Carburization-assisted conversion of N-doped Mo to N-doped Mo2C for efficient electrocatalytic hydrogen evolution

Advanced nanomaterials hold promise in accelerating electrocatalytic reactions, especially with respect to the hydrogen evolution reaction (HER). Their activity can be enhanced by engineering both intrinsic efficiency and surface features at the micro/nano scale. Here, we demonstrate a carburization-assisted chemical conversion of amorphous N-doped Mo film into crystallized N-doped Mo₂C film via high-temperature annealing in a CH₄ gas environment. The benefits of this process become evident when comparing the electrocatalytic efficiency of the pristine and annealed composites toward HER. The carbon substrate and CH₄ gas act as carbon sources, enabling Mo carburization during annealing due to the migration of carbon from the substrate and its reaction with the overlying metal. This phenomenon is verified by high-temperature annealing of N-doped Mo grown on a Si substrate under an inert gas environment. The columnar growth—an intrinsic feature of pulsed-laser deposition—enables the formation of a nanocomposite with an enhanced surface area. N-doped Mo₂C shows a low overpotential of −192 mV at 10 mA/cm², making it one of the best-performing Mo₂C thin films. This work offers a simple strategy for the preparation of N-doped nanostructured Mo₂C and provides insights into the high-temperature annealing of transition metals on carbon supports, which can be useful for applications in the energy sector.