Hydrogen production and simultaneous photoelectrocatalytic pollutant oxidation using a TiO2/WO3 nanostructured photoanode under visible light irradiation

Abstract

Photoelectrochemical (PEC) hydrogen production and simultaneous organic waste degradation is a re-emerging field. The main challenge of this technique has been the synthesis of new photoanode materials that are active towards visible light. Coupling close band gap energy oxides can be used to obtain materials with new optical and electronic properties. For this purpose, Ti/TiO 2 /WO 3 electrodes were prepared by electrochemical anodization followed by templating and cathodic electrodeposition. The nanostructured bicomponent material was used as a photoanode for simultaneous hydrogen generation and organic dye degradation. A good photoactivity response (11 mA cm -2 ) was obtained under UV and visible light irradiation, when compared to pure TiO 2 (8 mA cm -2 ). Optimization of photoelectrochemical conditions revealed that pH optimization had a major impact on H 2 production, resulting in satisfactory hydrogen generation efficiency (46%) and dye removal (100% discoloration and 85% reduction in TOC). A dye oxidation mechanism is proposed, based on LC-MS/MS analyses. The TiO 2 /WO 3 photoanode could potentially be used for environmental remediation and hydrogen generation under solar irradiation.

Semiconductor Electrode Materials Applied in Photoelectrocatalytic Wastewater Treatment—an Overview

“…This was attributed to the improvement of the solar spectrum absorption and, additionally, by the enhancement of the photogenerated carrier transport. The coupling of WO 3 with TiO 2 was also applied in Reactive Black 5 degradation in the PEC process [181]. The bicomponent material applied as a photoanode provided faster dye degradation combined with simultaneous improved hydrogen generation in comparison with the unmodified photoelectrode.…”

Photoelectrocatalytic Hydrogen Production Using a TiO2/WO3 Bilayer Photocatalyst in the Presence of Ethanol as a Fuel

“…On the contrary, deposition of titania on the top of the WO3 film may result in the passivation of surface defects of the latter, and this would limit charge recombination sites. Passivation of surface defects has been observed and recorded in TiO2/WO3 and other semiconductor combinations [24][25][26][27][28][29][30]. In addition, titania films are more stable than WO3 films; therefore, the top titania layer provided protection against aggressive electrolytes.…”

New trends on photoelectrocatalysis (PEC): nanomaterials, wastewater treatment and hydrogen generation

“…In this photoelectrochemical system, the holes oxidate the wastewater compounds in the photoanode, while the electrons are drawn to the photocathode through the external circuit, where the reduction occurs, producing hydrogen. Very diverse photoanodes have been used in the degradation of wastewater pollutants coupled to hydrogen production including TiO2 [27], TiO2/WO3 [29], TiO2/Pt [28], C-N-TiO2 nanotubes (TiNTs) [30], Bi/BiVO4 [31], g-C3N4 [32], Ti-Fe2O3 [34] and g-C3N4/Ag/AgCl/BiVO4 [35]. Platinum is the most used cathode material, as it has generally shown the best performance as a hydrogen evolution catalyst, with low overpotential and high reaction rates in acidic environments.…”

“…Commonly, studies are performed using small volume (i.e. <100 mL) one compartment reactors; alternatively, other studies use a H-type reactor where the anolyte and catholyte compartments are usually separated by a membrane [29,34]. It has also been proven the possibility of using a filter-press reactor operated in batch recirculation mode [27].…”