Fabrication of novel SnO2-Sb/carbon aerogel electrode for ultrasonic electrochemical oxidation of perfluorooctanoate with high catalytic efficiency

A novel SnO2-Sb/CA electrode, possessing high surface area, strong adsorption capacity, good electrical conductivity and electrocatalytic activity, was firstly proposed for ultrasonic electrochemical oxidation (US-EC) of persistent high concentration perfluorooctanoate (PFOA) in this study. The optimal calcination temperature for sinking micro-sized SnO2-Sb particles existed on the surface of CA into the structure of CA as nanoparticles was 600 °C. Its application on degrading PFOA (60 mL of 100 mg L−1) exhibited efficient electrocatalytic performance. After 5 h electrolysis, over 91% of PFOA was degraded with a first-order kinetic constant of 0.52 h−1 and over 86% TOC removal was achieved, while 47% PFOA removal and 33% TOC removal were obtained in traditional electrochemical (EC) process. The main role of determining the decomposition efficiency, i.e., the mass transport, hydroxyl radical (·OH) generation and electrode surface reaction, were greatly enhanced in US-EC system. Additionally, the generated intermediates existing on electrode surface and in solution were separately detected after different electrolysis time and the proper mechanism for efficient removing PFOA in US-EC process was investigated in detail. At early reaction stage (<0.5 h), the intermediate products on SnO2-Sb/CA surface were C5F11COO−, C4F9COO−, C3F7COO−, C2F5COO−, CF3COO−, while in solution were C5F11COO−, C4F9COO−, C3F7COO−. At late reaction stage (>5 h), the intermediates either on electrode surface or in solution became the same including C5F11COO−, C4F9COO−, C3F7COO−.

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► Novel SnO2-Sb/CA composite electrode with high efficiency was firstly fabricated.
► Optimal temperature for sinking micro SnO2-Sb into CA as nanoparticles was 600 °C.
► 91% and 86% of PFOA and TOC removal was respectively achieved after reaction 5 h.
► Reasonable catalytic mechanism of US-EC process with SnO2-Sb and CA was proposed.