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Trapezohedral Pt nanocrystals enclosed by 24 high-index {522} facets have been successfully prepared for the first time in high yield by a direct square wave electrodeposition method. They exhibit a significantly enhanced catalytic activity for C-1 molecules (CO, CH(3)OH, HCOOH).

Recent progresses in proton exchange membrane fuel cell electrocatalysts are reviewed in this article in terms of cathodic and anodic reactions with a focus on rational design. These designs are based around gaining active sites using model surface studies and include high-index faceted Pt and Pt-alloy nanocrystals for anodic electrooxidation reactions as well as Pt-based alloy/core-shell structures and carbon-based non-precious metal catalysts for cathodic oxygen reduction reactions (ORR). High-index nanocrystals, alloy nanoparticles, and support effects are highlighted for anodic catalysts, and current developments in ORR electrocatalysts with novel structures and different compositions are emphasized for cathodic catalysts. Active site structures, catalytic performances, and stability in fuel cells are also reviewed for carbon-based non-precious metal catalysts. In addition, further developmental perspectives and the current status of advanced fuel cell electrocatalysts are provided.

Figure 19. (a) Crystal structure of Al 2 (OH) 2 TCPP-Co and schematic diagram of CO 2 RR by 2D MOF films. Reproduced with permission from ref. [148].