Photocatalytic hydrogen evolution from water over hafnium oxyphosphate

Abstract

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.