Non-equilibrium plasma activated durable molybdenum oxycarbide electrocatalysts for acidic hydrogen evolution up to 10 A cm^-2.

Abstract

Electrocatalytic hydrogen evolution in acidic media at industrial-level current densities is limited by high overpotential, performance degradation, and consequently low throughput. To address these challenges, we develop nanoedge-enriched molybdenum oxycarbide (MoO_xC_y) electrocatalysts with a uniform phase by non-equilibrium plasma-enhanced chemical vapor deposition. The vertically standing MoO_xC_y exhibits a low overpotential of 415 mV and stable long-term operation (~ 0.11% performance degradation over 1000 h) at high current densities up to 10 A cm^-2, corresponding to a high hydrogen throughput of 4,477.4 L cm^-2, which exceeds the Department of Energy targets. Molybdenum oxycarbide catalysts are competitive with state-of-the-art transition-metal and even noble-metal catalysts in terms of throughput and lifetime throughput. The key mechanism involves carbon incorporation into MoO₂ lattices, which lowers the Mo valence and weakens Mo-H binding energy, thereby improving hydrogen evolution performance. Density functional theory results suggest that carbon atoms in MoO_xC_y increase the binding energy between Mo and the adjacent atoms, enhancing MoO_xC_y structural stability. This study establishes a pathway toward practical and efficient transition-metal catalysts for hydrogen evolution.