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

Abstract

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.

Surface-Oxidized Iron–Cobalt–Nickel Alloy with Continuous Variable Composition for Hydrogen and Oxygen Evolution Reaction

“…Because the covered hydroxides with low adsorption energy of H weakened the H 2 O adsorption on the surface of the FeCoNi alloy, as a whole, the RCS of FeCoNi/OH electrodes moved from the Tafel/Heyrovsky step (FeCoNi) to the Volmer step (FeCoNi/OH). Although the value of the Tafel slopes can reflect the activity to some degree and have been used as the activity descriptor showing that the higher Tafel slopes indicate lower activity, it must be based on the same or similar onset potential. − Therefore, the different onset potential resulted in the trends of Tafel slopes being incongruous against the HER current change at an overpotential of 300 mV. Moreover, although the Tafel slopes of FeCoNi/OH electrodes were higher than those of FeCoNi electrodes with the same composition, the synergistic effect between alloys and hydroxides led to higher HER performance of FeCoNi/OH electrodes compared to FeCoNi electrodes, which would be described in detail below.…”

High performance transition metal-based electrocatalysts for green hydrogen production

“…52 To improve the intrinsic catalytic properties of Ni, the synergistic effect with Ni has been investigated by discovering various combinations with transition metals, such as Co, 53,54 Cu, 55,56 W, 40,57 and Mo, 58 etc. 52,59,60 The optimized composition has a high intrinsic activity, which indicates the high density of the active site. With the DFT-based computational calculations, the relationship between the activity and active site at the atomic scale has been established.…”

“…The Ni–Mo alloys outperformed Pt/C catalysts, followed by Ni–Ge and Ni–Sn alloys, and the Ni 4 Mo alloy with a Ni–Mo ratio of 4 : 1 was shown to have an optimal Mo content compared to various molar ratios. 60 Using these probes, we synthesized a Ni 4 Mo/NiFe alloy with superior catalytic characteristics compared to pure Pt for hydrogen production (Fig. 4(e)).…”

Pt doping and strong metal–support interaction as a strategy for NiMo-based electrocatalysts to boost the hydrogen evolution reaction in alkaline solution

“…31,32 Aer adjustment, the catalytic performance of NiMo-based materials has been improved, but compared with the intrinsic activity of Pt/C in alkaline electrolyte, there is still a large space for reformation due to the poor electrical conductivity of Ni-based materials and the strong adsorption of H*. 11,[33][34][35][36] In addition, the rapid dissolution of Ni-based catalysts at high current density ($100 mA cm À2 ) results in the poor durability of the materials (#200 h), which greatly limits the practical commercial application of these electrocatalysts.…”