Unveiling Trifunctional Active Sites of a Heteronanosheet Electrocatalyst for Integrated Cascade Battery/Electrolyzer Systems

Herein, we identify the unique trifunctional active sites of ReS2 and NiFe layered double hydroxide (NiFe-LDH) heteronanosheets (ReS2/NiFe-LDH) for integrated cascade Zn–air battery/electrolyzer systems. Along with the edge and surface sites of NiFe-LDH for both oxygen evolution reaction and oxygen reduction reaction activities, the unprecedented activity of the ReS2/NiFe-LDH heteronanosheets for the hydrogen evolution reaction emerges from the S–O bonds at the heterointerfaces, together with the strong coupling effect and vertical alignment of NiFe-LDH and ReS2. The outstanding trifunctional activities and a well understood mechanism ensure the use of ReS2/NiFe-LDH heteronanosheets for the development of integrated cascade battery/electrolyzer systems, in which electricity storage in the battery mode and H2 production in the electrolyzer mode are efficiently switched with high round-trip efficiency (61%) and Faraday efficiency (96%). The systems show great promise for cost-effective energy storage and H2 production applications ranging from the distribution in households to the assembly for electrical vehicles.