Ionic liquids (ILs) are the safest solvent in various high-temperature applications due to their non-flammable properties. In order to obtain their thermal stability properties, thermogravimetric analysis (TGA) is extensively used to analyze the kinetics of the thermal decomposition process. This review summarizes the different kinetics analysis methods and finds the isoconversional methods are superior to the Arrhenius methods in calculating the activation energy, and two tools—the compensation effect and master plots—are suggested for the calculation of the pre-exponential factor. With both parameters, the maximum operating temperature (MOT) can be calculated to predict the thermal stability in long-term runnings. The collection of thermal stability data of ILs with divergent cations and anions shows the structure of cations such as alkyl side chains, functional groups, and alkyl substituents will affect the thermal stability, but their influence is less than that of anions. To develop ILs with superior thermal stability, dicationic ILs (DILs) are recommended, and typically, [C₄(MIM)₂][NTf₂]₂ has a decomposition temperature as high as 468.1 °C. For the convenience of application, thermal stability on the decomposition temperature and thermal decomposition activation energy of 130 ILs are summarized at the end of this manuscript.

Conversion of aqueous CO₂ into CO through the electrochemical reduction reaction (ERR) suffers from poor selectivity and low current density with the classic Ag-based catalysts due to the inert nature of CO₂ and the low activity of the active sites. Recently, it has been reported that nanostructured catalysts can display very distinctive behavior compared to their bulk counterparts. To explore the reasons behind this, the latest developments in Ag-based nanostructured materials in the CO₂ ERR are summarized into six aspects in this review: (1) the size effect, (2) the morphology effect, (3) the porous effect, (4) the alloying effect, (5) the support effect, and (6) the surface modification effect. In particular, Ag-based alloy catalysts could exhibit a superior catalytic activity and long-term stability owing to the synergistic effect. Besides, the morphology of Ag-based alloy catalysts could also be controlled through adjusting their compositions. From the current literature survey we find that the maximum FE for CO obtained from Ag-based nanocatalysts reaches as high as 99.3%, which is a breakthrough over that from the traditional Ag foil. This review aims to offer a comprehensive understanding of Ag-based nanostructured catalysts in the CO₂ ERR and consequently improve the catalyst design for active and selective electro-reduction of CO₂ to CO.

Electrochemical reduction of aqueous CO₂ into formate is subject to poor selectivity and low current density with conventional Sn-based catalysts owing to the inert nature of CO₂ molecules and the low number of active sites.

Electrocatalytic reduction of CO₂ to CO is usually subject to the competitive reduction of H⁺ to hydrogen.