Free standing bimetallic nickel cobalt selenide nanosheets as three-dimensional electrocatalyst for water splitting

Abstract Self-standing electrocatalysts for water splitting have been intensively exploited. Herein, 3D binder-free bimetallic nickel–cobalt selenide nanosheets anchored on a macroporous conducting carbon membrane (NiCoSe2@PCM) have been developed. A unique interconnected macropores PCM was prepared via cryogelation, freeze-drying, and subsequent carbonization. The PCM is used as a framework for the growth of a NiCoSe2 catalyst. Uniform and tightened nanosheets with a few-layers NiCoSe2 were obtained on the surface of the PCM, without the need for a transferring step or a conductive additive. The perpendicularly oriented NiCoSe2 nanosheets display superior electrochemical catalytic performance reflected in a low overpotential of 0.116 V (at 10 mA cm−2) with a Tafel slope of 66 mV dec−1 and 1.37 V (at 10 mA cm−2) with a Tafel slope of 60 mV dec−1 for HER and OER, respectively. Excellent stability with no current density decay was observed over a 23 h testing period. Bifunctional NiCoSe2@PCM was used in the assembly of a two-electrode electrolyzer, to obtain 10 mA cm−2, at a low voltage of 1.73 V. The low-cost and simplicity of membrane fabrication and catalyst synthesis could be extended to other metal dichalcogenides to develop new types of efficient water splitting electrocatalysts.