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Charge transfer driven by ultrafast spin transition in a CoFe Prussian blue analogue
Photoinduced charge-transfer is an important process in nature and technology and is responsible for the emergence of exotic functionalities, such as magnetic order for cyanide-bridged bimetallic coordination networks. Despite its broad interest and intensive developments in chemistry and material sciences, the atomic-scale description of the initial photoinduced process, which couples intermetallic charge-transfer and spin transition, has been debated for decades; it has been beyond reach due to its extreme speed. In this work we study this process in a prototype cyanide-bridged CoFe system by femtosecond X-ray and optical absorption spectroscopies, enabling the disentanglement of ultrafast electronic and structural dynamics. Our results demonstrate that it is the spin transition that occurs first on the Co site within ~50 fs, and it is this that drives the subsequent Fe-to-Co charge-transfer within ~200 fs. This study represents a step towards understanding and controlling charge-transfer-based functions using light.
Prussian blue analogue electrodes without zeolitic water content
A battery is provided with a hexacyanometallate cathode. The battery cathode is made from hexacyanometallate particles overlying a current collector. The hexacyanometallate particles have the chemical formula AXM1MM2N(CN)Z.d[H2O]ZEO.e[H2O]BND, where A is a metal from Groups 1A, 2A, or 3A of the Periodic Table, where M1 and M2 are each a metal with 2+ or 3+ valance positions, where “ZEO” and “BND” indicate zeolitic and bound water, respectively, where d is 0, and e is greater than 0 and less than 8. The anode material may primarily be a material such as hard carbon, soft carbon, oxides, sulfides, nitrides, silicon, metals, or combinations thereof. The electrolyte is non-aqueous. A method is also provided for fabricating hexacyanometallate with no zeolitic water content in response to dehydration annealing at a temperature of greater than 120 degrees C. and less than 200 degrees C.
Potassium Prussian blue-coated Li-rich cathode with enhanced lithium ion storage property
With high specific capacity, the layered Li-rich Mn-based oxide (LRMO) is a promising candidate cathode material for Li-ion batteries. However, the irreversible release of Li-ions during the first charging process, instability of LRMO/electrolyte interface and relatively low ion conductivity of LRMO result in low initial Coulombic efficiency (ICE), poor cycle stability and rate performance, which prohibit its further application. Furthermore, interface engineering via additive coating is expected to effectively address these issues. Herein, we rely on potassium Prussian blue (KPB), a Li + acceptor with good ion conductivity, as a new coating material on LRMO particles. The KPB coating not only forms a protective layer on the surface of LRMO against electrolyte corrosion, but also functions as a host for Li + transport and accommodation, leading to enhanced ion conductivity and ICE of LRMO cathode. Consequently, 2 wt% KPB coated LRMO cathode achieved an initial discharge capacity of up to 281.7 mA h g -1 with an ICE of 85.69% compared to an ICE of 79.52% for the LRMO cathode without coating. The cycling and rate performance are also greatly improved as evidenced by the well maintained capacity of up to 176.8 mA h g -1 after 100 cycles at a current density of 0.5 C, compared to the limited capacity of only 135.3 mA h g -1 for the LRMO cathode without coating. Overall, this work pioneers the use of potassium Prussian blue as additive coating material to enhance performance of LRMO cathode, and we expect it to inspire the battery community with new strategies of material engineering/design toward practical application in high-energy lithium-ion batteries.
Spectroscopic Characterization of Mn 1+ Low Oxidation State in Prussian Blue-Based Battery Anodes
Stabilization of ions in exotic oxidation states is beneficial for the development of new materials for green energy technologies. Exotic Mn 1+ was proposed to play a role in the function of sodium-based Prussian blue analogues (PBA) batteries, a highly sought-out technology for industrial energy storage. Here, we report the detailed electronic structure characterization of uncharged and charged sodium-based manganese hexacyanomanganate anodes via Mn K-edge X-ray absorption spectroscopy (XAS), Kβ nonresonant X-ray emission (XES), and resonant inelastic X-ray scattering (RIXS). The latter allowed us to obtain site-selective XANES information about two distinct Mn centers. The obtained spectroscopic data represent the first electronic structure characterization of low-spin Mn 1+ using hard X-ray RIXS and XES and allowed us to confirm its role in anode reduction. In conclusion, our experimental approach can be expanded to analysis of analogues with other 3d transition metals broadening the application of exotic ionic states in materials engineering.
