Promoting the Water-Reduction Kinetics and Alkali Tolerance of MoNi₄ Nanocrystals via a Mo₂TiC₂T_x Induced Built-In Electric Field

Mo-Ni alloy-based electrocatalysts are regarded as promising candidates for the hydrogen evolution reaction (HER), despite their vulnerable stability in alkaline solution that hampers further application. Herein, Mo₂TiC₂T_x MXene, is employed as a support for MoNi₄ alloy nanocrystals (NCs) to fabricate a unique nanoflower-like MoNi₄–MX_n electrocatalyst. A remarkably strong built-in electric field is established at the interface of two components, which facilitates the electron transfer from Mo₂TiC₂T_x to MoNi₄. Due to the accumulation of electrons at the MoNi₄ sites, the adsorption of the catalytic intermediates and ionic species on MoNi₄ is affected consequently. As a result, the MoNi₄–MX₁₀ nanohybrid exhibits the lowest overpotential, even lower than 10% Pt/C catalyst at the current density of 10 mA cm⁻² in 1 m KOH solution (122.19 vs 129.07 mV, respectively). Furthermore, a lower Tafel slope of 55.88 mV dec⁻¹ is reported as compared to that of the 10% Pt/C (65.64 mV dec⁻¹). Additionally, the MoNi₄–MX₁₀ catalyst also displays extraordinary chemical stability in alkaline solution, with an activity loss of only 0.15% per hour over 300 h of operation. This reflects the great potential of using MXene-based interfacial engineering for the synthesis of a highly efficient and stable electrocatalyst.