Pt/Pd Single-Atom Alloys as Highly Active Electrochemical Catalysts and the Origin of Enhanced Activity

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Pt single-atom catalysts are receiving more and more attention due to their different properties compared with nanostructures. As one typical kind of single-atom catalysts, Pt-based single-atom alloys (SAAs) have generated significant interest due to their application in several heterogeneous catalytic reactions. However, almost all of the reported Pt-based SAAs are on Cu surface. In addition, it is still great challenge to apply Pt single-atom alloys in electrocatalytic reactions. Herein, we demonstrated a fabrication of Pt/Pd SAA catalysts on nitrogen-doped carbon nanotubes by atomic layer deposition. The as-prepared octahedral Pt/Pd SAA catalysts exhibited greatly improved activity compared to commercial Pt/C catalysts for electrochemical catalytic reactions. According to the X-ray adsorption spectrum, the Pt atoms in Pt/Pd SAA catalysts exhibited higher unoccupied 5d character density of states and a lower Pt–Pt coordination number, compared to those in core–shell structures. In addition, we used density functional theory calculation results to explain the enhanced mechanism of Pt/Pd SAA catalysts for electrochemical reactions. This study opens up an avenue of developing different types of Pt-based catalysts for electrocatalytic reactions and brings insight understanding about catalytic performances of SAA catalysts.