Two-dimensional Semiconducting Ag2X (X = S, Se) with Janus-induced Built-in Electric Fields and Moderate Band Edges for Overall Water Splitting

Introduction of Two-Dimensional (2D) photocatalysts for solar water splitting has attracted significant attention in recent years, due to their considerably large surface areas and short pathways of charge carrier migration compared to their bulk counterparts. Herein, monolayers of Ag2S, Ag2Se, SAg4Se, SAg4Te, SeAg4Te and their heterostructures are predicted as promising overall-water-splitting photocatalysts according to first-principles calculations. Compared with Ag2S and Ag2Se monolayers, the Janus ones not only possess direct band gaps and moderate band edges for overall water splitting but also achieve the Janus-induced built-in electric fields of 0.14, 0.34 and 0.21 eV respectively, which could improve the photocatalytic efficiency via restraining the electron-hole recombination. Further investigations on their heterostructures show that they are also suitable for overall water splitting with enhanced optical absorbances and larger built-in electric fields. Our findings extend the scope of overall-water-splitting photocatalysts to monolayers of Ag2S, Ag2Se, SAg4Se, SAg4Te, SeAg4Te and their heterostructures, which is expected to inspire the experimental fabrications and relative investigations.