Unraveling the Role of N-Doped Mesoporous Graphene in Confining the Growth of Mo ₂ C Nanoparticles for Efficient Electrocatalytic Hydrogen Evolution

Molybdenum carbide (Mo2C) has emerged as a compelling nonprecious metal electrocatalyst for the hydrogen evolution reaction (HER), owing to its excellent catalytic activity and high stability. However, conventional synthesis strategies involving sacrificial templates or polymer self-assembly often face trade-offs, such as hazardous postprocessing, limited electrical conductivity, or uncontrolled particle growth, leading to diminished active sites. To address these challenges, we present a straightforward carburization strategy using N-doped mesoporous graphene (NMG), which simultaneously functions as the carbon precursor and a conductive matrix. The synthesized Mo2C nanoparticle-embedded NMG (MCNMG) nanohybrid is characterized by a homogeneous distribution of ultrafine β-Mo2C nanoparticles (<3 nm) confined within the NMG framework. Significantly, the superior structural properties of MCNMG are attributed to a synergistic dual-confinement effect: (1) the physical restriction by the mesoporous architecture and (2) the anchoring effect by pyridinic- and graphitic-N species. These synergistic effects not only suppress particle agglomeration but also mitigate the excessive consumption of the carbon scaffold during carburization, thereby preserving an average pore diameter of ∼7.0 nm and a large specific surface area of 696 m2 g–1, which maximize active site exposure and facilitate efficient charge/mass transport. In electrochemical evaluations, the MCNMG catalyst requires an overpotential of only 169 mV to deliver a current density of – 10 mA cm–2, accompanied by a Tafel slope of 77 mV dec–1. Furthermore, it exhibits robust durability over 120 h of continuous operation at high current densities (−50 mA cm–2), demonstrating its great potential for practical water electrolysis applications. This work highlights the critical role of anchoring effects in rational hybrid design, offering a pathway to durable, high-performance electrocatalysts for hydrogen production.