A Bio‐Inspired,Heavy‐Metal‐Free,Dual‐Electrolyte Liquid Battery towards Sustainable Energy Storage

Wide‐scale exploitation of renewable energy requires low‐cost efficient energy storage devices. The use of metal‐free, inexpensive redox‐active organic materials represents a promising direction for environmental‐friendly, cost‐effective sustainable energy storage. To this end, a liquid battery is designed using hydroquinone (H₂BQ) aqueous solution as catholyte and graphite in aprotic electrolyte as anode. The working potential can reach 3.4 V, with specific capacity of 395 mA h g⁻¹ and stable capacity retention about 99.7 % per cycle. Such high potential and capacity is achieved using only C, H and O atoms as building blocks for redox species, and the replacement of Li metal with graphite anode can circumvent potential safety issues. As H₂BQ can be extracted from biomass directly and its redox reaction mimics the bio‐electrochemical process of quinones in nature, using such a bio‐inspired organic compound in batteries enables access to greener and more sustainable energy‐storage technology.     

A Bio‐Inspired,Heavy‐Metal‐Free,Dual‐Electrolyte Liquid Battery towards Sustainable Energy Storage

Wide‐scale exploitation of renewable energy requires low‐cost efficient energy storage devices. The use of metal‐free, inexpensive redox‐active organic materials represents a promising direction for environmental‐friendly, cost‐effective sustainable energy storage. To this end, a liquid battery is designed using hydroquinone (H₂BQ) aqueous solution as catholyte and graphite in aprotic electrolyte as anode. The working potential can reach 3.4 V, with specific capacity of 395 mA h g^?1 and stable capacity retention about 99.7 % per cycle. Such high potential and capacity is achieved using only C, H and O atoms as building blocks for redox species, and the replacement of Li metal with graphite anode can circumvent potential safety issues. As H₂BQ can be extracted from biomass directly and its redox reaction mimics the bio‐electrochemical process of quinones in nature, using such a bio‐inspired organic compound in batteries enables access to greener and more sustainable energy‐storage technology.     

An Organic Mixed‐Valence Ligand for Multistate Redox‐Active Coordination Networks

The multistate redox‐active/multi‐interactive ligand 5,5′,8,8′‐tetra(4‐pyridyl)‐2,2′‐(1,4‐phenylene)bis‐1H‐perimidine (H₂TPP) was designed and synthesized. H₂TPP undergoes four one‐electron oxidation steps, and was used for the preparation of a multistate redox‐active coordination network in a solid–liquid interface reaction using molten Cd²⁺ salts. The multiple redox states of H₂TPP were confirmed spectroscopically by stepwise four‐electron oxidation. Spectroscopic analysis indicated that the mixed‐valence states of the ligand are class II on the UV/Vis/NIR timescale and borderline class II/class III on the ESR timescale.     

Redox‐Polymer‐Based High‐Current‐Density Gas‐Diffusion H2‐Oxidation Bioanode Using [FeFe] Hydrogenase from Desulfovibrio desulfuricans in a Membrane‐free Biofuel Cell

The incorporation of highly active but also highly sensitive catalysts (e.g. the [FeFe] hydrogenase from Desulfovibrio desulfuricans) in biofuel cells is still one of the major challenges in sustainable energy conversion. We report the fabrication of a dual‐gas diffusion electrode H₂/O₂ biofuel cell equipped with a [FeFe] hydrogenase/redox polymer‐based high‐current‐density H₂‐oxidation bioanode. The bioanodes show benchmark current densities of around 14 mA cm^?2 and the corresponding fuel cell tests exhibit a benchmark for a hydrogenase/redox polymer‐based biofuel cell with outstanding power densities of 5.4 mW cm^?2 at 0.7 V cell voltage. Furthermore, the highly sensitive [FeFe] hydrogenase is protected against oxygen damage by the redox polymer and can function under 5 % O₂.     

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices

Building on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost‐effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10‐anthraquinone‐2,7‐disulfonic acid (AQDS)/1,2‐benzoquinone‐3,5‐disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L^?1 and a solar‐to‐output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency.     

