Pd single atoms on g-C₃N₄ photocatalysts: minimum loading for maximum activity

Noble metal single atoms (SAs) on semiconductors are increasingly explored as co-catalysts to enhance the efficiency of photocatalytic hydrogen production. In this study, we introduce a "spontaneous deposition" approach to anchor Pd SAs onto graphitic carbon nitride (g-C₃N₄) using a highly dilute tetraaminepalladium(ii) chloride precursor. Maximized photocatalytic activity and significantly reduced charge transfer resistance can be achieved with a remarkably low Pd loading of 0.05 wt% using this approach. The resulting Pd SA-modified g-C₃N₄ demonstrates a remarkable hydrogen production efficiency of 0.24 mmol h^-1 mg^-1 Pd, which is >50 times larger than that of Pd nanoparticles deposited on g-C₃N₄ via conventional photodeposition. This significant enhancement in catalytic performance is attributed to improved electron transfer facilitated by the optimal coordination of Pd SAs within the g-C₃N₄ structure.