A conductive ZnO:Ga/ZnO core-shell nanorod photoanode for photoelectrochemical water splitting

•ZnO:Ga/ZnO core-shell array is prepared with a two-step hydrothermal method.•ZnO:Ga/ZnO junction with nearly the same lattice structure is obtained.•The ZnO:Ga/ZnO composite exhibits visible light absorption and improved conductivity.•The ZnO:Ga/ZnO photoanode exhibits remarkably enhanced PEC performance.•The ZnO:Ga/ZnO composite shows better photostability both in neutral and alkaline electrolyte.

We report a ZnO:Ga/ZnO isostructural nanojunction photoanode with core-shell structure for photoelectrochemical water splitting. Ga-doped zinc oxide (ZnO:Ga) shell is grown in situ on the vertically aligned ZnO array core in a hydrothermal process. The as-prepared ZnO:Ga/ZnO composite with nearly the same lattice structure in the two phases exhibits enhanced light absorption and improved electrical conductivity. The photocurrent density of the composite achieves 0.6 mA cm−2 under AM 1.5G simulated light irradiation with an applied bias of 1.23 vs. Ag/AgCl, which is three times higher than that of the anode made of pristine ZnO array. Under visible light (λ > 420 nm) irradiation, the current density reaches 0.06 mA cm−2 at the same condition. Moreover, the ZnO:Ga/ZnO composite shows better photostability than ZnO both in neutral and alkaline electrolyte. The isostructural nanojunction with excellent lattice match is thus demonstrated to be a promising material as the photoanode in water splitting.

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