Coupling polyoxometalate with CoOOH on BiVO4 photoanodes towards efficient photoelectrochemical water oxidation

BiVO4 photoanode shows severe recombination of photogenerated carriers, which limits its water oxidation performance for photoelectrochemical (PEC) water splitting. In this paper, the surface of BiVO4 photoanode was modified through the coupling of phosphotungstic acid (H3O40PW12·xH2O, denotes as PWO) with CoOOH to address such drawbacks. At 1.23 VRHE, the photocurrent density of BiVO4/PWO/CoOOH photoanode reaches 2.80 mA/cm2, which is 2.59-fold that of bare BiVO4 photoanode. Moreover, the initial onset potential of BiVO4/PWO/CoOOH photoanode is also negatively decreased by 270 mV than that of bare BiVO4 photoanode. Detailed structural and electrochemical characterizations demonstrate that the decoration of PWO serves as an intermediate layer to promote the transport of holes from BiVO4 to CoOOH, while the deposition of CoOOH acts as a protective layer as well as cocatalyst to reduce the photocorrosion and improve the PEC activities of BiVO4. The synergistic coupling of PWO and CoOOH not only makes efficient bulk and surface charge separation, but also takes full advantage of photo-generated holes on the surface, which accelerates water oxidation kinetics, ultimately achieving an improvement in PEC water oxidation.