A REVIEW ON ZINC OXIDE (ZnO) BASED COMPOSITES FOR PHOTOCATALYTIC HYDROGEN PRODUCTION VIA WATER-SPLITTING

Zinc oxide (ZnO) has been used for photocatalytic water splitting due to its excellent performance, low cost, nontoxicity, thermal stability, and chemical stability. However, despite its remarkable properties it has drawback of photocorrosion and unable to utilize visible light due to wide band gap of 3.3-3.4 eV. Structurally, ZnO exist in three different forms: rocksalt, cubic blend and hexagonal Wurtzite. It has been reported that Wurtzite produced more H2 compared to its counterparts. Herein, several techniques of zinc oxide synthesis are discussed and incorporation of zinc oxide nanoparticle with metal oxide, sulfide and other material enhance its performance in visible light region.

1. A REVIEW ON ZINC OXIDE (ZnO ) BASED COMPOSITES FOR PHOTOCATALYTIC HYDROGEN PRODUCTION VIA WATER-SPLITTING By Mam Ishaku Dagareh, Advanced Energy Materials Research Group Department of Physics, Federal University Dutse P.M.B. 7156, Ibrahim Aliyu Bye-Pass, Jigawa State International conference on energy materials and rechargeable batteries. Manav Rachna University, School of Sciences (Physics) & University Instrumentation Center. Faridabad, Haryana Delhi, India 12/20/2023 1 19 th -23 th December, 2023 1

2. 12/20/2023 2 Overview of the Presentation Section 1 Energy Crisis and Demand Section 2 photocatalysis Section 3 Why Zinc oxide nanoparticle ? Section 4 Synthesis and crystallographic structure of ZnO Section 5 Empirical review

3. INTRODUCTION 3 Energy crisis Renewable energy Carbon emission Hydropower Wind energy Geothermal e.t.c Green hydrogen 140 MJ/Kg Infinite Eco-friendly Burning to yield water Method of hydrogen production Electrolysis Thermolysis photolysis Photochemical Photocatalysis photobiological ZnO- rGO Photocatalysis is cynosure Photocatalytic Hydrogen evolution 12/20/2023

4. 12/20/2023 4 The catalyst which work in the presence of light (photon) of energy is known as Photocatalyst and this phenomenon is called Photocatalysis .

5. Requirements of a Photocatalyst for hydrogen production Must have band gap energy greater than 1.23 eV, well crystalline and high surface area Conduction Band of semiconductor must be more negative than the redox potential of Hydrogen and Valence Band must be more positive than oxidation potential  of Oxygen Resistance to photo-corrosion 12/20/2023 5 Electron-hole pair recombination separation and transportation of carrier inextensible to visible light photon

6. 5 Zinc oxide n -type Binding energy 60 MeV Bandgap 3.2 eV-3.4 eV UV-region Photocorrosion Recombination -2 -1 1 2 3     0.1eV 3.1ev ZnO low cost radiation resistance, Nontoxicity high chemical thermal stability Simplistic synthesis 12/20/2023

7. 12/20/2023 7 Hexagonal Wurtzite is the best due to high Thermodynamic stability Easy synthesis

8. HYDROTHERMAL SYNTHESIS OF ZnO 12/20/2023 8

9. Approaches to prevent electron-hole pair recombination via Heterojunction construction Doping with metal Use electron mediator i.e rGO 12/20/2023 9

10. heterojunction Fig. 13 Schematic illustration of p-n junction Fig.14 (a) Schematic illustration of liquid phase and all solid Z-scheme 12/20/2023 10

