Water splitting activity of layered oxides

Abstract

An efficient and economical process for H.sub.2 evolution by water splitting, catalyzed by layered oxides that function in UV and visible light.

Claims

1. A photocatalytic water splitting process for H.sub.2 generation, the process comprising: a) dispersing a catalyst powder having the formula InA(ZnO).sub.m in a reactant solution to provide a reactant mixture in a gas closed irradiation system, wherein A is FeO.sub.3 or GaO.sub.3 and m=1-5, and wherein the reactant solution comprises water and methanol in ratio of 4:1; and b) irradiating the reactant mixture as obtained in step (a) in the visible light range, in the UV light range, or both the visible and UV light range, to obtain hydrogen; wherein the catalyst powder of the reactant mixture irradiated in the visible light range is selected from the group consisting of InFeO.sub.3(ZnO).sub.m, InFeO.sub.3(ZnO).sub.m co-catalyzed with Pt, and InGaO.sub.3(ZnO).sub.m co-catalyzed with CuO; and wherein the catalyst powder of the reactant mixture irradiated in the UV light range or both the visible light range and the UV light range is selected from the group consisting of InFeO.sub.3(ZnO).sub.m, InFeO.sub.3(ZnO).sub.m co-catalyzed with Pt, InGaO.sub.3(ZnO).sub.m, InGaO.sub.3(ZnO).sub.m co-catalyzed with NiO, and InGaO.sub.3(ZnO).sub.m co-catalyzed with CuO.

2. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder is InFeO.sub.3(ZnO).sub.m.

3. The photocatalytic water splitting process according to claim 2, wherein a hydrogen evolution rate is in the range of 7 to 11 milli mol/g/h and 0.8 to 3.58 milli mol/g/h in the presence of the reactant mixture having InFeO.sub.3(ZnO).sub.m and InGaO.sub.3(ZnO).sub.m, respectively.

4. The photocatalytic water splitting process according to claim 1, wherein the irradiation process is carried out in the UV light range.

5. The photocatalytic water splitting process according to claim 1, wherein said process is carried for a period of 1-12 hours.

6. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InGaO.sub.3(ZnO).sub.m co-catalyzed with NiO, and wherein NiO is loaded onto InGaO.sub.3(ZnO).sub.m.

7. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InGaO.sub.3(ZnO).sub.m co-catalyzed with CuO, and wherein CuO is loaded onto InGaO.sub.3(ZnO).sub.m.

8. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InFeO.sub.3(ZnO).sub.m co-catalyzed with Pt, and wherein Pt is loaded onto InFeO.sub.3(ZnO).sub.m.

9. The photocatalytic water splitting process according to claim 1, wherein the irradiation process is carried out in the visible light range.

10. The photocatalytic water splitting process according to claim 1, wherein the irradiation process is carried out in the visible light range and the UV light range.

11. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InFeO.sub.3(ZnO).sub.m co-catalyzed with Pt.

12. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InGaO.sub.3(ZnO).sub.m co-catalyzed with CuO.

13. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InGaO.sub.3(ZnO).sub.m.

14. The photocatalytic water splitting process according to claim 1, wherein the catalyst powder of the reactant mixture is InGaO.sub.3(ZnO).sub.m co-catalyzed with NiO.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts the powder XRD pattern of InFeO.sub.3(ZnO).sub.1.

(2) FIG. 2 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3 (ZnO).sub.1 without loading Pt under visible light irradiation.

(3) FIG. 3 depicts the powder XRD pattern of InFeO.sub.3(ZnO).sub.2.

(4) FIG. 4 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3 (ZnO).sub.2 with Pt loading under UV irradiation.

(5) FIG. 5 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3 (ZnO).sub.2 without loading Pt under UV irradiation.

(6) FIG. 6 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3 (ZnO).sub.2 without loading Pt under visible irradiation.

(7) FIG. 7 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3 (ZnO).sub.2 with Pt loading under visible irradiation.

