Photocatalytic materials development is very important in the environmental perspective. They can be employed in clean energy production by hydrogen generation as well as in wastewater treatment by photocatalysis. One of the key subjects in this area is the advancement of materials with low band gap, thus the catalyst can use the sunlight more efficiently. Based on this issue, this research aims to develop photocatalysts based on bismuth, niobium and iron (Bi2FexNbO7), analyze the influence of iron concentration (x = 0, 0.8, 1 and 1.2) and characterize through optical and structural analysis. The powder samples were synthetized by sol gel method. Band gap estimation was performed throw UV-Vis analysis and Kubelka-Munk method. XRD technique was employed to phase determination and structural characterization. The catalyst with no iron (Bi2NbO7) presented a mix of three phases from reagents and a band gap of 3.14 eV. The iron addition promotes crystalline photocatalysts with high visible light absorption ability and hence lower band gap, 2.09 eV. Further analysis must be performed; however, based on structural and optical proprieties, these materials can efficiently be employed both in wastewater treatment and hydrogen production.

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Resumo O presente trabalho avaliou os efeitos da adição de resíduos de vidro sodo-cálcico e de erva-mate sobre a absorção de água, porosidade e resistência mecânica de um material cerâmico. Os pós homogeneizados foram compactados por prensagem uniaxial e submetidos a queima de 900 e 1100 °C a 2 °C.min-1. Os resultados mostraram que a adição de vidro e erva-mate à argila produziu materiais cerâmicos com retração linear entre 0,3 e 6%, absorção de água entre 5,3 e 34%, porosidade aparente de até 41% e resistência mecânica entre 0,5 e 20 MPa. Os materiais queimados a 1100 °C foram os que obtiveram as melhores combinações de propriedades, podendo ser aplicados na produção de blocos, telhas ou revestimento cerâmico de acordo com as necessidades específicas da aplicação.

The seek for feasible sustainable mobility alternatives is a major concern of the society nowadays. By its turn, the production of hydrogen represents one of the main lines of study on clean energy, since hydrogen presents the possibility of storage and association with other renewable energy sources. In this regard, photo-electrolysis is a promising option for hydrogen generation. This process optimizes the electrolysis of water by using external energy to increase the potential of a photo-electrode, which must be a material that absorbs sunlight (usually a semiconductor activated by solar radiation), promoting the generation of H2 at the cathode. Titanium dioxide (TiO2) is the most applied semiconductor in photocatalytic applications. However, the band gap of this material limits its activity only under UV light, disregarding about 90% of incident solar radiation. Researchers explore catalysts that can be activated under visible light, such as bismuth-based mixed oxide semiconductors, which have attracted interest because of their excellent stability, visible light absorption, and photocatalytic properties. This research aims to develop and characterize photo-anodes based on bismuth, niobium and iron oxides (Bi2FexNbO7), for production of hydrogen via photo-electrolysis of water. The films were produced by the sol-gel process and deposited under a conductive glass slide by dip-coating. The effect of the iron concentration was evaluated by UV-Vis spectroscopy and SEM analysis, in order to estimate its hydrogen production potential.