High-loading inducing Fe-dimer on carbon nitride promotes the generation of ·O2−
Xinran Zheng, Yuchao Wang, Jianping Guan, Xu Liu, Yu Bai, Yingbi Chen, Peiyao Yang, Jing Zhang, Houzheng Ou, Meng Wang, Yu Xiong, Haozhi Wang, Yongpeng Lei
Abstract
The research on metal dimer clusters is of great importance, owing to the potential in modulating the adsorption behavior towards reaction intermediates. Here, we develop a loading heightening strategy to obtain a 32.5 wt% Fe-dimer catalyst (Fe-32.5). The co-anchoring of two Fe atoms in a single triazine ring of carbon nitride with an atomic spacing of ∼0.23 nm is proved. Fe atoms occupy the pores of the triazine ring in the lower iron content sample (Fe-12.9 and Fe-17.1). However, with the increase of iron content to 32.5 wt%, two Fe atoms simultaneously occupy one triazine ring. For Fe-32.5, besides the main peak located at ∼1.5 Å corresponding to the Fe-N interaction, a peak attributed to Fe-Fe bonding is observed at ∼2.2 Å in Fourier-transformed k 3 -weithted extended X-ray absorption fine structure. Density functional theoretical (DFT) calculations reveal that Fe-dimer in Fe-32.5 induces a charge redistribution compared with that in Fe-12.9 and Fe-17.1. H 2 O* is adsorbed on O* via hydrogen bonding in Fe-12.9 and Fe-17.1. However, H 2 O*and O* in Fe-32.5 are adsorbed on Fe-Fe dimer, resulting in a decrease in the total energy of the reaction process. For the two former, O 2 - * adsorbs on individual Fe atoms. Fe-dimer in Fe-32.5 adsorbs O 2 - * in the form of bridge bonds, which facilitates the ·O 2 - release. Furthermore, an enhanced affinity for the substrate 3,3',5,5'-tetramethylbenzidine and higher peroxidase-like activity were displayed. This work provides an effective mean to synthesize metal dimer clusters through high loading.