Improved catalytic activity on transitioning from inverse to normal spinel in Zn2−xGa2xSn1−xO4: a robust bifunctional OER and HER electrocatalyst

• Published in: Sustainable energy & fuels 2024-05, Vol.8 (10), p.2144-2152
• Main Authors: Parayil, Reshmi T, Gupta, Santosh K, Garg, Kalpana, Mehta, Shivangi, Sudarshan, K, Mohapatra, M, Nagaiah, Tharamani C
• Format: Article
• Language: English
• Subjects: Catalysts; Catalytic activity; Current density; Electrocatalysts; Electrolysis; Hydrogen evolution reactions; Hydrogen production; Light emission; Oxygen; Oxygen evolution reactions; Photoelectron spectroscopy; Photoelectrons; Photoluminescence; Photons; Positron annihilation; Production methods; Spectroscopy; Spectrum analysis; Water splitting; X ray photoelectron spectroscopy; Zinc; Zinc stannate
• ISSN: 2398-4902
• DOI: 10.1039/d4se00264d

Water splitting by electrolysis is considered as one of the best methods for the production of hydrogen which is a clean and green fuel that can replace the existing non-renewable sources. Herein, Zn2−xGa2xSn1−xO4 with oxygen vacancies has been synthesized via a solid state method. Furthermore, the influence of oxygen vacancies on electrocatalytic activity is investigated systematically. The presence of oxygen vacancies has been confirmed by X-ray photoelectron spectroscopy (XPS) and positron annihilation lifetime spectroscopy (PALS) and it was found that higher oxygen vacancy concentration is present in zinc gallate. As a result, ZnGa2O4 exhibits prominent hydrogen evolution reaction (HER) achieving a current density of 20 mA cm−2 with a low overpotential of 360.0 mV and prominent oxygen evolution reaction (OER) achieving a current density of 10 mA cm−2 at an overpotential of 370.0 mV, and the voltage required for overall water splitting is 2.0 V @ 10 mA cm−2. The catalyst also exhibits good stability for up to 12 hours and it exhibited a faradaic efficiency of 92% for the OER and 95% for the HER. The role of oxygen vacancies adds multifunctionalities in these materials in terms of light emission. ZnGa2O4 has shown superior photoluminescence compared to Zn2SnO4 and interestingly there was also color tunability from orange to blue region going from zinc stannate to zinc gallate.