Synergistically Photo-Thermo-Catalytic Effect of Metal-Oxide Semiconductors with d10 Electronic Configuration for Hydrogen Generation in NaBH4 Hydrolyzation

The hydrogen generation rate (HGR) of NaBH4 hydrolyzation is sensitive to the pH value of its aqueous solution. The highly dispersed conduction band of metal-oxide semiconductors with d10 electronic configuration allows excellent mobility of photoexcited electrons, ensuring effective separation of photoexcited electron–hole pairs. In this study, ZnGa2O4, a conventional photocatalytic material with d10 electronic configuration was investigated for the synergistically photo-thermo-catalytic effect in NaBH4 hydrolyzation. The hydrogen generation tests revealed that photoexcited holes as OH−-trapping agent promoted hydrogen generated from NaBH4 hydrolyzation. Meanwhile, the consumption of photoexcited holes accelerated hydrogen generated from photoexcited electron reduction. Coupled with these two factors, ZnGa2O4 exhibited synergistically photo-thermo-catalytic effect in NaBH4 hydrolyzation. The HGR in photo-thermo driven condition offered several times higher than that in single-energy driven condition (irradiation or thermal radiation). The obtained catalysts, bare-ZnGa2O4 and ZnGa1.90Fe0.10O4 achieved optimum HGR at 313.15 K under ultraviolet-light (7.81 mmol h−1 g−1) and visible light (4.39 mmol h−1 g−1), respectively. In addition, the circular tests demonstrated ZnGa2O4 catalysts with high thermodynamic and chemical stability.