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.

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.