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Ballistic and delayed photodissociation channels in the tilde B 2 1A1 state of water studied with resonant inelastic x ray scattering
Get PDFPhotodissociation is one of the most important photoinduced chemical reactions. It occurs when the potential energy curve along a chemical bond is repulsive in an excited state. Typically, ballistic ultrafast dissociation leads to the broadening of absorption resonances and the smearing out of vibrational fine structure. We report on the photodissociation of H2 amp; 8290;O in the amp; 119861; 21 amp; 119860;1 electronic state, characterized by a 3 amp; 8290; amp; 119886; amp; 8722;1 1 amp; 8290;4 amp; 8290; amp; 119886;1 1 amp; 10217; configuration, which can be reached via resonant inelastic x ray scattering or direct ultraviolet absorption. In both cases the spectra show narrow vibrational resonances, in spite of the dissociative character of the state. We find that delayed dissociation pathways, caused by reflection of the nuclear wave packet, are responsible for this effect. In spite of the analogous topology of the potential energy surfaces of the core and valence excited states, the reflection of the wave packet takes place only in the latter. The two dimensional wave packet of the O H stretching coordinates becomes trapped in a cavity near the Franck Condon region, resulting from a mismatch between the OH vibrational frequency in the cavity and the one at the dissociation limi
Poly 3 hexylthiophene perovskite Heterointerface by Spinodal Decomposition Enabling Efficient and Stable Perovskite Solar Cells
No full textThe best research cell efficiency of perovskite solar cells PSCs is comparable with that of mature silicon solar cells SSCs ; However, the industrial development of PSCs lags far behind SSCs. PSC is a multiphase and multicomponent system, whose consequent interfacial energy loss and carrier loss seriously affect the performance and stability of devices. Here, by using spinodal decomposition, a spontaneous solid phase segregation process, in situ introduces a poly 3 hexylthiophene perovskite P3HT PVK heterointerface with interpenetrating structure in PSCs. The P3HT PVK heterointerface tunes the energy alignment, thereby reducing the energy loss at the interface; The P3HT PVK interpenetrating structure bridges a transport channel, thus decreasing the carrier loss at the interface. The simultaneous mitigation of energy and carrier losses by P3HT PVK heterointerface enables n i p geometry device a power conversion efficiency of 24.53 certified 23.94 and excellent stability. These findings demonstrate an ingenious strategy to optimize the performance of PSCs by heterointerface via Spinodal decompositio
Hollow Cathode Gas Flow Sputtering of Nickel Oxide Thin Films for Hole Transport Layer Application in Perovskite Solar Cells
Get PDFNickel oxide NiO1 amp; 948; is a versatile material used in various fields such as optoelectronics, spintronics, electrochemistry, and catalysis which is prepared with a wide range of deposition methods. Herein, for the deposition of NiO1 amp; 948; films, the reactive gas flow sputtering GFS process using a metallic Ni hollow cathode is developed. This technique is distinct and has numerous advantages compared to conventional sputtering methods. The NiO1 amp; 948; films are sputtered at low temperatures 100 amp; 8201; C for various oxygen partial pressures during the GFS process. Additionally, Cu incorporated NiO1 amp; 948; Cu x Ni1 amp; 8722;x O1 amp; 948; films are obtained with 5 and 8 at Cu. The thin films of NiO1 amp; 948; are characterized and evaluated as a hole transporting layer HTL in perovskite solar cells PSCs . The NiO1 amp; 948; devices are benchmarked against state of the art self assembled monolayers SAM [2 3,6 dimethoxy 9H carbazol 9 yl ethyl]phosphonic acid also known as MeO amp; 63743;2PACz based PSCs. The best performing NiO1 amp; 948; PSC achieves an efficiency amp; 951; of amp; 8776;16 without a passivation layer at the HTL interface and demonstrates better operational stability compared to the SAM device. The findings suggest that further optimization of GFS NiO1 amp; 948; devices can lead to higher performing and more stable PSC
Insights into the kinetics morphology relationship of 1 , 2 , and 3D TiNb2O7 anodes for Li ion storage
Get PDFUnderstanding the influence of electrode material s morphology on electrochemical behavior is of great significance for the development of rechargeable batteries, however, such studies are often limited by the inability to precisely control the morphology of electrode materials. Herein, nanostructured titanium niobium oxides TiNb2O7 with three different morphologies one dimensional 1D , two dimensional 2D , and three dimensional 3D were synthesized via a facile microwave assisted solvothermal method. The influence of the morphological dimension of TiNb2O7 as electrode material on the electrochemical performance in Li ion batteries LIBs and the underlying correlation with the electrochemical kinetics were studied in detail. 2D TiNb2O7 TNO 2D shows a superior rate capability and cycling stability, associated with improved kinetics for charge transfer and Li ion diffusion, compared to the 1D and 3D materials. Operando X ray diffraction measurements reveal the structural stability and crystallographic evolution of TNO 2D upon lithiation and delithiation and correlate the Li ion diffusion kinetics with the lattice evolution during battery charge and discharge. Moreover, carbon coated TNO 2D achieves enhanced rate capability 205 mAh g amp; 8722;1 at 50 C and long term cycling stability 87 after 1000 cycles at 5 C . This work provides insights into the rational morphology design of electrode materials for accelerated charge transfer and enhanced fast charging capability, pushing forward the development of electrode materials for high power rechargeable batteries in future energy storag
Unlocking the porosity of Fe N C catalysts using hydroxyapatite as a hard template en route to eco friendly high performance AEMFCs
