Visible-light Bi-Fe-Nb-O photoanodes for solar-light driven hydrogen production

Currently, CO₂ emission is the main cause of climate change and its various related environmental impacts. Therefore, we have as a prime the development of clean sources of energy. The hydrogen economy is very attractive in this regard, however, when generated from the methane reform, there are also large-scale CO₂ emissions. Thus, this research aims to develop and characterize bismuth and iron niobate-based photoanodes for hydrogen production via water photoelectrolysis. Bi₂Fe_xNbO₇ films were synthesized by the sol-gel method and deposited on FTO coated glass plates by dip-coating technique. The influence of heat treatment (400, 500 and 600°C) and amount of iron on the structure (Bi₂Fe_xNbO₇, x = 0, 0.8, 1, 1.2) were evaluated. Optical, structural and morphological properties were performed, as well as photoanode efficiency in photocurrent assays. The results indicate that the increase of temperature as well as the amount of iron leads to a higher absorption capacity and hence to lower band gap values. Regarding the structural properties, it was possible to observe the BFNO phase in the samples treated at 500 and 600°C. The films heat-treated at 400°C had a heterogeneous texture and a good covering. At 600°C there were some cracks in films surface. Therefore, samples with more iron and treated at 400°C showed better responses in photocurrent assays. It can be concluded that bismuth-iron niobate has a great potential to be applied in photoelectrolysis hydrogen production.