Schottky-like photo/electro-catalytic carbon nanotube composite ultrafiltration membrane reactors

Abstract

Stimuli-responsive membrane reactors offer advanced strategies towards simultaneous separation and degradation of persistent organic contaminants, allowing for triggered response through photo or electro stimuli. However, the scalable fabrication of stimuli-responsive nanoporous membranes with high selectivity and catalytic reactivity is still challenging in practical application. Here, photo-electro responsive membranes were designed by assembling carbon nanotubes (CNT) scaffolds decorated with conformal nanoscale SnO2 coatings. The membranes, built from spinnable CNT materials supported the generation of a unique class of ultrathin and flexible ultrafiltration membranes with thicknesses down to 25 nm and pore size as narrow as ∼20 nm. The CNTs were used as effective conductive photosensitizers to promote charge transfer from the graphitic to the SnO2 layer, supporting synergistic effects arising from generated Schottky-like diodes to improve the photo/electro-catalytic activity of nanocomposite membranes. The SnO2-CNT membranes exhibited high water permeance of 2.24 × 103 L m−2 h−1.bar−1, and faster reaction kinetics of 77.6 × 10−3 for acetaminophen degradation, which was 2–10 times higher than the kinetics achieved by currently available catalytic membrane reactors. The structural stability and outstanding performance of SnO2-CNT membranes were maintained over 8 reuse cycles with ∼99% degradation efficiency against acetaminophen in 60 min. The unique solid-state fabrication method of uniformly coated catalytic metal oxide on well aligned CNTs provides a scalable feasible approach to produce high-performance ultrafiltration photo/electro-catalytic membrane reactors towards cost-effective water purification at a competent reaction rate.