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Light driven electron transfer in a lipid bilayer with mixed valence molecular wires
Get PDFTriarylamines TAAs are one of the most important classes of redox active organic compounds, which are readily available from modular synthesis, thereby offering the possibility to easily adjust their intrinsic redox potentials. We present herein two bis triarylamines BTAAs with pi extended 2,7 diethynylfluorene or 2,2 1,3 butadiyne 1,4 diyl bis 7 ethynylfluorene bridges and two benzoic acid headgroups per TAA and their formally mixed valent radical cations. Owing to their amphiphilic character and favorable redox properties, these BTAAs are designed to serve as charge conduits through membranes. The lipid bilayer BTAA systems are water soluble, which allowed us to explore their photoactivity in aqueous solution and utilize their mixed valent form for membrane mediated photoinduced electron transfer. Our findings will be relevant for constructing artificial nanoreactors for solar light energy conversion and light driven redox chemistry in wate
Pre treated carbon additive enables reduction of metal loading in CoNiFe oxide based OER electrocatalysts while maintaining performance
No full textMixed oxides MO of Co, Ni, and Fe have emerged as promising catalysts for the oxygen evolution reaction OER in alkaline water electrolysis AWE . Although they are significantly cheaper than the precious metal catalysts used for proton exchange membrane PEM water splitting, the limited availability of Co and the exceptionally poor environmental footprint of Co and Ni mining remain challenges for scaling up AWE capacities. In this context, we present a promising approach toward reducing the metal content while preserving the catalytic performance. Based on a recent work on CoNiFeOx OER catalysts from our group, admixture of pretreated Vulcan carbon XC 72R VC at different synthesis stages in various loadings was evaluated in view of material structure and electrocatalytic activity. Attractive performance characteristics were obtained for the optimized MO VC composite material, e.g., a mass activity of 370 A g 1 39.0 mV dec 1. Stable long term performance under practical AWE conditions was confirmed in an anion exchange membrane AEM electrolyzer. An understanding of the effect of carbon admixture was achieved by combining in situ X ray absorption spectroscopy, analysis of the electrochemically active surface area, as well as electrochemical impedance spectroscopy. The results point toward a benign impact of carbon admixture on the electronic structure of the MO domains under potential bia
Impact of Growth Environment on the Crystal Growth and Magnetic and Electronic Properties of Ba2NiWO6 Single Crystals
No full textThis study introduces the effect of growth atmosphere and pressure on the as grown crystals and the physical characterization of the double perovskite compound Ba2NiWO6 BNWO . The Ni2 ions form a face centered cubic FCC lattice with an ideal octahedral arrangement. Our growth trials by the floating zone method revealed that BNWO exhibits two distinct colors depending on the growth atmosphere, suggesting that it influences its stoichiometry and phase purity. The antiferromagnetic properties of BNWO align with conventional antiferromagnetic behavior with a J 1 ground state, as determined by entropy calculation. Additionally, surface photovoltage SPV spectroscopy indicates that the impurity levels within the crystal influence the electronic properties of BNW
Enhancing deep visible light photoelectrocatalysis with a single solid state synthesis carbon nitride TiO2 heterointerface
Get PDFVisible light responsive, stable, and abundant absorbers are required for the rapid integration of green, clean, and renewable technologies in a circular economy. Photoactive solid solid heterojunctions enable multiple charge pathways, inhibiting recombination through efficient charge transfer across the interface. This study spotlights the physico chemical synergy between titanium dioxide TiO2 anatase and carbon nitride CN to form a hybrid material. The CN 10 TiO2 90 hybrid outperforms TiO2 and CN references and literature homologs in four photo and photoelectrocatalytic reactions. CN TiO2 achieved a four fold increase in benzylamine conversion, with photooxidation conversion rates of 51, 97, and 100 at 625, 535, and 465 nm, respectively. The associated energy transfer mechanism was elucidated. In photoelectrochemistry, CN TiO2 exhibited 23 photoactivity of the full spectrum measurement when using a 410 nm filter. Our findings demonstrate that CN TiO2 displayed a band gap of 2.9 eV, evidencing TiO2 photosensitization attributed to enhanced charge transfer at the heterointerface boundaries via staggered heterojunction type I
1D nanoporous membrane boosts the ionic conductivity of electrolytes
No full textSolid state batteries have attracted significant interest as promising candidates for high energy density and safe battery technology. However, they commonly experience low ionic conductivity at ambient temperature, which limits their power density. This study addresses this issue by developing a porous separator with one dimensional 1D nanometric channels that confine non flammable ionic liquid based electrolytes ILLi . We achieve 1D macroscopic ionic transport by confining the electrolytes within Vertically Aligned Carbon NanoTubes VA CNT composite membranes. Employing quasi elastic neutron scattering techniques, we conduct a multiscale analysis of the diffusive motion of both bulk and confined electrolytes. By extracting diffusion coefficients spanning from the molecular to macroscopic scale, we gain insights into the transport properties of IL Li. Our results show that nanometric confinement allows to lower the operational temperature of these electrolytes by up to 20 K compared to the non confined electrolytes. At ambient temperature, we show a tenfold increase in conductivity under 1D CNT confinement. Molecular Dynamics simulations shed light on the underlying physics, showing a unique intermolecular organization of the IL Li under confinement. Specifically, the molecules form a core shell structure, resulting in the creation of quasi 1D transport channels. This study presents promising avenues for exploring the use of 1D materials in energy storage application
Depth of Discharge Dependent Capacity Decay Induced by the Accumulation of Oxidized Lattice Oxygen in Li Rich Layered Oxide Cathode
