Theoretical studies of nitrogen-doped graphene loaded transition metal single-atom catalysts for electrochemical CO reduction

The electrochemical carbon monoxide reduction reaction (CORR) holds significant potential for sustainable fuel and chemical production, offering an effective means to reduce carbon emissions and maintain environmental sustainability. Graphene, a single layer of carbon atoms arranged in a unique two-dimensional structure, possesses properties that make it suitable for various applications. Nitrogen-doped graphene (NDG) based metal single-atom catalysts (SACs) have emerged as one of the most effective methods for converting CO into one carbon (C₁) products such as CH₄ and CH₃OH. In this study, defective graphene was doped with four nitrogen atoms, which stabilized the catalyst through complexation with metal species by binding with the nitrogen atoms. First-principles calculations were employed to investigate the catalytic performance of selected transition metals (TM₁ = Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) as SACs anchored on the NDG surface for hydrogen evolution reaction (HER) and CORR processes. Theoretical analysis indicated that NDG is highly favorable for binding transition metal single adatoms with excellent stability, facilitating rapid electron transfer during catalysis and yielding outstanding catalytic performance. Among the SACs, Cr supported by N₄-G catalyst selectively produces CH₄ with Cr-N₄-G exhibiting the lowest overpotential of 0.47 eV. This study demonstrates that the N₄-G support is a promising candidate for use as a single-atom catalyst for selective CO reduction and other electrochemical processes.