Iron phosphomolybdate complexes in electrocatalytic reduction of aqueous disinfection byproducts

The crystalline iron phosphomolybdate-bipyridylpropane complex (FePM-BPP) synthesized by hydrothermal method in water possesses two [P₄Mo₆^VO₃₁]¹²⁻ subunits bridged by one Fe center. We discovered that the FePM-BPP complex is an electrocatalyst active at close-to-neutral pH in aqueous electrolytes, catalyzing reduction of a variety of carcinogenic disinfection byproducts (DBPs) such as chloroform, N-nitrosodimethylamine (NDMA), and bromate. Deposition of FePM-BPP onto the surface of carbon electrodes led to accelerated chloroform electroreduction at near-neutral pH, at potentials in the −0.52 to −0.27 V vs standard hydrogen electrode (SHE) range, with surface-normalized rate constant of chloroform reduction at ca. 140 L m^-2h⁻¹, and over 40% of chloroform reduced at −0.27 V vs SHE after 1 h. The surface-normalized first-order rate constants of the NDMA and bromate electroreduction at − 0.77 V vs SHE and pH 5.5 or 6.4 were estimated to be 250 and 150 L m^-2h⁻¹, respectively. The simple synthetic route with low-cost, earth-abundant components, and versatility indicate that FePM-BPP can be considered for incorporation into DBP reduction processes as a heterogeneous catalyst.