A critical review of operating stability issues in electrochemical CO2 reduction

Electrocatalytic carbon dioxide reduction reaction (CO2RR) offers a promising solution for mitigating environmental challenges by converting CO2 into value-added chemicals and fuels. However, the long-term stability of CO2RR systems remains a major bottleneck impeding large-scale commercial implementation. This review summarizes recent progress on elucidating the root causes underlying stability declines in CO2RR and strategies to address them. First, catalysts undergo structural transformations (e.g., reconstruction, aggregation, dissolution) under applied reduction potentials, decreasing the density of active sites. Catalyst poisoning via carbon deposition or feed impurities (e.g., SO2) also reduces site availability. Second, gas diffusion layer (GDL) flooding and salt precipitation hinder reactant/product transport and destroy catalyst-electrolyte-gas three-phase interfaces. High applied pressures induce GDL cracking over prolonged operation. Third, alkaline electrolytes neutralize with CO2 and precipitate carbonate salts, while acidic media corrode catalysts and favor competing hydrogen evolution reaction. Metal ion impurities deposit on catalyst surfaces further exacerbating decays. Rational catalyst and GDL design can construct stabilized microenvironments, though additional advances in materials properties, operating conditions, and impurity removal are essential to extend CO2RR lifetime for commercial needs (>50,000 h). Understanding cross-coupling between the diverse deteriorative phenomena will advance the development of this important frontier.