Development of spray pyrolysis-synthesised Bi2O3 thin films for photocatalytic applications.

Photocatalysis is a green and cost-effective approach to environmental remediation. While TiO2 is considered one of the benchmark photocatalysts, alternative materials such as Bi2O3 have recently attracted increasing scientific attention as prospective visible light photocatalysts. This study aimed to develop a strategy for Bi2O3 thin film deposition via ultrasonic spray pyrolysis and systematically study process variables for the deposition of ß-Bi2O3 thin films for photocatalytic applications. To achieve the aim, the precursor solution concentration as well as deposition and annealing temperature were optimised. The structural, optical, morphological, chemical and wettability properties of the obtained Bi2O3 thin films were investigated with respect to the effect on the photocatalytic oxidation of 10 ppm methyl orange (MO). The highest photocatalytic activity (48% in 5 h) under UV-A was recorded for the ß-Bi2O3 film deposited using 0.1 M precursor solution at 300 °C and heat-treated for 1 h in air at 350 °C. Deposition at 300 °C resulted in an amorphous film structure, whereas annealing at 350 °C led to the formation of the ß-Bi2O3 phase with the dominant facet orientation (220). These results show the suitability of spray pyrolysis for the deposition of Bi2O3 thin films with promising results for MO dye degradation, expanding the range of suitable photocatalytic materials.

Efficient photoelectrocatalytic degradation of amoxicillin using nano-TiO2 photoanode thin films: A comparative study with photocatalytic and electrocatalytic methods.

Excessive utilization of antibiotics in human, animal, and aquaculture poses a substantial threat to human health and the environment. Photoelectrochemical processes are increasingly applied for water remediation because they generate oxidizing species and mineralize organic pollutants, making even small water quantities more amenable for utilization. Thus, this study presents the fabrication of an efficient nano-TiO2 photoanode thin film (PATF) specifically designed for the photoelectrocatalytic (PEC) degradation of amoxicillin (AMX). The TiO2 PATFs were deposited on fluorine-doped tin oxide (FTO) substrate using an ultrasonic spray pyrolysis process with various titanium isopropoxide (TTIP) acetylacetone (AcacH) molar ratios (1:1 to 1:10). The PEC oxidation of AMX was investigated using various molar ratios of TTIP:AcacH TiO2 PATF/FTO by linear sweep voltammetry, and a 1:8 M ratio of PATF exhibited superior PEC oxidation activity than other TiO2 PATFs. Subsequently, the PEC degradation efficiency of AMX was compared with that of photocatalytic (PC) and electrocatalytic (EC) methods. The results demonstrated that the PEC process effectively eliminated 76.2% of AMX within 120 min at 0.8 V, outperforming the removal rates attained by the EC (32.3%) and PC (52.6%). Notably, increasing the voltage to 1.0 V accelerated the PEC degradation of AMX, attaining a removal efficiency of 91.2% within 90 min and exceeding 95% within 120 min.

Transparent TiO2 thin films with high photocatalytic activity for indoor air purification.

The development of low-material-quantity, transparent, anatase TiO2 nanoparticle free thin films as photocatalytic materials together with a profound understanding of their photocatalytic activity under ultraviolet (UV-A) and visible (VIS) light is crucial for environmentally friendly indoor air photocatalytic coatings. In this work, a TiO2 thin film modified by an increased amount of acetylacetone in the precursor solution with a material quantity of 0.2 mg cm-2 was successfully deposited on a borosilicate glass substrate by ultrasonic spray pyrolysis. VOC degradation as a single model pollutant and in mixtures under different operating conditions was studied in a multi-section continuous flow reactor. Under UV-A the reaction rate constants for heptane and toluene oxidation as individual pollutants were 1.7 and 0.9 ppm s-1, respectively. In 9 ppm VOC mixtures of acetaldehyde, acetone, heptane and toluene all the compounds were completely oxidized in a reaction time of less than 50 s. The TiO2 film showed moderately high photocatalytic activity under VIS light. The conversions of acetaldehyde, acetone, heptane and toluene in 9 ppm VOC mixtures under VIS light reached 100, 100, 78 and 31%, respectively. The synthesized TiO2 film shows promising ability in indoor air purification from VOCs. The results of this study give an extensive estimation of the thin film's photocatalytic efficiency and provide valuable data for future applications in environmental remediation.

Synthesis Control of Charge Separation at Anatase TiO2 Thin Films Studied by Transient Surface Photovoltage Spectroscopy.

For the efficient photocatalytic oxidation of organic pollutants at surfaces of semiconductors, photogenerated holes shall be separated toward the surface and transferred to reactive surface sites, whereas the transfer of photogenerated electrons toward the surface shall be minimized. In this Research Article, the identification of suitable synthesis control of charge separation combined with an in-depth understanding of charge kinetics and trapping passivation mechanisms at the related surfaces can provide tremendous opportunities for boosting the photocatalytic performance. In this work, a comprehensive transient surface photovoltage spectroscopy study of charge separation at anatase TiO2 thin films, synthesized by ultrasonic spray pyrolysis from titanium(IV) isopropoxide (TTIP)-acetylacetone (AcacH) based precursor is reported. By varying the amount of AcacH in the precursor solution, an experimental approach of synthesis control of the charge transfer toward TiO2 surface is provided for the first time. An increased amount of AcacH in the precursor promotes transition from preferential fast electron to preferential fast hole transfer toward anatase surface, correlating with a strong increase of the photocatalytic decomposition rate of organic pollutants. Suitable mechanisms of AcacH-induced passivation of electron traps at TiO2 surfaces are analyzed, providing a new degree of freedom for tailoring the properties of photocatalytic systems.