Columnar activated carbon (GAC) supported SnO2, SnO2-Sb2Ox, and SnO2-Sb2Ox -CeO2 as three-dimensional particle electrode for electrochemical degradation of phenol: Mechanism of metal doping effect

Granular activated carbon (GAC) supported SnO2, SnO2-Sb2Ox, and SnO2-Sb2Ox-CeO2 were prepared as particle electrodes for phenol electro-degradation. Sb doping could enhance surface property by providing more exposed active surface. Furthermore, Sb doping also enhances the voltammetry charge and the oxygen evolution potential of SnO2/GAC, and reduces the charge transfer resistance of SnO2/GAC particle electrode. Enhanced voltammetry charge indicates more active sites for phenol degradation; higher oxygen evolution potential indicates lower oxygen evolution and higher ▪OH formation; while lower charge transfer resistance indicates higher charge transfer capability of electrodes which favors phenol degradation. Although further doping of Ce could reduce carrier transfer efficiency, one the other hand, it reduces the Oads content on electrode surface, the voltammetry charge and the oxygen evolution potential of electrode, all of which could restrain phenol degradation efficiency. Due to above reasons, SnO2-Sb2Ox/GAC was the most active particle electrode for phenol degradation with the highest average current efficiency (ACE) of 60% and lower energy consumption (Esp) of 28.7 kWh/kg COD. Uv-vis and LG-MS reveal that Sb doping significantly suppressed benzenediol and benzoquinone formation, hence favoring phenol degradation.