Stacking Faults Defect-Rich MoNi Alloy for Ultrahigh-Performance Hydrogen Evolution

Abstract

Abstract Producing green hydrogen in a cost-competitive manner via water electrolysis will make the long-held dream of meeting energy needs with hydrogen instead of fossil fuel a reality. Although platinum-based catalysts show good performance towards hydrogen evolution reaction (HER), the high cost and scarce abundance challenge their economic viability for large-scale implementation. Here, we engineer high fractions of stacking fault defects in MoNi nanosheets to form a high-performance electrocatalyst (d-MoNi) through a combined chemical and thermal reduction strategy. Using d-MoNi as an electrode for HER afforded ultralow overpotential of 63 and 120 mV at current densities of -500 and -1000 mA cm-2 in 1 M KOH, respectively. Besides, the stacking fault defect-rich d-MoNi exhibits 4 orders of magnitude higher turnover frequency than benchmark 20% Pt/C, together with excellent durability (>100 h) at high current density of 1000 mA cm-2, making it one of the best-performing non-platinum catalysts for HER. The experimental and theoretical results reveal that the abundant stacking faults in d-MoNi induce a compressive strain, decreasing the proton adsorption energy and promoting the concomitant combination of adsorbed hydrogen into molecular hydrogen and the desorption of the molecular hydrogen, therefore enhancing the HER performance. This work provides a new synthetic route to engineer defective metal and metal alloy electrocatalysts for emerging applications in electrochemical energy conversion and storage.