Nitrogen functionalized metal-free catalysts enabling active hydrogen-meditated pathway toward efficient H 2 O 2 electro-synthesis

Abstract

The electrosynthesis of H2O2 via the two-electron oxygen reduction reaction represents a promising alternative to the anthraquinone oxidation process. However, concurrently achieving high Faradaic efficiency (FE) and industrial-level productivity remains challenging, largely due to the intrinsically sluggish kinetics of proton-coupled electron transfer (PCET). Herein, we first report the generation of active hydrogen (•H) over metal-free catalyst, thereby regulating hydrogenation pathway and facilitating H2O2 electrosynthesis through nitrogen functionalization in a carbon matrix. In situ characterizations and theoretical calculations reveal a dual-site synergistic mechanism in which pyridinic N sites facilitate H2O dissociation to generate •H species, while graphitic N sites electronically activate adjacent carbon atoms, facilitating efficient O2 adsorption and activation. The generated •H subsequently participate in the *O2-to-*OOH reaction, thus bypassing the •O2- intermediate and lowering the free energy effectively. As a result, the optimized metal-free carbon catalyst, delivers a high FE of 96.4% with productivity of 14.3 mol/g/h at a current density of ~400 mA/cm2 in flow cell, outperforming the counterpart governed by a PCET-mediated pathway. This work demonstrates that metal-free active site can promote •H generation and regulate hydrogenation pathways, thereby enhancing O2-to-H2O2 conversion.