Visible-light-driven Fe2O3 nanoparticles/TiO2 array photoelectrode and its photoelectrochemical property

Optimization of optical and structural properties of Al2O3/TiO2 nano-laminates deposited by atomic layer deposition for optical coating

Optimizing the atomic layer deposition (ALD) process of films is particularly important in preparing multilayer interference films. In this work, a series of Al₂O₃/TiO₂ nano-laminates with a fixed growth cycle ratio of 1:10 were deposited on Si and fused quartz substrates at 300 °C by ALD. The optical properties, crystallization behavior, surface appearance and microstructures of those laminated layers were systematically investigated by spectroscopic ellipsometry, spectrophotometry, X-ray diffraction, atomic force microscope and transmission electron microscopy. By inserting Al₂O₃ interlayers into TiO₂ layers, the crystallization of the TiO₂ is reduced and the surface roughness becomes smaller. The TEM images show that excessively dense distribution of Al₂O₃ intercalation leads to the appearance of TiO₂ nodules, which in turn leads to increased roughness. The Al₂O₃/TiO₂ nano-laminate with a cycle ratio 40:400 has relatively small surface roughness. Additionally, oxygen-deficient defects exist at the interface of Al₂O₃ and TiO₂, leading to evident absorption. Using O₃ as an oxidant instead of H₂O for depositing Al₂O₃ interlayers was verified to be effective in reducing absorption during broadband antireflective coating experiments.

Shape Controlled Synthesis of Copper Vanadate Platelet Nanostructures, Their Optical Band Edges, and Solar-Driven Water Splitting Properties

We report the morphological and size tailored rational and facile synthesis of copper vanadate nanostructures via sonication assisted sol gel method. Field emission scanning electron microscopy (FESEM), indicated irregular and nanoflakes morphologies for the as synthesized copper vanadate (CV-120) and copper vanadate calcined at 250 °C (CV-250). The semispherical platelets shaped morphology revealed for the copper vanadate calcined at 550 °C (CV-500). The XRD patterns confirm the monoclinic and triclinic crystal phases for CV-250 and CV-500, respectively. The optical properties of CV-250 and CV-500 via UV-DRS showed significant absorption in the visible regime at λ = 565 nm and 670 nm with band gap 2.2 eV and 1.84 eV, respectively as calculated from Kubelka-Munk (KM) equation via Tauc’s plot. The values of band edge positions of CV-250 and CV-550 straddle with the hydrogen (HER) and oxygen evolution reaction (OER) potentials. The photoelectrodes of CV-250 and CV-500 fabricated by adsorption desorption method to test their photoelectrochemical (PEC) water splitting performance in the three-electrode cell. The onset photocurrent potential is observed at ~0.42 V, which reached to saturation at 1.05 V. The photocurrent density at saturation is ~0.65 mA/cm² for CV-250 and CV-500, respectively.