All‐Surface‐Atomic‐Metal Chalcogenide Sheets for High‐Efficiency Visible‐Light Photoelectrochemical Water Splitting

Artificial all‐surface‐atomic 2D sheets can trigger breakthroughs in tailoring the physical and chemical properties of advanced functional materials. Here, the conceptually new all‐surface‐atomic semiconductors of SnS and SnSe freestanding sheets are realized using a scalable strategy. As an example, all‐surface‐atomic SnS sheets undergo surface atomic elongation and structural disordering, which is revealed by X‐ray absorption fine structure spectroscopy and first‐principles calculations, endowing them with high structural stability and an increased density of states at the valence band edge. These exotic atomic and electronic structures make the all‐surface‐atomic SnS sheet‐based photoelectrode exhibit an incident photon‐to‐current conversion efficiency of 67.1% at 490 nm, much higher than the efficiencies of other visible‐light‐driven water splitting. A photocurrent density of 5.27 mA cm^‐2, which is two orders of magnitude higher than that of the bulk counterpart, is also achieved for the all‐surface‐atomic SnS sheets‐based photoelectrode. This will allow the manipulation of the basic properties of advanced materials on the atomic scale, thus paving the way for innovative applications.