A Stable Graphitic, Nanocarbon-Encapsulated, Cobalt-Rich Core-Shell Electrocatalyst as an Oxygen Electrode in a Water Electrolyzer
The oxygen electrode plays a vital role in the successful commercialization of renewable energy technologies, such as fuel cells and water electrolyzers. In this study, the Prussian blue analogue-derived nitrogen-doped nanocarbon (NC) layer-trapped, cobalt-rich, core–shell nanostructured electrocatalysts (core–shell Co@NC) are reported. The electrode exhibits an improved oxygen evolution activity and stability compared to that of the commercial noble electrodes. The core–shell Co@NC-loaded nickel foam exhibits a lower overpotential of 330 mV than that of IrO2 on nickel foam at 10 mA cm-2 and has a durability of over 400 h. The commercial Pt/C cathode-assisted, core–shell Co@NC–anode water electrolyzer delivers 10 mA cm-2 at a cell voltage of 1.59 V, which is 70 mV lower than that of the IrO2–anode water electrolyzer. Over the long-term chronopotentiometry durability testing, the IrO2–anode water electrolyzer shows a cell voltage loss of 230 mV (14%) at 95 h, but the loss of the core–shell Co@NC–anode electrolyzer is only 60 mV (4%) even after 350 h cell-operation. The findings indicate that the Prussian blue analogue is a class of inorganic nanoporous materials that can be used to derive metal-rich, core–shell electrocatalysts with enriched active centers.
The nature of iron deposits differs between symptomatic and asymptomatic carotid atherosclerotic plaques
Iron within atherosclerotic plaque has been implicated as a catalyst of oxidative stress that causes progression of plaque, and plaque rupture. Iron is believed to accumulate within plaque by incorporation of erythrocytes following plaque rupture and hemorrhage. There is only indirect evidence to support this hypothesis. Plaque specimens were obtained from ten symptomatic and fifteen asymptomatic patients undergoing carotid endarterectomy at a single institution. Plaques were sectioned for study using synchrotron radiation induced X-ray fluorescence the study the distribution of zinc, calcium and iron. Histologic staining was carried out with Prussian Blue, and immunohistochemical staining was done to localize macrophages with CD68. Data were compared against patient clinical variables. Ten symptomatic (15 ± 10 days between index symptoms and surgery) and fifteen asymptomatic carotid plaques were studied. Zinc and calcium co-localized in mineralized areas of symptomatic and asymptomatic plaque. Iron was identified away from zinc and calcium in both symptomatic and asymptomatic plaques. Within the symptomatic plaques, iron was found within the thrombus associated with plaque rupture and hemorrhage. It did not stain with Prussian Blue, but was found in association with CD68 positive macrophages. In symptomatic plaques, the abundance of iron showed an association with the source patient’s LDL cholesterol (R 2 = 0.39, Significance F = 0.05). Iron in asymptomatic plaque was present as hemosiderin/ferritin that stained positive with Prussian Blue, and was observed in association with CD68 positive macrophages. Iron in acutely symptomatic plaques is found within thrombus, in the presence of macrophages. Moreover, the abundance of iron in symptomatic plaques is associated with the source patient’s LDL cholesterol. Within asymptomatic plaques, iron is found in association with macrophages, as hemosiderin/ferritin.
Monovalent manganese based anodes and co-solvent electrolyte for stable low-cost high-rate sodium-ion batteries
The demand of sustainable power supply requires high-performance cost-effective energy storage technologies. Here in this paperwe report a high-rate long-life low-cost sodium-ion battery full-cell system by innovating both the anode and the electrolyte. The redox couple of manganese(I/II) in Prussian blue analogs enables a high-rate and stable anode. Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering provide direct evidence suggesting the existence of monovalent manganese in the charged anode. There is a strong hybridization between cyano ligands and manganese-3d states, which benefits the electronic property for improving rate performance. Additionally, we employ an organic-aqueous cosolvent electrolyte to solve the long-standing solubility issue of Prussian blue analogs. A full-cell sodium-ion battery with low-cost Prussian blue analogs in both electrodes and co-solvent electrolyte retains 95% of its initial discharge capacity after 1000 cycles at 1C and 9 5% depth of discharge. The revealed manganese(I/II) redox couple inspires conceptual innovations of batteries based on atypical oxidation states.
Potassium-based Aqueous Flow Battery for Grid Application
The objective of this one-year project was to determine the feasibility and economics of an aqueous, potassium-ion flow battery based on slurries of Prussian Blue Analogs (PBA). We have developed all the critical elements of the battery and finally demonstrated a flow battery prototype with a Prussian Blue analog cathode and a Methylene Blue anode. The project did provide a number of insights into this new approach for flow batteries.
