Fan_NW_SourceData

Current methods for electrocatalytic destruction of nitrate in drinking water require metal catalysts to achieve sufficient nitrate removal. However, metal-based catalysts involve complicated synthesis, increase treatment costs, and can lead to leaching of metals into treated water. In this study, we achieved nitrate reduction performance comparable to that of metal-based catalysts via electrofiltration through a metal-free nanoporous electrified membrane (EM) containing unmodified pristine carbon nanotubes (CNTs). Experimental results coupled with computational fluid dynamics simulations elucidated how the decreased diffusion boundary layer in the flow-through CNT-EM mitigates diffusion limitations to enhance overall nitrate reaction activity. Furthermore, defects in CNTs were identified as the catalytic active sites by comparing the activity of EMs containing acid-treated metal-free CNTs and CNTs with added defects. Through density functional theory and molecular dynamics calculations, we demonstrated enhanced *NO₂ and *NO adsorption energies at intrinsic defect sites, which are present in most commercial CNTs and become more accessible to nitrate ions under flow-through operation. Finally, the long-term stability, tolerance of environmental interferences, and sufficient nitrate removal and scalability to meet drinking water standards were demonstrated in real surface water, exhibiting the outstanding performance of the metal-free CNT-EM for practical applications. By elucidating how nanoporous electrofiltration enables dynamic matching of reaction and transport rates, this study demonstrates a new strategy to drastically improve electrocatalytic reaction performance without complex catalyst materials innovation, bridging existing gaps for nitrate removal in drinking water treatment related to the use of metal-based catalysts.