High Cathodic Potentials Research Articles

Novel Composite Fuel Electrode for CH4-SOFC and CO2-SOEC

Reversible solid oxide cells (RSOCs) represent a promising technology for the efficient exploitation of intrinsically intermittent renewable energy sources. RSOCs allow to derive fuel and chemicals from power (power-to-gas technology, P2G) and power from fuel and chemicals (gas-to-power technology, GTP) and can be interchangeably operated either as a solid oxide fuel cell (SOFC) or as a solid oxide electrolyzer cell (SOEC). The key aspect to render these devices competitive on a market scale is the development of multi-tasking, reliable, cost-effective and long-lasting electrodes (1,2). Besides, to overcome the issues related to hydrogen production, storage and distribution (e.g. impractical conversion of the existing grid to hydrogen-based infrastructures), the fuel-electrode of RSOCs should ensure high catalytic activity and coking resistance toward carbon-containing species (3-4). Using a hydrocarbon-tolerant fuel electrode, energy can be obtained by natural gas and biogas (SOFC-mode), with useful recovery of CO2 in the exhausts (carbon capture and storage, CCS). Besides, if the electrode is also active towards CO2 electrolysis (SOEC mode), CO2 is reduced to CO and O2 (carbon capture and utilization, CCU).Ni-YSZ is the reference fuel-electrode material for both H2 fed SOFC and for CO2 electrolysis in SOEC. Nevertheless, Ni-based cermets cannot be used in SOFCs fed with methane-containing fuels, as they suffer from two main drawbacks: mechanical instability upon NiO-Ni redox cycles (5) and passivation due to coking, being Ni a catalyst for methane cracking (3, 4). Moreover, during Ni-YSZ operation in CO2-SOEC mode, ZrO2 reduction can occur at high cathodic potential, resulting in Ni-Zr compounds formation (6).In this work, a recently developed (7, 8) composite material containing La0.6Sr0.4Fe0.8Mn0.2O3-δ (LSFMn) and 5wt% Ni-containing Ce0.58Sm0.15O2-δ (NiSDC) is tested as fuel electrode for LSGM-electrolyte supported cells. In reducing conditions, Fe exsolved from the LSFMn perovskite forms a Fe-Ni alloy with Ni present on SDC. In SOFC mode, the composite is designed to operate in dry methane: Fe-Ni catalytic sites activate CH4, which is successively oxidized on Mn-containing LSFMn, while SDC increases the O2- supply at the anode to get rid of any carbonaceous deposits. As Fe-Ni alloy was reported to be highly active for CO2 reduction (9), the composite was also tested as SOEC cathode in different CO2:CO ratios. LSFMn+NiSDC was tested in SOFC-mode as anode for hydrogen, dry methane and carbon monoxide oxidation and showed power density outputs of 657, 668 and 527 mW/cm2, respectively (Fig. a), a redox stable behavior and coking resistance for over 120 h. LSFMn+NiSDC in SOEC-mode delivered 2.66 A/cm2 at 2 V in 95:5 CO2:CO mixture (Fig. b), keeping 1 A/cm2 of current density output for over 40 h. (1) - M. Mogensen, M. Chen, H. Frandsen, C. Graves, J. Hansen, K. Hansen, A. Hauch, T. Jacobsen, S. Jensen, T. Skafte, Reversible solid-oxide cells for clean and sustainable energy, Clean Energy, 3 (2019) 175-201. (2) - M.B. Mogensen, Materials for Reversible Solid Oxide Cells, Current Opinion in Electrochemistry, (2020). (3) - M. Mogensen, K. Kammer, Conversion of hydrocarbons in solid oxide fuel cells, Annual Review of Materials Research, 33 (2003) 321-331. (4) - S. McIntosh, R.J. Gorte, Direct hydrocarbon solid oxide fuel cells, Chemical reviews, 104 (2004) 4845-4866. (5) - J. Malzbender, R. Steinbrech, Advanced measurement techniques to characterize thermo-mechanical aspects of solid oxide fuel cells, Journal of Power Sources, 173 (2007) 60-67 (6) - A. Hauch, K. Brodersen, M. Chen, M.B. Mogensen, Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability, Solid State Ionics, 293 (2016) 27-36 (7) - L. Duranti, I. Luisetto, S. Licoccia, C. Del Gaudio, E. Di Bartolomeo, Electrochemical performance and stability of LSFMn+ NiSDC anode in dry methane, Electrochimica Acta, (2020) 137116. (8) - L. Duranti, I.N. Sora, F. Zurlo, I. Luisetto, S. Licoccia, E. Di Bartolomeo, The role of manganese substitution on the redox behavior of La0.6Sr0.4Fe0.8Mn0.2O3-δ, Journal of the European Ceramic Society, (2020) ( 9 ) - Liu, S., Liu, Q., & Luo, J. L. (2016). Highly stable and efficient catalyst with in situ exsolved Fe–Ni alloy nanospheres socketed on an oxygen deficient perovskite for direct CO2 electrolysis. ACS Catalysis, 6(9), 6219-6228. Figure 1

