Boosting hematite photoelectrode water splitting activity by dopant addition
The development of new sources of energy free from fossil fuels is currently increasing due to the global demand for energy and the reduction of environmental impacts. The production of H2 from the electrolysis of water-assisted by solar energy is gaining attention nowadays, in order to produce clean and renewable energy. Hematite (α-Fe2O3) has been intensively investigated as a promising photoanode due to its wide absorption range of sunlight spectra, narrow band gap (2.1 eV) and good chemical stability. However, the low electronic conductivity and the short service life of the photogenerated charges decrease the material's efficiency for oxygen evolution reactions (OER). Thus, aiming to overcome the presented limitations, some strategies were used in this work, such as the use of hydrothermal synthesis methodology for the fabrication of highly homogeneous α-Fe2O3 photoelectrodes with precise control of nanostructured morphology, combined with the use of Nb as modifier element, which is abundant in the Brazilian region and has excellent catalytic properties. After the initial success and the good photoelectrochemical results obtained with the α-Fe2O3 materials modified with Nb, problems related to the reproducibility of such electrodes were faced. Thus, considering the restrictions arising from the COVID-19 pandemic, during the gradual return to the laboratory, efforts were dedicated to developing a new strategy for the materials manufacturing process, in order to guarantee their reproducibility. Once this stage was reached, investigations combining different characterization techniques were carried out. The preliminary results obtained showed an effective improvement in the photoelectrochemical performance of α-Fe2O3 photoanodes modified with Nb when compared to pure films, and justify the interest in pursuing the objectives proposed in this work.