Surface Confinement of FeNiCo Nanoparticles by Bicontinuous Conductive Networks toward Overall Water Splitting

The development of low-cost and high-performance dual-function electrocatalysts for stable water electrolysis is crucial for realizing a sustainable energy supply. Herein, the conductive carbon layer confined ultrasmall FeNiCo trimetallic nanoparticles are successfully synthesized directly on a carbon cloth surface. The outer carbon shell can act as a protective armor and confinement structure to anchor and confine the nanoparticles. The ultrathin carbon coating layer effectively shortens the charge diffusion pathways, while the direct contact between active nanoparticles and the current collector enhances the electron conductivity. Therefore, the average size of the metal nanoparticles is only 8.8 nm, which greatly increases the effective surface area and enhances the exposure of active sites. Thus, the optimized 0.25C@FeNiCo/CC and 0.75C@FeNiCo/CC composites reveal onset overpotentials of 46 and 236 mV in HER/OER, respectively. The cell voltage for water electrolysis is only 1.59 V at 20 mA cm–2 with high stability for 40 h. This rational design strategy of carbon-supported ultrasmall multimetal nanoparticles and fast electron/ion transfer pathways provides an effective strategy for design of highly efficient bifunctional electrocatalysts for overall water splitting