Electrochemical oxidation of phenol in chloride containing electrolyte using a carbon-coated Ti4O7 anode

Abstract

Magnéli-phase Ti4O7 is an excellent anode material for electrochemical advanced oxidation process (EAOP). However, the development of Ti4O7 electrodes is always limited by the high cost and high energy consumption in their preparation process. In this study, the carbon-coated Ti4O7 electrode was successfully synthesized by an in-situ pyrolysis method, which exhibited high specific surface area (143.8 m2 g−1) and efficient electron transfer (47.3 Ω). The accelerated service life was measured to be 102.5 h, demonstrating its excellent stability. EAOP performance of the C-coated Ti4O7 electrode was evaluated under various operating conditions. The result showed that a complete degradation of phenol (100 mg L−1) was obtained in 60 min, under the condition of 0.1 M NaCl electrolyte and 20 mA cm−2 current density. Owing to the high oxygen evolution potential (OEP, 2.25 V vs. RHE) of the C-coated Ti4O7 electrode, high TOC removal ratio (68.9%) and low energy consumption (113.8 kWh kg−1TOC) were achieved under the optimal condition. Moreover, the mechanism of phenol degradation was investigated by linear sweep voltammetry (LSV) and free radical scavenging experiments. The results indicated that the degradation of phenol can be mainly attributed to the synergistic effects between adsorbed ·OH (M(·OH)) and Cl−, rather than the direct electron transfer process (DET) on the surface of the C-coated Ti4O7 electrode. This study provides an efficient strategy for the mineralization of phenolic wastewater by the C-coated Ti4O7 electrode.