Optical Properties and UV Sensing Response of Nitrogendoped TiO2 Thin Film by CVD

This work was demonstrated a cold-wall chemical vapour deposition (CVD) setup to prepare nitrogen (N)-doped titanium dioxide (TiO2) thin film on glass substrates, which presents semi-transparent yellowish surface. The prepared N-doped TiO2 film is homogeneous and possesses polycrystalline anatase structure. The transmittance measurement was carried out in the ultraviolet-visible spectral region to evaluate the film thickness, optical constants, and the optical band gap was determined by Tauc plot. A metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector by the Pt/N-doped TiO2 film has shown a positive response towards UV illumination

2D Germanane-MXene Heterostructures for Cations Intercalation in Energy Storage Applications

Heterostructures offer an exceptional possibility of combining individual 2D materials into a new material having altered properties compared to the parent materials. Germanane (GeH) is a 2D material with many favorable properties for energy storage and catalysis, however, its performance is hindered by its low electrical conductivity. To address the low electrochemical performance of GeH, a heterostructure of GeH and Ti3C2Tx is fabricated. The Ti3C2TX is a layered material belonging to the family of MXenes. The resulting heterostructure (GeMXene) at a defined mass ratio of GeH and Ti3C2Tx shows superior capacitive performance that surpasses that of both pristine materials. The effect of the size of cations and anions for intercalation into GeMXene in different aqueous salt solutions is studied. GeMXene allows only cation intercalation, which is evidenced by the gravimetric electrochemical quartz crystal microbalance (EQCM) technique. The capacitive performance of the GeMXene is compared in neutral, acidic, and alkaline electrolytes to determine the best electrochemical performance. This unleashes the potential use of GeMXene heterostructure in different electrolytes for supercapacitors and batteries. This work will pave the way to explore the heterostructures of other 2D materials such as novel MXenes and functionalized germanane for highly energy-storage efficient systems, and beyond.Web of Science34

TiO2 ALD Coating of Amorphous TiO2 Nanotube Layers: Inhibition of the Structural and Morphological Changes Due to Water Annealing

The present work presents a strategy to stabilize amorphous anodic self-organized TiO2 nanotube layers against morphological changes and crystallization upon extensive water soaking. The growth of needle-like nanoparticles was observed on the outer and inner walls of amorphous nanotube layers after extensive water soakings, in line with the literature on water annealing. In contrary, when TiO2 nanotube layers uniformly coated by thin TiO2 using atomic layer deposition (ALD) were soaked in water, the growth rates of needle-like nanoparticles were substantially reduced. We investigated the soaking effects of ALD TiO2 coatings with different thicknesses and deposition temperatures. Sufficiently thick TiO2 coatings (≈8.4 nm) deposited at different ALD process temperatures efficiently hamper the reactions between water and F− ions, maintain the amorphous state, and preserve the original tubular morphology. This work demonstrates the possibility of having robust amorphous 1D TiO2 nanotube layers that are very stable in water. This is very practical for diverse biomedical applications that are accompanied by extensive contact with an aqueous environment

2D functionalized germananes: Synthesis and applications

In the realm of 2D layered materials, the monoelemental group 14 Xene, germanene, as the germanium analog of graphene, has emerged as the next prospective candidate. Preceded by silicon, germanium is widely used in the semiconductor industry; thus, germanene is deemed compatible with existing semiconductor technologies. Germanene consists of mixed sp(2)-sp(3)-hybridized networks in a buckled hexagonal honeycomb structure. Chemical exfoliation of Zintl phases, such as CaGe2, specifically the topotactical deintercalation in acidic media, removes the alkaline earth metal ions Ca2+, giving rise to layered germanane (germanene with the Ge centers covalently saturated with terminal hydrogen atoms). Diverse variants of functionalized germananes (with covalent group(s) termination) can be obtained by varying the topotactical deintercalation precursors, elevating the game with limitless functionalization possibilities for customizable properties or new functionalities. The preparation of Zintl phases to the details of functionalized and modified germananes and their properties, and the additional exfoliation step to achieve mono- or few-layer germananes, are comprehensively covered. The progress and challenges of 2D functionalized germananes in optoelectronics, catalysis, energy conversion and storage, sensors, and biomedical areas are reviewed. This review provides insight into designing and exploring this class of atomically thin semiconductors in realizing future nanoarchitectonics.Web of Scienc

Photoelectrolysis of TiO2 is highly localized and the selectivity is affected by the light

