Oxygen vacancy-rich high-pressure rocksalt phase of zinc oxide for enhanced photocatalytic hydrogen evolution.

The generation of hydrogen as a clean energy carrier by photocatalysis, as a zero-emission technology, is of significant scientific and industrial interest. However, the main drawback of photocatalytic hydrogen generation from water splitting is its low efficiency compared to traditional chemical or electrochemical methods. Zinc oxide (ZnO) with the wurtzite phase is one of the most investigated photocatalysts for hydrogen production, but its activity still needs to be improved. In this study, an oxygen-deficient high-pressure ZnO rocksalt phase is stabilized using a high-pressure torsion (HPT) method, and the product is used for photocatalysis under ambient pressure. The simultaneous introduction of oxygen vacancies and the rocksalt phase effectively improved photocatalytic hydrogen production to levels comparable to benchmark P25 TiO, due to improving light absorbance and providing active sites for photocatalysis without any negative effect on electron-hole recombination. These results confirm the high potential of high-pressure phases for photocatalytic hydrogen generation.