The global practical implementation of proton exchange membrane fuel cells (PEMFCs) heavily relies on the advancement of highly effective platinum (Pt)-based electrocatalysts for the oxygen reduction reaction (ORR). To achieve high ORR performance, electrocatalysts with highly accessible reactive surfaces are needed to promote the uncovering of active positions for easy mass transportation. In this critical review, we introduce different approaches for the emerging development of effective ORR electrocatalysts, which offer high activity and durability. The strategies, including morphological engineering, geometric configuration modification via supporting materials, alloys regulation, core–shell, and confinement engineering of single atom electrocatalysts (SAEs), are discussed in line with the goals and requirements of ORR performance enhancement. We review the ongoing development of Pt electrocatalysts based on the syntheses, nanoarchitecture, electrochemical performances, and stability. We eventually explore the obstacles and research directions on further developing more effective electrocatalysts.

The increasing CO₂ emission, as the chief culprit causing numerous environmental problems, could be addressed by the electrochemical CO₂ reduction (CO₂R) to the added-value carbon-based chemicals. Ionic liquids (ILs) as electrolytes and co-catalysts have been widely studied to promote CO₂R owing to their unique advantages. Among the potential products of CO₂R, those only containing one carbon atom, named C1 products, including CO, CH₃OH, CH₄, and syngas, are easier to achieve than others. In this study, we first summarized the research status on CO₂R to these C1 products, and then, the state-of-the-art experimental results were used to evaluate the economic potential and environmental impact. Considering the rapid development in CO₂R, future scenarios with better CO₂R performances were reasonably assumed to predict the future business for each product. Among the studied C1 products, the research focuses on CO, where satisfactory results have been achieved. The evaluation shows that producing CO via CO₂R is the only profitable route at present. CH₃OH and syngas of H₂/CO (1 : 1) as the targeted products can become profitable in the foreseen future. In addition, the life cycle assessment (LCA) was used to evaluate the environmental impact, showing that CO₂R to CH₄ is the most environmentally friendly pathway, followed by the syngas of H₂/CO (2 : 1) and CO, and the further improvement of the CO₂R performance can make all the studied C1 products more environmentally friendly. Overall, CO is the most promising product from both economic and environmental impact aspects.

Quasi-solid-state lithium metal batteries are considered as one of the most promising energy storage devices, and the application of ionic liquids (ILs) as a new generation of functionalized electrolyte components in lithium metal batteries has become one of the research focuses. In this review, the very recent research work related to using ILs to develop quasi-solid-state electrolytes and their influences on the performances of quasi-solid-state lithium metal batteries were surveyed and summarized, suggesting that the introduction of ILs can improve the ionic conductivity, broaden the electrochemical stability window, and enhance the electrochemical stability of the selected electrolytes. Moreover, using ILs to prepare high-performance electrodes with unique microstructures and uniform distribution of fillers were also introduced. The composite quasi-solid-state electrolytes were suggested as the mainstream of electrolytes in the future due to the combination of the advantages of inorganic and polymer quasi-solid-state electrolytes, and their development challenges in high energy and high safety quasi-solid-state lithium metal batteries were also discussed.