Nickel–Cobalt Diselenide 3D Mesoporous Nanosheet Networks Supported on Ni Foam: An All‐pH Highly Efficient Integrated Electrocatalyst for Hydrogen Evolution

Novel 3D Ni 1− x Co x Se 2 mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni 1− x Co x Se 2 MNSN/NF with x ranging from 0 to 0.35). The collective effects of special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni 0.89 Co 0.11 Se 2 MNSN/NF is revealed to exhibit an overpotential (η 10 ) of 85 mV at −10 mA cm −2 in alkaline medium (pH 14) and η 10 of 52 mV in acidic solution (pH 0), which are the best among all selenide‐based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η 10 of 82 mV for all noble metal‐free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all‐pH HER activity of Ni 0.89 Co 0.11 Se 2 is originated from the enhanced adsorption of both H + and H 2 O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all‐pH HER electrocatalysts.