Understanding and Steering the Surface-Pollutant Interaction over Nanoscale Zero-Valent Iron toward Proton-Coupled...

Surface engineering strategies and interfacial reaction mechanisms are of fundamental significance to the development of material-based environmental remediation technologies. Despite the tremendous efforts in manipulating the surface properties of materials exemplified by nanoscale zerovalent iron (nZVI), the interfacial reaction mechanism has scarcely been steered through modulating the surface-pollutant interaction. Herein, we demonstrate that extracellular polymeric substance (EPS) modification essentially reshapes the reactivity and selectivity of nZVI via the surface-pollutant interaction toward various nitroaromatics, based on a spectrum of degradation experiments, fluorescence quenching experiments, proton conductivity measurements, kinetic isotopic effect determination, and computational analysis. Distinctively, EPS modification diverges the nZVI reactivity with remarkable promotion, negligible change, and significant inhibition toward 4-nitrophenol (PNP), nitrobenzene, and 3-nitrobenzenesulfonate (NBS), respectively. Moreover, the corresponding interfacial reaction mechanism is fundamentally changed. The desirable proton-coupled electron transfer (PCET) route is activated via the association of hydrogen-bonding networks harnessing the phenolic group of PNP and the proton-shuttling characteristic of EPS, while the electrostatic repulsion induced by the sulfonate group of NBS significantly impedes the reaction by eliminating the PCET pathway. Through understanding and steering the surface-pollutant interaction, this study illuminates the precision design and selection of materials for efficient water decontamination and site remediation.