Scalable synthesis of coordinatively unsaturated metal-nitrogen sites for large-scale CO2 electrolysis

Practical electrochemical CO2-to-CO conversion requires a non-precious catalyst to react at high selectivity and high rate. Atomically dispersed, coordinatively unsaturated metal-nitrogen sites have shown great performance in CO2 electroreduction; however, their controllable and large-scale fabrication still remains a challenge. Herein, we report a general method to fabricate coordinatively unsaturated metal-nitrogen sites doped within carbon nanotubes, among which cobalt single-atom catalysts can mediate efficient CO2-to-CO formation in a membrane flow configuration, achieving a current density of 200 mA cm(-2) with CO selectivity of 95.4% and high full-cell energy efficiency of 54.1%, outperforming most of CO2-to-CO conversion electrolyzers. By expanding the cell area to 100 cm(2), this catalyst sustains a high-current electrolysis at 10 A with 86.8% CO selectivity and the single-pass conversion can reach 40.4% at a high CO2 flow rate of 150 sccm. This fabrication method can be scaled up with negligible decay in CO2-to-CO activity. In situ spectroscopy and theoretical results reveal the crucial role of coordinatively unsaturated metal-nitrogen sites, which facilitate CO2 adsorption and key *COOH intermediate formation. Scalable fabrication of coordinatively unsaturated metal-nitrogen is challenging. Here the authors report a general method for synthesize such material for CO2 electrochemical conversion at a high catalytic current of 10 A for more than 60 h stability using a 100 cm2 membrane flow cell.

Automated summary

The authors report a general method to synthesize coordinatively unsaturated metal-nitrogen sites doped within carbon nanotubes, which can mediate efficient CO2-to-CO formation in a membrane flow configuration, achieving high current density and CO selectivity. This fabrication method can be scaled up with negligible decay in CO2-to-CO activity.