Highly efficient electrochemical carbon dioxide reduction to syngas with tunable ratios over pyridinic- nitrogen rich ultrathin carbon nanosheets.

Abstract Developing nonmetallic carbon-based electrocatalysts that are affordable and have high activity and stability for carbon dioxide (CO2) reduction to syngas is a new and challenging strategy for solving the energy crisis. Here, we prepared a highly active ultrathin nitrogen (N)-doped carbon nanosheet (UNCN) electrocatalyst. By tuning the applied potential of the UNCN-900 (900 represents the carbonization temperature) electrode, we could tune the H2/CO ratio in clean syngas within a wide range with extra-high Faradic efficiency (FE). The maximum FECO reached 91%, which represented the highest value among the reported nonmetallic carbon-based electrocatalysts for CO2 reduction to syngas. According to the results of experiments and density functional theory calculations, we proved that pyridinic-N in UNCNs-900 is the active site of the CO2 reduction reaction (CO2RR) and that graphitic-N may be the active site for the hydrogen evolution reaction. These results provide a useful case for electrochemical CO2 reduction to syngas with a tunable H2/CO ratio using nonmetallic carbon-based electrocatalysts.