Photocatalytic Color Switching of Transition Metal Hexacyanometalate Nanoparticles for High-Performance Light-Printable Rewritable Paper
Developing efficient photoreversible color switching systems for constructing rewritable paper is of significant practical interest owing to the potential environmental benefits including forest conservation, pollution reduction, and resource sustainability. Here we report that the color change associated with the redox chemistry of nanoparticles of Prussian blue and its analogues could be integrated with the photocatalytic activity of TiO 2 nanoparticles to construct a class of new photoreversible color switching systems, which can be conveniently utilized for fabricating ink-free, light printable rewritable paper with various working colors. The current system also addresses the phase separation issue of the previous organic dye-based color switching system so that it can be conveniently applied to the surface of conventional paper to produce an ink-free light printable rewritable paper that has the same feel and appearance as the conventional paper. In conclusion, with its additional advantages such as excellent scalability and outstanding rewriting performance (reversibility > 80 times, legible time > 5 days, and resolution > 5 μm), this novel system can serve as an eco-friendly alternative to regular paper in meeting the increasing global needs for environment protection and resource sustainability.
Porous Hexacyanometalates for CO2 capture applications
Prussian blue analogues of M3[Fe(CN)6]2 x H2O (where M=Fe, Mn and Ni) were synthesized, characterized and tested for their gas sorption capabilities. The sorption studies reveal that, these Prussian blue materials preferentially sorb CO2 over N2 and CH4 at low pressure (1bar).
Novel Co{sub 3}O{sub 4} porous polyhedrons derived from metal–organic framework toward high performance for electrochemical energy devices
Co{sub 3}O{sub 4} polyhedrons with porous structure have been synthesized simply by annealing Prussian blue analogue (PBA) Co{sub 3}[Co(CN){sub 6}]{sub 2} polyhedrons at 400 °C in air. The product was characterized by a series of techniques, such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), High-resolution TEM (HRTEM), X-ray Photoelectron Spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) gas adsorption. Interestingly, when evaluated as an anode material for lithium-ion batteries (LIBs), the Co{sub 3}O{sub 4} porous polyhedrons manifested high reversible capacity (about 1200 mAh g{sup −1} at 50 mA g{sup −1}) and excellent cycling performance. Moreover, they also exhibited a high specific capacitance of 110 Fg{sup −1} when used as an electrode in the supercapacitor. It is suggested that the special morphology and porous nanostructure lead to the promising electrochemical properties. - Graphical abstract: Novel and complicated mesoporous architectures of Co{sub 3}O{sub 4} have been fabricated by thermal decomposition of Prussian Blue Analog (PBA) Co{sub 3}[Co(CN){sub 6}]{sub 2} polyhedrons which obtained at the room temperature. When Co{sub 3}O{sub 4} product was evaluated for Li-ion batteries (LIBs), they exhibited high reversible capacity of 1000 mAh g{sup −1} with excellent cycle life because of the hollow/porous structure. Display Omitted.
Cluster-Expanded Solids: A Strategy for Assembling Functional Porous Materials
This grant provided (partial) support for the research efforts of three graduate students and two undergraduate students. The intention of the program was to explore the use of molecular precursors in generating functional porous materials with precisely tailored structures and properties. Prior work in our laboratory had demonstrated the feasibility of employing face-capped octahedral clusters of the type [Re 6 Q 8 (CN) 6 ] 3-/4- (Q = S, Se, Te) in the expansion of known metal-cyanide frameworks. For example, the use of [Re 6 Se 8 (CN) 6 ] 4- as a reactant in place of [Fe(CN) 6 ] 4- resulted in formation of Fe 4 [Re 6 Se 8 (CN) 6 ] 3 ·36H 2 O, featuring an expanded form of the porous three-dimensional framework of Prussian blue (Fe 4 [Fe(CN) 6 ] 3 ·14H 2 O). This compound could be dehydrated without loss of integrity, and the increase in void volume significantly enhances its capacity as a molecular sieve, enabling absorption of larger molecules. For this project, we continued with our efforts to devise new routes to microporous coordination solids that function as molecular sieves, sensors, or catalysts. In particular, our focus was on: (i) the synthesis of new molecular precursors of specific utility for such purposes, and (ii) attempts to incorporate these and existing molecular precursors into new coordination solids. Investigations of the terminal ligand substitution chemistry of the carbon-centered, trigonal prismatic cluster [W 6 CCl 18 ] 2- generated the solvated species [W 6 CCl 12 (DMF) 6 ] 2+ and [W 6 CCl 12 (py) 6 ] 2+ , as well as the potential framework building units [W 6 C(CN) 18 ] 3- , [W 6 CCl 12 (pyrazine) 6 ] 2+ , [W 6 CCl 12 (4-cyanopyridine) 6 ] 2+ , and [W 6 CCl 12 (4,4'-bipyridine) 6 ] 2+ . Efforts to produce microporous magnets capable of performing magnetic separations led to characterization of the microporous Prussian blue analogues CsNi[Cr(CN) 6 ] and Cr 3 [Cr(CN) 6 ] 2 ·6H 2 O. With BET surface areas of 370 m 2 /g and 390 m 2 /g, respectively, these compounds exhibit show ferrimagnetic ordering at temperatures of 65 and 220 K, respectively, the highest ordering temperatures yet observed for any microporous magnet. Efforts to produce actinide-based cluster building units were also undertaken, as were experiments probing the reactivity of new metal-organic frameworks possessing coordinatively-unsaturated metal centers. This research further provided an excellent opportunity for training graduate and undergraduate students in the synthesis and characterization of inorganic materials.
