Ultrahigh Mass Activity Pt Entities Consisting of Pt Single atoms, Clusters, and Nanoparticles for Improved Hydrogen Evolution Reaction

Abstract Platinum is one of the best‐performing catalysts for the hydrogen evolution reaction (HER). However, high cost and scarcity severely hinder the large‐scale application of Pt electrocatalysts. Constructing highly dispersed ultrasmall Platinum entities is thereby a very effective strategy to increase Pt utilization and mass activities, and reduce costs. Herein, highly dispersed Pt entities composed of a mixture of Pt single atoms, clusters, and nanoparticles are synthesized on mesoporous N‐doped carbon nanospheres. The presence of Pt single atoms, clusters, and nanoparticles is demonstrated by combining among others aberration‐corrected annular dark‐field scanning transmission electron microscopy, X‐ray absorption spectroscopy, and electrochemical CO stripping. The best catalyst exhibits excellent geometric and Pt HER mass activity, respectively ≈4 and 26 times higher than that of a commercial Pt/C reference and a Pt catalyst supported on nonporous N‐doped carbon nanofibers with similar Pt loadings. Noteworthily, after optimization of the geometrical Pt electrode loading, the best catalyst exhibits ultrahigh Pt and catalyst mass activities (56 ± 3 A mg −1 Pt and 11.7 ± 0.6 A mg −1 Cat at −50 mV vs. reversible hydrogen electrode), which are respectively ≈1.5 and 58 times higher than the highest Pt and catalyst mass activities for Pt single‐atom and cluster‐based catalysts reported so far.