Photocatalytic hydrogen evolution from water over hafnium oxyphosphate

Hafnium oxyphosphate was prepared as a novel photocatalyst for hydrogen production from water. Here, Hf4+ with d0 electronic configuration was selected as the constituent cation, because efficient photocatalysts generally contain d0 or d10 metal cations. In addition, most phosphates are reported to have high photoreduction ability of water due to their wide bandgap compared to oxides. By using Hf2O(PO4)2, hydrogen gas was generated from water under the ultraviolet light irradiation, while a simple hafnium oxide, HfO2, did not show a hydrogen evolution ability. The hydrogen production rate of Hf2O(PO4)2 was estimated to be 800 µmol·h−1. Also, oxygen gas evolution was observed for Hf2O(PO4)2.