Improved catalytic activity on transitioning from inverse to normal spinel in ZnGaSnO: a robust bifunctional OER and HER electrocatalyst

• Published in: Sustainable energy & fuels 2024-05, Vol.8 (1), p.2144-2152
• Main Authors: Parayil, Reshmi T, Gupta, Santosh K, Garg, Kalpana, Mehta, Shivangi, Sudarshan, K, Mohapatra, M, Nagaiah, Tharamani C
• Format: Article
• 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, Zn 2− x Ga 2 x Sn 1− x O 4 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, ZnGa 2 O 4 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. ZnGa 2 O 4 has shown superior photoluminescence compared to Zn 2 SnO 4 and interestingly there was also color tunability from orange to blue region going from zinc stannate to zinc gallate. ZnGa 2 O 4 acts as a bifunctional catalyst for both the OER and HER with a faradaic efficiency of 92 and 95% respectively. Fuel cell study also suggests higher stability of the electrodes for the overall water splitting up to 24 h.