From single-atom catalysis to dual-atom catalysis: A comprehensive review of their application in advanced oxidation processes

Single-atom catalysts (SACs) have emerged as leading contenders in the domain of environmental catalysis. Dual-atom catalysts (DACs), an extension of SACs, anchor two metal elements onto a substrate material, overcoming SAC limitations in accommodating multistep reactions with a sole active site. The synergetic effect between the two metal atoms enhances catalytic activity and selectivity by offering greater flexibility in adjusting geometrical configurations and electronic structures. In the realm of advanced oxidation processes (AOPs), while SACs/DACs have been studied for years, a comprehensive summary of their unique advantages remains elusive. This review aims to bridge a significant gap by offering a comprehensive overview of SACs and DACs applications in AOPs. It explores various preparation strategies, encompassing both universal and distinctive methodologies for SACs/DACs. Additionally, it thoroughly examines the effective utilization of SACs/DACs in eliminating contaminants across various AOPs, including a detailed analysis of reactive oxygen species (ROS), and highlights real-world applications. The review also delves into essential characterization techniques for accurately determining the physical and morphological features of SACs/DACs, along with their geometric configurations. Furthermore, it discusses the use of Density Functional Calculations (DFT) and Machine Learning (ML) tools to understand the underlying mechanisms for rational design and reliable performance. Finally, the review concludes by addressing the challenges and proposing a promising research direction for SACs/DACs in AOPs.