Platinum Ensemble Heterogeneity Enables Efficient Solvent-Free Hydrogen Production.

Abstract

Liquid organic hydrogen carriers (LOHCs) based on cycloalkane/aromatic pairs are promising for safe hydrogen storage and transportation, but their practical implementation is limited by sluggish dehydrogenation kinetics and catalyst deactivation under working conditions. Herein, we report a rationally designed platinum catalyst supported on curved graphene-coated nanodiamond (ND@G), in which fully exposed subnanometric Pt clusters (Ptn) and three-dimensional Pt clusters (Ptc) are integrated in close proximity on the support (Ptn+c/ND@G), which delivers remarkably enhanced hydrogen production in the solvent-free dehydrogenation of bicyclohexyl and other representative cycloalkanes, outperforming either single-counterpart catalysts or their physical mixtures while maintaining good recyclability. Mechanistic investigations combined with density functional theory calculations demonstrate that this synergistic effect originates from the cooperation between these respective Pt ensembles: Ptc sites possess higher intrinsic activity for C-H bond activation than Ptn clusters, yet are more susceptible to poisoning. By contrast, Ptn clusters, although less active for substrate activation, remain operative in the presence of aromatic adsorbates. Hydrogen generated on Ptn clusters can weaken product binding on adjacent Ptc sites via support-mediated spillover. As a result, poisoning is mitigated, active Ptc sites are continuously regenerated, and overall dehydrogenation performance is enhanced. These findings provide a general design principle for developing high-performance LOHC dehydrogenation catalysts through Pt ensemble engineering and support-mediated hydrogen management.