayashi, A. Kudo, J. Am. Chem. Soc. 126 (41) (2004) 13406], layered zirconium titanium phosphate [M.P. Kapoor, S. Inagaki, H. Yoshida, J. Phys. Chem. B 109 (2005) 9231], CdS/mesoporous zirconium titanium phosphate [D. Jing, L. Guo, J. Phys. Chem. C 111 (2007) 13437] have been reported by esteem investigators. The water splitting over porphyrin nanotube [John A. Shelnutt, James E. Miller, Z. Wang, C.J. Medforth, US patent 7,338,590 (2008)], supramolecular complexes [K.J. Brewer, M. Elvington, US patent 7,582,584 (2009)], electron conducting membranes [U. Balachandran, S. Wang, S.E. Dorris, T.H. Lee, US patent 7,087,211 (2006)], tantalum nitride [K. Domen, M. Hara, T. Takata, G. Hitoki, US patent 6,864,211 (2005)], oxysulfide [K. Domen, M. Hara, T. Takata, A. Ishikawa, US patent 6,838,413 (2005)], graphite intercalation compounds [B.W. McQuillan, J.H. Norman, US patent 4,663,144 (1987)] have been patented. Till date neither any report has been published nor patented on N-doped TiV mixed oxides for overall water splitting. In this invention, we report herein a solid state reaction route for the synthesis of N-doped TiV mixed oxide which is used here for water splitting without using any co-catalyst and which is all together different material and superior to the literature reported inventions [J. Yuan, M. Chen, J. Shi, W. Shangguan, Inter. J. Hydro. Ener. 31 (2006) 1326; P. Charvin, S. Abanades, E. Beche, F. Lemont, G. Flamant, Solid State Ionics 180 (2009) 1003] and our own work [K.M. Parida, N. Biswal, D.P. Das, S. Martha, Inter. J. Hydro. Ener. 35 (2010) 5262].

The draw back and demerits of the existing photocatalytic materials such as TiO2, TiO2/ZrO2 (J. Andrews, US patent 7,261,942 (2007)) and Fe (III)-HY (M. Subrahmanyam et al., US patent 7,407,908 (2008)) are that they are active and effective under UV light. The semiconducting materials such as tantalum nitride, oxynitrides of La, Ta, Nb, Ti, Zr are also very much active for H2 production under UV-illumination. CdS and ZnS are the first studied visible light responsive catalyst for water splitting and photocatalytic degradation of pollutants in water. But both are prone to dissociation under light illumination, thus chemical unstable under reaction conditions. In order to utilize the free solar light, there is a need for the development of visible light responsive and chemically stable photocatalytic materials.
CdS-ZTP samples were prepared by ionexchange and subsequent sulfurisation by taking sodium sulfide as the reagent. The preparation of photocatalysts takes very long time. All the photocatalysts absorb light at wavelength less than 450nm (Int journal of Hydrogen Energy, Vol 35, 11(2010) 5262-5269).
Synthesis of Nitrogen (N)-doped TiO2 from TiCL; as precursor by heating urea and TiO2 was carried out at 350-700 °C in air and tested towards water splitting reaction for production of hydrogen gas. (Int journal of Hydrogen Energy, 31, 10, (2006), 1326-1331).
OBJECTIVES OF THE INVENTION
The main object of the present invention is to provide N-doped TiV mixed oxide.
Another objective of the present invention is to provide the process for the preparation of
a N-doped TiV mixed oxide for overall water splitting to liberate hydrogen which
obviates the drawbacks of the hitherto known prior art as detailed above.
Another objective of the present invention is to provide use of different N- doped TiV-
mixed oxides with some physical/chemical pretreatment.
Still another objective of the present invention is to provide easily controllable
experimental conditions.
The process for the synthesis of N-doped TiV mixed oxides by varying N-precursors is
not available in the literature and it has been processed for the first time.

