Potentiostatic Electrodeposition of Cu2O under Light and Dark for Photoelectrochemical Hydrogen Generation Applications

Potentiostatic electrodeposition conducted at various deposition voltages from lactate-stabilized copper sulfate electrolyte was used for preparation of Cu2O layers for Photoelectrochemical (PEC) production of hydrogen. A novel approach based on an application of light during the electrodeposition is utilized to suppress the potential drop in the Cu2O layer during the potentiostatic deposition. Structures prepared under dark and light on an Ag substrate are analyzed by X-Ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM) and Linear Sweep Voltammetry (LSV). It was shown that the application of light increases the deposition rate due to the contribution of the photogenerated carriers. The deposition voltage affects the photoresponse of light deposited structures but causes only a negligible change in dark deposited structures. The light deposited samples exhibited a higher photoresponse for all deposition voltages. The presented study suggests the light potentiostatic electrodeposition as an attractive approach for the preparation of Cu2O structures for cheap and efficient photoelectrochemical water splitting applications

Comprehensive Degradation Analysis of NCA Li-Ion Batteries via Methods of Electrochemical Characterisation for Various Stress-Inducing Scenarios

Lithium-ion (Li-ion) batteries with Ni-based cathodes are leading storage technology in the fields of electric vehicles and power-grid applications. NCA (LiNiCoAlO2) batteries are known for their troublesome degradation tendencies, and this susceptibility to degradation raises questions regarding the safety of their usage. Hence, it is of vital importance to analyse the degradation of NCA batteries via methods which are applicable to onboard systems, so that the changes in the battery’s state of health can be addressed accordingly. For this purpose, it is crucial to study batteries stressed by various conditions which might induce degradation of different origins or magnitudes. Methods such as electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and incremental capacity analysis (ICA) have been used in battery research for years, however, there is a lack of published studies which would analyse the degradation of NCA batteries by simultaneous usage of these methods, which is essential for a comprehensive and confirmatory understanding of battery degradation. This study intends to fill this research gap by analysing the degradation of NCA batteries via simultaneous usage of EIS, GITT, and ICA methods for common stress-inducing operating conditions (over-charge, over-discharge, and high-current charging)

Preparation and gas-sensing properties of very thin sputtered NiO films

We present results on very thin NiO films which are able to detect 3 ppm of acetone, toluene and n-butyl acetate in synthetic air and to operate at 300°C. NiO films with 25 and 50 nm thicknesses were prepared by dc reactive magnetron sputtering on alumina substrates previously coated by Pt layers as heater and as interdigitated electrodes. Annealed NiO films are indexed to the (fcc) crystalline structure of NiO and their calculated grain sizes are in the range from 22 to 27 nm. Surface morphology of the examined samples was influenced by a rough and compact granular structure of alumina substrate. Nanoporous NiO film is formed by an agglomeration of small grains with different shapes while they are created on every alumina grain

Fabrication of passive and active photonic coupling structures using fs-laser ablation

Femtosecond laser ablation on Si generates 2D ripple structures, known as laser induced periodic surface structures (LIPSS) and pinholes. We fabricated membranes with 20 to 50 μm thickness perforated by an array of tapered pinholes up to 5 μm in diameter and 10 to 20 μm spacing. Within several micrometer the pinholes transform into hollow photonic waveguides with constant diameter from 1μm to 2μm. Such structures offer a 3D photonic coupling device for polymer Y-branch- and MMI-splitter. We measured a considerable change of electrical resistivity for 500 ppm H2 in air using Si/SiO2/TiO2 substrates with 2D LIPSS. We propose to investigate 3D waveguide arrays also for photonic-chemical sensors

Preparation of laser induced periodic surface structures (LIPSS) and their transfer into sensing elements

Semiconducting metal oxides are widely used for solar cells, poto-catalysis, bio-active materials and gas sensors. Besides the material properties of the used semiconductor,the specific surface topology of the sensor determines the device performance. We investigate the preparation and transfer suitable metals onto LIPPS structures on glass for gas sensing applications