Capacitance Effects Superimposed on Redox Processes in Molecular‐Cluster Batteries: A Synergic Route to High‐Capacity Energy Storage

Rechargeable molecular‐cluster batteries (MCBs) based on the manganese cluster complex [Mn₁₂O₁₂(CH₃CH₂C(CH₃)₂COO)₁₆(H₂O)₄] ([Mn12]) that exhibited a capacity of approximately 200 A h kg^?1 in the battery voltage range of 4.0 to 2.0 V were developed. In these batteries, the capacity of approximately 100 A h kg^?1 in the range of 4.0–3.0 V is caused by a chemical reduction from [Mn12]⁰ to [Mn12]^8?, whereas the other half in the range of 3.0–2.0 V cannot be explained by a redox change of the Mn ions. We performed the cyclic voltammetry (CV) and ⁷Li solid‐state NMR measurements on the Mn12‐MCBs to investigate the origin of the capacity below 3.0 V. Pseudo‐rectangular‐shaped CV curves in the range of 3.0–2.0 V demonstrate the presence of an electrical double‐layer (EDL) capacitance in Mn12‐MCBs, which corresponds to approximately 100 A h kg^?1. ⁷Li NMR studies suggest that Li ions form an EDL with electrons in carbon black electrodes in the capacitance voltage range. The capacitance effects are not formed by the single‐carbon electrodes alone, but appear only in the mixture of Mn12 and the carbon black electrodes. This type of coexistence of capacitance effects and redox reaction in one electrochemical cell is quite unusual and can serve as a new working principle for high‐performance energy‐storage devices.     

Enhancing Capacity Performance by Utilizing the Redox Chemistry of the Electrolyte in a Dual‐Electrolyte Sodium‐Ion Battery

A strategy is described to increase charge storage in a dual electrolyte Na‐ion battery (DESIB) by combining the redox chemistry of the electrolyte with a Na⁺ ion de‐insertion/insertion cathode. Conventional electrolytes do not contribute to charge storage in battery systems, but redox‐active electrolytes augment this property via charge transfer reactions at the electrode–electrolyte interface. The capacity of the cathode combined with that provided by the electrolyte redox reaction thus increases overall charge storage. An aqueous sodium hexacyanoferrate (Na₄Fe(CN)₆) solution is employed as the redox‐active electrolyte (Na‐FC) and sodium nickel Prussian blue (Na_x‐NiBP) as the Na⁺ ion insertion/de‐insertion cathode. The capacity of DESIB with Na‐FC electrolyte is twice that of a battery using a conventional (Na₂SO₄) electrolyte. The use of redox‐active electrolytes in batteries of any kind is an efficient and scalable approach to develop advanced high‐energy‐density storage systems.     

A quasi‐diamondoid hydrogen‐bonded framework in an­hydro­us sulfanilic acid

The title compound (C₆H₇NO₃S) exists as a zwitterion (4‐ammonio­benzene­sulfonate), ⁺H₃NC₆H₄SO₃^?, and these units are linked into a three‐dimensional framework by two distinct two‐centre N—H?O hydrogen bonds [H?O 1.84 and 1.87 Å; N?O 2.767 (2) and 2.746 (2) Å; N—H?O 166 and 172°] and a planar three‐centre N—H?(O)₂ hydrogen bond [H?O 2.03 and 2.37 Å; N?O 2.816 (2) and 2.877 (2) Å; N—H?O 162 and 111°; O?H?O 86°].     

Neue Kronenether‐stabilisierte Oxoniumhalogenochalkogenate: [H3O(Dibromo‐benzo‐18‐Krone‐6)]2[Se3Br10] und [H5O2(Bis‐dibromo‐dibenzo‐24‐Krone‐8]2[Se3Br8]

Novel Oxonium Halogenochalcogenates Stabilized by Crown Ethers: [H₃O(Dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] and [H₅O₂(Bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] Two novel complex oxonium bromoselenates(II,IV) and –(II) are reported containing [H₃O]⁺ and [H₅O₂]⁺ cations coordinated by crown ether ligands. [H₃O(dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] ( 1 ) and [H₅O₂(bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] ( 2 ) were prepared as dark red crystals from dichloromethane or acetonitrile solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal structures and by vibrational spectra. 1 is triclinic, space group (Nr. 2) with a = 8.609(2) Å, b = 13.391(3) Å, c = 13.928(3) Å, α = 64.60(2)°, β = 76.18(2)°, γ = 87.78(2)°, V = 1404.7(5) ų, Z = 1. 2 is also triclinic, space group with a = 10.499(2) Å, b = 13.033(3) Å, c = 14.756(3) Å, α = 113.77(3)°, β = 98.17(3)°, γ = 93.55(3)°. V = 1813.2(7) ų, Z = 1. In the reaction mixture complex redox reactions take place, resulting in (partial) reduction of selenium and bromination of the crown ether molecules. In 1 the centrosymmetric trinuclear [Se₃Br₁₀]^2? consists of a central Se^IVBr₆ octahedron sharing trans edges with two square planar Se^IIBr₄ groups. The novel [Se₃Br₈]^2? in 2 is composed of three planar trans‐edge sharing Se^IIBr₄ squares in a linear arrangement. The internal structure of the oxonium‐crown ether complexes is largely determined by the steric restrictions imposed by the aromatic rings in the crown ether molecules, as compared to complexes with more flexible unsubstituted crown ether ligands.     