On the way to sustainable prosperity for future generations, photoelectrochemistry is becoming a key area for energy conversion and the environmentally friendly generation of chemical resources because it combines the advantages of electrochemical and photochemical processes. Highly active catalyst materials with excellent selectivity towards the desired reaction are certainly required for efficient processes. Understanding the underlying processes, including detailed in situ information, facilitates the design and development of catalyst materials. In this work, we utilize the scanning photoelectrochemical microscopy for the spatially resolved in situ investigation of the electrochemical and photoelectrochemical evolution of hydrogen, oxygen, reactive oxygen species, and chlorine for energy conversion. Herein, we demonstrate that the activity and the selectivity of the TiO2 photoelectrocatalyst are highly localized despite their apparently uniform composition based on regular morphological characterization. Furthermore, the results suggest that the illumination dramatically changes the selectivity in electrolysis reactions, which is demonstrated on the competing oxygen- and chlorine- evolution reaction. Consequently, this leads to the critical implication that the activity and selectivity should not be considered uniform per se, especially under the illumination. This implies that light might be used for controlling the selectivity in electrolysis reactions. Such discovery shall dramatically impact the optimization of photoelectrocatalysts in general.Web of Science446art. no. 13699

Al2O3/covalent organic framework on 3D-printed nanocarbon electrodes for enhanced biomarker detection

With the advantages of on-demand customization, 3D-printing techniques have elevated the horizon of various fields. The as-printed 3D structures often require postmodification to enhance their properties. Here, we describe the use of molecularly precise covalent framework modification in combination with atomic layer deposition (ALD) to construct advanced sensors. First, a high-stability electrode was obtained by covalent modification of porous nanomaterial [covalent organic frameworks, (COF)] on the activated 3D electrode for the first time. Subsequently, the Al2O3 nanomaterial was coated on the COF-based 3D electrode by the ALD technique. The constructed sensor termed Al2O3/COF/3DE was chosen for the determination of important biomarkers including ascorbic acid, catechol, and dopamine, which showed a high sensitivity for detecting these biomarkers. This work opens avenues for the covalent modification of porous materials on 3D-printed electrodes and deposition of functional material using the ALD technique on the modified 3D electrode surface.Web of Scienc

2D Methyl Germanane Enhanced 3D Printed Photoelectrodes

Abstract 3D printing is a cutting‐edge technology, that allows the printing of 3D objects according to the design provided. Nanocarbon electrodes that can be fabricated using 3D printing technology, suffer from a lack of required properties. For enhancing the photoelectrochemical properties of 3D printed electrodes, functionalized germanenes, belonging to the family of 2D materials are used here. Functionalized germananes are becoming popular for application in photoelectrochemical processes, due to their photoactivity in the visible spectral region and their tunable optoelectronic properties, thanks to covalent functionalization. It is shown that 2D methyl germanane has great potential for photoelectrocatalytic enhancement of 3D printed structures, and this potential goes beyond the demonstrated application of water splitting

The unexpected photoelectrochemical activity of MAX phases: the role of oxide impurities

MAX phases are layered ternary compounds that are mainly studied for their physical properties and their use in the synthesis of MXenes. Their application in energy generation has been investigated and recently, the unexpected photoactivity of MAX phases under the influence of a visible light source has been reported. To investigate the origin of this photoactivity, theoretical calculations and experimental characterisation of the structural and optical properties of three MAX phases, Nb2AlC, Ta2AlC and Ti3AlC2, were performed. Although the theoretical calculations confirmed that the phases presented no band gap in the vicinity of the Fermi level, the experimental evaluation showed two main absorptions for Nb2AlC and Ta2AlC (2.2 eV, 3.1 eV, and 2.2 eV, 3.3 eV, respectively) and one for Ti3AlC2 (2.4 eV). To confirm the observations from the optical characterisation, the phases were applied as photoelectrocatalysts for hydrogen generation under the influence of light of different wavelengths. Nb2AlC and Ta2AlC performed better when exposed to UV light, while Ti3AlC2 showed the lowest overpotential under the influence of visible light, in accordance with the experimentally estimated band gaps. The materials were extensively characterised and the photoactivity of MAX phases was attributed to the presence of photoactive oxide impurities on the surface of the material, which are naturally formed from contact with air and solvents. In this work, we show how these impurities can lead to better performances thanks to their intrinsic photoactivity, indicating the prospects for the use of MAX phases in other photoelectrochemical processes.Web of Science1163090308

Depozice atomárních vrstev fotoelektrokatalytického materiálu na 3D tištěné uhlíkové nanostruktury.

