Synergistic Effects Between Pd Single Atoms and Nanoscopic Pd Atom Clusters: Facilitating Formation of Pd-N Charge Channels and Strong Internal Electric Fields for Large-scale Photocatalytic Hydrogen Evolution

Single atoms (SAs) and nanoscale atom clusters (ACs) catalysts have garnered significant attention owing to their exceptional selectivity and abundant active sites. In this study, a chemical reduction method was employed to successfully anchor Pd, Au, and Pt elements onto COF (Tatp). Notably, the Tatp loaded with Pd exhibits superior hydrogen evolution performance. Utilizing AC-STEM and synchrotron radiation techniques, we demonstrate the coexistence of Pd SAs and Pd ACs on the Tatp (Pd SAs-ACs). Combined with DFT calculations, we have demonstrated a strong interaction between the electron-delocalized Pd SAs and the electron-localized N atoms within the imine bond. This interaction facilitates the establishment of the Pd-N electron transport channel. The incorporation of Pd ACs introduces numerous active sites for photocatalytic reactions while spontaneously generating a strong internal electric field (IEF). The synergistic interplay between Pd SAs and Pd ACs not only significantly reduces the charge transfer distance but also provides ample driving force for the efficient separation and migration of photogenerated electrons. We employed PdTatp3 for the square-meter-scale hydrogen evolution test, and the hydrogen production volume reached 22.96 mmol over a period of 10 h. This study proposes a promising strategy for harnessing the synergistic effect of SAs and nanoscale ACs to enhance photocatalytic hydrogen evolution performance.