Atomic palladium on graphitic carbon nitride as a hydrogen evolution catalyst under visible light irradiation

Developing single-atom catalysts is extremely attractive for maximizing atomic efficiency and activity. However, the properties a nd roles of atomic catalysts in catalyzing water splitting reactions remain unclear. Here we report atomic palladium on graphitic carbon nitride with low palladium loading (0.1？wt%). The hydrogen evolution of this graphitic carbon nitride increases from 1.4 to 728？μmol？g？1？h？1 under visible light irradiation, which is also 10 times higher than that of palladium nanoparticles (3？wt%) counterpart. The electronic structure of graphitic carbon nitride is modified after isolated palladium is introduced, which results in efficient charge separation, appropriate sites for adsorption for hydrogen, as well as accumulation of photoinduced electrons. Our results suggest that the pyridine nitrogen in the adjacent cavity to the palladium rather than the isolated palladium site is the active site which differs to that of the palladium nanoparticle counterpart