The thermal stabilities of 66 ionic liquids (ILs) were investigated using the thermogravimetric analysis (TGA) method. Isothermal TGA studies on the ILs showed that ILs exhibit decomposition at temperatures lower than the onset decomposition temperature (T_onset), which is determined from ramped temperature TGA experiments. Thermal decomposition kinetics of ILs was analyzed using pseudo-zero-order rate expression and their activation energy was obtained. Parameter T_0.01/10h, the temperature at which 1% mass loss occurs in 10 h, was used to evaluate the long-term thermal stability of ILs. The thermal stability of the ILs was classified to five levels according to T_onset. The ILs thermal stability is dependent on the structure of ILs, i.e., cation modification, cation and anion type. The correlations between the stability and the hydrophilicity of ILs were discussed. Finally, the thermal stabilities of acetate-based ILs, amino acid ILs, and dicyanamide ILs were analyzed.

Electrochemical conversion is emerging as a powerful and promising method to produce a wide range of high-value chemicals on account of mild operation conditions, controllable selectivity, and scalability. 5-Hydroxymethylfurfural (HMF), with simple molecular structures including furan rings, –CO, and –OH groups, is considered one of the most versatile platform molecules. The electrooxidation of bio-based HMF to furandicarboxylic acid (FDCA), a crucial bio-based precursor of polyethylene furanoate (PEF), which would probably replace petroleum-based polyethylene terephthalate (PET), has recently attracted increasing attention. Here, we review the HMF electrochemical oxidation, from reaction pathway/mechanism to catalysts and coupling reactions. First, a pH-dependent reaction pathway is proposed, and the reaction mechanism (direct oxidation and indirect oxidation) is summarized systematically, which is also suitable for electrochemical oxidation of other small organic molecules containing aldehyde/alcohol groups (e.g., methanol, ethanol, glycerol, and glucose) to some extent. Then, the progress, advantages and disadvantages of HMF electrooxidation catalysts of noble metals, non-noble metals, and non-metals are reviewed, particularly on non-noble metal catalysts. Furthermore, for more efficient energy utilization, HMF electrooxidation coupled with H₂ evolution, CO₂ reduction, N₂ reduction, and organic reduction are discussed. Finally, a few unique insights into reaction mechanism, an assessment about catalyst performance and an outlook for further development of this topic are provided. This review can offer a guideline for the in-depth understanding of electrochemical oxidation of small organic molecules as well as the design of advanced anodic electrocatalysts towards the utilization and production of renewable resources.

Ionic liquids show instability when exposed to high temperature, to high voltage as electrolytes, or under irradiation.

Various eutectic systems including eutectic metals, eutectic salts, and deep eutectic solvents have been proposed and applied in engineering, energy and environmental fields.

The thermal, electrochemical and photochemical conversion of CO₂mediated by ionic liquids is systematically reviewed.