Effective electrochemical trichloroethylene removal from water enabled by selective molecular catalysis

Electrochemistry can provide a viable and sustainable way to treat water polluted by chlorinated volatile organic compounds. However, the removal and valorization of trichloroethylene (TCE) remains as a challenge due to the lack of suitable electrocatalysts with high selectivity and activity. We herein present a catalyst, comprising cobalt phthalocyanine (CoPc) molecules assembled onto multiwalled carbon nanotubes (CNTs), that can electrochemically decompose aqueously dissolved TCE into ethylene and chloride ions at record high rates with close to 100% Faradaic efficiency. Kinetics studies reveal that the rate-determining step is the first electron transfer without proton involvement. We further show that replacing the CNT support with reduced graphene oxide (rGO) can improve the TCE treatment efficacy because of the two-dimensional nanostructure of rGO and its stronger interaction with CoPc molecules. Incorporating the CoPc/rGO catalyst into an electrified membrane filtration device, we demonstrate 95% TCE removal from simulated water samples with environmentally relevant TCE and electrolyte concentrations.