Tuning the microenvironment and electronic structure of support materials is essential strategy to induce electron transfer between supports and active centers, which is of great importance in optimizing catalytic kinetics. In this study, the molybdenum oxycarbide supported Rh‐clusters are synthesized with modulated interstitial C–O microenvironments (Rh/MoOC) for promoting efficient hydrogen evolution in water splitting. Both electronic structure characterizations and theoretical calculations uncover the apparent charge transfer from Rh to MoOC, which optimizes the d‐band center, H2O adsorption energy, and hydrogen binding energy, thus enhancing its intrinsic hydrogen‐evolving activities. In addition, the co‐occurrence of interstitial C and O atoms in MoOC supports plays a vital role in the dissociation reaction of water during the hydrogen‐evolving process. Impressively, the Rh/MoOC exhibits excellent hydrogen‐evolving activities in terms of exceptional turnover frequency values (11.4 and 39.41 H2 s−1 in alkaline and acidic media) and mass activities (21.3 and 73.87 A mg−1 in alkaline and acidic media) at an overpotential of 100 mV, which is more than 40 times higher than that of the benchmark commercial Rh/C catalysts. This work sheds new light on designing water dissociation materials that surpasses most of the reported catalysts.

The hydrogen evolution reaction (HER) from the electrocatalysis of water splitting is the most promising approach to producing green and renewable hydrogen energy for sustainable development. The precious metal platinum is the best electrocatalyst for HER. However, its scarcity and high cost still hinder the large-scale application. It is highly desirable to fabricate efficient Pt electrocatalysts with low Pt loading. Herein, we report an efficient ultralow Pt-loading HER catalyst, which was obtained by the electroreduction of a preprepared supramolecular self-assembly. Utilizing the strong hydrogen bonding formation ability of macrocyclic cucurbit[8]uril (CB[8]), a porous supramolecule (CB[8]-[PtCl6]) composed of [PtCl6]2– and CB[8] is obtained as the HER catalyst precursor. By the electroreduction of the as-prepared supramolecular compound, Pt nanoparticles (NPs) protected by CB[8] (CB[8]-Pt) exhibit high catalytic activity and excellent long-term stability toward HER with ultralow Pt loading. CB[8]-Pt with a Pt loading of only 1.2 μg/cm2 presents 23 times higher HER activity than commercial Pt/C. Moreover, CB[8]-Pt shows excellent stability under 10 000-cycle cyclic voltammetry (CV) and at least 120 h for chronopotentiometry at 10 mA/cm2 in 0.5 M H2SO4, which greatly outperforms commercial Pt/C. This work provides a strategy for the rational design of ultralow-loading Pt catalysts with good activity and stability for hydrogen production.

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