Hydroxyl-blocking lignin-derived carbon catalysts for selective and durable hydrogen peroxide electrosynthesis

Abstract

Metal-free oxygen-functionalized carbon materials are promising electrocatalysts for selective hydrogen peroxide (H2O2) production via the two-electron oxygen reduction reaction (ORR). However, precisely controlling oxygen moieties while maintaining scalability remains challenging. Herein, we present a scalable and sustainable Friedel-Crafts reaction-assisted carbonization strategy that converts lignin into oxygen-tunable carbon catalysts for efficient H2O2 electrosynthesis. Electrochemical measurements reveal a strong correlation between carbonization temperature, oxygen speciation, and catalytic performance. Specifically, carbonyl and carboxyl groups enhance H2O2 selectivity, while hydroxyl groups suppress H2O2 formation by preferentially binding O* intermediates. Density functional theory corroborates these findings, indicating that carbonyl and carboxyl groups favor the two-electron pathway. Accordingly, selective blocking of hydroxyl groups achieves > 95 % H2O2 selectivity, a production rate of 575.5 mmol g(cat)(-1) h(-1) at 0.4 V-RHE, and stable operation for 40 h. This renewable, low-cost platform couples mechanistic control with scalable synthesis, potentially enabling decentralized H2O2 generation in on-site disinfection and wastewater treatment.