Heteroatom doping strategies in single-atom catalysts: tuning electronic structure for selective peroxymonosulfate activation

Abstract

The performance of atomically dispersed catalysts, especially single-atom catalysts (SACs), has attracted increasing attention due to their atomically dispersed active sites, which are closely related to the local electronic structure and coordination of the isolated metal atoms. Although the introduction of heteroatoms, such as phosphorus, boron, or sulfur, can break the symmetric configuration of conventional transition metal–nitrogen (M–N₄) sites, redistribute the charge density, and modulate the oxidation states of metal centers, systematic correlations between the dopant electronegativity, coordination-shell position, and reactive oxygen species (ROS) selectivity remain ambiguous. Mechanistic opinion suggests that the electronegativity mismatch between the dopant and the metal, as well as the dopant's spatial location, plays a crucial role in determining the charge-transfer polarity and, consequently, ROS selectivity. Based on density functional theory, advanced spectroscopic techniques, and catalytic performance studies, this review proposes the guiding principles linking the characteristics of the dopants to ROS selectivity, which provides the conceptual basis for the rational design of next-generation SACs for selective PMS activation, and outlines the major issues that remain in practice, such as long-term catalyst stability and catalyst scaling beyond laboratory conditions.