A π‐Conjugation Extended Viologen as a Two‐Electron Storage Anolyte for Total Organic Aqueous Redox Flow Batteries

Extending the conjugation of viologen by a planar thiazolo[5,4‐d]thiazole (TTz) framework and functionalizing the pyridinium with hydrophilic ammonium groups yielded a highly water‐soluble π‐conjugation extended viologen, 4,4′‐(thiazolo[5,4‐d]thiazole‐2,5‐diyl)bis(1‐(3‐(trimethylammonio)propyl)pyridin‐1‐ium) tetrachloride, [(NPr)₂TTz]Cl₄ , as a novel two‐electron storage anolyte for aqueous organic redox flow battery (AORFB) applications. Its physical and electrochemical properties were systematically investigated. Paired with 4‐trimethylammonium‐TEMPO (N^Me‐TEMPO) as catholyte, [(NPr)₂TTz]Cl₄ enables a 1.44 V AORFB with a theoretical energy density of 53.7 Wh L^?1. A demonstrated [(NPr)₂TTz]Cl₄ /N^Me‐TEMPO AORFB delivered an energy efficiency of 70 % and 99.97 % capacity retention per cycle.     

Solvent‐Vapor‐Induced Reversible Single‐Crystal‐to‐Single‐Crystal Transformation of a Triphosphaazatriangulene‐Based Metal–Organic Framework

A triphosphaazatriangulene (H₃L) was synthesized through an intramolecular triple phospha‐Friedel–Crafts reaction. The H₃L triangulene contains three phosphinate groups and an extended π‐conjugated framework, which enables the stimuli‐responsive reversible transformation of [Cu(HL)(DMSO)?(MeOH)]_n, a 3D‐MOF that exhibits reversible sorption characteristics, into (H₃L?0.5 [Cu₂(OH)₄?6 H₂O] ?4 H₂O), a 1D‐columnar assembled proton‐conducting material. The hydrophilic nature of the latter resulted in a proton conductivity of 5.5×10^?3 S cm^?1 at 95 % relative humidity and 60 °C.     

A Sustainable Redox‐Flow Battery with an Aluminum‐Based,Deep‐Eutectic‐Solvent Anolyte

Nonaqueous redox‐flow batteries are an emerging energy storage technology for grid storage systems, but the development of anolytes has lagged far behind that of catholytes due to the major limitations of the redox species, which exhibit relatively low solubility and inadequate redox potentials. Herein, an aluminum‐based deep‐eutectic‐solvent is investigated as an anolyte for redox‐flow batteries. The aluminum‐based deep‐eutectic solvent demonstrated a significantly enhanced concentration of circa 3.2 m in the anolyte and a relatively low redox potential of 2.2 V vs. Li⁺/Li. The electrochemical measurements highlight that a reversible volumetric capacity of 145 Ah L⁻¹ and an energy density of 189 Wh L⁻¹ or 165 Wh kg⁻¹ have been achieved when coupled with a I₃⁻/I⁻ catholyte. The prototype cell has also been extended to the use of a Br₂‐based catholyte, exhibiting a higher cell voltage with a theoretical energy density of over 200 Wh L⁻¹. The synergy of highly abundant, dendrite‐free, multi‐electron‐reaction aluminum anodes and environmentally benign deep‐eutectic‐solvent anolytes reveals great potential towards cost‐effective, sustainable redox‐flow batteries.     

