Potentiostatic Reversible Photoelectrochromism: An Effect Appearing in Nanoporous TiO₂/Ni(OH)₂ Thin Films

Abstract

In the field of energy saving, finding composite materials with the ability of coloring upon both illumination and change of the applied electrode potential keeps on being an important goal. In this context, chemical bath deposition of Ni(OH)2 into nanoporous TiO2 thin films supported on conducting glass leads to electrodes showing both conventional electrochromic behavior (from colorless to dark brown and vice versa) together with photochromism at constant applied potential. The latter phenomenon, reported here for the first time, is characterized by fast and reversible coloration upon UV illumination. The bleaching kinetics shows first order behavior with respect to the Ni(III) centers in the film, and an order 1.2 with respect to electrons in the TiO2 film. From a more applied point of view, this study opens up the possibility of having two-mode smart windows showing not only conventional electrochromism but also reversible darkening upon illumination.

High‐Temperature Photochromism of Fe‐Doped SrTiO3 Caused by UV‐Induced Bulk Stoichiometry Changes

“…In analogy to the voltage‐induced electrochromism due to a redistribution of oxygen vacancies in Fe:STO (electrocoloration), one might thus also expect existence of light‐induced photochromism. Photochromic effects based on color centers have been frequently reported for oxides with metals (SrTiO 3 , TiO 2 , and many other oxides) . However, those photochromic experiments usually take place around room temperature or much below and the corresponding phenomena are not caused by oxygen stoichiometry changes of the bulk under illumination.…”

Bi2O3 nanoparticles incorporated porous TiO2 films as an effective p‐n junction with enhanced photocatalytic activity

“…Semiconductor photocatalysis is an active area of research owing to the increasing concern over environmental cleaning and hydrogen production . Among the semiconductors, anatase titanium dioxide (TiO 2 ) has been widely used because of its wide applications in dye‐sensitized solar cells, photocatalysis, smart surface coatings, lithium‐ion batteries, photo/electrochromics, and sensors . As for water purification, TiO 2 thin films are preferred to separate easily after the degradation process .…”

Carbon Black-Doped Anatase TiO2 Nanorods for Solar Light-Induced Photocatalytic Degradation of Methylene Blue

“…The photoelectric properties of the specimens were characterized by an Autolab Electrochemical workstation (Nova2.1.1 software, Metrohm, China). EIS was measured by a three-electrode system, glassy carbon electrode was selected as a counter electrode, saturated calomel electrode as a reference electrode, stainless steel mesh (10 μm) as the base of the working electrode, a 1.0 M KOH solution as an electrolyte, and the light source was a 300 W xenon lamp (PLS–SXE300/300UV, PerfectLight, Beijing). , During the test of AC impedance, the frequency range and amplitude were set at 100–10 MHz and 0.01 V, respectively. The PL spectra were measured by a steady/transient fluorescence spectrometer (FLS 980-STM, Edinburgh, U.K.), and the excitation wavelength was set at 250 nm.…”