Enhanced electrochromic performance of nickel oxide-based ceramic precursor films

An electrochromic (EC) material is able to change colour under the influence of an electric potential. The development of energy efficient smart windows for architectural applications is at present the subject of intense research for both economic and environmental reasons. Thus there is now a considerable research effort to develop smart windows with natural colour switching properties, i.e. shades of grey. In this regard, a promising metal oxide with a brown-black anodic colouring state is NiO or hydrated nickel oxide (also called nickel hydroxide , Ni(OH)2). The present work outlines the preparation and optimisation of EC nickel oxide-based ceramic precursor films onto various conducting substrates towards smart window applications. The literature review chapter outlines the different methods used for generating ceramic materials, a review of electrochromism and history of nickel oxide-based EC materials are also provided. Thins films have been deposited by an electrochemical cathodic deposition and by aerosol assisted chemical vapour deposition (AACVD) technique. For hydrated NiO films prepared by electrochemical cathodic deposition, various deposition factors at small-scale area (30 x 7 mm) have been investigated in order to optimise the films properties towards EC applications. With deposition on fluorine-doped tin oxide (SnO2:F, FTO) on glass, use of nickel nitrate (0.01 mol dm-3) solution at an applied current of -0.2 mA (-0.1 mA cm-2) for 800 s was optimal for preparing uniform deposits with a porous interconnecting flake-like structure, which is generally regarded as favourable for the intercalation/deintercalation of hydroxide ions during redox cycling. The as-deposited hydrated NiO films showed excellent transmittance modulation (Δ%T = 83.2 at 432 nm), with average colouration efficiency (CE) of 29.6 cm2 C-1 and low response times. However, after 50 voltammetric cycles, the cycle life was found to fade by 17.2% from charge measurements, and 28.8 % from in-situ transmittance spectra measurements. In an attempt to prepare films with improved durability, AACVD has been used for the first time in the preparation of thin-film EC nickel(II) oxide (NiO). The as-deposited films were confirmed to be cubic NiO from analysis of powder X-ray diffraction data, with an optical band gap that decreased from 3.61 to 3.48 eV with an increase in film thickness (in the range 330 820 nm). The EC properties of the films were investigated as a function of film thickness, following 50, 100 and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm-3). Light modulation of the films increased with the number of conditioning cycles. EC response times were < 10 s and generally longer for the colouration than the bleaching process. The films showed excellent stability when tested for up to 10000 colour/bleach cycles. Using a calculation method based on the integration of experimental spectral power distributions derived from in-situ visible region spectra over the CIE 1931 colour-matching functions, the colour stimuli of the NiO-based films, and the changes that take place on reversibly switching between the bleached and coloured forms have been calculated. Films prepared by both deposition techniques gave positive a* and b* values to produce orange. However, in combination with low L* values, the films were perceived as brown-grey. Hydrated NiO prepared via electrochemical cathodic deposition suffers from two well-known limitations; firstly, it shows catalytic properties towards the oxygen evolution reaction (OER), which is a process very close to the Ni(II)/Ni(III) redox process. Secondly, hydrated NiO shows poor cycling durability in alkaline solution. The co-deposition of single or bimetallic additives is an effective way to overcome these problems. Electrochemical studies revealed that the combination of cobalt (10%) with lanthanum (5%) was found to be the optimal composition for preparing hydrated NiO films with improved film durability. Finally, the emphasis of this work was on scale-up of deposition. Therefore, optimised deposition conditions from small scale (3.0 x 0.7 cm) have been used to successfully deposit films on two different sized large-area (10 x 7.5 and 30 x 30 cm) conducting substrates

Electrochromic and colorimetric properties of nickel(II) oxide thin films prepared by aerosol-assisted chemical vapor deposition