High Performance Fe Porphyrin/Ionic Liquid Co‐catalyst for Electrochemical CO2 Reduction

The efficient and selective catalytic reduction of CO₂ is a highly promising process for both of the storage of renewable energy as well as the production of valuable chemical feedstocks. In this work, we show that the addition of an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, in an aprotic electrolyte containing a proton source and FeTPP, promotes the in situ formation of the [Fe⁰TPP]^2? homogeneous catalyst at a less negative potential, resulting in lower overpotentials for the CO₂ reduction (670 mV) and increased kinetics of electron transfer. This co‐catalysis exhibits high Faradaic efficiency for CO production (93 %) and turnover number (2 740 000 after 4 hour electrolysis), with a four‐fold increase in turnover frequency (TOF) when compared with the standard system without the ionic liquid.     

High resolution‐HMBC (HR‐HMBC), a new method for measuring heteronuclear long‐range coupling constants

A useful pulse sequence for measuring long‐range C? H coupling constants (J_{C? H}) named high resolution‐HMBC (HR‐HMBC) has been developed. In this pulse sequence, the J‐scaling pulse [(nt₁)/2? 180° (H/C) ? (nt₁)/2] is incorporated after the spin evolution period, and then followed by an ¹H 180° pulse to reverse the magnetization of J_{C? H} couplings. As a result, splittings of the cross peaks due to the long‐range J_{C? H} are realigned with separations of nJ_{C? H} along the F₁ dimension, and thus even the small long‐range J_{C? H} values can easily be determined. The efficiency of measuring the long‐range J_{C? H} using the proposed pulse sequences has been demonstrated in application to the complicated natural product, portmicin. Copyright © 2010 John Wiley & Sons, Ltd.     

Field‐Induced Slow Magnetic Relaxation in a Mononuclear Manganese(III)–Porphyrin Complex

We report on a novel manganese(III)–porphyrin complex with the formula [Mn^III(TPP)(3,5‐Me₂pyNO)₂]ClO₄?CH₃CN ( 2 ; 3,5‐Me₂pyNO=3,5‐dimethylpyridine N‐oxide, H₂TPP=5,10,15,20‐tetraphenylporphyrin), in which the Mn^III ion is six‐coordinate with two monodentate 3,5‐Me₂pyNO molecules and a tetradentate TPP ligand to build a tetragonally elongated octahedral geometry. The environment in 2 is responsible for the large and negative axial zero‐field splitting (D=?3.8 cm^?1), low rhombicity (E/|D|=0.04) of the high‐spin Mn^III ion, and, ultimately, for the observation of slow magnetic‐relaxation effects (E_a=15.5 cm^?1 at H=1000 G) in this rare example of a manganese‐based single‐ion magnet (SIM). Structural, magnetic, and electronic characterizations were carried out by means of single‐crystal diffraction studies, variable‐temperature direct‐ and alternating‐current measurements and high‐frequency and ‐field EPR spectroscopic analysis followed by quantum‐chemical calculations. Slow magnetic‐relaxation effects were also observed in the already known analogous compound [Mn^III(TPP)Cl] ( 1 ; E_a=10.5 cm^?1 at H=1000 G). The results obtained for 1 and 2 are compared and discussed herein.     

Site‐Directed Dimerization of Bowl‐Shaped Radical Anions to Form a σ‐Bonded Dibenzocorannulene Dimer

Designed site‐directed dimerization of the monoanion radicals of a π‐bowl in the solid state is reported. Dibenzo[a,g]corannulene (C₂₈H₁₄) was selected based on the asymmetry of the charge/spin localization in the C₂₈H₁₄^.? anion. Controlled one‐electron reduction of C₂₈H₁₄ with Cs metal in diglyme resulted in crystallization of a new dimer, [{Cs⁺(diglyme)}₂(C₂₈H₁₄?C₂₈H₁₄)^2?] ( 1 ), as revealed by single crystal X‐ray diffraction study performed in a broad range of temperatures. The C?C bond length between two C₂₈H₁₄^.? bowls (1.560(8) Å) measured at ?143 °C does not significantly change upon heating of the crystal to +67 °C. The single σ‐bond character of the C?C linker is confirmed by calculations. The trans‐disposition of two bowls in 1 is observed with the torsion angles around the central C?C bond of 172.3(5)° and 173.5(5)°. A systematic theoretical evaluation of dimerization pathways of C₂₈H₁₄^.? radicals confirmed that the trans‐isomer found in 1 is energetically favored.     