No full textIn this work, we propose hydroxyapatite HA as a hard template to unlock the porosity of Fe N C catalyst materials. Using HA, a naturally occurring mineral that can be removed with nitric acid, in the synthesis generates a catalyst material with a unique porous network comprising abundant pores and interparticle cavities ranging from 10 to 3000 nm. Hard templating with HA alongside ZnCl2 as a micropore former results in a Fe N C catalyst based on naturally abundant peat with excellent oxygen reduction activity in alkaline conditions. A half wave potential of 0.87 V vs RHE and a peak power density of 1.06 W cm 2 were achieved in rotating ring disk electrode and anion exchange membrane fuel cell experiments, respectively, rivaling the performance of other state of the art platinum free catalysts presented in the literature. A combined approach of using renewable peat as a carbon source and HA as a hard template offers an environmentally friendly approach to high performance Fe N C catalysts with abundant porosit
The Influence of Melting on Catalysis in Propane Oxidation
No full textA model catalyst composed of crystalline potassium pentavanadate K3V5O14 supported on silica was studied to elucidate the effect of phase transitions on the performance of potassium promoted vanadia catalysts in propane oxidation. Operando calorimetry shows a clear correlation between a drop in activity and an increase in selectivity to propylene upon melting of the crystalline K3V5O14 phase under reaction conditions. The pentavanadate phase itself is not active in propane oxidation, neither in the solid nor in the molten state. The activity of the catalyst mainly originates from highly active, i. amp; 8201;e., unselective VxOy surface species anchored to silica and formed during synthesis in addition to the supported pentavanadate phase. Melting of K3V5O14 leads to the coverage of these VxOy species preventing the overoxidation of propylene and leading to an increase in propylene selectivity. The change in catalyst properties is therefore due to a physical effect and not to a change in the chemical properties of the predominant crystalline phas
Elucidating the Role of Dimensionality on the Electronic Structure of the Van der Waals Antiferromagnet NiPS3
Get PDFThe sustained interest in investigating magnetism in the 2D limit of insulating antiferromagnets is driven by the possibilities of discovering, or engineering, novel magnetic phases through layer stacking. However, due to the difficulty of directly measuring magnetic interactions in 2D antiferromagnets, it is not yet understood how intralayer magnetic interactions in insulating, strongly correlated, materials can be modified through layer proximity. Herein, the impact of reduced dimensionality in the model van der Waals antiferromagnet NiPS3 is explored by measuring electronic excitations in exfoliated samples using Resonant Inelastic X ray Scattering RIXS . The resulting spectra shows systematic broadening of NiS6 multiplet excitations with decreasing layer count from bulk down to three atomic layers 3L . It is shown that these trends originate from a decrease in transition metal ligand and ligand ligand hopping integrals, and by charge transfer energy evolving from amp; 120491; 0.83 eV in the bulk to 0.37 eV in 3L NiPS3. Relevant intralayer magnetic exchange integrals computed from the electronic parameters exhibit a decrease in the average interaction strength with thickness. This study underscores the influence of interlayer electronic interactions on intralayer ones in insulating magnets, indicating that magnetic Hamiltonians in few layer insulating magnets can greatly deviate from their bulk counterpart
Simulating selected magnetic properties of TbxPr1 xAl2, a magnetocaloric compound
No full textTbxPr1 amp; 8722;xAl2 are ferrimagnetic materials exhibiting magnetocaloric effect that have gained considerable attention due to their potential use as an alternative in refrigeration, magnetic sensors and in information storage technology. Here using the mean field approach numerical simulations were conducted for x 0.1, 0.2, 0.3, 0.4, 0.5, and 0.75, to analyze selected physical properties, such as x ray and neutron powder diffraction, magnetization and heat capacity. The simulations successfully reproduced the experimental data providing a comprehensive characterization and improved understanding of this family of compoun
Exploring an Electrochemical Route for Water Enhanced Oxygenation Reactions Utilizing Nickel Molecular Structures A Case Study
No full textRecently, Ni molecular catalysis has been extensively applied in oxygenation reactions. This work is underpinned by the characterization techniques and the discovered instability of the Ni bipyridine phenanthroline system, which results in Ni hydr oxide production under oxidative conditions. The practical applications of this mechanism by employing a prepared Ni hydr oxide based electrode specifically in the oxygenation of sulfides, achieving noteworthy yields in contrast to noncatalyst control experiments, are explored. Thus, a Ni hydr oxide based material is proposed as a candidate for the true catalyst for sulfide oxidation in the presence of the Ni bipyridine phenanthroline system. The findings of this study are expected to stimulate discussion and encourage new viewpoints within the chemical community regarding the potential applications and mechanisms of molecular catalysts in oxidation reaction
Biomimetic Approach for Sustainable Magnetite Nanoparticle Synthesis Using Polycations
No full textMagnetotactic bacteria produce magnetite nanoparticles called magnetosomes at ambient conditions via a protein stabilized transient amorphous precursor to obtain precise control over particle size and morphology. In a bioinspired approach, such biomineralization processes are emulated, mimicking proteins involved in magnetosome formation using the positively charged analog poly L arginine. While the additive is expensive, it remains elusive whether the change in magnetite formation mechanism arises solely from the polymer s cationic nature. This study uses different mass produced and sustainably sourced polycations to induce the biomineralization reminiscent formation of magnetite nanoparticles. These findings present how to achieve control over nanoparticle size from 10 to 159 nm and morphology compact and sub structured as well as magnetic properties superparamagnetic, stable single domain, vortex state at ambient temperature and pressure using these additives. Furthermore, the formation of large nanoparticles with the addition of poly diallyldimethylammonium chloride PDADMAC at low alkalinity highlights how magnetotactic bacteria may produce magnetite nanoparticles under similar conditions. Confirming the polycations ability to electrostatic stabilize amorphous ferrihydrite, it is anticipated that parametric in vitro studies on polymer properties will provide valuable insights into magnetite biomineralization and aid in rationally designing magnetic nanomaterial