The conditions prescribed in this invention are not specified by any other invention so far.
SUMMARY OF THE INVENTION
Accordingly, present invention relates to N-doped TiV mixed oxide and process for the preparation of thereof. The present invention provides synthesis of N-doped TiV mixed oxides for water splitting to liberate hydrogen. The process for the synthesis of N-doped TiV mixed oxides comprised, (a) making of a solid-solid mixture of 1-2 g of vanadyl (IV) sulfate, 2-3 g of titanium (IV) oxysulfate sulfuric acid complex and 1-2 g of N-precursors (hexamine, pyridine, urea, glycine), (b) pretreatment of the mixture at 110 °C, (c) physical and chemical treatment of 1-2 g N-doped TiV mixed oxide, (e) calcination of the residue at 300-800 °C for 2-3 h and grinding.
In an embodiment of the present invention, N-doped Ti V mixed oxide catalyst comprising:
a) Ti oxide in the range of 66-67%.
b) V oxide in the range of 33-34% and N-precursor in the range of 0.04 to 0.1%.
In another embodiment of the present invention, a process for the preparation of N-doped
TiV mixed oxide, which comprises (a) mixing of salt of vanadyl (IV), salt of Ti (IV) and
N-precursors in the ratio ranging between 1:1:1 -2:2:2 (b) pretreating mixture as obtained
in step (a) at temperature in the range of 300-800 °C for a time period in the range of 2-3
h to obtain residue, (c) activating the residue as obtained in step (b) at temperature in the
range of 300-800 °C for a period in the range of 2-3 hrs followed by grinding to obtain
N-doped Ti V mixed oxide.
In another embodiment of the present invention, wherein salts of Vanadyl (IV) used is
Vanadyl (IV) sulphate.
In another embodiment of the present invention, wherein salts of Ti (IV) used is Titanium
(IV) oxysulphate.
In another embodiment of the present invention, wherein N-precursor used in step (a) is
selected from the group consisting of hexamine, pyridine, urea and glycine.
In another embodiment of the present invention, a process for water splitting to liberate
hydrogen using N-doped Ti (V) mixed oxide catalyst, wherein said method comprising

a. charging N-doped Ti (V) mixed oxide catalyst and aqueous solution of sacrificial
agent in molecular ratio ranging between 20-22 mmol in quartz batch reactor. , b. exposing the reaction mixture as obtained in step (a) to the light source of 125 W UV (low) and Visible ( medium) pressure mercury for a period ranging between 2-3 h minutes to obtain liberated hydrogen.
In another embodiment of the present invention, wherein sacrificial agent used in step (a)
is selected from the group consisting of Na2S and Na2( SO4)2.
In another embodiment of the present invention, wherein source light used in step (b) is
selected from the group consisting of a Mercury visible lamp and Mercury UV lamp.
In another embodiment of the present invention, wherein hydrogen liberated in step (b) is
in the range of 2679 to 8482 micro mol.
BRIEF DESCRIPTION OF THE FIGURES
Fig. 1. Optical absorption spectra of the material prepared in Example 1 (NTiV-300),
Example 3 (NTiV-600), used in Example 6, 9 (NTiV-400), Example 7, 10 (NTiV-500),
Example 8 (NTiV-800).
Fig. 2. Optical absorption spectra of the material prepared in Example 2 (NTiV-
Pyridine), Example 4 (NTiV-Urea) and Example 5 (NTiV-glycine).
Fig. 3. XRD patterns of the material prepared in Example 1 (NTiV-300), Example 3
(NTiV-600), used in Example 6, 9 (NTiV-400), Example 7, 10 (NTiV-500), Example 8
(NTiV-800).
Fig. 4. XRD patterns of the material prepared in Example 2 (NTiV-Pyridine), Example
4 (NTiV-Urea) and Example 5 (NTiV-glycine).
DETAILED DESCRIPTION OF THE INVENTION
The PXRD pattern of all the samples was recorded on a X'pert PRO PANanalytica diffractometer with automatic control. The patterns were run with monochromatic CuKa radiation from 28 = 10-70 ° with a scan rate of 2 °/min. Diffused reflectance UV-vis (DRUV-vis) spectra of the catalyst samples were taken with a Varian Cary 100 spectrophotometer equipped with a diffuse reflectance accessory in the region 200-800 nm, with boric acid as reference. The reflectance spectra were converted into Kubelka-

Munk function (F (R)) which is proportional to the absorption co-efficient for low values of F(R). EXAMPLES
The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention. Example 1: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (TV) sulphate = 1.63 g, Titanium (IV) oxysulphate = 2.762 g, Hexamine = 1.4014 g)
A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 300 °C for 2 hrs in a muffle furnace. The product was found to be 1.71 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.2 %, 33.5 %, 0.06%, respectively.
Example 2: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 3.26 g, Titanium (IV) oxysulphate = 5.524 g, Pyridine = 1.64 ml)
A silica crucible is charged with 3.26 g of vanadyl (IV) sulfate, 5.524 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.64 ml pyridine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 400 °C for 2 hrs in a muffle furnace. The product was found to be 3.44 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.3 %, 33.2 %, 0.05 %, respectively.
Example 3: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 3.26 g, Titanium (IV) oxysulphate = 5.524 g, Hexamine = 2.8028 g)
A silica crucible is charged with 3.26 g of vanadyl (IV) sulfate, 5.524 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 2.8028 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 600 °C for 2 hrs in a muffle furnace. The product was

