Bi2Ga4O9: An undoped single-phase photocatalyst for overall water splitting under visible light

[Display omitted] •Bi2Ga4O9 shows an intrinsic dual edge of light absorption at ∼433 and ∼382nm.•The estimated valence and conduction band potentials allow water splitting.•Bi2Ga4O9–0.5wt.% RuOx photocatalyzes overall water splitting under visible light.•The optimal gas generation rates are 41.5 (H2) and 19.6 (O2)μmol/h/g.•The apparent quantum yield at 420nm is 0.09%. Visible-light-driven overall water splitting via semiconductors is one of the most challenging topics in photocatalysis, because it raises harsh requirements for photocatalysts both thermodynamically and kinetically. With the rationale of combining Bi3+ and Ga3+, we developed an oxide photocatalyst, Bi2Ga4O9 (loaded with RuOx), capable of overall water splitting under visible light due to its specific band structure, i.e., suitable potentials for valence and conduction bands, and most importantly its characteristic of anisotropic charge migration. Band structure engineering of Fe3+-to-Ga3+ doping and a sol–gel synthetic method were both applied to further enhance the light-harvesting ability and eventually lead to optimal gas generation rates of 41.5 and 19.6μmol/h/g for H2 and O2, respectively. The apparent quantum yield at 420nm is 0.09%; nevertheless, it represents a successful effort to develop a single-phase visible light catalyst for overall water splitting.