LAUSR

Abstract The realization of semiconductor p–n junctions is essential for improved photoelectrochemical (PEC) performance in water splitting. Concerning the traditional p-n junctions, although the p- and n-type materials that are utilized to build them have been decreased from bulk to only two unit cells, the PEC water splitting efficiency is still tough to be satisfactory due to the obstacle of interlayer carrier separation/transport. Herein, we report that p-n junctions based on n-type (sulfur vacancies) and p-type (phosphorus incorporation) domains of single-unit-cell thick ZnIn2S4 (ZIS) nanosheet arrays present a quite different carrier separation/transport characteristic. As a result, such peculiar nanostructure of the optimal phosphorus-incorporated n-type ZIS (n-ZIS-P) photoelectrode delivers the highest photogenerated current density of 6.34 mA cm-2 at 1.23 V versus reversible hydrogen electrode (VRHE) among all the reported ZIS-based photoanodes. Besides, the hydrogen and oxygen production in the stoichiometric ratio (2:1) is achieved at a Faradaic efficiency of almost unity.