found to be 3.42 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.3%, 33.3 %, 0.08 %, respectively.
Example 4: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 1.63 g, Titanium (IV) oxysulphate = 2.762 g, Urea = 0.6g)
A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 0.6 g urea. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 500 °C for 2 hrs in a muffle furnace. The product was found to be 1.72 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.6%, 33.1 %, 0.07 %, respectively.
Example 5: Preparation of N-doped TiV (1:1:1) mixed oxide (Reactants: Vanadyl (IV) sulphate = 3.26 g, Titanium (IV) oxysulphate = 5.524 g, Glycine = 1.5164
8)
A silica crucible is charged with 3.26 g of vanadyl (IV) sulfate, 5.524 g of
titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.5164 g glycine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 700 °C for 2 hrs in a muffle furnace. The product was found to be 3.43 g. In the prepared mixed oxides, Ti02, V205, N- content was found to be 66.1%, 33.4 %, 0.08 %, respectively.
Example 6: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1,
Hexamine as N-precursor) (Reactants: N-TiV(activation temperature 400
°C) = 1 g/L, Light source = 125 W UVlamp) (The catalyst was prepared in
the procedure similar to that of Example 1, but it was activated at 400 °C
instead of 300 °C)
Photochemical hydrogen generation experiments are carried out using a quartz batch
reactor that is exposed to the light of medium pressure 125 W UV mercury lamp. The
photon flux in the quartz flask was found to be 7 x 1019 photons/s for the 254 nm spectral
region,as determined with ferrioxalate chemical actinometry. For catalytic measurements,
the quartz flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S
solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation,
the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved

gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 4911 umol using 0.02 g of catalyst in 120 min of light illumination
Example 7: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1,
Hexamine as N-precursor) {Reactants: N-TiV (activation temperature 500
°C) = 1 g/L, Light source = 125 W UVlamp) (The catalyst was prepared in
the procedure similar to that of Example 1, but it was activated at 500 °C
instead of 300 °C)
Photochemical hydrogen generation experiments are carried out using a quartz
batch reactor that is exposed to the light of medium pressure 125 W mercury lamp. The
photon flux in the quartz flask was found to be 7 x 1019 photons/s for the 254 nm spectral
region,as determined with ferrioxalate chemical actinometry. For catalytic measurements,
the quartz flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S
solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation,
the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved
gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve
column in TCD mode. A comparison of the retention time of the only peak that appeared
on the chromatogram with standard, confirmed that the gas was only hydrogen.
The H2 liberated was observed to be 7143 umol using 0.02 g of catalyst in 120 min of
light illumination.
Example 8: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) {Reactants: N-TiV (activation temperature 800 °C) = 1 g/L, Light source = 125 W UVlamp)
A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 800 °C for 2 hrs in a muffle furnace.

Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury lamp. The photon flux in the quartz flask was found to be 7 x 1019 photons/s for the 254 nm spectral region,as determined with ferrioxalate chemical actinometry. For catalytic measurements, the quartz flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen. The H2 liberated was observed to be 2679 µmol using 0.02 g of catalyst in 120 min of light illumination.
Example 9: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) (Reactants: N-TiV (activation temperature 400 °C) = 1 g/L, Light source = 125 W visible lamp)
A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 400 °C for 2 hrs in a muffle furnace.
Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury visible lamp. The photon flux in the quartz flask was found to be 0.748475 x 1019 photons/m2s for the > 420 nm spectral region, as determined with LUX meter with inbuilt Si-diode. For catalytic measurements, the glass flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen.

The H2 liberated was observed to be 7143 µmol using 0.02 g of catalyst in 120 min of
light illumination.
Example 10: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1,
Hexamine as N-precursor) (Reactants: N-TiV (activation temperature 500
°C) = 1 g/L, Light source = 125 W visible lamp) A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 500 °C for 2 hrs in a muffle furnace.
Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury visible
lamp. The photon flux in the quartz flask was found to be 0.748475 x 1019 photons/m2s for the > 420 nm spectral region, as determined with LUX meter with inbuilt Si-diode. For catalytic measurements, the glass flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen.
The H2 liberated was observed to be 8482 umol using 0.02 g of catalyst in 120 min of light illumination.
Example 11: Photocatalytic water splitting over N-doped TiV mixed oxide (1:1:1, Hexamine as N-precursor) (Reactants: N-TiV (activation temperature 600 °C) = 1 g/L, Light source = 125 W visible lamp)
A silica crucible is charged with 1.63 g of vanadyl (IV) sulfate, 2.762 g of titanium (IV) oxysulfate sulphuric acid complex hydrate and 1.4014 g hexamine. The mixture was pretreated at 110 °C in an air oven for 12 hour. The residue is ground to powdered form and activated at 600 °C for 2 hrs in a muffle furnace.
Photochemical hydrogen generation experiments are carried out using a quartz batch reactor that is exposed to the light of medium pressure 125 W mercury visible

