Self-assembled electrocatalytic TiO2 nanowire membrane for multifunctional water purification

Abstract

To overcome the limitations of conventional membranes that rely solely on size exclusion, we present an innovative strategy for fabricating functional nanowire membranes with integrated electrocatalytic properties. Starting from a titanium mesh, we employ an alkali hydrothermal process to dissolve and restructure it into layered titanate crystals (NaTi₃O₆(OH)·2H₂O), which are subsequently converted into hydrogen titanate (H₂Ti₃O₇) nanowires under acidic conditions. Calcination then yields anatase-phase TiO₂ nanowires forming a robust, self-supporting membrane with a hierarchical submicron pore network. The incorporation of Sb-doped SnO₂ as an electrocatalyst imparts high electrochemical activity, with the membrane achieving a charge density of 140 mC/cm² when loaded with 2.5 mg/cm² of Sb–SnO₂. Pore size can be precisely tuned by adjusting hydrothermal reaction parameters, such as pH, temperature, and duration, yielding a membrane with an average pore diameter of 0.28 μm. The resulting electrocatalytic microfilter demonstrates multifunctional water treatment capabilities in both batch and continuous operation modes, effectively removing turbidity (∼90 %), organic contaminants (>50 %), and bacteria (>3 log removal) from secondary wastewater effluents through a synergistic combination of electrochemical oxidation and size-based filtration. Scavenger experiments reveal that reactive chlorine species and hydroxyl radicals (•OH) are the dominant oxidants involved in organic degradation, with hydrogen peroxide acting synergistically, and quantification results confirm that •OH is the primary species contributing to the degradation process. In addition, the membrane exhibits reduced fouling propensity due to its ability to decompose organic matter, which contributes to organic fouling, and to inactivate bacteria, which are responsible for biofouling. This electrocatalytic nanowire membrane represents a significant advancement in next-generation filtration technologies, offering integrated separation and redox functions for enhanced water purification and sanitation in large facilities and home use.