Engineering Isolated CoV–N _<i>x</i> Sites and CoV Nanoparticles on Graphene: A Synergistic Platform for Oxygen Reduction Catalysis

The oxygen reduction reaction (ORR) has attracted significant interest as a key cathode reaction in emerging energy technologies, such as fuel cells and metal–air batteries, aimed at improving the present energy landscape and advancing sustainable energy solutions. Metal–nitrogen–carbon (M–Nx–C) materials have been extensively investigated as potential alternatives to Pt-based catalysts due to their promising ORR activity. In this study, cobalt–vanadium isolated atoms/nanoparticles on nitrogen-doped graphene oxide (CVSA-NP/NG) were synthesized as an ORR catalyst. Different compositions of CVSA-NP/NG, besides the control samples, were prepared and analyzed by employing spectroscopy and electrochemical methods. Electrochemical results demonstrate that the best composition (CV(11)SA-NP/NG) exhibits high ORR catalytic performance, achieving an onset potential (Eonset) value of 0.92 and 0.79 V in 0.1 M KOH and 0.1 M HClO4, respectively. CV(11)SA-NP/NG catalyzes the ORR via a four-electron transfer process, converting O2 directly to OH– or H2O. The KSCN test confirms the presence of two types of active sites, namely CoV–Nx and CoV nanoparticles.