Single-atom catalysts-based Fenton-like processes for water contaminant management: a review

Fenton reaction is particularly effective for mineralizing stubborn organic pollutants due to the high oxidation potential of •OH with the green end product of H2O. However, exogenous addition of hydrogen peroxide (H2O2) is usually accompanied by the high operation risks and economic costs along with the storage and transportation of H2O2. Besides, inefficient activation of H2O2 due to the rapid accumulation of Fe3+ and slow regeneration of Fe2+ constrains the efficiency. Hence, heterogeneous catalysts that overcome those limitations by in-situ regenerating and activating H2O2 with high efficiency in the Fenton-like processes are promising alternatives to the conventional Fenton reactions. In this review, we give an overall summarization on the single-atom catalysts (SACs) attempted in the Fenton-like processes recently, and discuss their potential roles in the wastewater contaminant alleviation. Firstly, a brief introduction is made on the basic principles of H2O2 generation and activation in the Fenton-like processes, and the coordination environment of SACs is emphasized. Then, a detailed discussion on how the type of central metal sites and their coordination environment influence the catalytic performance from three perspectives: H2O2 activation, selective H2O2 generation via 2e− oxygen reduction reaction, and bifunctional SACs for electro-Fenton. After that, the recent advances on SACs catalyzed Fenton-like processes in the contaminant removal are introduced, and the kinetic perspective, influence of water quality, the stability and long-term performance, as well as the mass transfer and reactor scale up are discussed, respectively. Finally, the major challenges for the applications in real wastewater treatment are outlooked.