Acid-directed morphology control of molybdenum carbide embedded in a nitrogen doped carbon matrix for enhanced electrocatalytic hydrogen evolution

Abstract

As a promising hydrogen evolution reaction (HER) electrocatalyst, molybdenum carbide materials have attracted great attention owing to their Pt-like electronic structure. The morphology control of Mo₂C usually involves complicated procedures, and porous structures are desirable for electrocatalytic applications. Herein, we present a facile acid-directed synthesis strategy for β-Mo₂C nanoparticles embedded in a nitrogen doped carbon matrix (β-Mo₂C/NC) with controllable morphologies through heat treatment of Mo–melamine complexes for electrocatalytic HER applications. It is found that the applied acid can effectively tune the morphology of Mo–melamine complexes, and thus the final β-Mo₂C/NC materials. With oxalic acid, the as-prepared β-Mo₂C/NC materials possess a porous structure and high surface area (23.3 m² g⁻¹), leading to distinguished electrocatalytic HER activities in both acidic and alkaline media, requiring low overpotentials of 152 and 135 mV vs. reversible hydrogen electrode (RHE) to reach a current density of −10 mA cm⁻², with a Tafel slope of 58 and 56 mV dec⁻¹, respectively. The synthetic route proposed in this work may offer a new thinking for the morphology-controllable synthesis of transition metal carbide materials for heterogeneous (electro)catalysis applications.