Improvement of the oxidation efficiency of photogenerated holes at ferric single-atom catalysts via ferric-nitrogen co-sculpted carbon defect engineering

Direct oxidation of organic pollutants by visible-light-generated holes is considered a promising technique for remediating contaminated water bodies. However, random and rapid recombination of photogenerated holes and electrons hampers the accumulation of holes on catalyst surface. To address this challenge, a strategy involving the co-etching of bagasse pith parenchyma cells with iron and nitrogen was proposed, creating an Fe-N-C catalyst with a web-like fibrous structure and abundant carbon defects. This iron and nitrogen co-etching strategy endowed the Fe-N-C catalyst with not only ultrafast photogenerated electron transfer and capture capabilities but also enabled it to have abundant and accessible surface-active sites, co-facilitating rapid and efficient electron transfer between pollutants and holes. Thus, compared to pure bagasse pith carbon or nitrogen-doped carbon, the optimized Fe-N-C single-atom catalysts (SACs) exhibited a significant enhancement in the photocatalytic oxidation kinetics of tetracycline (TC) by 16.47 and 5.38 times, respectively, with the maximum degradation efficiency increasing from 25.6% and 48.6% to 99.6%. Based on theoretical and experimental analyses, the toxicity of TC-contaminated water was significantly reduced after treatment with the Fe-N-C catalyst. Through analyzing the material characterization and photocatalytic behavior, a structure-performance correlation that links intrinsic carbon defects to effective surface hole transfer in Fe-N-C was established and validated. From the perspective of holes as the primary active sites, this work offered a promising approach to enhancing the overall photocatalytic oxidation efficiency of Fe-N-C SACs.