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-C 3 N 4 catalysts with various contents of Ni-N 4 coordination. Experimental investigations and quantum chemical calculations disclosed that the Ni-N 4 and g-C 3 N 4 host are two active sites for photocatalysis and play different roles in photocatalysis. The promoting and suppressing effects of Ni-N 4 coordination on g-C 3 N 4 matrix at Ni-N 4 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.
In this work, we revealed a dual-pathway nonradical oxidation (NRO) system catalyzed by Ni single atom catalyst (NiN 4 ) accommodated in the carbon nitride substrate. The monatomic Ni coordinated with four N atoms (Ni-N 4 ) is determined as the dynamic catalytic center for peroxymonosulfate (PMS) activation, showing an exceptional specific rate constant of 3.34 min −1 g −2 L −2 (29.7 times that of CN/PMS system) in oxidizing bisphenol A and other refractory organics. In situ Raman, X-ray absorption, and electrochemical analyses as well as theoretical simulations demonstrate that the Ni-N 4 sites exhibit strong interaction with PMS benefited from the modulated electronic structures, resulting in nonradical surface-bonding active complexes (NiN 4 -PMS*) and deuterogenic high-valent Ni(IV)-Oxo species. The dual-pathway NRO process will spontaneously coordinate both electron transfer process via CN matrix and direct electron transfer by Ni(IV)-Oxo for selective organic oxidation with excellent anti-interference ability and adaptability.
In this work, composite thin films comprising the 2D/2D MOF/rGO heterostructures assembled via Coulomb interaction are employed as the cocatalyst for photocatalytic CO 2 reduction for the first time. The electrostatic charge transfer and the strong π-π interaction induced in the heterostructure effectively modulate the electronic structure of the metal centers in the conductive 2D MOF (Ni 3 HITP 2 ), evidenced by Zeta Potentials, HR-TEM, XPS and XANES. The best thin-film catalyst with an optimal MOF/rGO ratio demonstrates a high CO evolution rate of 3.8 × 10 4 μmol h −1 g film −1 (0.46 min −1 in TOF) and a good selectivity of 91.74%, synergically contributed by the improved photoelectron harvesting on the rGO scaffold, the efficient charge transportation/transfer within the conductive and intimate 2D heterostructure, the coherent energy flow owing to aligned energy levels, and the enriched electron density at the isolated Ni-N 4 sites boosted by electrostatic charge transfer.
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