Pyrolyzed polydopamine-modified carbon black for selective and durable electrocatalytic oxygen reduction to hydrogen peroxide in acidic medium

Abstract

Electrochemical production of H2O2 from O2 via the two-electron reaction pathway (2e-ORR) is a promising alternative to the energy- and organic pollutant-intensive industrial anthraquinone process. However, irrespective of numerous research efforts on catalyst design and remarkable advances made in this area, the catalysts displaying high H2O2 production rate so far unexceptionally required expensive/hazardous catalyst precursors and involved tedious steps and/or harsh treating conditions. Herein, we report a slightly nitrogen-doped carbon 2e-ORR catalyst that was synthesized simply by pyrolyzing a polydopamine (PDA) coating on Vulcan XC72 carbon black (p-PDA/XC). In H2O2 production via ORR in an acidic electrolyte, the catalyst showed 185 mV less overpotential than XC and remarkably high selectivity up to 96%. Highly efficient and durable H2O2 production was demonstrated by the stable accumulation of H2O2 to 1368 mmol gcat−1 within 8 h, translating to a H2O2 production rate of 171 mmol gcat−1 h−1. A good linear relationship was identified between the H2O2 partial current and the surface content of the C–O/C–N and CO species for the XC and p-PDA/XC catalysts, inferring that the C atoms in or adjacent to these species serve as the active sites for 2e-ORR to H2O2. The inexpensive starting materials, facile synthetic strategy, and excellent catalytic performance of the p-PDA/XC catalyst may accelerate the establishment of an affordable, safe, and direct O2-to-H2O2 electrochemical process.