Unveiling the Nature of Pt Single-Atom Catalyst during Electrocatalytic Hydrogen Evolution and Oxygen Reduction Reactions

Single-atom catalysts (SACs) have attracted significant attention due to their superior catalytic activity and selectivity. However, the nature of active sites of SACs under realistic reaction conditions is ambiguous. In this work, high loading Pt single atoms on graphitic carbon nitride (g-C3N4)-derived N-doped carbon nanosheets (Pt-1/NCNS) is achieved through atomic layer deposition. Operando X-ray absorption spectroscopy (XAS) is performed on Pt single atoms and nanoparticles (NPs) in both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The operando results indicate that the total unoccupied density of states of Pt 5d orbitals of Pt-1 atoms is higher than that of Pt NPs under HER condition, and that a stable Pt oxide is formed during ORR on Pt-1/NCNS, which may suppress the adsorption and activation of O-2. This work unveils the nature of Pt single atoms under realistic HER and ORR conditions, providing a deeper understanding for designing advanced SACs.

Automated summary

This study achieves high loading of Pt single atoms on carbon nanosheets through atomic layer deposition and investigates the activity of Pt single atoms and nanoparticles using operando X-ray absorption spectroscopy in the hydrogen evolution reaction and oxygen reduction reaction. The results reveal differences in the unoccupied density of states of Pt 5d orbitals between Pt single atoms and nanoparticles, as well as the formation of a stable Pt oxide during ORR on the Pt-1/NCNS catalyst.