Catalyst Regeneration via Chemical Oxidation Enables Long-Term Electrochemical Carbon Dioxide Reduction
2022
Nguyen, Tu N. | Chen, Zhu | Zeraati, Ali Shayesteh | Shiran, Hadi Shaker | Sadaf, Sharif Md | Kibria, Md Golam | Sargent, Edward H. | Dinh, Cao-Thang
Electrochemical CO₂ reduction (ECR) with industrially relevant current densities, high product selectivity, and long-term stability has been a long-sought goal. Unfortunately, copper (Cu) catalysts for producing valuable multicarbon (C₂₊) products undergo structural and morphological changes under ECR conditions, especially at high current densities, resulting in a rapid decrease in product selectivity. Herein, we report a catalyst regeneration strategy, one that employs an electrolysis method comprising alternating “on” and “off” operating regimes, to increase the operating stability of a Cu catalyst. We find that it increases operating lifetime many times, maintaining ethylene selectivity ≥40% for at least 200 h of electrolysis in neutral pH media at a current density of 150 mA cm–² using a flow cell. We also demonstrate ECR to ethylene at a current density of 1 A cm–² with ethylene selectivity ≥40% using a three-dimensional Cu gas diffusion electrode, finding that this system under these conditions is rendered stable for greater than 36 h. This work illustrates that Cu-based catalysts, once they have entered into the state conventionally considered to possess degraded catalytic activity, may be recovered to deliver high C₂₊ selectivity. We present evidence that the combination of short periods of electrolysis, which minimizes the morphological changes during “on” segments, with the progressive chemical oxidation of Cu atoms on the catalyst surface during “off” segments, united with the added effects of washing the accumulated salt and decreasing the catholyte temperature prolong together the catalyst’s operating lifetime.
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