Optimizing hematite photoanodes: a critical review of hydrothermal, sol–gel, ALD, and electrodeposition techniques

In pursuing efficient and sustainable solar energy conversion, hematite (α-Fe₂O₃) photoanodes have garnered considerable attention as promising material due to their following advantages—band gap, abundance, and stability. Therefore, this comprehensive review meticulously evaluates four prominent fabrication techniques for α-Fe₂O₃ photoanodes: hydrothermal synthesis, sol–gel method, atomic layer deposition (ALD), and electrodeposition. Each technique is assessed based on its principles, advantages, limitations, and influence on the resulting photoanodes' structural, morphological, and photoelectrochemical properties. The review underscores the importance of these techniques in solar energy conversion. Moreover, through comparative analysis, the review emphasizes the potential of these methods to optimize photoanode performance and proposes future research directions to surmount prevailing challenges. Furthermore, the review briefly delves into additional fabrication techniques and their contributions to the evolution of α-Fe₂O₃ photoanodes.