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Germanium nitride (Ge3N4) powder prepared by thermal ammonolysis of GeO2 is examined as a photocatalyst for overall water splitting. Nitridation of GeO2 under a flow of NH3 at temperatures higher than 1123 K for 10 h results in production of either a single phase of β-Ge3N4 or a mixture of elemental Ge, α-Ge3N4, and β-Ge3N4, depending on the nitridation conditions. β-Ge3N4 exhibits activity for the stoichiometric decomposition of pure water into H2 and O2 under ultraviolet (UV) irradiation (λ > 200 nm) when loaded with nanoparticulate RuO2 as a cocatalyst. Improving the crystallinity of the β-Ge3N4 catalyst results in greater activity for overall water splitting and markedly reduced N2 release due to self-decomposition by photogenerated holes.
Maeda et al. (Tue,) studied this question.