Bismuth nanoparticles@carbon composite as a stable and high capacity anode for high-voltage bismuth-manganese batteries

Bismuth (Bi) electrochemistry holds great potential for aqueous energy storage in terms of its highly-reversible redox capability in alkaline solution, low-cost, and safety. However, Bi-based batteries still suffer from limited performance of Bi anodes and unsatisfying output voltage. Herein, to address these issues, we develop an advanced Bi electrode consisting of oxygen-functionalized Bi nanoparticles embedded in porous carbon frameworks (Bi@C), which was paired with a high potential MnO2 cathode via an electrolyte-decoupling configuration to achieve a high voltage bismuth-based battery. The presence of the subtly-designed oxygen interface favors efficient adsorption of OH− ions while its unique 3D carbon matrix provides an interconnected pathway for electron charge transport. As a result, the Bi@C anode exhibits a remarkable capacity (347.2 mAh g−1 at 3 A g−1) close to its theoretical value, an excellent rate capability (60% capacity retention at a high current density of 20 A g−1) and outstanding long-term cyclability (96% capacity retention over 9500 cycles). Furthermore, this new Bi//MnO2 hybrid battery possesses merits of high energy density (213 Wh kg−1) and output voltage (1.62 V). This work is expected to shed some lights on properly elevating the energy density of aqueous Bi batteries via electrode design.

Performance of Recirculatory Microbial Desalination Cell-Microbial Electrolysis Cell Coupled System with Different Catholytes

Microbial Desalination Cell-Microbial Electrolysis Cell (MDC-MEC) coupled system, are very important and efficient in several processes including wastewater treatment; heavy metal removal; desalination; and chemical production. The performances of ferricyanide (MDCF) and 100mM potassium phosphate buffer (MDCP100) as catholytes in the MDC were tested over a fed-batch cycle. The MDC systems (MDCF and MDCP100) were coupled with MEC to determine their effect on Pb and Fe removal. The COD removal efficiencies in MDCF, MDCP100, and control 1 were 92.96%, 90.54%, and 89.03% respectively. All the MDC systems were able to achieve a very high Pb2+ and Fe2+ removal efficiency, >90%. A high cathodic reduction potential was reached and maintained by the MDC-MEC systems, enable the reduction of Pb2+ and Fe2+ to Pb and Fe metals, through precipitation at the cathode of the MEC. MDCF had higher current and power densities of 550 mAm-2 and 166.08 mWm-2 respectively than that of MDCP100. More wastewater can be treated in the MDCP100 for ammonium removal in the middle chamber than that of MDCF. Therefore, the volume ratio of COD and NH4Cl removal in the MDC for balanced COD/Ammonium ions removal is a key driving force to the Industrial scale-up of the coupled system.

Enhanced H2 evolution reaction due to H spillover during electrolytic reduction of water on a Au/TiO2 electrode

TiO2 has limited applicability as an alternative to noble metal electrocatalysts for the hydrogen evolution reaction in aqueous solution due to the possibility of hydrogen intercalation under cathodic potential. In this work, the electrolytic reduction of H2O on TiO2 electrodes in alkaline media is investigated. Cyclic voltammetry experiments, combined with X-ray diffraction and in situ UV–vis results, indicate that most of the H species produced during the reaction diffuse into the TiO2 bulk at high cathodic potential. However, the presence of Au particles on the TiO2 electrodes greatly enhances H2O reduction and H2 production due to the H spillover effects, i.e., the H species produced on the TiO2 spill over to the Au nanoparticles and recombine to form H2. This result provides a new way of thinking about the design of more effective catalysts for the hydrogen evolution reaction using transition metal oxides.