(8) FIG. 8 depicts the powder XRD pattern of InFeO.sub.3(ZnO).sub.3.

(9) FIG. 9 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3 (ZnO).sub.3 without loading Pt under visible irradiation.

(10) FIG. 10 depicts the powder XRD pattern of InFeO.sub.3(ZnO).sub.4.

(11) FIG. 11 depicts the effect of irradiation time on hydrogen generation by InFeO.sub.3(ZnO).sub.4 without loading Pt under visible irradiation.

(12) FIG. 12 depicts the comparison of water splitting activity in visible light without Pt impregnation for the three catalysts.

(13) FIG. 13 depicts H.sub.2 evolution with IGZ InGaO.sub.3(ZnO)m, where m=1-4 catalysts under UV light irradiation.

(14) FIG. 14 depicts H.sub.2 evolution with 1 wt %, 2 wt % NiO loaded IGZ catalyst.

(15) FIG. 15 depicts H.sub.2 evolution with 2 wt % NiO loaded IGZ catalysts.

(16) FIG. 16 depicts H.sub.2 evolution with 1 wt %, 2 wt % CuO loaded IGZ catalyst at 4 hours.

(17) FIG. 17 depicts H.sub.2 evolution with 2 wt % CuO loaded IGZ catalysts.

(18) FIG. 18 depicts H.sub.2 evolution from IGZ1 with different CuO loading.

DETAILED DESCRIPTION

(19) Embodiments of the invention provide an efficient and economic process for H.sub.2 evolution by water splitting employing layered oxides as photo catalysts, which are functional in UV and visible light.

(20) In an aspect, embodiments of the present invention provide a process for H.sub.2 evolution, wherein the photocatalyst is InA(ZnO).sub.m, wherein m=1-5, A is selected from an oxide of Fe or Ga, such that the catalyst evolves H.sub.2 in UV as well as visible range.

(21) In another aspect the present invention provides a process of evolution of H.sub.2 carried out optionally in the presence of a co-catalyst selected from Pt, CuO or NiO.

(22) UV and visible light range as used in the specification refer to wavelengths in the range of 180-800 nm.

(23) Accordingly, embodiments of the present invention disclose a photocatalytic water splitting process for H.sub.2 generation catalyzed by InA(ZnO).sub.m, wherein A is selected from an oxide of Fe or Ga and m=1-5 in the absence of a metal co-catalyst and is carried out in the UV or visible range.

(24) Embodiments of the present invention disclose a photocatalytic process for H.sub.2 generation in the presence of a catalyst InA(ZnO)m, wherein A is selected from an oxide of Fe or Ga and m=1-5.

(25) Further, embodiments of the present invention disclose a photocatalytic process for H2 generation in the presence of a layered oxide catalyst InA(ZnO)m, wherein A is selected from an oxide of Fe or Ga and m=1-5 comprising: a. dispersing InA(ZnO)m powder in a reactant solution comprising water and methanol in a ratio of 4:1 in a gas closed irradiation system, and b. irradiating the reactant mixture obtained in step a.

(26) Accordingly, the photocatalytic activity of InA(ZnO)m is determined by measuring the H.sub.2 evolution in reactions that are carried out in a gas-closed system having a dead volume in the range of 45-55 ml.

(27) The instant photocatalyst InA(ZnO)m, wherein A is selected from an oxide of Fe or Ga and m=1-4 is dispersed by magnetic stirring in the reactant solution (25 mL) in an irradiation cell made of quartz.

(28) The reactant solution for water splitting comprises (20 mL) pure/distilled water and (5 mL) methanol in a ratio of 4:1.

(29) The reactant mixture is irradiated and methanol as the sacrificial reagent is oxidized by the resulting photogenerated holes.

(30) Embodiments of the present invention disclose a water splitting catalyst for H.sub.2 generation selected from the group consisting of InFeO.sub.3(ZnO)m and InGaO.sub.3(ZnO)m, where m=1-5.

