Photoelectrochemical performance and photoelectrocatalytic degradation of organic compounds using Ga:WO 3 thin films

Photoelectrocatalytic reactor improvement towards oil-in-water emulsion degradation

Oil-in-water (O/W) emulsion is critical wastewater that is challenging to eliminate and requires a long treatment process, and it is necessary to develop highly effective removal methods before releasing it into natural water sources. This research has selected the photoelectrocatalytic (PEC) technique to solve this problem by developing a PEC reactor for high efficiency in O/W degradation and understanding the essential factors related to the PEC reactor's efficiency improvement. The PEC reactor has been designed on a large scale with suitable positioning of an electrode that is, designing a light source near the anode electrode to enhance light irradiation efficiency and including a circulating pump to provide continuous flow to the solution through the electrode surface. We studied the main factors of supporting the electrolyte, electrode characteristics, and catalytic process. We investigated the O/W-degradation efficiency using a UV/Vis spectrophotometer, chemical oxygen demand (COD) measurement, and GC-MS analysis. We optimized the PEC reactor using the developed BiVO₄ photoanodes and placed them parallel with the zinc plates. Then, we controlled the applied potential at 1.0 V in 0.1 M Na₂SO₄ supporting an electrolyte under visible light irradiation. The developed PEC reactor can be degraded in the O/W emulsion up to 76% and decreased the COD value up to 78% for 7h. This PEC cell can be completely decomposed of many functional groups, such as carbonyl, ester, nitrile, amine, phosphate, chloro group, and nitro group, that were contained in the O/W substance. The highlight of this research is the designed light source and circulating pump inside of the PEC reactor to enhance the light irradiation, refresh the anode electrode, and understand the critical factor for the improvement of O/W-degradation efficiency. This PEC reactor presents a high-efficiency O/W degradation with practical use and a fast process suitable for further application in high turbidity of wastewater treatment from the oil industry.

Photocurrent Response and Progesterone Degradation by Employing WO3 Films Modified with Platinum and Silver Nanoparticles

The effect of silver (Ag⁰ ) and platinum (Pt⁰ ) metallic nanoparticles (NPs) on WO₃ film was investigated by studying the photocurrent response under polychromatic irradiation. The structural phase revealed by X-ray diffraction analysis indicates a monoclinic crystal nanostructure. WO_3, Ag⁰ /WO_3, and Pt⁰ /WO₃ electrodes were used to degrade 0.35 mg L^-1 progesterone hormone in aqueous solution under polychromatic irradiation for 3h. The studies on degradation were investigated under electrochemically assisted heterogeneous photocatalysis (EHP) conditions. For photodegradation of progesterone, higher performance was achieved when WO₃ was functionalized and when the EHP configuration was adopted with bias at +0.7 V vs Ag/AgCl. This study reveals that incorporation of metallic NPs onto a semiconductor increases its efficiency, thereby preventing electron-hole recombination in the photocatalyst and photoelectrochemical limitations of WO₃ due to surface plasmon resonance and the trapping state. Therefore, efficient advances in the degradation of organic contaminants during water treatment can be realized.

Visible-light photoelectrodegradation of diuron on WO3 nanostructures

The degradation of pesticide diuron has been explored by photoelectrocatalysis (PEC) under visible light illumination using two different WO₃ nanostructures, obtained by anodization of tungsten. The highest degradation efficiency (73%) was obtained for WO₃ nanosheets synthesized in the presence of small amounts of hydrogen peroxide (0.05 M). For that nanostructure, the kinetic coefficient for diuron degradation was 133% higher than that for the other nanostructure (anodized in the presence of fluoride anions). These results have been explained by taking into account the different architecture and dimensions of the two WO₃ nanostructures under study.