Semiconductor oxide nanostructures for converting and storing solar energy into chemical energy: A clean and sustainable way to produce hydrogen
High-performance photoelectrodes play a crucial role in the development of the technological application of photoelectrochemical cells (PEC) for green hydrogen production. In general, a photoelectrode consists of two essential components: the photoabsorber and the substrate. The photoabsorber is often the protagonist while the substrate is often considered a supporting resource. Elevated temperatures are predominantly employed in the manufacture of photoelectrodes for PEC as a resource to obtain the desired phase and/or activation of the photoabsorber layer. However, the effect of this process on the substrate, widely used glass coated with a conductive layer of fluorine-doped tin oxide (FTO, chemical formula F:SnO2), is often overlooked in the literature or related exclusively to ion diffusion from the FTO (Sn4+) to the photoabsorber. Here, a systematic study was conducted to evaluate the potential impact of ion diffusion from a glass/FTO substrate on the properties of the hematite photoabsorber. This investigation explores the beneficial and harmful impacts of heat treatments on photoelectrode fabrication, revealing the phenomenon of ion diffusion and its consequences. The polymeric precursor synthesis (PPS) method for industrial use was chosen as the manufacturing route. For substrate evaluation, two types of glass substrates, aluminoborosilicate and quartz, coated with FTO (ABS/FTO and QTZ/FTO respectively), were subjected to thermal treatments following the PPS protocol. The findings related to intentional and unintentional ion doping emphasize the importance of understanding the true effect of heat treatments on photoelectrode properties to unlock their full potential in photoelectrochemical applications.