ZIF-8-derived carbon substrates embedded with atomically dispersed FeN₂O₂ active sites as bifunctional catalysts for electrochemical carbon dioxide and oxygen reduction

Transition metal assemblies on nitrogen-containing carbon substrates have promising applications as bifunctional electrocatalysts for electrochemical carbon dioxide reduction reaction (CO₂RR) and oxygen reduction reaction (ORR). In this study, ZIF-8 with a rhombic dodecahedral morphology was grown from zinc nitrate and 2-methylimidazole feedstock. Then, a nitrogen-containing carbon substrate with a pore structure was formed after the release of Zn through high-temperature calcination. During the calcination process at 700°C, Fe atoms were physically adsorbed on the nitrogen-containing carbon substrate and ligated with N/O to form FeN₂O₂ reactive sites. For CO₂RR, FeN₂O₂/NC exhibited excellent catalytic properties for converting CO₂ to CO, achieving a high Faraday efficiency of 95.5 % at −0.7 V. Under alkaline conditions, it demonstrated ORR performance (E_1/2 = 0.83 V) comparable with that of Pt/C (E_1/2 = 0.82 V). This study not only presents an energy-efficient method for CO₂RR but also provides new insights into highly active catalysts for ORR.