Hierarchical Cross-Linked Carbon Aerogels with Transition Metal-Nitrogen Sites for Highly Efficient Industrial-Level CO2 Electroreduction

Developing highly efficient carbon aerogels (CA) electrocatalysts based on transition metal-nitrogen sites is critical for the CO2 electroreduction reaction (CO2RR). However, simultaneously achieving a high current density and high Faradaic efficiency (FE) still remains a big challenge. Herein, a series of unique 3D hierarchical cross-linked nanostructured CA with metal-nitrogen sites (M-N, M = Ni, Fe, Co, Mn, Cu) is developed for efficient CO2RR. An optimal CA/N-Ni aerogel, featured with unique hierarchical porous structure and highly exposed M-N sites, exhibits an unusual CO2RR activity with a CO FE of 98% at -0.8 V. Notably, an industrial current density of 300 mA cm(-2) with a high FE of 91% is achieved on CA/N-Ni aerogel in a flow-cell reactor, which outperforms almost all previously reported M-N/carbon based catalysts. The CO2RR activity of different CA/N-M aerogels can be arranged as Ni, Fe, Co, Mn, and Cu from high to low. In situ spectroelectrochemistry analyses validate that the rate-determining step in the CO2RR is the formation of *COOH intermediate. A Zn-CO2 battery is further assembled with CA/N-Ni as the cathode, which shows a maximum power density of 0.5 mW cm(-2) and a superior rechargeable stability.

Automated summary

Developing highly efficient carbon aerogels with transition metal-nitrogen sites is critical for CO2 electroreduction. An optimal CA/N-Ni aerogel shows exceptional CO2RR activity, achieving a CO FE of 98% at -0.8 V and industrial current density of 300 mA cm(-2). Analysis suggests the rate-determining step in CO2RR is the formation of *COOH intermediate, with CA/N-Ni outperforming other M-N/carbon catalysts.