(31) Embodiments of the present invention disclose a photocatalytic water splitting process for H.sub.2 evolution, wherein the catalysis is carried out in the UV range and visible range of light.

(32) The light source used for irradiation in the closed system is a 400 W mercury lamp for UV irradiation and a 400 W Tungsten lamp for visible irradiation.

(33) Embodiments of the present invention disclose a photocatalytic process in the presence of a catalyst having formula InA(ZnO)m, wherein the process is carried for a period of 1 to 8 hours.

(34) The evolving gas mixture from the closed system is taken in a syringe at an interval of 1 hour. The amount of H.sub.2 evolved can be determined using gas chromatography (Agilent GC with Carbosphere column and N.sub.2 as carrier gas).

(35) Embodiments of the present invention disclose a photocatalyst, InA(ZnO).sub.m, wherein A is selected from an oxide of Fe or Ga and m=1-5 for catalyzing water splitting reactions for H2 generation.

(36) The instant catalyst InA(ZnO)m, is prepared by grinding indium oxide (In.sub.2O.sub.3), a metal oxide selected from FeO.sub.3 or GaO.sub.3Fe.sub.2O.sub.3; and ZnO under acetone in an agate mortar and pestle and subjecting it to calcination at 700 C., 900 C. and 1000 C. overnight with intermitted grinding in a muffle furnace. The resulting powder is pelleted by adding 2.5% polyvinyl alcohol in an aqueous solution as a binder. The pellet is sintered two times at 1350 C. for 15 h. The catalyst is characterized by XRD. Pt is loaded onto InFeO.sub.3(ZnO)m, where m=1-5, by a wet impregnation method and heated at 400 C. for 1 hour. Metal oxides selected from NiO and CuO are used as co-catalysts for water splitting reactions catalyzed by InGaO.sub.3(ZnO)m, where m=1-5.

(37) Embodiments of the present invention disclose a process for catalyzing H.sub.2 generation wherein the process is optionally co-catalysed by metals or metal oxides selected from the group consisting of, but not limited to Pt, CuO or NiO.

(38) Embodiments of the present invention disclose a photocatalytic water splitting process, wherein the hydrogen evolution rate is in the range of 7 to 11 milli mol/g/h in the presence of catalyst InFeO.sub.3(ZnO)m. The hydrogen evolution rate is in the range of 0.8 to 3.58 milli mol/g/h in the presence of catalyst InGaO.sub.3(ZnO)m.

(39) Embodiments of the present invention disclose the use of the instant photocatalyst composition InA(ZnO)m, wherein A is selected from metal oxides of Ga or Fe and m=1-5 for catalyzing a water splitting reaction for the evolution of H.sub.2.

EXAMPLES

(40) The following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

Example 1

(41) i. Synthesis of InFeO.sub.3(ZnO).sub.1

(42) For 1 g of InFeO.sub.3(ZnO).sub.1, 0.4627 g, 0.2661 g and 0.2712 g of In.sub.2O.sub.3, Fe.sub.2O.sub.3 and ZnO were weighed respectively and ground thoroughly under acetone in an agate mortar and pestle. The mixed powders were transferred to a platinum crucible and calcined at 700 C., 900 C. and 1000 C. overnight with intermitted grinding in a muffle furnace. The resulting powder was made into pellet by adding 2.5% polyvinyl alcohol in aqueous solution as a binder. The pellet was sintered two times at 1350 C. for 15 h.

(43) ii. Characterization of InFeO.sub.3(ZnO).sub.1

(44) X Ray Diffraction

(45) The phase formation was confirmed with XRD. Powder X-ray diffraction (XRD) was carried out in a PANalytical X'pert Pro dual goniometer diffractometer working under 40 kV and 30 mA. The radiation used was Cu K (1.5418 ) with a Ni filter and the data collection was carried out using a flat holder in Bragg-Brentano geometry with 1 slit at the source and receiving sides. An X'celerator solid-state detector with a scan speed of 0.012 min.sup.1 was employed.

