Photocatalytic Properties of RuO₂-Loaded β-Ge₃N₄ for Overall Water Splitting

Abstract

Germanium nitride, β-Ge3N4, is studied as a non-oxide photocatalyst for overall water splitting. Nitridation of GeO2 at 1153 K for 10 h under a flow of NH3 results in the production of well-crystallized β-Ge3N4 particles with a phenacite structure belonging to the hexagonal crystal system. Although the as-prepared β-Ge3N4 displays negligible activity for overall water splitting, the material becomes photocatalytically active under ultraviolet (UV) irradiation (λ > 200 nm) when loaded with RuO2 nanoparticles as H2 evolution sites. The photocatalytic activity of RuO2-loaded β-Ge3N4 for overall water splitting is strongly dependent on the reaction conditions. The highest activity is obtained when the reaction is carried out in 1 M H2SO4 aqueous solution. The rates of both H2 and O2 evolution decreases as the reaction progresses, attributable to photoreduction of O2, collapse of the catalyst surface by elusion of Ge cations, and loosened interfacial contact between the β-Ge3N4 and the loaded RuO2 nanoparticles. Up to 80% of the initial activity can be recovered by calcination of the used catalyst at 673 K in air for 5 h followed by reloading with RuO2.

Keywords

Affiliated Institutions

• Japan Science and Technology Agency JP
• Nagaoka University of Technology JP
• The University of Tokyo JP

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