Selective conversion of carbon dioxide to formate using few-layer nitrogen-doped graphene on copper foam with enhanced suppression of the hydrogen evolution reaction

Abstract

This research presents a novel electrocatalyst, a three-dimensional, few-layered nitrogen-doped graphene-coated copper foam (N-GP/Cu-foam), engineered for the selective electrochemical reduction of carbon dioxide (CO₂) to formate. Formate serves as a versatile hydrogen carrier and carbon source, pivotal for subsequent conversion processes into hydrocarbons and oxygenates. Synthesized via chemical vapor deposition, this catalyst markedly suppresses the hydrogen evolution reaction (HER), a predominant competitive reaction in electrochemical CO₂ reduction processes. The N-GP/Cu-foam electrocatalyst exhibits a faradaic efficiency of 66.5% for formate production at an overpotential of −1.0 V versus the reversible hydrogen electrode (RHE), demonstrating exceptional selectivity and efficiency. This enhanced performance is attributed primarily to the stabilization of HCOOH* intermediates through the interaction with electron-rich nitrogen dopants embedded within the graphene matrix. Complementary Density Functional Theory (DFT) calculations have further elucidated that the catalyst exhibits a significantly lower Gibbs free energy for HCOOH* compared to CO*, underscoring a strong thermodynamic favorability towards formate production over other potential products. Moreover, the N-GP/Cu-foam catalyst achieves a more than two-fold reduction in the undesired HER, significantly enhancing the overall energy efficiency of the CO₂ electrochemical reduction system. These findings underscore the potential of nitrogen-doped graphene to significantly enhance catalytic selectivity and efficiency, offering insightful contributions to the advancement of CO₂ utilization technologies. This study provides foundational insights for the future development of more efficient catalytic systems for environmental remediation and sustainable chemical synthesis.