Hydrothermal Synthesized CoS2 as Efficient Co-Catalyst to Improve the Interfacial Charge Transfer Efficiency in BiVO4

The bare surface of BiVO4photoanode usually suffers from extremely low interfacial charge transfer efficiency which leads to a significantly suppressed photoelectrochemical water splitting performance. Various strategies, including surface modification and the loading of co-catalysts, facilitate the interface charge transfer process in BiVO4. In this study, we demonstrate that CoS2synthesized from the hydrothermal method can be used as a high-efficient co-catalyst to sufficiently improve the interface charge transfer efficiency in BiVO4. The photoelectrochemical water splitting performance of BiVO4was significantly improved after CoS2surface modification. The BiVO4/CoS2photoanode achieved an excellent photocurrent density of 5.2 mA/cm2at 1.23 V versus RHE under AM 1.5 G illumination, corresponding to a 3.7 times enhancement in photocurrent compared with bare BiVO4. The onset potential of the BiVO4/CoS2photoanode was also negatively shifted by 210 mV. The followed systematic combined optical and electrochemical characterization results reveal that the interfacial charge transfer efficiency of BiVO4was largely improved from less than 20% to more than 70% due tor CoS2surface modification. The further surface carrier dynamics study performed using an intensity modulated photocurrent spectroscopy displayed a 6–10 times suppression in surface recombination rate constants for CoS2modified BiVO4, which suggests that the key reason for the improved interfacial charge transfer efficiency possibly originates from the passivated surface states due to the coating of CoS2.Keywords:BiVO4;CoS2;photoelectrochemical water splitting;intensity modulated photocurrent spectroscopy;surface recombination