Harnessing Optimized Surface Reconstruction of Single-Atom Ni-Doped Ni-NiO/NC Precatalysts toward Robust H2O2 Production

Decentralized H2O2 production from a 2e– oxygen reduction reaction (ORR) pathway is appealing, wherein the rational design of electrocatalysts is the cornerstone rendering favorable catalytic activity/selectivity. Nevertheless, the real active moiety is elusive and the catalyst evolution during the reaction remains unexplored to date. Herein, we decipher in situ evolved surface chemistry of a Ni-based precatalyst (Ni SAC/Ni-NiO/NC-500) during the 2e– ORR process that results in a reconstructed catalyst (Ni SAC/Ni-NiO/NC-500-R). The phase transformation of the electrocatalyst is monitored by operando Raman spectroscopy and ex situ X-ray analysis. With the optimized catalyst in hand, a 2e– ORR potential of 0.78 V (at 1.0 mA cm–2) and a high selectivity of 95% in an alkaline electrolyte are harvested. More encouragingly, high-flux H2O2 is produced via photomediated electrosynthesis, enabling on-site degradation of organic pollutants with an impressive degradation rate approaching 100%.