11. Fig.14 (b) Schematic illustration of direct z -scheme 12/20/2023 11 S-scheme

12. 6.1 Water splitting by ZnO/metal-oxide composites Table 2 . Zinc oxide / metal oxide Main catalyst Co-catalyst Source light Method Amount of H 2 [mmol g − 1 h − 1 ] Reference CoOCu 2 OZnO TiO 2 -rGO A 60 W LED lamp Improve hummer’s method 0.630 [141] Ag-ZnO CeO 2 Sun light Combustion 18.345 [138] ZnO Y-Tb 2 O 3 Xe lamp 300W Combustion 21270 [142]             ZnO TiO-Au UV Pen-Ray lamp Deposition-precipitation with urea (DPU) 9.130 [143] ZnO CuO-Au 300W Xe light So-gel 4.655 [127] Ta 3 N 5 ZnO 300W Xe lamp Electron spinning 1.19375 [144] ZnO CeO 2 -Ag 300 W Xe Hydrothermal 3.1420 [139] TiO 2 ZnO-Au 300 W Xe Solvothermal 0.001068 [140] ZnO TiO 2 -Ag 300 Xe lamp Hydrothermal 60.4 [103] Cu-ZnO   Visible light Sol-gel 0.007.49 to 0.04155 [3] 12/20/2023 12

13. 6.2 Water splitting by ZnO/metal-sulfides composites Table 3: zinc oxide and sulfides Main catalyst Co-catalyst Source light Method Amount of H 2 [mmol g − 1 h − 1 ] Reference ZnO Cds Visible light Solvathermal 0.6696 [147] Pt-ZnS ZnO Visible light Emulsion Polymerization 0.0876 [152] CdIn2S4 ZnS Xe lamp Hydrothermal 0.3743 [115] ZnO ZnS Mercury lamp Solvathermal 0.580 [151] CuS/PbS ZnO 300W solar simulator Precipitation Hydrothermal 6.654 [153] ZnO ZnS Xe lamp 300W Hydrothermal 2.4 [154] Pt-ZnS ZnO Xe lamp 300W Hydrothermal 46.8 [146] ZnO ZnS-Cu(OH) 2 Xe Lamp 350 W Hydrothermal Precipitation   1.350 [155] ZnO ZnS Xe lamp 300W Hydrothermal 757.07 [149] ZnO CdS Visible light Hydrothermal 7.669 [117] 12/20/2023 13

14. 6.0 Water splitting by ZnO/2D-materials composites Table 1. Zinc oxide / 2D material S/N Main catalyst Co-catalyst Source light Method Amount of H 2 [mmol h − 1 g − 1 ] Reference   Tb –ZnO CNT A 350 Xe lamp So-gel 0.2683 [135]   g-sC3N4 ZnO-Au 300 w Xe lamp Polymerization method 46.46 [137]   Ce@Cds-rGO ZnO 300 w Xe lamp Microwave-assisted method 10.55 [183]   ZnTPPO ZnO 225 W Xenon lamp Thermal exfoliation Phosphating 31.037 [187]   CuS-ZnO rGO/CdS 300 w Xe lamp Electrochemical method Modified hummer’s method 1073 [189]   g-C3N4 Ag/ZnO Solar light 80w Thermal decomposition 1.6375 [192]   ZnO g-C 3 N 4 300 W Xe lamp Solution-phase mixing. 1.358 [196]   g-C3N4 ZnO 1000 W Xe Hydrothermal 0.30625 [174]   ZnO nanorod g-C 3 N 4 Solar light Hydrothermal 1497.5 [175] 12/20/2023 14

15. Summary and conclusion of ZnO nanoparticle 15 Hydrothermal method Ternary photocatalyst Enhance photocatalytic hydrogen evolution 12/20/2023

16. 12/20/2023 16 Thanks for your time Mam .I Dagareh Thanks for listening [email protected]

17. 12/20/2023 17 Acknowledgements Dr. Hafeez Yusuf Hafeez, HOD, Department of Physics, FUD Advanced Energy Materials Lab members All staff of Department of Physics of Federal U niversity Dutse Nigeria Manav Rachna University, School of Sciences (Physics) & University Instrumentation Center. Faridabad, Haryana, Delhi, India The World Academy of Science (TWAS)- Germany Seed Grant for New African Principal Investigators (SG-NAPI):4500454078

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