(46) The powder XRD patterns depicted in FIGS. 1, 3, 8 and 10, show highly crystalline diffraction peaks, clearly indicating the formation of required structures, JCPDS Card Numbers 40-0250, 40-0243, 40-024, 40-0245 for IFZ1, IFZ2, IFZ3 and IFZ4 respectively, with reference to Kimizuka, N et al., Solid State Chem. 1988, 74, 98-109.

(47) The XRD pattern (FIG. 1) matches that of the reported compound corresponding to JCPDS PDF number 40-0250.

(48) iii. Photocatalytic Activity

(49) InFeO.sub.3(ZnO).sub.1 was dispersed in 20 ml water and 5 ml methanol by means of a magnetic stirrer in a gas closed irradiation cell made of quartz having 70 ml capacity. Here methanol was taken as a sacrificial reagent which gets oxidized by the resulting photogenerated holes. The light source was a 400 Watt tungsten lamp for visible irradiation. The amount of H.sub.2 evolved was determined using gas chromatography (Agilent GC with Carbosphere column and N.sub.2 as carrier gas). The reaction was carried out for 5 hours. The evolving gas mixture was taken in a syringe at an interval of 1 hour and injected into the GC. With reference to Table 1 and FIG. 2, H.sub.2 evolution is observed to be greater than 1 milli mole for five hours, in the absence of a co catalyst selected from Pt or NiO.

(50) TABLE-US-00001 TABLE 1 Water splitting activity of InFeO.sub.3(ZnO).sub.1 Irradiation Catalyst Irradiation Time (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.1.sub.without Visible 1 1689.437 Pt 2 1741.901 3 1463.899 4 1421.402 5 1413.016

Example 2

(51) i. Synthesis of InFeO.sub.3(ZnO).sub.2

(52) For 1 g of InFeO.sub.3(ZnO).sub.2 0.3639 g, 0.2093 g and 0.4267 g of In.sub.2O.sub.3, Fe.sub.2O.sub.3 and ZnO were weighed respectively and ground thoroughly under acetone in an agate mortar and pestle. The mixed powders were transferred to a platinum crucible and calcined at 700 C., 900 C. and 1000 C. overnight with intermitted grinding in a muffle furnace. The resulting powder was made into pellet by adding 2.5% polyvinyl alcohol in aqueous solution as binder. The pellet was sintered two times at 1350 C. for 15 h.

(53) ii. Characterization of InFeO.sub.3(ZnO).sub.2

(54) X Ray Diffraction

(55) The phase formation was confirmed with XRD. Powder X-ray diffraction (XRD) was carried out in a PANalytical X'pert Pro dual goniometer diffractometer working under 40 kV and 30 mA. The radiation used was Cu K (1.5418 ) with a Ni filter and the data collection was carried out using a flat holder in Bragg-Brentano geometry with 1 slit at the source and receiving sides. An X'celerator solid-state detector with a scan speed of 0.012 min.sup.1 was employed. The XRD pattern (FIG. 3) matches that of the reported compound corresponding to JCPDS PDF number 40-0243.

(56) iii. Impregnation of Platinum

(57) Tetraamine platinum nitrate ([Pt(NH.sub.3).sub.4](NO.sub.3).sub.2) was used as the platinum precursor. In order to load 2% platinum 0.002 g of [Pt(NH.sub.3).sub.4](NO.sub.3).sub.2 was weighed and dissolved in minimum amount of water and added to 0.049 g of InFeO.sub.3(ZnO).sub.2, mixed well and dried at 60 C. The mixture was transferred to an alumina crucible and heated at 400 C. for 1 h.

