Hierarchical Co–Pi Clusters/Fe2O3 Nanorods/FTO Micropillars 3D Branched Photoanode for High-Performance Photoelectrochemical Water Splitting

Abstract

In this study, an efficient hierarchical Co–Pi cluster/Fe2O3 nanorod/fluorine-doped tin oxide (FTO) micropillar three-dimensional (3D) branched photoanode was designed for enhanced photoelectrochemical performance. A periodic array of FTO micropillars, which acts as a highly conductive “host” framework for uniform light scattering and provides an extremely enlarged active area, was fabricated by direct printing and mist-chemical vapor deposition (CVD). Fe2O3 nanorods that act as light absorber “guest” materials and Co–Pi clusters that give rise to random light scattering were synthesized via a hydrothermal reaction and photoassisted electrodeposition, respectively. The hierarchical 3D branched photoanode exhibited enhanced light absorption efficiency because of multiple light scattering, which was a combination of uniform light scattering from the periodic FTO micropillars and random light scattering from the Fe2O3 nanorods. Additionally, the large surface area of the 3D FTO micropillar, together with the surface area provided by the one-dimensional Fe2O3 nanorods, contributed to a remarkable increase in the specific area of the photoanode. Because of these enhancements and further improvements facilitated by decoration with a Co–Pi catalyst that enhanced water oxidation, the 3D branched Fe2O3 photoanode achieved a photocurrent density of 1.51 mA cm−2 at 1.23 VRHE, which was 5.2 times higher than that generated by the non-decorated flat Fe2O3 photoanode.