Novel Cross-Linked Gel Polymer Electrolyte (GPE) with Long-Term Cycle Life for Li-Metal Batteries

Lithium metal batteries (LMBs) are considered among the most promising energy storage technologies due to their very high energy density and lightweight. While liquid electrolytes (LEs) offer high ionic conductivities (10−3−10−2 S cm−1) and low interfacial resistance with electrodes, yet the risks of leakage and combustion of organic solvents, lithium (Li) dendrite formation, thermal runaway, and environmental concerns regarding using organic solvents hinder their full potential applications. Li dendrites are mainly induced by nonuniform distribution of charge or ions and formation of a fragile, unstable solid electrolyte interphase (SEI) layer on Li metal anode during electrochemical Li deposition. The dendritic morphology of electrochemically deposited Li results in inefficient lithiation/delithiation and the formation of inactive or dead Li and constant degradation of organic solvents during Li plating/stripping, leading to capacity decade and decline in cycle life. Furthermore, lithium dendrites can pose a safety issue by penetrating through a porous or mechanically soft separator and making a short-circuit. High voltage instability of conventional electrolytes is another issue restricting application of high potential cathodes to enhance the energy density of LMBs. Gel polymer electrolytes (GPEs) are considered a promising alternative for LEs because of their high ionic conductivities (10−3−10−2 S cm−1), prevention of liquid leakage, low flammability, chemical and electrochemical stability, high flexibility for portable and wearable electronics, suppression of dendrite formation, and ample chemistry and design [1-4].In this work, we have developed a novel, highly efficient PEO-based GPE by a simple, facile chemical method and using UV light-induced cross-linking. Cross-linking is essential to retain the structure of the polymer electrolyte and it is also shown to suppress Li dendrite growth by offering a high stiffness and rigidity (high shear modulus) toward Li dendrites. The designed GPE owns a very high ionic conductivity similar to commercial LEs, electrochemical stability up to 5 V, long-term cycle life and stability. While Li|Li symmetric cells made with 1 M LiPF6 in EC/DEC and 1 M LiTFSI in DOL/DME LEs showed an increase in overpotential during cycling (mainly due to the formation of dead Li and evolution of SEI) followed by a short-circuit (probably due to penetration of Li dendrites through Celgard separator), Li|Li cells made with GPE exhibit a long-term stability with a low voltage polarization of less than 0.1 V at a high current density of 0.5 mAh cm−2 for 500 cycles. Furthermore, Li|LFP full cells made with GPE display a long-term cycle life with discharge capacity of ~120 mAh g−1 at 0.5 C in ambient temperature with around 80% capacity retention after 500 cycles.In situ light microscopy which is a simple, versatile technique to study the nucleation and growth of Li particles during electrochemical platting/stripping was also used to further illustrate uniform deposition of Li by the developed GPEs. Hence, we have also performed light microscopy analysis to investigate Li deposition in Li|Li cells made of LEs and GPEs during electrochemical deposition process. It was observed that unlike LEs made of 1 M LiPF6 in EC/DEC and 1 M LiTFSI in DOL/DME which results in non-uniform, dendritic growth of Li, a uniform and non-dendritic deposition of Li was observed in case of GPE, which can be due to uniform regulation of Li through complexation with oxygen atoms of the PEO-based GPE.

An aqueous 2.1 V pseudocapacitor with MXene and V-MnO2 electrodes

MXenes have shown record-breaking redox capacitance in aqueous electrolytes, but in a limited voltage window due to oxidation under anodic potential and hydrogen evolution under high cathodic potential. Coupling Ti3C2Tx MXene negative electrode with RuO2 or carbon-based positive electrodes expanded the voltage window in sulfuric acid electrolyte to about 1.5 V. Here, we present an asymmetric pseudocapacitor using abundant and eco-friendly vanadium doped MnO2 as the positive and Ti3C2Tx MXene as the negative electrode in a neutral 1 M Li2SO4 electrolyte. This all-pseudocapacitive asymmetric device not only uses a safer electrolyte and is a much less expensive counter-electrode than RuO2, but also can operate within a 2.1 V voltage window, leading to a maximum energy density of 46 Wh/kg. This study also demonstrates the possibility of using MXene electrodes to expand the working voltage window of traditional redox-capable materials.