(58) iv. Photocatalytic Activity

(59) The 2% platinum loaded InFeO.sub.3(ZnO).sub.2 was dispersed in 20 ml water and 5 ml methanol by means of a magnetic stirrer in a gas closed irradiation cell made of quartz having 70 ml capacity. Here methanol was taken as sacrificial reagent which gets oxidized by the resulting photogenerated holes. The light source was a 400 W mercury lamp for UV and 400 W Tungsten lamp for visible irradiation. The amount of H.sub.2 evolved was determined using gas chromatography (Agilent GC with Carbosphere column and N.sub.2 as carrier gas). The reaction was carried out for 1 to 5 hours as tabulated herein. The evolving gas mixture was taken in a syringe at an interval of 1 hour and injected into the GC. The experiments were carried out with bare and platinum loaded catalyst under UV and visible irradiation. With reference to FIGS. 4-7 and Tables 2, 3, 4 and 5 it is observed that H.sub.2 evolves in the presence of co catalyst exemplified as Pt, in both UV and visible ranges.

(60) TABLE-US-00002 TABLE 2 Irradiation Time Catalyst Irradiation (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.2 UV 2 233.5063 with Pt 3 199.6466 4 174.612 5 158.0367

(61) TABLE-US-00003 TABLE 3 Catalyst Irradiation Irradiation Time (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.2 UV 2 445.5616 without Pt 3 517.2267 4 407.1339 5 209.6826

(62) TABLE-US-00004 TABLE 4 Catalyst Irradiation Irradiation Time (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.2 Visible 1 1761.588 without Pt 2 1536.928 3 1284.246 4 1114.3

(63) TABLE-US-00005 TABLE 5 Irradiation Catalyst Irradiation Time (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.2 with Visible 1 1686.829 Pt 2 1230.631 3 1310.478

Example 3

(64) i. Synthesis of InFeO.sub.3(ZnO).sub.3

(65) For 1 g of InFeO.sub.3(ZnO).sub.3 0.2999 g, 0.1725 g and 0.5275 g of In.sub.2O.sub.3, Fe.sub.2O.sub.3 and ZnO were weighed respectively and ground thoroughly under acetone in an agate mortar and pestle. The mixed powders were transferred to a platinum crucible and calcined at 700 C., 900 C. and 1000 C. overnight with intermitted grinding in a muffle furnace. The resulting powder was made into pellet by adding 2.5% polyvinyl alcohol in aqueous solution as binder. The pellet was sintered two times at 1350 C. for 15 h.

(66) ii. Characterization of InFeO.sub.3(ZnO).sub.3

(67) X Ray Diffraction

(68) The phase formation was confirmed with XRD. Powder X-ray diffraction (XRD) was carried out in a PANalytical X'pert Pro dual goniometer diffractometer working under 40 kV and 30 mA. The radiation used was Cu K (1.5418 ) with a Ni filter and the data collection was carried out using a flat holder in Bragg-Brentano geometry with 1 slit at the source and receiving sides. An X'celerator solid-state detector with a scan speed of 0.012 min.sup.1 was employed.

(69) The XRD pattern (FIG. 8) matches that of the reported compound corresponding to JCPDS PDF number 40-0244.

(70) iii. Photocatalytic Activity

(71) InFeO.sub.3(ZnO).sub.3 was dispersed in 20 ml water and 5 ml methanol by means of a magnetic stirrer in a gas closed irradiation cell made of quartz having 70 ml capacity. Here methanol was taken as sacrificial reagent which gets oxidized by the resulting photogenerated holes. The light source was a 400 Watt tungsten lamp for visible irradiation. The amount of H.sub.2 evolved was determined using gas chromatography (Agilent GC with Carbosphere column and N.sub.2 as carrier gas). The reaction was carried out for 1 to 6 hours. The evolving gas mixture was taken in a syringe at an interval of 1 hour and injected into the GC. It may be concluded from FIG. 9 and Table 6 that the catalyst of this example evolves H.sub.2 up to 1 milli mole even without presence of co catalyst. Further, the catalyst of this example has exhibited stability and activity over 6 hours.

