文摘
The practical recycling of carbon dioxide (CO<sub>2sub>) by the electrochemical reduction route requires an active, stable, and affordable catalyst system. Although noble metals such as gold and silver have been demonstrated to reduce CO<sub>2sub> into carbon monoxide (CO) efficiently, they suffer from poor durability and scarcity. Here we report three-dimensional (3D) graphene foam incorporated with nitrogen defects as a metal-free catalyst for CO<sub>2sub> reduction. The nitrogen-doped 3D graphene foam requires negligible onset overpotential (?0.19 V) for CO formation, and it exhibits superior activity over Au and Ag, achieving similar maximum Faradaic efficiency for CO production (~85%) at a lower overpotential (?0.47 V) and better stability for at least 5 h. The dependence of catalytic activity on N-defect structures is unraveled by systematic experimental investigations. Indeed, the density functional theory calculations confirm pyridinic N as the most active site for CO<sub>2sub> reduction, consistent with experimental results.