Nb2O5 is a promising photocatalyst for degradation of organic pollutants and production of H2 (renewable and green fuel) from water is an alternative to overcome environmental and energy concerns. Therefore, the effect of Nb precursor and synthesis method on the Nb2O5 physical-chemical properties and photocatalytic performance were investigated in this work. X-ray diffraction and Raman spectroscopy results showed that synthesis parameters had a significant impact on the structural properties of the materials obtained. The synthesis parameters were able to tune Nb2O5 crystalline phase, morphology and specific surface area. Nb2O5 sample obtained by hydrothermal method resulted in materials with smaller size and homogeneous particles compared to the other samples, which resulted in a higher specific surface area (200 m2 g-1) and surface hydroxylation. Nb2O5 samples were active to promote both the degradation of Rhodamine B and amiloride, the specific surface area and surface hydroxylation play a key role in the performance of the materials. The most active sample for organic pollutant degradation was also active in H2 production, additionally, the decoration with Pt nanoparticles increased its performance. This work describes the effect of synthesis parameters of Nb2O5 on its photocatalytic properties and demonstrates the potential application of this material in heterogeneous photocatalysis. NbO O Nb2O H renewable fuel concerns Therefore physicalchemical physical chemical Xray X ray phase 200 (20 m g1 g 1 g-1 amiloride additionally photocatalysis 20 (2 g- 2 (

The development of visible-light active photocatalysts is vital to harvest the solar irradiation and build efficient photoelectrochemical devices. Bismuth oxyhalide (BiOCl, BiOBr and BiOI) materials stand out due to their remarkable properties, e.g., the band gap energy can be tuned from 1.9 to 3.4 eV depends on the halide employed. However, the hydrothermal synthesis of this material class was not properly investigated and compared. Then, we evaluated the effect of the hydrothermal treatment in the BiOX’s structural, electronic, morphological and textural properties and the relationship with their photocatalytic performance. Methylene blue (MB) dye was used as probe for photocatalytic performance evaluation under ultraviolet (UV) and visible (Vis) radiation. BiOCl and BiOBr samples showed a good photoactivity under both UV and visible radiation, on other hand the BiOI samples was not active, likely due to the fast charge recombination. BiOCl and BiOBr samples exhibit a favorably interaction with MB dye, because their surfaces are negatively charged. BiOCl samples were able to promote around 40 and 80% of the MB dye degradation under visible and UV radiation, respectively. The samples were also employed as photoanode for O2 evolution, BiOI sample exhibited the best performance, due to the synergistic effect of photocatalysis and electrocatalysis.

CO2 REDUCTION TO HYDROCARBONS AND OXYGENATES: FUNDAMENTALS, STRATEGIES AND CHALLENGES. The development of renewable energy sources (e.g., solar and wind) moves foward, the tendance for replacing fossil fuels increases. However, these technologies have as primary barriers to industrial processes’ efficiency and especially storage. Thus, CO2 reduction routes using these energy sources could chemically store part of the energy as fuels or chemicals, offering alternatives to current oil and gas industry. This process is inspired by photosynthesis, e.g., photochemical or electrochemical processes, using homogeneous or heterogeneous catalysts. Nevertheless, this reaction is thermodynamically unfavorable and has very slow kinetics, given the high stability of the CO2 molecule and the complexity of the redox reactions involved. Therefore, this review addresses this process’s kinetic and thermodynamic challenges, and the fundamental concepts of the photo(electro)chemical processes for CO2 reduction, besides presenting and discussing the materials with the potential to act as catalysts. The main reaction mechanisms and advances in the understanding of such processes are discussed, as well as future perspectives

Heterostructured semiconductors are materials with unique features formed by combination of two or more semiconductors with suitable interface between them. The study of the heterostructures aim the development of physico-chemical and photocatalytic properties higher than their isolated phases, which makes it possible to obtain higher efficiency and lower cost in several technological processes. Recently the heterostructured materials have been extensively used in the development of alternative technologies either for environmental pollution control or for renewable energy production, among other applications. However, the obtaining of a heterostructure with suitable features is not trivial. In this way, this review article presents a broad discussion about methods of obtaining heterostructures formed by semiconductors and their applications in the photochemical processes, mainly in the environmental field. It will be addressed the use of the heterostructures in photocatalytic application for the organic pollutants degradation, heavy metals removal, the inactivation of pathogenic microorganisms, beyond of the volatile organic compounds (VOC’s) photooxidation and the photocatalytic abatement of nitrogen oxide (NOx) in gaseous phase. Finally, a discussion about the carbon dioxide (CO2) photoreduction and hydrogen (H2) production focusing mainly in the chemical energy production will be presented.

Despite the fact that Brazil is the world’s largest niobium mineral producer, governmental interest in exploration of the mineral leading to more valuable derived materials is scarce, which has reduced the country’s knowledge about a wider range of technological applications for this metal. Niobium pentoxide stands out due its remarkable electronic, structural, and textural properties. Therefore, this review aims to highlight its main properties, synthetic methods, and applications, with a particular focus on photocatalysts based on Nb2O5. This review will highlight the potential of Nb2O5 and encourage the study of niobium and its compounds in technological and environmental applications.