Simultaneously Tuning Charge Separation and Surface Reaction Kinetics on ZnIn2S4 Photoanode by P-Doping for Highly Efficient Photoelectrochemical Water Splitting and Urea Oxidation

ZnIn2S4 nanosheets are a promising photoanode for driving photoelectrochemical (PEC) hydrogen fuel production; nevertheless, poor charge separation and sluggish surface reaction kinetics hinder its PEC performance to an extreme degree. Herein, a facile element doping strategy (i.e., P element) was developed to obtain the desired photoanode. As a result, the ZnIn2S4-P (ZIS-P5) photoanode exhibits a remarkable photocurrent density of 1.66 mA cm−2 at 1.23 V versus a reversible hydrogen electrode (VRHE) and a much lower onset potential of 0.12 V vs. RHE for water oxidation. Careful electrochemical analysis confirms that the P doping and sulfur vacancies (Sv) not only facilitate the hole transfer, but also boost surface reaction kinetics. Finally, the “killing two birds with one stone” goal can be achieved. Moreover, the optimized photoanode also presents high PEC performance for urea oxidation, obtaining a photocurrent density of 4.13 mA cm−2 at 1.23 V vs. RHE. This work provides an eco-friendly, simple and effective method to realize highly efficient solar-to-hydrogen conversion.