Synergistic electrochemical and bimetallic (FeMo@C) catalytic activation of periodate for high-efficiency degradation of contaminants: Role of electron-rich Mo(IV) sites

This study explores the strategic integration of electrochemistry and transition-metal catalysis to achieve efficient activation of periodate (PI) in advanced oxidation processes (AOPs). A bimetallic FeMo@C-coated graphite felt cathode was synthesized via an impregnation–pyrolysis approach and applied for the degradation of bisphenol A (BPA) through enhanced electro- and co-catalytic PI activation (E-FeMo@C-GF-PI). Comprehensive structural, chemical, and electrochemical characterization of the electrocatalyst revealed the significant role of electron-rich Mo(IV) sites in promoting efficient electron transfer and potential regeneration of low-valent metal species via the Fe(III)/Fe(II) redox cycle. As a result, the electro-assisted FeMo@C-GF system exhibited markedly superior BPA degradation kinetics (kapp = 0.35 min−1) compared with catalytic (0.02 min−1) or electrochemical (0.01 min−1) activation alone. The pronounced synergistic effect based on kapp (synergy index = 9.3) underscores the outstanding performance of the coupled electro-catalytic PI activation strategy. Mechanistic investigations using electron paramagnetic resonance (EPR) spectroscopy, radical quenching experiments, and probe molecule degradation tests identified iodate radicals (IO3•⁻) as the possible dominant reactive species in the E-FeMo@C–GF–PI system, with significant contribution of high-valent molybdenum species and only minor contributions from hydroxyl radicals (∼4%) to contaminant degradation. Furthermore, the FeMo@C–GF–PI system demonstrated robust degradation of a mixture of organic contaminants in real water matrices (DI water, tap water, secondary effluent and primary effluent), highlighting it potential for practical water and wastewater treatment applications.