Insights into synergistic effect of Pd single atoms and sub-nanoclusters on TiO2 for enhanced photocatalytic H2 evolution

The metal atom-supported catalysts have emerged as one of the most promising candidates for practical applications of photocatalytic hydrogen evolution (PHE) due to their maximized atom utilization efficiency. However, electronic modulation of the active species (single atoms, clusters or nanoparticles) on metal atom-supported catalysts remains a great challenge. In this work, the well-dispersed Pd single atom (PdSA) and Pd sub-nanocluster (PdSNC) on TiO2 substrate (Pd0.75/TiO2) exhibit superb PHE activity with the hydrogen evolution rate (HER) of 53.64 mmol g-1h−1 under simulated solar light irradiation and apparent quantum efficiency (AQE) of 40.16% at 365 nm. Theoretical calculations reveal that the synergistic effect of PdSNC and PdSA can optimize the d-band center, and equilibrate the adsorption and desorption of intermediates during the reaction. In particular, PdSNC can effectively promote the electron transfer of PdSA, resulting in excellent carrier separation efficiency of Pd0.75/TiO2 and thus optimizing its catalytic activity.