In situ/operando characterization techniques for electrochemical CO2 reduction

Utilizing CO2 as a carbon feedstock for producing fuels and useful chemicals is attractive due to the advantages of being abundant, nontoxic, and economical. Electrochemical CO2 reduction (CO2RR) provides an avenue to close the anthropogenic carbon cycle. However, the reaction process of multi-electronic products of CO2RR is quite complex. It is hard to yield a target product with high selectivity, high current density, low overpotential, and good stability simultaneously. In recent years, in situ/operando characterization techniques have played important roles in the catalysis field via establishing the structure-reactivity/selectivity relationships of catalysts and thereby obtaining information about mechanisms. As a result, it is necessary to apply in situ/operando characterization technologies to clarify the reaction pathway of CO2RR. In this mini-review, we discuss recent progress on the in situ/operando characterizations for electrochemical CO2RR, including microscopies, infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption fine spectroscopy. Moreover, the capabilities of these in situ/operando characterizations and the remaining challenges are also discussed.