Creating Energy- and Carbon-Efficient Acidic CO2 Electrolysis

Renewable electricity-driven carbon dioxide (CO₂) electrolysis can transform CO₂ into valuable chemicals and fuels. Nevertheless, one of the main difficulties hampering CO₂ electrolysis in the direction of practical application is the extreme carbon loss in neutral and alkaline conditions, which leads to low CO₂ utilization efficiency (<50%).

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A study group headed by Profs. Xinhe Bao, Guoxiong Wang, and Dunfeng Gao from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has suggested a new strategy for energy- and carbon-efficient acidic CO₂ electrolysis.

The study was published in Energy & Environmental Science on February 23^rd, 2023.

The scientists adjusted the microenvironments (local concentrations of K⁺, H⁺, and CO₂) of the Ni-N-C cathode catalyst by altering input CO₂ pressure and anolyte composition in an acid membrane electrode assembly (MEA) electrolyzer.

Using customized catalyst microenvironments, researchers achieved acidic CO₂ electrolysis to CO with high energy efficiency and high CO₂ utilization efficiency at current industrial densities.

At 500 mA cm^-2, they achieved CO Faradaic efficiency as maximum as 95% in optimal reaction conditions, and the equivalent total cell energy efficiency was 39%. Compared with alkaline electrolysis, the CO₂ loss was decreased by 86%, and the single-pass CO₂ utilization efficiency was as high as 85%.

Furthermore, they have shown that the co-existence of K⁺ and H⁺ played a significant role in stabilizing the initial *CO₂ intermediate, which leads to increased CO formation with theoretical calculation findings.

They also arranged an acid/alkaline tandem CO₂ electrolysis system, establishing carbon-efficient CO₂ conversion to multicarbon products (C₂₊) through a CO₂-CO-C₂₊ route.

“This work provides new insights into tuning catalyst microenvironments for carbon-efficient CO₂ electrolysis towards practical application,” concluded Prof. Wang.

Journal Reference:

Li, H., et al. (2023). Tailoring acidic microenvironments for carbon-efficient CO₂ electrolysis over a Ni–N–C catalyst in a membrane electrode assembly electrolyzer. Energy & Environmental Science. doi.org/10.1039/d2ee03482d.