Promoting the Water-Reduction Kinetics and Alkali Tolerance of MoNi 4 Nanocrystals via a Mo 2 TiC 2 T 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, Mo 2 TiC 2 T x MXene, is employed as a support for MoNi 4 alloy nanocrystals (NCs) to fabricate a unique nanoflower-like MoNi 4 -MX n electrocatalyst. A remarkably strong built-in electric field is established at the interface of two components, which facilitates the electron transfer from Mo 2 TiC 2 T x to MoNi 4 . Due to the accumulation of electrons at the MoNi 4 sites, the adsorption of the catalytic intermediates and ionic species on MoNi 4 is affected consequently. As a result, the MoNi 4 -MX 10 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 MoNi 4 -MX 10 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.