Directed plant cell-wall accumulation of iron: Embedding co-catalyst for efficient biomass conversion
Plant lignocellulosic biomass is an abundant, renewable feedstock for the production of biobased fuels and chemicals. Previously, we showed that iron can act as a co-catalyst to improve the deconstruction of lignocellulosic biomass. However, directly adding iron catalysts into biomass prior to pretreatment is diffusion limited, and increases the cost of biorefinery operations. Recently, we developed a new strategy for expressing iron-storage protein ferritin intracellularly to accumulate iron as a catalyst for the downstream deconstruction of lignocellulosic biomass. In this study, we extend this approach by fusing the heterologous ferritin gene with a signal peptide for secretion into Arabidopsis cell walls (referred to here as FerEX). The transgenic Arabidopsis plants. FerEX. accumulated iron under both normal and iron-fertilized growth conditions; under the latter (iron-fertilized) condition, FerEX transgenic plants showed an increase in plant height and dry weight by 12 and 18 %, respectively, compared with the empty vector control plants. The SDS- and native-PAGE separation of cell-wall protein extracts followed by Western blot analyses confirmed the extracellular expression of ferritin in FerEX plants. Meanwhile, Perls' Prussian blue staining and X-ray fluorescence microscopy (XFM) maps revealed iron depositions in both the secondary and compound middle lamellae cell-wall layers, as well as in some of the corner compound middle lamella in FerEX. Remarkably, their harvested biomasses showed enhanced pretreatability and digestibility, releasing, respectively, 21 % more glucose and 34 % more xylose than the empty vector control plants. These values are significantly higher than those of our recently obtained ferritin intracellularly expressed plants. This study demonstrated that extracellular expression of ferritin in Arabidopsis can produce plants with increased growth and iron accumulation, and reduced thermal and enzymatic recalcitrance. Here, the results are attributed to the intimate colocation of the iron co-catalyst and the cellulose and hemicellulose within the plant cell-wall region, supporting the genetic modification strategy for incorporating conversion catalysts into energy crops prior to harvesting or processing at the biorefinery.
An insoluble iron complex coated cathode enhances direct electron uptake by Rhodopseudomonas palustris TIE-1
Microbial electrosynthesis (MES) is a promising bioelectrochemical approach to produce biochemicals. A previous study showed that Rhodopseudomonas palustris TIE-1 can directly use poised electrodes as electron donors for photoautotrophic growth at cathodic potentials that avoid electrolytic H2 production (photoelectroautotrophy). To make TIE-1 an effective biocatalyst for MES, we need to improve its electron uptake ability and growth under photoelectroautotrophic conditions. Because TIE-1 interacts with various forms of iron while using it as a source of electrons for photoautotrophy (photoferroautotrophy), here we tested the ability of iron-based redox mediators to enhance direct electron uptake. Our data show that soluble iron cannot act as a redox mediator for electron uptake by TIE-1 from a cathode poised at +100 mV vs. Standard Hydrogen electrode. We then tested whether an immobilized iron-based redox mediator Prussian blue (PB) can enhance electron uptake by TIE-1. Chronoamperometry indicates that cathodic current uptake by TIE-1 increased from 1.47 ± 0.04 to 5.6 ± 0.09 μA/cm 2 (3.8 times). Overall, our data show that immobilized PB can enhance direct electron uptake by TIE-1.
Transgenic Ferritin Overproduction Enhances Thermochemical Pretreatments in Arabidopsis
Abstract not provided