Edge/Defect-Rich, Metallic, and Oxygen-Heteroatom-Doped WS Superstructure with Superior Electrocatalytic Performance for Green Solar Energy Conversion.

Two-dimensional tungsten sulfide is widely applied in electrocatalysis. However, WS possesses catalytic active sites located at the layer edge and an inert surface for catalysis. Therefore, increasing the exposure of active sites at the edge and effectively activating the inert sites on the surface is an important challenge. Here, an edge/defect-rich and oxygen-heteroatom-doped WS (ED-O-WS ) superstructure was synthesized. The power-conversion efficiency (PCE) of dye-sensitized solar cells (DSCs) based on an ED-O-WS counter electrode reached 10.36 % (under 1 sun, AM 1.5, 100 mW cm ) and 11.19 % (under 40 mW cm ). These values are, to our knowledge, the highest reported efficiency for DSCs based on Pt-free counter electrodes in I /I electrolytes. Analysis of the micro/nano structure and the electrocatalytic mechanism indicate that ED-O-WS exhibits metallic properties in the electrolyte, and that abundant edges and defects as well as oxygen doping in ED-O-WS play an important role in improving the catalytic activity of WS . Moreover, ED-O-WS displays better catalytic reversibility for I /I electrolytes than Pt.