Arc plasma-deposited Co single-atom catalysts supported on an aligned carbon nanofiber for hydrogen peroxide electrosynthesis and an electro-Fenton process

Atomically dispersed single-atom catalysts (SACs) on carbon supports show great promise for H₂O₂ electrosynthesis, but conventional wet chemistry methods using particulate carbon blacks in powder form have limited their potential as two-electron (2e⁻) oxygen reduction reaction (ORR) catalysts. Here, we demonstrate high-performance Co SACs supported on a free-standing aligned carbon nanofiber (CNF) using electrospinning and arc plasma deposition (APD). Based on the surface oxidation treatment of aligned CNF and precise control of the deposition amount in a dry-based APD process, we successfully form densely populated Co SACs on aligned CNF. Through experimental analyses and density functional theory calculations, we reveal that Co SAC has a Co–N₂–O₂ moiety with one epoxy group, leading to excellent 2e⁻ ORR activity. Furthermore, the aligned CNF significantly improves mass transfer in flow cells compared to randomly oriented CNF, showing an overpotential reduction of 30 mV and a 1.3-fold improvement (84.5%) in Faradaic efficiency, and finally achieves an outstanding production rate of 15.75 mol g_cat⁻¹ h⁻¹ at 300 mA cm⁻². The high-performance Co SAC supported on well-aligned CNF is also applied in an electro-Fenton process, demonstrating rapid removal of methylene blue and bisphenol F due to its exceptional 2e⁻ ORR activity.