Renewable electricity-driven carbon dioxide (CO₂) electrolysis can convert CO₂ into valuable fuel and chemicals. However, one of the key challenges hindering CO₂ electrolysis towards practical application is the severe carbon loss under alkaline and neutral conditions, resulting in low CO₂ utilization efficiency (<50%).

Recently, a research team led by Profs. BAO Xinhe, WANG Guoxiong and GAO Dunfeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has proposed a new strategy for carbon- and energy-efficient acidic CO₂ electrolysis.

This study was published in Energy & Environmental Science on Feb. 23.

The researchers tuned the microenvironments (local concentrations of H⁺, K⁺ and CO₂) of Ni-N-C cathode catalyst by changing anolyte composition and input CO₂ pressure in an acid membrane electrode assembly (MEA) electrolyzer. Benefiting from tailored catalyst microenvironments, they achieved acidic CO₂ electrolysis to CO at industrial current densities with high CO₂ utilization efficiency and high energy efficiency.

Under optimal reaction conditions, they obtained CO Faradaic efficiency as high as 95% at 500 mA cm^-2, and the corresponding full cell energy efficiency was 39%. Compared with alkaline electrolysis, the CO₂ loss was reduced by 86%, and the single-pass CO₂ utilization efficiency reached as high as 85%.

Moreover, they have revealed that the co-existence of H⁺ and K⁺ played a crucial role in stabilizing the initial *CO₂ intermediate, resulting in enhanced CO formation with theoretical calculation results.

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

"This work provides new insights into tuning catalyst microenvironments for carbon-efficient CO₂ electrolysis towards practical application," said Prof. WANG.