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 recent development of Aurum (Au) introduced Platinum (Pt) based nanomaterials is of great significance to direct methanol fuel cell as electrocatalysts for anode reactions, due to its stability and anti-poisoning features. Therefore, the performance of PtAu based catalysts with different elements, atomic ratio, and morphology was studied in methanol solution to further improve its electrocatalytic activity. Furthermore, the effects of Au have aroused the researchers' attention in Pt-based nanocatalysts. In this review, we summarize the controllable synthesis, mechanism, and catalytic performance of Au introduced Pt-based electrocatalysts such as PtAu core-shell nanostructures, PtAu dendrite, PtAu nanowires, self-supporting Au@Pt NPs, and Au@Pt star-like nanocrystals for the methanol oxidation reaction. Finally, the challenges and research directions for the future development of PtAu based catalysts are provided.

Carbon nanotube (CNT) clusters grown in situ in three-dimensional (3D) porous graphene networks (3DG-CNTs), with integrated structure and remarkable electronic conductivity, are desirable S host materials for Li–S batteries. 3DG-CNT exhibits a high surface area (1, 645 m²·g^-1), superior electronic conductivity of 1, 055 S·m^-1, and a 3D porous networked structure. Large clusters of CNTs anchored on the inner walls of 3D graphene networks act as capillaries, benefitting restriction of agglomeration by high contents of immersed S. Moreover, the capillary-like CNT clusters grown in situ in the pores efficiently form restricted spaces for Li polysulfides, significantly reducing the shuttling effect and promoting S utilization throughout the charge/discharge process. With an areal S mass loading of 81.6 wt.%, the 3DG-CNT/S electrode exhibits an initial specific capacity reaching 1, 229 mA·h·g^-1 at 0.5 C and capacity decays of 0.044% and 0.059% per cycle at 0.5 and 1 C, respectively, over 500 cycles. The electrode material also reveals a remarkable rate performance and the large capacity of 812 mA·h·g^-1 at 3 C.