Recent advances on solar water splitting using hematite nanorod film produced by purpose-built material methods

Photoelectrochemical cells offer a more elegant, clean, and sustainable way to store solar energy as chemical energy through the splitting of water into its primitive form (H-2 and O-2). Among many metal oxides pointed as candidates for this application, the fundamental characteristics of hematite (alpha-Fe2O3), such as abundance, excellent chemical stability in an aqueous environment, and favorable optical band gap, emerged as a promising photoanode. Although attractive, the poor optoelectronic properties necessitate a large application of overpotential for split water assisted by solar irradiation, limiting the high performance of this material. Since the electrode was built using materials in nanoscale, significant advances were achieved. This review highlights new insights and recent progress in the use of a purpose-built material process to build hematite electrodes for improving photocatalytic activity. In addition, reduction on the required overpotential by effective control-treatment of morphology and surface of vertically aligned hematite nanorods will be addressed. An interesting set of results were also discussed revisiting a novel strategy recently presented in the literature and complementary advances was illustrated. These latest efforts aid in pointing out the challenges or obstacles to be overcome using this morphology and in defining new opportunities.