3D-printing is an excellent tool for the prototyping and fabrication of a variety of devices. The ability to rapidly create on demand structures opens the vast possibilities for the innovations in catalysis and energy conversion/storage devices. The major bottleneck is that the materials which are suitable for 3D-printing usually do not possess the required energy conversion/storage ability. Atomic layer deposition (ALD) strategically offers homogeneous and conformal deposition of functional layers without compromising the 3D topography. Here, we show that readily fabricated fused deposition modeling extruded nanocarbon/polylactic acid (PLA) electrodes can be modified by a photoelectrocatalytic material with atomic precision. We use an archetypal material, MoS2, with high electrocatalytic hydrogen evolution reaction (HER) activity, whilst possesses high photons absorption in the visible spectral region. We optimized the ALD process at low temperature to coat 3D-printed nanocarbon/PLA electrodes with different number of MoS2 ALD cycles for photoelectrocatalytic HER. We present for the first time, the feasibility of low temperature transition metal dichalcogenide coatings on 3D-printed nanocarbon surface, unequivocally elevate the benchmark of functional coatings by ALD on any 3D-printed platforms.3D tisk je excelentní nástroj pro přípravu prototypů a výrobu různých zařízení. Schopnost tohoto tisku rychle připravit požadované struktury otevírá možnosti pro inovaci v katalýze a zařízení na přemenu a uchování energie. Hlavní nevýhodou 3D tištěných materiálů zůstává jejich nedostatečná stabilita pro tyto aplikace. Depozice atomárních vrstev je strategická v tom, že nabízí homogenní a rovnoměrnou depozici funkčních vrstev bez kompromisů s ohledem na 3D tvarovost. V této práci ukazujeme, že elektrody na bázi směsi nanouhlíku a kyseliny polymléčné (PLA) tištěné 3D technologií filamentů bez formy mohou být modifikovýny fotoelektrokatalytickým materiálem s atomární přesností. Použili jsme pro tento účel typický materiál - MoS2 - který disponuje vysokou elektrokatalytickou aktivitou pro vývoj vodíku (HER), a který zároveň vykazuje vysokou absorpci fotonů ve viditelné spektrální oblasti. Optimalizovali jsme ALD proces při nízké teplotě s cílem pokrýt elektrody na bázi nanouhlíku/PLA s různými počty ALD MoS2 cyklů pro fotokatalytickou reakci HER. V této práci poprvé představujeme možnosti pokrýtí 3D tisknutých elektrod chalkogenidy kovů, které jednoznačně posouvají měřítko funkčních ALD vrstev na jakékoliv 3D tisknuté platformě

Významné zlepšení foto- a elektro-aktivity sířením 1D anodických vrstev TiO2 nanotrubic

n this work, we show that sulfur treated 1D anodic TiO2nanotube layers lead to improved photo-electrochemical and catalytic properties compared to the blank nanotube layers. This treatment wasperformed in the evacuated quartz ampoules in the temperature range from 250 to 450◦C. Inspectionof the sulfurized nanotube layers via scanning electron microscopy (SEM) and X-ray diffraction (XRD)has disclosed a gradual crystal growth within nanotube walls, represented by TiS2or TiS3phases. Opti-mally sulfurized TiO2nanotube layers exhibit 3 times enhanced photocurrent in the UV spectral region,compared to the blank counterpart, with a shift of the light absorption up to the wavelength of 550 nm.In addition, the photocatalytic decomposition of a methylene blue aqueous solution using a wavelengthof 365 nm is gradually improved with increasing sulfurization temperature. The highest photocatalyticdecomposition rate is 2.3 times larger compared to the blank TiO2nanotube layer. The application ofsulfurized TiO2nanotube layers for the electrocatalytic hydrogen evolution is also discussed.V této práci jsme ukázali, že modifikace 1D anodických TiO2 nanotrubic sírou vede ke zlepšení fotoelektrochemických a katalytických vlastností ve srovnání s nesířenými nanotrubicemi. Síření bylo provedeno v evakuovaných křemenných ampulích v teplotním rozmezí od 250 do 450 ° C. Pozorování vrstev sířených nanotrubic pomocí skenovací elektronové mikroskopie (SEM) a rentgenové difraktometrie (XRD) odhalilo postupný růst krystalů ve stěnách nanotrubic, reprezentovaných fázemi TiS2 nebo TiS3. Optimálně sířené vrstvy TiO2 nanotubic vykazují ve srovnání s nesířenými vrstvami v UV spektrální oblasti 3krát vyšší fotoproud a posun absorpce světla až do vlnové délky 550 nm. Navíc, fotokatalytický rozklad vodného roztoku methylenové modři při použití vlnového délky 365 nm se postupně zlepšuje se zvyšující se teplotou síření. Nejvyšší rychlost fotokatalytického rozkladu je 2.3krát větší ve srovnání s nesířenou vrstvou TiO2 nanotrubic. Diskutováno je také použití sířených vrstev TiO2 nanotrubic. pro elektrokatalytický vývoj vodíku