Enhancement in the photo-electrocatalytic activity of SnO2-Sb2O4 mixed metal oxide anode by nano-WO3 modification: Application to trypan blue dye degradation

The SnO2-Sb2O4 (MMO) and SnO2-Sb2O4-WO3 (MMO-WO3) electrodes were prepared by electrodeposition followed by dip coating and characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. The electrochemical (EC) and photoelectrochemical (PEC) degradation studies were carried out on trypan blue (TB) dye. These studies revealed that the characteristics and performance of MMO electrode improved significantly on nano-WO3 modification. The oxygen evolution potential (OEP) increased from 2.07 V (vs Ag/AgCl) to 2.21 V and the accelerated service life increased by 1.7 times. 88 and 93% color removal was achieved on electrolysis for 240 min using MMO electrode; whereas, 100% color removal was achieved within 120 min by both EC and PEC using MMO-WO3. The percentage chemical oxygen demand (COD) removal achieved using MMO electrode by EC and PEC were only 60 and 63% respectively; whereas, it increased to 78 and 84% with MMO-WO3 electrode. A probable pathway for TB degradation was proposed on the basis of liquid chromatography-mass spectrometry (LC-MS) analysis and quantum chemical calculations were performed on TB molecule to corroborate the proposed degradation pathway.