Photoelectrochemical (PEC) water splitting reactions are promising for sustainable hydrogen production from renewable sources. We report here, the preparation of α-Fe 2 O 3 /Fe 3 O 4 composite films via a single-step chemical vapor deposition of [Fe(O t Bu) 3 ] 2 and their use as efficient photoanode materials in PEC setups. Film thickness and phase segregation was controlled by varying the deposition time and corroborated through cross-section Raman spectroscopy and scanning electron microscopy. The highest water oxidation activity (0.48 mA/cm 2 at 1.23 V vs RHE) using intermittent AM 1.5 G (100 mW/cm 2 ) standard illumination was found for hybrid films with a thickness of 11 μm. This phenomenon is attributed to an improved electron transport resulting from a higher magnetite content toward the substrate interface and an increased light absorption due to the hematite layer mainly located at the top surface of the film. The observed high efficiency of α-Fe 2 O 3 /Fe 3 O 4 nanocomposite photoanodes is attributed to the close proximity and establishment of 3D interfaces between the weakly ferro-(Fe 2 O 3 ) and ferrimagnetic (Fe 3 O 4 ) oxides, which in view of their differential chemical constitution and valence states of Fe ions (Fe 2+ /Fe 3+ ) can enhance the charge separation and thus the overall electrical conductivity of the layer.

Innovative coatings that can shield functional surfaces from environmental and temperature impact are essential to increase the life time of devices and reduce the maintenance costs. Superhydrophobic ceramic coatings with self‐cleaning properties and stability at high‐temperatures (up to 300 °C) are eco‐friendly alternative to aggressive surface‐cleaning agents. Despite the wide range of possible applications for hydrophobic surfaces, the practical implementation of currently used polymeric fluoro‐silanes is restricted by their low thermal stability, which is an essential figure of merit. Herein, a nonadhesive coating with an exceptionally low surface‐energy (contact angle ≈180°) is developed by chemical conjugation of MgAl2O4 spinel nanoparticles (NPs) with perfluorodecyltrichlorosilane (FDTS). The cross‐conjugation of FDTS and MgAl2O4 is substantiated by condensation reactions between the surface‐rooted hydroxyl groups and chloride ligands of fluorosilane. Compared with the coatings based on pure fluorosilanes, the FDTS@MgAl2O4 core‐shell particles unify optical transparency and high‐temperature stability imparted by spinel reinforcement with the superhydrophobicity induced by FDTS periphery. Addition of TiO2 NPs to MgAl2O4 sol unifies the ultrahydrophobicity of FDTS@MgAl2O4 with UV‐absorption properties of TiO2 to produce a new UV‐ and temperature‐resistant ultrahydrophobic coating system.