Fig. 2.

a, The degradation mechanisms of CTO by ZVI system. Reproduced with permission from Ref. [56]. Copyright 2022, Elsevier. b, The degradation mechanism of SMT in the Cu⁰/C-air system. Reproduced with permission from Ref. [62]. Copyright 2021, Elsevier. c, Mechanism for active species generation in the Zn⁰-CNTs-O₂ system. Reproduced with permission from Ref. [66]. Copyright 2017, Elsevier. d, Ascorbic acid enhances the activation of oxygen by the Fe²⁺/air process. Reproduced with permission from Ref. [71]. Copyright 2016, Elsevier. e, Mechanisms of activating O₂ by Cu(I) on Cu-Al/KIT-6. Reproduced with permission from Ref. [73]. Copyright 2020, Elsevier. f, Degradation mechanism of nitrobenzene (NB) in air/CuCoFe/Tar-LDH reaction systems. Reproduced with permission from Ref. [80]. Copyright 2022, ACS. g, The mechanism of ROS generation in the CoS_2–1.5 h system. Reproduced with permission from Ref. [85]. Copyright 2021, Wiley. h, The oxygen molecule activation by carbon defects. Reproduced with permission from Ref. [86]. Copyright 2023, Elsevier.