(72) TABLE-US-00006 TABLE 6 Water splitting activity of InFeO.sub.3(ZnO).sub.3 Irradiation Catalyst Irradiation Time (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.3.sub.without Visible 1 766.4058 Pt 2 747.9462 3 788.8368 4 984.5972 5 1052.739 6 960.1463

Example 4

(73) i. Synthesis of InFeO.sub.3(ZnO).sub.4

(74) For 1 g of InFeO.sub.3(ZnO).sub.4 0.2551 g, 0.1467 g and 0.5982 g of In.sub.2O.sub.3, Fe.sub.2O.sub.3 and ZnO were weighed respectively and ground thoroughly under acetone in an agate mortar and pestle. The mixed powders were transferred to a platinum crucible and calcined at 700 C., 900 C. and 1000 C. overnight with intermitted grinding in a muffle furnace. The resulting powder was made into pellet by adding 2.5% polyvinyl alcohol in aqueous solution as binder. The pellet was sintered two times at 1350 C. for 15 h.

(75) ii. Characterization of InFeO.sub.3(ZnO).sub.4

(76) X Ray Diffraction

(77) The phase formation was confirmed with XRD. Powder X-ray diffraction (XRD) was carried out in a PANalytical X'pert Pro dual goniometer diffractometer working under 40 kV and 30 mA. The radiation used was Cu K (1.5418 ) with a Ni filter and the data collection was carried out using a flat holder in Bragg-Brentano geometry with 1 slit at the source and receiving sides. An X'celerator solid-state detector with a scan speed of 0.012 min.sup.1 was employed. The XRD pattern (FIG. 10) matches that of the reported compound corresponding to JCPDS PDF number 40-0245.

(78) iii. Photocatalytic Activity

(79) InFeO.sub.3(ZnO).sub.4 was dispersed in 20 ml water and 5 ml methanol by means of a magnetic stirrer in a gas closed irradiation cell made of quartz having 70 ml capacity. Here methanol was taken as sacrificial reagent which gets oxidized by the resulting photogenerated holes. The light source was 400 Watt tungsten lamp for visible irradiation. The amount of H.sub.2 evolved was determined using gas chromatography (Agilent GC with Carbosphere column and N.sub.2 as carrier gas). The reaction was carried out for 5 hours. The evolving gas mixture was taken in a syringe at an interval of 1 hour and injected into the GC. With reference to Table 7 and FIG. 11, H.sub.2 evolution is observed to be greater than 1 milli mole for five hours, in the absence of a co catalyst selected from Pt or NiO.

(80) TABLE-US-00007 TABLE 7 Water splitting activity of InFeO.sub.3(ZnO).sub.4 Irradiation Catalyst Irradiation Time (h) H.sub.2 evolved (mol/g/h) InFeO.sub.3(ZnO).sub.4.sub.without Visible 1 1406.202 Pt 2 1368.77164 3 1330.18205 4 1679.50397 5 1754.50057

Example 5

(81) Photocatalytic Water Splitting Activity of InGaO.sub.3ZnO

(82) Photocatalytic water splitting activities for the instant IGZ (InGaO.sub.3ZnO) compounds were evaluated with or without a co-catalyst. The results of hydrogen evolved with IGZ catalyst in the absence of a co-catalyst are tabulated in Table 8 and represented graphically in FIG. 13. The experiments were performed for 2 hours under UV light irradiation.

(83) TABLE-US-00008 TABLE 8 H.sub.2 evolution with IGZ catalysts without co-catalyst under UV light Catalysts H.sub.2 evolved (milli mol/g) IGZ1 3.31258 IGZ2 3.36874 IGZ3 4.48085 IGZ4 4.72560

(84) The H.sub.2 evolution experiments using InGaO.sub.3ZnO catalysts were performed in presence of visible light irradiation. However, H.sub.2 evolution was negligible.

(85) Therefore, co-catalysts such as CuO, NiO in combination with IGZ catalysts were used in order to enhance the water splitting activity in the visible region. 1 wt % and 2 wt % NiO loaded IGZ catalysts were used for water splitting under both UV and visible light irradiations for 4 hours.

