Electrochemical oxidation degradation of polystyrene nanoplastics by Sm-Mn intermediate layer Ti/Sb-SnO2 anode: Composite metal elements enhance electron transfer and promote the generation of hydroxyl radicals

As an emerging pollutant, Micro/nano plastics (M/NPs) pose a serious threat to the aquatic ecosystem and human health. Electrochemical oxidation technology has advantages such as high catalytic performance, environmental friendliness, and simple operation, and it has the potential to degrade M/NPs in water. In this work, we proposed a Ti/Sb-SnO anode modified by co-doping with Sm-Mn composite intermediate layer for the electrochemical oxidation degradation of polystyrene nanoplastics (PS NPs) in water. Experimental results showed that the Ti/Sm-Mn-Sb-SnO anode exhibited the best PS NPs removal efficiency (58.75 %) and the longest electrode lifespan (825 h). The doping of composite intermediate layer elements possessed a more uniform and dense crack structure on the anode surface, as well as the formation of a fuller crystal structure, effectively increasing the active sites and specific surface area for electrochemical process. Moreover, material characterization and theoretical calculations confirmed that the synergistic effect of the bimetal facilitates the electron transfer process between Sn and Sb, improves current mass transfer efficiency, and promotes the occurrence of redox reactions. Combined with DFT calculations and the identification of intermediate products, the degradation pathways of PS NPs were analyzed, which mainly included electrophilic substitution (benzene ring hydroxylation), C-C and C-H bond cleavage (chain breakage and ring opening), and hydrogen atom addition reactions. This modification strategy not only provides a new approach for NPs degradation through electrochemical oxidation but also offers theoretical basis and technical support for the future application of M/NPs pollution control in water environments.