Synthesis and Prospects of Holey Two-dimensional Platinum-group Metals in Electrocatalysis.

Advanced electrocatalysts can enable the widespread implementation of clean energy technologies. This paper reviews an emerging class of electrocatalytic materials comprising holey two-dimensional free-standing Pt-group metal (h-2D-PGM) nanosheets, which are categorically challenging to synthesize but inherently rich in all the qualities necessary to counter the kinetic and thermodynamic challenges of an electrochemical conversion process with high catalytic efficiency and stability. Although the 2D anisotropic growth of typical nonlayered metal crystals has succeeded and partly improved their atom-utilization efficiency, regularly distributed in-planar porosity can further optimize three critical factors that govern efficient electrocatalysis process: mass diffusion, electron transfer, and surface reactivity. However, producing such advanced morphological features within h-2D-PGMs is difficult unless they are specially engineered using approaches such as templating or kinetic ramification during 2D growth or controlled etching of preformed 2D-PGM solids. Therefore, this review highlighting the successful fabrication of various porous PGM nanosheets and their electrocatalytic benefits involving smart nanoscale features could inspire next-generation scientific and technological innovations toward securing a sustainable energy future.