The double-edged effect of single atom metals on photocatalysis

Single atom catalysts (SACs) are suggested to be ideal materials for catalysis and will exhibit the highest performance at the maximum single atom loading. However, their influences on the intrinsic structure and properties of a photocatalytic substrate should not be neglected. Herein, we proposed a facile and green approach for large scale synthesis of Ni-SA/g-C₃N₄ catalysts with various contents of Ni-N₄ coordination. Experimental investigations and quantum chemical calculations disclosed that the Ni-N₄ and g-C₃N₄ host are two active sites for photocatalysis and play different roles in photocatalysis. The promoting and suppressing effects of Ni-N₄ coordination on g-C₃N₄ matrix at Ni-N₄ adjacency are also revealed. Maximum efficiency in photocatalytic water splitting and contaminant oxidation processes can only be realized at an optimized SA loading by the balance of the two effects. Extra loading of SA will make adjacent carbon nitride matrix lose semiconducting properties for generating hot carriers toward photocatalysis. This work reveals the intrinsic correlation between SAC structure and photocatalysis, shedding light on the fundamental understandings of structure-catalysis correlation and providing new insight into SACs.