One-pot hydrothermal oxidation enables in situ construction of CDs/Ni(OH)2 composite for electrocatalytic oxygen evolution

Electrochemical water splitting is a promising solution to energy challenges, yet the kinetically sluggish oxygen evolution reaction (OER) at the anode demands highly active and cost-effective catalysts. Herein, we develop a facile one-pot hydrothermal oxidation strategy to simultaneously achieve the oxidative cleavage of petroleum coke into nanoscale carbon dots (HO-CDs) and the <i>in situ</i> growth of nickel hydroxide (Ni(OH)₂) on nickel foam (NF), yielding an HO-CDs-Ni(OH)₂/NF composite catalyst. The in situ-formed HO-CDs efficiently modulate Ni(OH)₂ crystallization by suppressing oriented growth to create a nanostructure with abundant active sites. This synergistic interplay significantly enhances both active site accessibility and charge transfer efficiency, leading to exceptional OER performance. The optimized HO-CDs-Ni(OH)₂/NF catalyst delivers an overpotential of 353 mV at a current density of 50 mA cm^-2 with a small Tafel slope of 81.2 mV dec^-1. Furthermore, it demonstrates excellent stability, retaining 92% of its initial current density after a 24-h chronoamperometric test. This work presents a straightforward approach for designing high-performance transition metal-based electrocatalysts through carbon dot-mediated crystal engineering via <i>in situ</i> incorporation.