Anion-Induced Size Selection of β-Mo2C Supported on Nitrogen-Doped Carbon Nanotubes for Electrocatalytic Hydrogen Evolution

Molybdenum carbide materials are considered to be promising hydrogen evolution reaction (HER) electrocatalysts due to their similar electronic structures and catalytic activities to Pt-based catalysts. Here, we report a facile synthesis of β-Mo2C nanoparticles supported on nitrogen-doped carbon nanotubes (Mo2C/N–C) through a one-step carbonization of Mo-containing anion-doped polyaniline nanotubes. It has been revealed that the size of the obtained Mo2C nanoparticles can be effectively tuned by applying different Mo-containing anions. With MoO42– from Na2MoO4, the as-prepared Mo2C/N–C(S) with ultrasmall (2–3 nm) Mo2C nanoparticles shows excellent electrocatalytic HER activity in acidic media, with an overpotential of 189 mV vs reversible hydrogen electrode (RHE) at a geometric current density of −10 mA cm–2 and a Tafel slope of 58 mV dec–1. This study opens up a new avenue for the size-controllable synthesis of transition metal carbide nanoparticles loaded on carbon supports for energy conversion applications.