A Promoted Charge Separation/Transfer System from Cu Single Atoms and C3 N4 Layers for Efficient Photocatalysis

Abstract

Establishing highly effective charge transfer channels in carbon nitride (C₃ N₄ ) for enhancing its photocatalytic activity is still a challenging issue. Herein, for the first time, the engineering of C₃ N₄ layers with single-atom Cu bonded with compositional N (CuN_x ) is demonstrated to address this challenge. The CuN_x is formed by intercalation of chlorophyll sodium copper salt into a melamine-based supramolecular precursor followed by controlled pyrolysis. Two groups of CuN_x are identified: in one group each of Cu atoms is bonded with three in-plane N atoms, while in the other group each of Cu atoms is bonded with four N atoms of two neighboring C₃ N₄ layers, thus forming both in-plane and interlayer charge transfer channels. Importantly, ultrafast spectroscopy has further proved that CuN_x can greatly improve in-plane and interlayer separation/transfer of charge carriers and in turn boost the photocatalytic efficiency. Consequently, the catalyst exhibits a superior visible-light photocatalytic hydrogen production rate (≈212 µmol h^-1 /0.02 g catalyst), 30 times higher than that of bulk C₃ N₄ . Moreover, it leads to an outstanding conversion rate (92.3%) and selectivity (99.9%) for the oxidation of benzene under visible light.

Keywords: Cu single atoms; benzene oxidation; carbon nitride; charge transfer dynamics; hydrogen evolution reactions.