Self‐Supporting Ni‐M (M = Mo, Ge, Sn) Alloy Nanosheets via Topotactic Transformation of Oxometallate Intercalated Layered Nickel Hydroxide Salts: Synthesis and Application for Electrocatalytic Hydrogen Evolution Reaction

Metal alloys are valuable for achieving energy‐ and cost‐efficient electrocatalysis. To maximize active sites exposure and electron transport, a general method to prepare binder‐free Ni‐M (M = Mo, Ge, Sn) bimetallic alloy nanosheets electrocatalyst for the hydrogen evolution reaction (HER) is successfully developed for the first time, via topotactic transformation of layered nickel hydroxide salts (Ni‐LHS). The obtained bimetallic alloys show much improved HER performance to that of Ni. In particular, Ni4Mo alloy nanosheets exhibit HER activity with an overpotential of only 69.6 mV at 100 mA cm−2 and a low Tafel slope of 37 mV decade−1 in alkaline medium, due to large electrochemical active surface area and low charge transfer resistance. Moreover, Ni4Mo alloy nanosheets also show high HER activity in both acidic and neutral electrolytes with long‐term stability, demonstrating superior activity comparable to or better than state‐of‐the‐art commercial Pt/C catalyst. This topotactic transformation method using LHS precursors provides a way to design and fabricate cost‐effective and energy‐efficient ultrathin 2D bimetallic alloy nanosheets for electrocatalysis, greatly broadening the scope of the currently available self‐supporting metal alloy electrocatalysts. Topotactic transformation of layered nickel hydroxide salts intercatalated with oxometallate anions is used to synthesize a series of self‐supporting Ni‐based alloy nanosheets, which exhibit excellent activity toward hydrogen evolution reaction. In particular, Ni4Mo/Ni foam demonstrates superior pH universal activity better than state‐of‐the‐art commercial Pt/C catalyst.