Дослідження характеристик композитних електрохромних плівок на основі Ni(OH)2, полівінілового спірту і полівінілпірролідону

The cost of electrochromic “smart” windows ranges from 200–800 USD/m2. The high cost is determined by the small volume of production and the high cost of vacuum methods for applying device layers. The development of other methods could lead to lower costs and further mass use of “smart” windows. The paper presents the work on improving the electrochemical method of deposition of electrochromic films based on Ni(OH)2. Composite electrochromic films were deposited from Ni(NO3)2 solutions with the addition of water-soluble polymers – polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and mixtures thereof. Two PVA grades and one PVP grade were used in the experiments. As a result, six films were obtained from solutions of different compositions and concentrations of polymers. An investigation of the optical properties of the films in the initial state showed that there is no intense absorption of light in the entire visible spectrum and the transmission corresponds to a glass substrate. Thus, the formed electrochromic films will not produce tints and visible light absorption in the finished electrochromic element. The electrochemical and electrochromic characteristics of the films differed significantly depending on the amount and specific polymers used. The film obtained from a solution containing PVA grade 24-99 was the most electrochemically active, while the best electrochromic characteristics were in the film deposited from a solution of a mixture of PVP grade 24-99 and PVP. Moreover, the films obtained in solutions containing separately PVA grade 24-99 and PVP had worse electrochromic characteristics, and the electrochemical characteristics were the same or worse relative to the film obtained in a mixture of polymers. The results of the method of electrochemical impedance spectroscopy showed compliance with the found electrochromic and electrochemical characteristics of the formed films.Ціна електрохромних «розумних» вікон коливається у інтервалі 200–800 USD/м2. Висока вартість визначається малим обсягом виробництва та дорожнечею вакуумних методів нанесення шарів пристрою. Розробка інших методів може призвести до зниження вартості та масового використання «розумних» вікон. Представлено роботу з удосконалення електрохімічного методу нанесення електрохромних плівок на основі Ni(OH)2. Нанесення композитних електрохромних плівок здійснювали з розчинів Ni(NO3)2 з додаванням водорозчинних полімерів – полівінілового спирту (ПВС), полівінілпіралідону (ПВП) та їх сумішей. В експериментах використовували дві марки ПВС та одну марку ПВП. В результаті було отримано 6 плівок з розчинів різних складів та концентрацій полімерів. Дослідження оптичних властивостей плівок у початковому стані показало, що в них відсутнє інтенсивне поглинання світла у всьому видимому спектрі та пропускання відповідає скляній підкладці. Таким чином, сформовані електрохромні плівки не будуть давати відтінків і видимого поглинання світла готовому електрохромному елементі. Електрохімічні та електрохромні характеристики плівок залежно від кількості та конкретних використовуваних полімерів значно відрізнялися. Найбільш електрохімічно активною була плівка, отримана з розчину, що містить ПВС марки 24-99, при цьому найкращі електрохромні характеристики були плівки осадженої з розчину суміші ПВП марки 24-99 і ПВП. Більш того, плівки, отримані в розчинах, що містять окремо ПВС марки 24-99 і ПВП, мали електрохромні характеристики гірші, а електрохімічні характеристики такі ж або гірші у порівнянні з плівкою, отриманої з суміші полімерів. Результати методу електрохімічної імпедансної спектроскопії показали відповідність знайденим електрохромним та електрохімічним характеристикам сформованих пліво

AWG-spectrometer to analyze absorption spectra of optical gas sensors fabricated by femtosecond laser processing

By a simple femtosecond laser process, we fabricated metal-oxide/gold composite films for electrical and optical gas sensors. We designed a dripple wavelength AWG-spectrometer, matched to the plasma absorption wavelength region of the composite films. H2/CO absorptions fit well with the AWG design for multi gas detection sensor array