Decoding the true active site in cobalt single-atom catalysts: pyridinic nitrogen-dominated electrosynthesis of hydrogen peroxide in acidic media

• • The Co1-NNH3-C catalyst achieves 99% H2O2 selectivity at −3.5 mA cm−2 in 0.1 M H2SO4, outperforming most acidic 2e− ORR catalysts and enabling efficient on-site H2O2 generation under corrosive conditions. • • Pyridinic N, not Co single atoms, is identified as the direct active site via site-selective poisoning (SCN−/EDTA) and acetyl-group functionalization, which induced a 60% selectivity loss, confirming the metal's indirect role. • • DFT calculations show pyridinic N sites exhibit a near-optimal ΔG*OOH of 4.0 eV and an overpotential of only 0.20 V, providing a rational descriptor for designing high-performance carbon-based catalysts. • • The catalyst delivers a production rate of 907.5 mmol gcat−1 h−1 (or 2500 mg L−1 cm−2 in H-cell) with FE > 90%, demonstrating practical scalability for decentralized H2O2 electrosynthesis.