(86) Even though these catalysts were shown to be active for water splitting under UV light, it did not indicate any visible light activity. The amount of hydrogen evolved under UV light when using 1 wt % and 2 wt % NiO co-catalyst is tabulated in the Table 9 and also represents graphically in FIG. 14.

(87) TABLE-US-00009 TABLE 9 H.sub.2 evolution with 1 wt %, 2 wt % NiO loaded IGZ catalyst H.sub.2 evolved in 4 h, UV light irradiation Catalysts 1% NiO 2% NiO IGZ1 5.49722 13.57300 IGZ2 6.80806 14.35979 IGZ3 6.14817 11.48355 IGZ4 8.35684 12.55806

(88) From FIG. 14, it is observed that NiO co-catalyst functions efficiently for InGaO.sub.3(ZnO).sub.m (m=1-4) series under UV irradiation. 2 wt % NiO loaded IGZ exhibits enhanced activity compared to 1 wt % NiO loaded. This proves the role of co-catalyst in water splitting.

(89) 2 wt % NiO loaded IGZ samples were used for detailed study by varying time of light irradiation. The results obtained from these experiments are graphically represented in FIG. 15. From the figure it is observed that as time of irradiation increases, the water splitting activity also increases. The NiO loaded IGZ based photocatalysts work under UV light irradiation.

(90) As known from earlier experiments, IGZ water splitting catalysts were found to be less active under visible light.

(91) In view of the weak activity of IGZ catalyst under visible light, it is necessary to provide a photocatalyst which functions under visible light. Sunlight consists of 50% visible light and only 4% UV light. In order to utilize solar energy efficiently, a photocatalyst which is visible light active for water splitting is more favorable.

(92) It is reported that CuO loaded photocatalysts work efficiently under visible light irradiation. Water splitting experiments with 1 wt %, 2 wt % CuO loaded IGZ catalysts were conducted under visible light irradiation and the results obtained from these experiments are tabulated in Table 10 and graphically represented in FIG. 16.

(93) TABLE-US-00010 TABLE 10 H.sub.2 evolution with 1 wt %, 2 wt % CuO loaded IGZ catalysts at 4 hours under visible light. H.sub.2 evolved (milli mol/g) Catalysts 1 wt % CuO 2 wt % CuO IGZ1 2.99879 5.18061 IGZ2 3.62655 4.54663 IGZ3 2.18242 3.23298 IGZ4 3.392526 3.35715

(94) From FIG. 16 it is observed that the 2 wt % CuO loaded IGZ catalysts shows more water splitting activity than the corresponding 1 wt % CuO loaded IGZ catalysts. This proves that the addition of CuO as co-catalyst improves the activity. More experiments were conducted with 2 wt % CuO loaded IGZ catalysts by varying time of visible light irradiation and the results are graphically represented in FIG. 17.

(95) It is observed that as time of irradiation increases, H.sub.2 production also increases. Experiments were also done by varying the CuO loading in IGZ1 catalyst viz. 1 wt %, 4 wt % and 10 wt % CuO and the results obtained are tabulated in Table 11 and graphically represented in FIG. 18.

(96) TABLE-US-00011 TABLE 11 H.sub.2 evolution with IGZ1 catalyst with different CuO loading. Amount of H.sub.2 evolved (Milli mol/g) IGZ1 under visible light for 2 h 1 wt % CuO 1.49939 2 wt % CuO 2.58468 4 wt % CuO 1.645000 10 wt % CuO 0.69134

(97) Results shown in Table 11, indicate that IGZ1 loaded with 2 wt % CuO exhibits enhanced water splitting activity in visible light irradiation. Increase in loading concentration of CuO results in a decrease in the water splitting activity therefore increase in concentration of metal oxide adversely affects the water splitting activity. Moreover, loading with 2 wt % CuO loaded IGZ catalysts indicates better hydrogen evolution activity.

(98) Advantages of the embodiments of the invention include economical process, since metal oxide co-catalyst is optional; and the photo catalyst is UV and visible active, with more activity in visible, especially in the absence of a co catalyst.