RESUMO
The continued pollution, waste, and unequal distribution of the limited amount of fresh water on earth are pushing the world into water scarcity crisis. Consequently, development of revolutionary, cost-effective, and efficient techniques for water purification is essential. Herein, molten flux method was used for the preparation of micro-sized Al-doped SrTiO3 photocatalyst loaded with RhCr2O3 and CoOOH cocatalysts via simple impregnation method for the photo-assisted degradation of Congo red dye under UV and visible irradiation compared with P25 standard photocatalyst. In addition, photoelectrochemical analysis was conducted to reveal the separation and transfer efficiency of the photogenerated e-/h+ pairs playing the key role in photocatalysis. SEM and TEM analyses revealed that both P25 and the pristine SrTiO3 have spherical shapes, while Al-doped SrTiO3 and the sample loaded with cocatalysts have cubic shapes with a relatively higher particle size reaching 145 nm. In addition, the lowest bandgap is due to Al+3 ion doping and excessive surface oxygen vacancies, as confirmed by both UV-Vis diffuse-reflectance and XPS analyses. The loading of the cocatalysts resulted in a change in the bandgap from n-type (pristine SrTiO3 and Al-SrTiO3) into p-type (cocatalyst loaded sample) as exhibited by Mott-Schottky plots. Besides, the cocatalyst-loaded sample exhibited good performance stability after 5 cycles of the photocatalytic removal of Congo red dye. OH· radical was the primary species responsible for CR degradation as confirmed by experiments with radical scavengers. The observed performance of the prepared samples under both UV and visible light could foster the ongoing efforts towards more efficient photocatalysts for water purification.
RESUMO
Although anodic nanoporous (ANP) WO3 has gained a lot of attention for photoelectrochemical water splitting (PEC-WS), there is still a lack of efficient WO3-based photoanodes with sufficient light absorption and good e-/h+ separation and transfer. The decoration of ANP WO3 with narrow bandgap semiconductor quantum dots (QDs) can enhance charge carrier transfer while reducing their recombination, resulting in a high PEC efficiency. In this study, ANP WO3 was synthesized via an anodic oxidation process and then modified with Bi2S3 QDs via successive ionic layer adsorption and reaction (SILAR) process and examined as a photoanode for PEC-WS under ultraviolet-visible illumination. The ANP WO3 photoanode modified with ten cycles of Bi2S3 QDs demonstrated the highest current density of 16.28 mA cm-2 at 0.95 V vs RHE, which is approximately 19 times that of pure ANP WO3 (0.85 mA cm-2). Furthermore, ANP WO3/Bi2S3 QDs (10) photoanode demonstrated the highest photoconversion efficiency of 4.1 % at 0.66 V vs RHE, whereas pure ANP WO3 demonstrated 0.3 % at 0.85 V vs RHE. This can be attributed to the proper number of Bi2S3 QDs significantly enhancing the visible light absorption, construction of type-II band alignment with WO3, and improved charge separation and migration. The modification of ANP WO3 with nontoxic Bi2S3 QDs as a prospective metal chalcogenide for enhancing visible light absorption and PEC-WS performance has not yet been investigated. Consequently, this study paves the path for a facile technique of designing effective photoelectrodes for PEC-WS.