Dependence of Activity and Stability of Germanium Nitride Powder for Photocatalytic Overall Water Splitting on Structural Properties

Germanium nitride (Ge 3 N 4 ) powder prepared by thermal ammonolysis of GeO 2 is examined as a photocatalyst for overall water splitting. Nitridation of GeO 2 under a flow of NH 3 at temperatures higher than 1123 K for 10 h results in production of either a single phase of β-Ge 3 N 4 or a mixture of elemental Ge, α-Ge 3 N 4, and β-Ge 3 N 4, depending on the nitridation conditions. β-Ge 3 N 4 exhibits activity for the stoichiometric decomposition of pure water into H 2 and O 2 under ultraviolet (UV) irradiation (λ > 200 nm) when loaded with nanoparticulate RuO 2 as a cocatalyst. Improving the crystallinity of the β-Ge 3 N 4 catalyst results in greater activity for overall water splitting and markedly reduced N 2 release due to self-decomposition by photogenerated holes.