No full textMore and more basic practical application scenarios have been gradually ignored disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths of discharge DODs . Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium rich layered oxide LRLO cathodes present anomalously poor capacity retention at low DOD cycling, which is essentially different from typical layered cathodes e.g. NCM , and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen On amp; 8722; . Upon low DOD cycling, the accumulation of On amp; 8722; and the persistent presence of vacancies in the transition metal TM layer intensified the in plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out of plane TM migration. As a result, the aggravated structural degradation of LRLO at low DOD impeded reversible Li intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of On amp; 8722; persistently corroded the electrode electrolyte interface, especially negative for pouch type full cells with the shuttle effect. Once the double edged sword effect of anionic redox being elucidated under practical condition, corresponding modification strategies routes would become distinct for accelerating the practical application of LRL
High entropy 2D metals sulfides Fast synthesis, exfoliation and electrochemical activity in overall water splitting at alkaline pH
Get PDFNovel simple and efficient method for synthesis of 2D high entropy sulfides of iron group metals is described. The method utilizes inorganic salts as precursors and CS2 as a sulfurizing agent, which makes it possible to achieve high entropy composition through combination of freezing of the precursor solution, subsequent freeze drying step, sulfurization, and exfoliation in liquid nitrogen. The created material was investigated as a catalyst for electrochemical water splitting at different pH. Measured overpotentials at 10 and 100 mA cm amp; 8722;2 current densities for hydrogen evolution reaction HER were found to be 49 and 315 mV respectively, while for oxygen evolution reaction OER the overpotentials required for reaching 10 and 100 mA cm amp; 8722;2 current densities were 370 and 591 mV respectively, both in 1 M KOH solution. The Tafel slopes for HER were found to be 235, 105, and 111 mV dec in basic, neutral, and acidic conditions, respectively, while only 63 mV dec for OER in basic conditions. The calculated values of the turnover frequency were 0.62 s amp; 8722;1 for HER and 0.10 s amp; 8722;1 for OER. We also confirmed the key role of high entropy in the catalytic activity of the material by excluding individual elements from the composition of the HE
Tailor made polymer tracers reveal the role of clay minerals on colloidal transport in carbonate media
Get PDFHypothesis Host rock weathering and incipient pedogenesis result in the exposition of minerals, e.g., clay minerals in sedimentary limestones. Once exposed, these minerals provide the surfaces for fluid solid interactions that control the fate of dissolved or suspended compounds such as organic matter and colloids. However, the functional and compositional diversity of organic matter and colloids limits the assessment of reactivity and availability of clay mineral interfaces. Such assessment demands a mobile compound with strong affinity to clay surfaces that is alien to the subsurface. Experiment We approached this challenge by using poly ethylene glycol PEG as interfacial tracer in limestone weathering experiments. Findings PEG adsorption and transport was dependent on the availability of clay mineral surfaces and carbonate dissolution dynamics. In addition, PEG adsorption featured adsorption desorption hysteresis which retained PEG mass on clay mineral surfaces. This resulted in different PEG transport for experiments conducted consecutively in the same porous medium. As such, PEG transport was reconstructed with a continuum scale model parametrized by a Langmuir type isotherm including hysteresis. Thus, we quantified the influence of exposed clay mineral surfaces on the transport of organic colloids in carbonate media. This renders PEG a suitable model colloid tracer for the assessment of clay surface exposition in porous medi
Combined Experimental and Theoretical Approach to the Electronic and Magnetic Properties of Cu Doped LaMnO3 Perovskites
Get PDFCu doped LaCuxMn1 amp; 8722;xO3 perovskites have been used as a model system for a joint experimental and theoretical assessment of the influence of the Cu doping level on the structural, electronic, and magnetic properties. The different Cu doped phases LaCu0.3Mn0.7O3 LCM37 , LaCu0.5Mn0.5O3 LCM55 , and LaCu0.7Mn0.3O3 LCM73 including the respective Cu and Mn free benchmark materials La2CuO4 LC and LaMnO3 LM have been studied by magnetization measurements and electronic paramagnetic resonance. Ferromagnetic behavior was detected for pure LM and all Cu doped perovskites, whereas antiferromagnetic behavior was revealed for La2CuO4. Generally, an increased antiferromagnetic contribution was shown for higher Cu doping levels. Equally, magnetization was highlighted to decrease with increasing Cu content. Sophisticated hybrid density functional theory calculations of the electronic and magnetic properties using defect free, idealized Cu doped model structures agree well with the experimental results. The findings reveal that copper incorporation influences both the electronic conductivity and the magnetic properties. Notably, the materials exhibit a tunable degree of half metallicity and significant electronic spin polarization, establishing them as promising candidates for advanced technological applications in spintronics and catalysis. The insights gained from this study contribute to a broader understanding of perovskite materials and their versatile application
High Spin Manganese V in an Active Center Analogue of the Oxygen Evolving Complex
Get PDFIn a comprehensive investigation of the dinuclear [Mn2O3] cluster, the smallest dimanganese entity with two amp; 956; oxo bridges and a terminal oxo ligand, and a simplified structural model of the active center in the oxygen evolving complex, we identify antiferromagnetically coupled high spin manganese centers in very different oxidation states of 2 and 5, but rule out the presence of a manganese IV oxyl species by experimental X ray absorption and X ray magnetic circular dichroism spectroscopy combined with multireference calculations. This first identification of a high spin manganese V center in any polynuclear oxidomanganese complex underscores the need for multireference computational methods to describe high valent oxidomanganese specie