Metal Oxide-Stabilized Hetero-Single-Atoms for Oxidative Cleavage of Biomass-Derived Isoeugenol to Vanillin
Xin Zhao, Ruiqi Fang, Fengliang Wang, Xiangpeng Kong, Yingwei Li
Abstract
Hetero-single-atom (hetero-SA) catalysts provide extensive possibilities for advanced catalysis, while their fabrication is still a challenging task to date. Here, we report an in-situ deposition strategy for the immobilization of isolated hetero-SAs into a metal-oxide support. Systematic characterizations including X-ray absorption spectroscopy and spherical aberration-corrected Z-contrast imaging demonstrate the atomic dispersion of Ir and Cu atoms in In2O3 stabilized by covalent Ir–O and Cu–O bonds, and the electron transfer is clearly observed by differential phase contrast-scanning transmission electron microscopy. The obtained Ir1Cu1–In2O3 composite exhibits good catalytic performances in the selective oxidative cleavage of isoeugenol to vanillin, achieving 90.5% vanillin yield under mild conditions, far surpassing the those of Ir- and Cu-based SA counterparts. Density functional theory studies uncover the reaction mechanisms, that is, the adjacent Cu sites enhance the charge accumulation over the Ir sites, leading to facilitated O2 adsorption and disassociation. Besides, Cu sites also play critical roles in accelerating the subsequent oxidative reaction due to the lowered energy barriers.