Direct Writing of Oxygen-Doped Mo₂C Enabled by Low-Temperature Laser Deposition for High-Performance Acidic Hydrogen Evolution Reaction.

Abstract

Molybdenum carbides have gained tremendous attention for the electrocatalytic hydrogen evolution reaction (HER) due to their high electrical conductivity and similar d-band structure to platinum. Among molybdenum carbides, Mo₂C catalysts have exhibited greater potential for acidic HER. However, their performance is restricted by the strong binding interaction between molybdenum and hydrogen. Herein, a series of Mo₂C catalysts are synthesized using a rapid, low-temperature laser deposition method to dope oxygen atoms into the Mo₂C lattices. The metastable oxygen-doped Mo₂C exhibits a low overpotential of 125 mV at 10 mA cm^-2, showing significant improvement compared to Mo₂C (≈182 mV). Density functional theory (DFT) calculations suggest that the introduction of oxygen into the lattices of Mo₂C can reduce the hydrogen adsorption free energy, indicating that hydrogen production is more favorable on oxygen-doped Mo₂C electrocatalyst. At the industrial-level current density of 1 A cm^-2, the oxygen-doped Mo₂C electrocatalyst demonstrates exceptional performance with a low overpotential of 312 mV. Moreover, it exhibits remarkable stability, maintaining consistent hydrogen production for 200 h (>8 days) in 0.5 M H₂SO₄, potentially outperforming most non-noble metal electrocatalysts. This work highlights a new method to synthesize high-performance transition metal carbide catalysts with a tunable electronic structure to enhance HER performance.