Aerosol-assisted chemical vapor deposition (AACVD) was used for the first time in the preparation of thin-film electrochromic nickel(II) oxide (NiO). The asdeposited films were cubic NiO, with an octahedral-like grain structure, and an optical band gap that decreased from 3.61 to 3.48 eV on increase in film thickness (in the range 500−1000 nm). On oxidative voltammetric cycling in aqueous KOH (0.1 mol dm−3) electrolyte, the morphology gradually changed to an open porous NiO structure. The electrochromic properties of the films were investigated as a function of film thickness, following 50, 100, and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm−3). Light modulation of the films increased with the number of conditioning cycles. The maximum coloration efficiency (CE) for the NiO (transmissive light green, the “bleached” state) to NiOOH (deep brown, the colored state) electrochromic process was found to be 56.3 cm2 C−1 (at 450 nm) for films prepared by AACVD for 15 min followed by 100 “bleached”-to-colored conditioning oxidative voltammetric cycles. Electrochromic response times were <10 s and generally longer for the coloration than the bleaching process. The films showed good stability when tested for up to 10 000 color/bleach cycles. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry the color stimuli of the electrochromic NiO films and the changes that take place on reversibly oxidatively switching to the NiOOH form were calculated from in situ visible spectra recorded under electrochemical control. Reversible changes in the hue and saturation occur on oxidation of the NiO (transmissive light green) form to the NiOOH (deep brown) form, as shown by the track of the CIE 1931 xy chromaticity coordinates. As the NiO film is oxidized, a sharp decrease in luminance was observed. CIELAB L*a*b* coordinates were also used to quantify the electrochromic color states. A combination of a low L* and positive a* and b* values quantified the perceived deep brown colored state

Economic Independence of Muslim Women: Importance, Need and Impact

In modern times the unstable economic situation of the MuslimWorld is a matter of fact that it is important to eliminateself-imposed and baseless restrictions on women's economicactivities. As well as it is important that the current Islamic societyis extremist in terms of ban and homelessness for Muslim womenand it is important to do this in the Islamic context. Developingcenturies can eliminate the economic crisis by eliminating thepotential of women. The role of ideal women is a role model of thewomen of the Muslim Ummah. In this article under consideration it has been analyzed in the light of the ideal of Muslim women and their economic self-sufficiency of the period of the post and post. What can be the guidingprinciples of Muslim women's economic self-determination in thepresent situation

Fabrication of NiO photoelectrodes by aerosol-assisted chemical vapour deposition (AACVD)

Nanostructured nickel oxide (NiO) photoelectrodes were fabricated with controlled morphology and texture using single-step aerosol-assisted chemical vapour deposition (AACVD). The durable one-step film fabrication process resulted in highly crystalline columnar structure. Texture controlled films were also fabricated from granular to crystalline columnar morphology by controlling the deposition temperature. The thin film electrodes are highly reproducible and possess an optical bandgap of ∼3.7 eV and exhibit cathodic photocurrent

Electrochromic and Colorimetric Properties of Nickel(II) Oxide Thin Films Prepared by Aerosol-Assisted Chemical Vapor Deposition

Aerosol-assisted chemical vapor deposition (AACVD) was used for the first time in the preparation of thin-film electrochromic nickel­(II) oxide (NiO). The as-deposited films were cubic NiO, with an octahedral-like grain structure, and an optical band gap that decreased from 3.61 to 3.48 eV on increase in film thickness (in the range 500–1000 nm). On oxidative voltammetric cycling in aqueous KOH (0.1 mol dm^–3) electrolyte, the morphology gradually changed to an open porous NiO structure. The electrochromic properties of the films were investigated as a function of film thickness, following 50, 100, and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm^–3). Light modulation of the films increased with the number of conditioning cycles. The maximum coloration efficiency (CE) for the NiO (transmissive light green, the “bleached” state) to NiOOH (deep brown, the colored state) electrochromic process was found to be 56.3 cm² C^–1 (at 450 nm) for films prepared by AACVD for 15 min followed by 100 “bleached”-to-colored conditioning oxidative voltammetric cycles. Electrochromic response times were <10 s and generally longer for the coloration than the bleaching process. The films showed good stability when tested for up to 10 000 color/bleach cycles. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry the color stimuli of the electrochromic NiO films and the changes that take place on reversibly oxidatively switching to the NiOOH form were calculated from in situ visible spectra recorded under electrochemical control. Reversible changes in the hue and saturation occur on oxidation of the NiO (transmissive light green) form to the NiOOH (deep brown) form, as shown by the track of the CIE 1931 <i>xy</i> chromaticity coordinates. As the NiO film is oxidized, a sharp decrease in luminance was observed. CIELAB <i>L*a*b*</i> coordinates were also used to quantify the electrochromic color states. A combination of a low <i>L*</i> and positive <i>a*</i> and <i>b*</i> values quantified the perceived deep brown colored state