Nanostructured Anodic Iron Oxides for Photoelectrochemical Applications: Recent Advances and Perspectives

The growing global demand for energy has positioned photoelectrochemical water splitting as a highly promising method for producing gaseous hydrogen. For this process to be sufficiently effective, the use of semiconductor electrodes with specific properties is required. Among the already proposed semiconductors for this purpose, iron oxides are particularly promising. Therefore, this review paper aims to discuss recent advancements in the fabrication of nanostructured iron oxides through an anodic oxidation of metallic iron and, above all, the possibilities of utilizing these materials in photoelectrochemical systems. The first part of the paper discusses the procedure of Fe anodization with particular emphasis on the correlation between synthesis conditions and the morphology, composition, and properties of the obtained oxide layers. The most important part of the paper is a detailed discussion of the applications of anodically generated iron oxides in photoelectrochemical systems. Strategies for modifying Fe2O3 layers to enhance their photoelectrochemical properties have also been presented. Finally, examples of other applications of anodic iron oxides, as well as challenges and perspectives of the anodic oxidation method, were described.