Interlayer-release synthesis of Cu single atoms anchored on a heterogeneous photocatalyst for constructing Cu–Ov–Fe bimetallic active sites with ultrafast kinetics of activation of H2O2

Abstract

The efficient and selective generation of highly active ˙OH in a heterogeneous Fenton-like process is closely related to the spatial arrangement of active sites, local electron density of reactive atoms, and configuration of H₂O₂ adsorption to the active centers. Herein, a facile interlayer-release approach for the synthesis of a Cu single atom coordinated defect-rich Fe₂O₃/CuFeO₂ heterogeneous photo-Fenton-like catalyst (Cu–O_v–Fe₂O₃/CuFeO₂) with abundant atomically exposed Cu–O_v–Fe sites is developed. The asymmetric Cu–O_v–Fe sites, coupled with their acidic microenvironment, significantly enhance the adsorption of the Lewis-base H₂O₂ in a side-on configuration. This, in turn, promotes the homolytic cleavage of O–O bonds and selectively generates ˙OH. Fe₂O₃/CuFeO₂ and agglomerated Cu clusters serve as the photosensitizers for efficient generation of photoexcited electrons, which are driven by a built-in electric field to the defect-rich Fe₂O₃ shell. Upon being trapped by the oxygen vacancies of Fe₂O₃, the electrons then flow directionally and get concentrated at the bimetallic Cu–O_v–Fe active sites, enhancing their electron density. The formation of the highly condensed localized electron density greatly improves the H₂O₂ activation kinetics. Benefitting from the excellent synergic effects of photocatalysis, single-atom catalysis, and asymmetric bimetallic activation effects, the well-designed Cu–O_v–Fe₂O₃/CuFeO₂ exhibits record-breaking outstanding activity with TOF as high as 1.168 h⁻¹ (99% degradation of phenol in 15 min), a remarkable selectivity of 78% for ˙OH, excellent durability with only 8% loss of activity after four runs and 23% loss after eight runs, and wide pH adaptability ranging from pH 4.5 to 9.