Precise synthesis of single-atom Mo, W, Nb coordinated with oxygen functional groups of graphene oxide for stable and selective two-electron oxygen reduction in neutral media

Abstract

Herein, we propose a one-pot solvothermal method for a series of single-atom catalysts (SACs) anchored on mildly reduced graphene oxide (mrG) with active moieties of –CO₃M, –CO₂M and –COOM (M: Mo, W, Nb). The chemical inertness of polar aprotic dimethylsulfoxide (DMSO) enables a constant reaction environment where the MCl₅ dimer can be dissociated to give monomeric pentahalides, leaving behind one unpaired electron on the metal center to coordinate with the OFGs. Theoretical studies revealed that all M–O_x–C moieties have an overwhelming preference to form H₂O₂ as a result of the downhill reaction. Among the materials prepared, Mo-SACs/mrG achieved the best selectivity (η ∼ 94.5%, V_onset = 0.65 V vs. RHE, Tafel slope of 53 mV dec⁻¹) under neutral conditions. Furthermore, at the device level, the production rate of H₂O₂ is about 12.9 μmol min⁻¹ with an average FE of over 80%, which is superior to other catalysts reported.