Modulation of oxygen-etching for generating nickel single atoms for efficient electroreduction of CO2 to syngas (CO/H2)

Metal single-atom catalysts (SACs) supported on carbon mainly produce syngas in electrochemical CO2 reduction reaction (CO2RR), in comparison with the dominant H2 production on nanoparticles. However, it is a major challenge to prepare the carbon-supported SACs without the presence of nanoparticles using conventional pyrolysis. Here, we report the approach involving oxygen etching at 250 °C to produce MOF-derived nickel/carbon SAC (Ni1@C-250A). The combination of oxygen etching with acid treatment completely removes the Ni nanoparticles, only showing the existence of single-atom Ni species. In CO2RR, the Ni1@C-250A exhibits excellent faradaic efficiency (FE) of ∼ 100% for syngas production with the excellent stability for 360 min time-on-stream. In addition, the CO/H2 ratio can be adjusted in a wide range from 1.5:1 to 4.3:1. This approach involving oxygen etching offers a promising strategy to dominantly produce SACs used for CO2RR to generate syngas, which is an important platform feedstock for the utilization of carbon-based energy.