Synergistic Acid Hydrogen Evolution of Neighboring Pt Single Atoms and Clusters: Understanding Their Superior Activity and Mechanism.

The hydrogen evolution reaction (HER) involves two-step elementary reactions, providing an opportunity to establish dual-site synergistic catalysts. This work demonstrates carbon-supported Pt single atoms and clusters (Pt-NPC) as an efficient catalyst for acidic HER, which exhibits an ultralow Tafel slope of 12.5 mV/dec and an overpotential of 24 mV at 10 mA/cm with an ultralow platinum content of 3.8 wt %. The Pt mass activity and turnover frequency (TOF) are 10.2 times and 5.4 times that of commercial Pt/C, respectively. The density functional theory (DFT) study shows that the Pt cluster regulates the electronic state structure of the adjacent Pt single atom, so that the Δ at the Pt site approaches 0. Moreover, the DFT study confirms that Pt clusters and neighboring Pt single atoms can synergistically catalyze the Tafel step and reduce the energy barrier in forming the H-H bond. At the same time, the platinum cluster reduces the energy barrier of the nearby platinum single-atom site to the Heyrovsky step and accelerates the reaction with hydrated hydrogen ions. Studies have shown that platinum clusters and platinum single-atom composite loading structures exhibit excellent activity for the Volmer-Tafel or Volmer-Heyrovsky reaction paths of HER reactions. This work provides a clear understanding of the synergistic effect of Pt-NPC, which provides guidance for developing efficient HER catalysts.