Origin and effect of surface oxygen-containing species on electrochemical CO or CO2 reduction reactions

This mini-review is led by Prof. Bingjun Xu (College of Chemistry and Molecular Engineering, Peking University). Renewable-energy-powered electrochemical CO or CO₂ reduction reactions (CO₍₂₎RR) is one of the most promising strategies to upgrade CO₂ to valuable products. A key question and bone of contention is whether any surface or subsurface oxygen remains on the electrocatalysts under the reducing CO₍₂₎RR conditions, and if so, whether they play any role in facilitating the reaction. Thermodynamically, the oxides are expected to be reduced to the metallic form under the CO₍₂₎RR conditions according to the Pourbaix diagram. However, multiple experimental studies reported the evidences for oxygen-containing species on electrocatalysts at CO₍₂₎RR conditions, which could be attributed either to the difference in reaction and characterization conditions, or to the distinct thermodynamic stabilities of surface and bulk oxides.

This mini-review summarizes recent literature on this topic and discusses the possible sources of oxygen-containing species at or near the electrode-electrolyte interfaces under CO₍₂₎RR conditions. Potential (sub)surface oxygen-containing species are grouped into three main categories based on the conditions at which they are introduced: (1) via the exposure to ambient air; (2) via the pretreatment of the catalyst; and (3) with the assistance of additional oxygen sources via in-situ redox reactions. Potential impact of oxygen-containing species on the activity and product distribution in the CO₍₂₎RR, and the perspectives on future efforts to reveal the identity and role of oxygen-containing species in the CO₍₂₎RR are also discussed.

See the article:

Origin and effect of surface oxygen-containing species on electrochemical CO or CO₂ reduction reactions

https://doi.org/10.1007/s11426-022-1459-3