Electronic configuration of carbon regulated by Mo2C clusters encapsulated in nitrogen self-doped biochar for efficient hydrogen evolution reaction

Regulating the activity of carbon (C) atoms on encapsulating carbon layers through metal clusters has emerged as a promising strategy for achieving efficient and stable hydrogen evolution reaction (HER) catalysis. Herein, we report a biochar-based electrocatalyst (BC_Mo900-1)synthesized via a one-step pyrolysis method using molybdenum (Mo)-enriched biomass as the precursor, featuring molybdenum carbide (Mo₂C) clusters encapsulated within nitrogen (N)-doped biochar. In acidic electrolytes, BC_Mo900-1 exhibits superior HER performance, achieving a low overpotential of 30.0 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 33 mV dec^-1, comparable to the benchmark Pt/C catalyst. Density functional theory (DFT) calculation reveal that Mo₂C clusters more effectively regulate the electron density of N-coordinated C atoms than MoC, significantly reducing the Gibbs free energy for H* adsorption (ΔG_H* = −0.32 eV) and lowering the dissociation energy barrier of H* in acidic solution. This regulatory mechanism is identified as a key factor in enhancing H* activation and dissociation on C atoms, while maintaining excellent stability and durability. This proof-of-concept study highlights a sustainable and innovative approach for developing green, efficient, and durable HER electrocatalysts by leveraging solid waste resources.