Size and Synergy Effects of Ultrafine 2.6 nm CoNi Nanoparticles Within 3D Crisscross N-Doped Porous Carbon Nanosheets for Efficient Water Splitting

A non-precious metal-based catalyst for water electrolysis provides great promise for cost-effective and highly efficient sustainable hydrogen production. It herein rationally synthesizes uniform superminiature CoNi nanoparticles (2.6 nm) embedded in 3D N-doped randomly oriented and erected porous carbon nanosheets (CoNi@N-PCNS). Taking advantage of the large specific surface area, expedited intermediate transport, and effectively exposed active sites of the hierarchical architecture, located CoNi nanoparticles yield a high atom utilization efficiency. Density functional theory calculations indicate that synergetic and cooperative interactions inside CoNi alloy modulate the d-band center, leading to a moderate adsorption and desorption energy of reaction intermediates, further accelerating both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. Accordingly, the as-synthesized CoNi@N-PCNS catalyst establishes superb catalytic activities for HER and OER, revealing overpotentials of 71.2 and 263.8 mV at 10 mA cm(-2), respectively. Remarkably, when assembled as a two-electrode electrolyzer, a satisfying cell voltage of 1.59 V at 10 mA cm(-2), and superior stability are demonstrated, highlighting great promise toward water electrolysis.