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

Molybdenum carbide (Mo 2 C) 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 Mo H 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 Mo 2 C hollow microspheres (CoNi@Mo 2 C/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 Co Ni bimetallic components were introduced to downshift the Mo d-band center, which weakened the Mo H bond strength and boosted the electrocatalytic activity. Moreover, Co and Ni spontaneously form an active oxyhydroxide phase through self-oxidation, which effectively protects Mo 2 C from oxidative corrosion and leaching, thereby substantially improving operational stability. Among the series, the CoNi@Mo 2 C/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. Download: Download high-res image (205KB) Download: Download full-size image