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.
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