Cobalt single-atom catalyst as a multifunctional electrocatalyst for boosting radical generation

Electro-generated hydroxyl radicals (•OH) are of fundamental importance in electrochemical advanced oxidation processes (EAOPs). Herein, a cobalt single-atom (Co1) dispersed on N-doped carbon black (NCB) was synthesized and used for the first time as a multifunctional electrocatalyst on both the anode and cathode to boost the generation of •OH. Specifically, the Co1–NCB anode electrochemically generates •OH through water oxidation reaction (WOR), whereas the Co1–NCB cathode generates hydrogen peroxide (H2O2) through oxygen reduction reaction (ORR), followed by its subsequent electrochemical/catalytic activation by Co1–NCB, which synergistically promotes the formation of •OH. In an electrochemical system with the optimized coordination structure and operating conditions, the Co1–NCB electrode-based EAOP exhibited high phenol-removal efficiency (>95%) over a wide pH range (pH = 3–9). This study provides a new strategy for maximizing radical production and suggests its application in the electrochemical oxidation of recalcitrant organic pollutants.