Crystal Phase Engineering and Heterostructure Construction of Co/MoC/Mo2C for Ampere-Level Hydrogen Evolution

Abstract Molybdenum carbide (Mo2C) is a promising Pt/C alternative electrocatalyst for hydrogen evolution reaction, however the activity is limited by strong Mo–H bond that hinders hydrogen desorption. To address this issue, we designed a self-supported ternary Co/MoC/Mo2C/NF electrocatalyst featuring with a unique ball-stick hierarchical architecture with abundant Co/MoC/Mo2C heterostructures through crystal phase and heterostructure engineering. Consequently, the ternary electrocatalyst exhibits outstanding activity (257 mV overpotential at 1000 mA cm–2) and stability (>100 h). Theoretical analyses reveal that these MoC/Mo2C interfaces modulate the hydrogen adsorption energy on Mo sites. Crucially, electron donation from Co to Mo sites across the heterointerface tailors the local electronic structure, resulting in a lowered barrier for water dissociation and an optimized hydrogen desorption. When configured in an anion exchange membrane water electrolyzer, it delivers efficient overall water splitting at 1.85 V. This work establishes heterostructure and crystal phase engineering as a general approach for designing advanced transition metal carbide electrocatalysts.