Tunable-template-guided synthesis of CoNi@Mo₂C/carbon hollow microspheres for highly efficient electrocatalytic...

Molybdenum carbide (Mo₂C) is recognized as a promising electrocatalyst for water splitting owing to its platinum-like electronic structure. However, its practical application is severely impeded by the agglomeration of active sites, excessively strong MoH bonding, and poor resistance to oxidation and corrosion. To address these limitations, we propose a "template size control-multimetal coordination" strategy to fabricate nitrogen-doped carbon-supported CoNi-modified Mo₂C hollow microspheres (CoNi@Mo₂C/C). By rationally tuning the template architecture, an optimal balance between graphitic carbon and carbon defects is achieved, enabling rapid electron transport while preserving a high density of active sites. The CoNi bimetallic components were introduced to downshift the Mo d-band center, which weakened the MoH bond strength and boosted the electrocatalytic activity. Moreover, Co and Ni spontaneously form an active oxyhydroxide phase through self-oxidation, which effectively protects Mo₂C from oxidative corrosion and leaching, thereby substantially improving operational stability. Among the series, the CoNi@Mo₂C/C catalyst synthesized with a 500 nm polystyrene (PS) template exhibits exceptional bifunctional activity and durability in 1.0 M KOH. At a current density of 10 mA·cm^-2, the catalyst delivers an overpotential of 73.2 ± 2.2 mV for the hydrogen evolution reaction (HER), 212.8 ± 2.8 mV for the oxygen evolution reaction (OER), and a full-cell voltage of 1.515 V for overall water splitting. This work not only offers critical experimental insights but also establishes a theoretical foundation for the rational design of high-performance non-precious-metal electrocatalysts.