lamp. The photon flux in the quartz flask was found to be 0.748475 x 10 photons/m s for the > 420 nm spectral region, as determined with LUX meter with inbuilt Si-diode. For catalytic measurements, the glass flask is charged with 20 mg of catalyst in 20 mL of aqueous 20 mmol Na2S solution. The solution was kept under stirring with a magnetic stirrer. Prior to irradiation, the reaction mixture was purged with N2 in order to remove dissolved gases. The evolved gas was accumulated and analyzed by GC-17A (Shimadzu) using 5 A molecular sieve column in TCD mode. A comparison of the retention time of the only peak that appeared on the chromatogram with standard, confirmed that the gas was only hydrogen.
The H2 liberated was observed to be 6250 µmol using 0.02 g of catalyst in 120 min of light illumination. ADVANTAGES OF THE INVENTION
1. The above mentioned inventions are novel and cost effective process of preparation of N-doped TiV mixed oxide.
2. The preparation of N-doped TiV mixed oxides includes the use of very cheap and easily available chemicals.
3. These N-doped TiV mixed oxides can be use in UV-light as well as visible light for production of hydrogen gas. 5% of solar spectrum accounts for UV whereas visible light accounts for 43% which has not yet been exploited. Therefore, the development of visible light responsive semiconducting materials has become one of the most challenging topics today to efficiently utilize the solar radiation. So, the present invention might be useful for efficient H2 production from water under solar light illumination.
4. The preparation of N-doped mixed TiV oxide includes easy steps.

We claim
1. N-doped Ti V mixed oxide catalyst comprising:
Ti oxide in the range of 66-67%,
V oxide in the range of 33-34% and N-precursor in the range of 0.04 to 0.1%.
2. A process for the preparation of N-doped TiV mixed oxide as claimed in claim 1, which comprises (a) mixing of salt of vanadyl (IV), salt of Ti (IV) and N-precursors in the ratio ranging between 1:1:1-2:2:2 (b) pretreating mixture as obtained in step (a) at temperature in the range of 100- 110°C for a time period in the range of 10- 12h to obtain residue, (c) activating the residue as obtained in step (b) at temperature in the range of 300-800 °C for a period in the range of 2-3 hrs followed by grinding to obtain N-doped Ti V mixed oxide.
3. A process as claimed in claim 2, wherein salts of Vanadyl (IV) used in step (a) is Vanadyl (IV) sulphate.
4. A process as claimed in claim 2, wherein salts of Ti (IV) used in step (a) is Titanium (IV) oxysulphate.
5. A process as claimed in claim 2, wherein N-precursor used in step (a) is selected from the group consisting of hexamine, pyridine, urea and glycine.
6. A process for water splitting to liberate hydrogen using N-doped Ti (V) mixed oxide catalyst as claimed in claim 1, wherein said method comprising
a. charging N-doped Ti (V) mixed oxide catalyst and aqueous solution of
sacrificial agent in molecular ratio ranging between 20-22 mmol in quartz
batch reactor;
b. exposing the reaction mixture as obtained in step (a) to the light source of
125 W UV (low) and Visible ( medium) pressure mercury for a period
ranging between 2-3 h to obtain liberated hydrogen.
7. A process as claimed in claim 6, wherein sacrificial agent used in step (a) is selected from the group consisting of Na2S and Na2( SO4)2.
8. A process as claimed in claim 6, wherein source light used in step (b) is selected from the group consisting of g Mercury visible lamp and Mercury UV lamp.
9. A process as claimed in claim 6, wherein hydrogen liberated in step (b) is in the range of 2679 to 8482 micro mol.

10. N-doped Ti V mixed oxide catalyst, process for the preparation thereof and process for liberation of hydrogen substantially as herein described with reference to the examples accompanying this specification.

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Patent Number

277132

Indian Patent Application Number

536/DEL/2010

PG Journal Number

47/2016

Publication Date

11-Nov-2016

Grant Date

11-Nov-2016

Date of Filing

09-Mar-2010

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KULAMANI PARIDA	INSTITUTE OF MINERALS AND MATERIALS TECHNOLOGY (CSIR), BHUBANESWAR-751013, ORISSA, INDIA
2	SATYABADI MARTHA	INSTITUTE OF MINERALS AND MATERIALS TECHNOLOGY (CSIR), BHUBANESWAR-751013, ORISSA, INDIA
3	NIRANJAN BISWAL	INSTITUTE OF MINERALS AND MATERIALS TECHNOLOGY (CSIR), BHUBANESWAR-751013, ORISSA, INDIA
4	DIPTI PRAKASINI DAS	INSTITUTE OF MINERALS AND MATERIALS TECHNOLOGY (CSIR), BHUBANESWAR-751013, ORISSA, INDIA

PCT International Classification Number

A61K

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA