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Enhancing the oxygen evolution reaction activity of CuCo based hydroxides with V2CTx MXene
Get PDFThe oxygen evolution reaction OER is a key reaction in the production of green hydrogen by water electrolysis. In alkaline media, the current state of the art catalysts used for the OER are based on non noble metal oxides. However, despite their huge potential as OER catalysts, these materials exhibit various disadvantages including lack of stability and conductivity that hinder the wide spread utilization of these materials in alkaline electrolyzer devices. This study highlights the innovative chemical functionalization of a mixed copper cobalt hydroxide with the V2CTx MXene to enhance the OER efficiency, addressing the need for effective electrocatalytic interfaces for sustainable hydrogen production. The herein synthesized CuCo V2CTx electrocatalysts demonstrate remarkable activity, outperforming the pure CuCo catalysts for the OER and moreover show increased efficiency after 12 hours of continuous operation. This strategic integration improved the water oxidation performance of the pure oxide material by improving the composite s hydrophilicity, charge transfer properties and ability to hinder Cu leaching. The materials were characterized using an array of materials characterization techniques to help decipher both structure of the composite materials after synthesis and to elucidate the reasoning for the OER enhancement for the composites. This work demonstrates the significant potential of TMO based nanomaterials combined with V2CTx for advanced innovative electrocatalytic interfaces in energy conversion application
Investigation of hydrothermally produced ZnO nanorods and the mechanisms of Li incorporation as a possible dopant
No full textZinc oxide ZnO has emerged as one of the most promising candidates for mass producing cost efficient optoelectronic devices. This is primarily because it can be synthesized in high quality nanostructures on a wide range of substrates through relatively simple chemical methods. However, producing p type ZnO, regardless of the chosen method, remains an open and controversial issue. In this work, Li doped ZnO nanostructures of varying Li cocnentration were produced via a two step hydrothermal growth synthesis and an in depth analysis based on with Field Emission Scanning Electron Microscopy FE SEM , X ray diffraction XRD , Raman Spectroscopy, Extended X Ray Absorption Fine Structure EXAFS Spectroscopy, and temperature dependent Photoluminescence PL was carried out in an effort to gain insights into the Li incorporation mechanisms. The findings indicated a strong interplay between the native defects responsible for the inherent n type character of the material and Li incorporation. It is suggested that this interplay hinders the successful conversion of the Li doped nanorods into p type nanostructures and that when employing the hydrothermal approach it is essential to identify the precise conditions necessary for genuine Li incorporation as a Zn substitutiona
Grain boundaries are not the source of Urbach tails in Cu In,Ga Se2 absorbers
Get PDFThe presence of Urbach tails in Cu In,Ga Se2 CIGSe absorbers has been identified as a limiting factor for the performance of the CIGSe solar cells. The tail states contribute to both radiative and non radiative recombination processes, ultimately leading to a reduction in the open circuit voltage and, consequently, decreasing the overall efficiency of CIGSe devices. Urbach tails result from structural and thermal disorders. The Urbach tails can be characterized by the Urbach energy, which is associated with the magnitude of the tail states. Within polycrystalline CIGSe absorbers, grain boundaries can be considered as structural disorder and, therefore, can potentially contribute to the Urbach tails. In fact, it has been proposed that the band bending at grain boundaries contribute significantly to the tail states. This study focuses on examining the correlation between Urbach tails and the band bending at the grain boundaries. The Urbach energies of the CIGSe samples are extracted from photoluminescence PL measurements, which reveal that the introduction of Sodium Na into the material can lead to a reduction in the Urbach energy, and an even further decrease can be achieved through the RbF post deposition treatment. The band bending at the grain boundaries is investigated by Kelvin probe force microscopy measurements. A thorough statistical analysis of more than 340 grain boundaries does not show any correlation between Urbach tails and grain boundaries. We measure small band bending values at the grain boundaries, in the range of the thermal energy 26 meV at room temperature . Furthermore, our intensity dependent PL measurements indicate that Urbach tails are, at least in part, a result of electrostatic potential fluctuations. This supports the model that the introduction of alkali elements mainly decreases the magnitude of electrostatic potential fluctuations, resulting in a subsequent reduction in the Urbach energ
Outdoor Exposure Study on the Performance of Nine Different Types of Industrial PV Modules under 35 and under 90 Tilt
Get PDFDevelopment towards high resolution kHz speed rotation free volumetric imaging
Get PDFX ray multi projection imaging XMPI has the potential to provide rotation free 3D movies of optically opaque samples. The absence of rotation enables superior imaging speed and preserves fragile sample dynamics by avoiding the centrifugal forces introduced by conventional rotary tomography. Here, we present our XMPI observations at the ID19 beamline ESRF, France of 3D dynamics in melted aluminum with 1000 frames per second and 8 amp; 956;m resolution per projection using the full dynamical range of our detectors. Since XMPI is a method under development, we also provide different tests for the instrumentation of up to 3000 frames per second. As the high brilliance of 4th generation light sources becomes more available, XMPI is a promising technique for current and future X ray imaging instrument
Phase selectivity upon flash lamp annealing of sputter deposited amorphous titanium oxide films
No full textWe report the impact of flash lamp annealing FLA on the structural evolution of amorphous titania TiO2 films produced by DC reactive magnetron sputtering. TiO2 films were grown at room temperature at different oxygen partial pressure PO2 and subsequently annealed as a function of the FLA energy density. X ray diffraction confirms that FLA induces phase formation from the initial amorphous state with a general transition from anatase to rutile by increasing the FLA energy density temperature . Interestingly, the transformation onset of anatase to rutile is achieved at lower energy densities for higher PO2. On the contrary, films with a highly resilient anatase phase can be produced at relatively low PO2. A detailed analysis of the pristine amorphous structure carried out by X ray absorption near edge structure indicates the role of oxygen sites in the observed phase transformation. In particular, oxygen vacancies seem to stabilize the anatase phase at high temperatures. The results show the relevance of subtle changes in the initial amorphous structure for phase selectivity in TiO2 films upon FL
Spin crossover in dinuclear iron ii complexes bridged by bis bipyridine ligands dimer effects on electronic structure, spectroscopic properties and spin state switching
No full textInspired by the well studied mononuclear spin crossover compound [Fe H2B pz 2 2 bipy ], the bipyridine based bisbidentate ligands 1,2 di 2,2 amp; 8242; bipyridin 5 yl ethyne ac bipy 2 and 1,4 di 2,2 amp; 8242; bipyridine 5 yl 3,5 dimethoxybenzene Ph OMe 2 bipy 2 are used to bridge two [Fe H2B pz 2 2] units, leading to the charge neutral dinuclear iron II compounds [ Fe H2B pz 2 2 2 amp; 956; ac bipy 2 ] 1 and [ Fe H2B pz 2 2 2 amp; 956; Ph OMe 2 bipy 2 ] 2 , respectively. The spin crossover properties of these molecules are investigated by temperature dependent PPMS measurements, Mössbauer, vibrational and UV Vis spectroscopy as well as X ray absorption spectroscopy. While compound 1 undergoes complete SCO with T1 2 125 K, an incomplete spin transition is observed for 2 with an inflection point at 152 K and a remaining high spin fraction of 40 below 65 K. The spin transitions of the dinuclear compounds are also more gradual than for the parent compound [Fe H2B pz 2 2 bipy ]. This is attributed to steric hindrance between the molecules, limiting intermolecular interactions such as amp; 960; amp; 960; stackin
Proton FLASH Irradiation Setup for Preclinical Studies at HZB
Get PDFThe HZB cyclotron continues to provide protons for eye tumor treatment in collaboration with the Charit Universitätsmedizin Berlin after 24 years and more than 4400 patients so far. With the perspective of broadening its research capabilities in the field of radiation therapy, intensive effort has been dedicated towards proton FLASH irradiation, which requires ultra high dose rates or beam intensities. By combining a fast and reliable switch off mechanism, accurate dosimetry, and a double scattering beam nozzle with a static 3D printed range modulator, HZB is now able to deliver a dose rate above 150 Gy s within a flat circular irradiation field of 18mm diameter and a 27mm spread out Bragg peak with a distal fall off of 1mm in water. The reproducibility of the delivered dose meets the clinical acceptance criteria for a total irradiation time as low as 2.5 ms. The first experiments with this setup were used on fibroblastic and sarcoma organoids. By adapting the design to a 35mm lateral field and using optimal accelerator tuning to increase beam transmission, similar or even higher dose rates are expected, satisfying thus the FLASH conditions for eye tumor treatment with protons
