Preparation of CuBi2O4 photocathodes for overall water splitting under visible light irradiation

In this study, the CuBi2O4 films were prepared by a facile drop-casting method for visible-light-driven water splitting, while the effect of film thickness and annealing temperature on the actual photoelectrochemical (PEC) performance were investigated. The annealing temperature was optimized as 550 °C. With increasing the layer number, the PEC performance was firstly increased and then decreased, reaching a maximum photocurrent density of 1.1 mA/cm2 at a layer number of 3 under a bias of 0 V vs. reverse hydrogen electrode (RHE). Besides, both the electrochemical impedance and photoluminescence (PL) spectra were collected to reveal the mechanism underlying the performance changes. It was found that the enhanced PEC performance was attributed to high specific surface area and broad spectral response of CuBi2O4 photocathodes. Moreover, a tandem PEC cell was constructed by combining CuBi2O4 with a ZnIn2S4 photoanode for unbiased solar water splitting. The photocurrent density at the joint point was 0.13 mA/cm2, corresponding to an unbiased solar water splitting efficiency of 0.056%. This work shows that CuBi2O4 has a good potential as a photocathode for solar-driven overall water splitting. •CuBi2O4 photocathodes have been prepared by drop-casting.•Effect of film thickness was investigated on surface morphology and PEC performance.•Excellent PEC performance is ascribed to efficient visible light absorption and carrier transport.•PEC tandem cell was constructed for overall water splitting, leading to a photocurrent of ~0.0309 mA/cm2 under zero bias.