(Invited) Bioinspired Design: Hybrid Nifeooh/α-Fe2O3/Graphene Photoelectrodes with Advanced Water Oxidation Performance

Abstract

In this talk, I am going to present how electrodeposition allows the synthesis of complex photoelectrode architectures with precisely controlled structure and composition. The presented photoelectrode assembly follows a bioinspired design, where the different components have different function. Fe2O3 was responsible for light absorption, the graphene (GR) framework ensured proper charge transport, while the FeNiOOH overlayer allowed facile water oxidation kinetics. Photocurrent densities were notably higher compared to the respective single- and two-component counterparts. However, introducing a carbon component to a photoanode raised an additional concern, namely that photogenerated holes can oxidize the underlying nanocarbon framework. By adding a third component to the system (i.e., a FeNiOOH overlayer), we were able to suppress the corrosion of the nanocarbon matrix, while all the benefits gained by the presence of GR were still present. When graphene nanoflakes are present, two additional processes occur: better transport of photogenerated electrons towards the back contact, due to the highly conductive nature of graphene and some of the photogenerated holes can also be transported to graphene and oxidize it (note the metallic nature of graphene). Finally, if the surface of hematite is decorated with a co-catalyst, which passivates the surface states, holes are rapidly transported to the co-catalyst and to the substrate. Most importantly, because of the rapid hole-transfer to the co-catalyst, the pathway leading to the corrosion of graphene is successfully eliminated.