The high‐anti conformation of 8‐aza‐1,3‐dide­aza‐2′‐deoxy­adenosine

In the title compound, 4‐amino‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐1H‐benzotriazole, C₁₁H₁₄N₄O₃, the conformation of the N‐glycosidic bond is in the high‐anti range [χ = ?77.1 (4)°] and the 2′‐deoxy­ribo­furan­ose moiety adopts a 2′‐­endo (²E) sugar puckering. The 5′‐hydroxyl group is disordered and has conformations ap with γ = 171.1 (3)° [occupation of 61.4 (3)%] and +sc with γ = 52.4 (6)° [occupation of 38.6 (3)%]. The nucleobases are stacked in the crystal state.     

Regulating Fast Anionic Redox for High‐Voltage Aqueous Hydrogen‐Ion‐based Energy Storage

The ionic conductivity and small size of the hydrogen ion make it an ideal charge carrier for hydrogen‐ion energy storage (HES); however, high‐voltage two‐electrode configurations are difficult to construct as the result of the lack of efficient cathodic energy storage. Herein, the high potential fast anionic redox at the cathode of reduced graphene oxide (rGO) was applied by introducing redox additive electrolytes. By coupling the storing hydrogen ion in the Ti₃C₂T_x at the anode, a HES with a voltage of 1.8 V and a plateau voltage at 1.2 V was constructed. Compared with 2.2 Wh kg^?1 for the low‐voltage Ti₃C₂T_x//Ti₃C₂T_x, the specific energy of asymmetric rGO//Ti₃C₂T_x reaches 34.4 Wh kg^?1. Furthermore, it possesses an energy density of 23.7 Wh kg^?1 at high power density of 22.5 kW kg^?1. Thus, this study provides a novel guideline for constructing high‐voltage fast HES full cells.     

Redox Chemistry of Molybdenum Trioxide for Ultrafast Hydrogen‐Ion Storage

Hydrogen ions are ideal charge carriers for rechargeable batteries due to their small ionic radius and wide availability. However, little attention has been paid to hydrogen‐ion storage devices because they generally deliver relatively low Coulombic efficiency as a result of the hydrogen evolution reaction that occurs in an aqueous electrolyte. Herein, we successfully demonstrate that hydrogen ions can be electrochemically stored in an inorganic molybdenum trioxide (MoO₃) electrode with high Coulombic efficiency and stability. The as‐obtained electrode exhibits ultrafast hydrogen‐ion storage properties with a specific capacity of 88 mA hg^?1 at an ultrahigh rate of 100 C. The redox reaction mechanism of the MoO₃ electrode in the hydrogen‐ion cell was investigated in detail. The results reveal a conversion reaction of the MoO₃ electrode into H_0.88MoO₃ during the first hydrogen‐ion insertion process and reversible intercalation/deintercalation of hydrogen ions between H_0.88MoO₃ and H_0.12MoO₃ during the following cycles. This study reveals new opportunities for the development of high‐power energy storage devices with lightweight elements.     

Self‐assembly of a cobalt(II)‐based metal–organic framework as an effective water‐splitting heterogeneous catalyst for light‐driven hydrogen production

The solar photocatalysis of water splitting represents a significant branch of enzymatic simulation by efficient chemical conversion and the generation of hydrogen as green energy provides a feasible way for the replacement of fossil fuels to solve energy and environmental issues. We report herein the self‐assembly of a Co^II‐based metal–organic framework (MOF) constructed from 4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetrabenzoic acid [or tetrakis(4‐carboxyphenyl)ethylene, H₄TCPE] and 4,4′‐bipyridyl (bpy) as four‐point‐ and two‐point‐connected nodes, respectively. This material, namely, poly[(μ‐4,4′‐bipyridyl)[μ₈‐4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetrabenzoato]cobalt(II)], [Co(C₃₀H₁₆O₈)(C₁₀H₈N₂)]_n, crystallized as dark‐red block‐shaped crystals with high crystallinity and was fully characterized by single‐crystal X‐ray diffraction, PXRD, IR, solid‐state UV–Vis and cyclic voltammetry (CV) measurements. The redox‐active Co^II atoms in the structure could be used as the catalytic sites for hydrogen production via water splitting. The application of this new MOF as a heterogeneous catalyst for light‐driven H₂ production has been explored in a three‐component system with fluorescein as photosensitizer and trimethylamine as the sacrificial electron donor, and the initial volume of H₂ production is about 360 µmol after 12 h irradiation.