An overlooked issue for high-voltage Li-ion batteries: Suppressing the intercalation of anions into conductive carbon

Summary High-voltage Li-ion batteries have been extensively studied to increase energy density of batteries. However, their cycling stability has remained poor, despite various strategies being proposed to overcome the issues of high-potential cathodes, such as electrolyte oxidation and transition metal dissolution. Herein, we report anion intercalation into the cathode conductive carbon as an overlooked yet critical issue. We propose a concentrated sulfolane (SL)-based electrolyte that prevents anion intercalation via two mechanisms: (1) by offering a high activation barrier to intercalation via its strong anion-Li+ interaction and (2) by forming a sulfur-containing, anion-blocking SL-derived interphase. This electrolyte, used with graphitized acetylene black, which is oxidatively stable but usually susceptible to anion intercalation, enables the stable operation of a Li2CoPO4F/graphite full cell (cut-off voltage = 5.2 V), with 93% capacity retention after 1,000 cycles and an average Coulombic efficiency of ≥99.9%. This is a pivotal strategy to enhance the reversibility of >5 V Li-ion batteries on a commercial level.

Constructing FeN4/graphitic nitrogen atomic interface for high-efficiency electrochemical CO2 reduction over a broad potential window

Summary Atomically dispersed Fe–N–C catalyst has shown great performance in the CO2-to-CO conversion, yet the high CO selectivity is achieved only within a rather narrow potential range, which cannot well meet the requirements for the following CO dimerization or hydrogenation. Here, we developed a hydrogen-pyrolysis etching strategy to precisely manipulate the uncoordinated N dopants in the Fe–N–C catalyst. This strategy could preferentially eliminate pyridinic and pyrrolic N atoms while leaving graphitic N. The resulting catalyst gave a CO faradaic efficiency (FECO) above 90% over a broad window from −0.3 to −0.8 V (versus RHE) (in particular, FECO > 97% at −0.6 V). In situ ATR-SEIRAS and first-principle calculations further revealed that this strategy can not only suppress the parasitic H2 generation but also promote CO2 activation and protonation with the assistance of co-adsorbed H2O on the “atomic interface” of “FeN4/graphitic N.”

Dual cationic modified high Ni-low co layered oxide cathode with a heteroepitaxial interface for high energy-density lithium-ion batteries

Abstract Lithium-ion batteries (LIBs) with high energy density, safety with longer service life, cost-effectiveness, and superior cycling stability is a demand to achieve the driving range of 300 miles per charge in electric vehicles (EVs). High Ni-low Co cathodes are among the high potential cathodes for next-generation lithium-ion batteries. Despite its numerous advantages, it still hinders from poor cycling stability and structural degradation, mainly affecting its commercialization. Herein, a facile high-temperature solid-state method is employed to synthesize dual cation doped NCM (LiNi0.94Co0.03Mn0.03O2) by concurrent substitution of Zirconium and Gallium. It has been found that Ga doping can promote cation order, strengthen the TM-O bond energy, diminish oxygen loss, thus stabilize the reversible anionic redox processes. Meanwhile, the strong Zr-O bond intensifies TM-O slabs, facilitating Li+ intercalation/de-intercalation. As a result, Zr-Ga dual-doped (NCMZG) develops a heteroepitaxial interface, which significantly reduces cation mixing, suppresses layered to spinel/rock-salt phase transition and alleviates cyclability as well as voltage decay. Hence, NCMZG exhibits outstanding capacity retention of 91.9% at 0.5C after 100 cycles, while NCM can only maintain 72.64% of initial discharge capacity. Additionally, NCMZG possesses superior rate capability even at an ultrahigh C-rate of 10C as compared to NCM. Hence, the dual-doping phenomenon is beneficial to enhance the electrochemical performance of high Ni-low Co layered oxide cathodes.

Lithium Metal Anode for High-Power and High-Capacity Rechargeable Batteries

Because lithium metal exhibits high specific capacity and low potential, it is the best candidate for fabricating anodes for batteries. Rechargeable batteries fabricated using lithium anode exhibit high capacity and high potential cathode; these can be potentially used to fabricate high energy density batteries (>500 Wh kg–1) that can be used for the development of next-generation electric vehicles. However, the formation and growth of lithium dendrites and the low coulombic efficiency recorded during lithium plating and stripping under conditions of high current density hinder the use of lithium metal as the anodic material for the development of practical rechargeable batteries. In this short review, we outline the current status and prospects of lithium anodes for fabricating batteries in the presence of non-aqueous liquid, polymer, and solid electrolytes operated under conditions of high current density.

Understanding morphological degradation of Ag nanoparticle during electrochemical CO2 reduction reaction by identical location observation

Electrocatalytic systems affording stable performance beyond the initial catalytic activity and selectivity have been actively discussed. Understanding the long-term stability of nanoparticle catalysts requires careful monitoring of the morphological changes. Herein, we demonstrate the relationship between the degradation of the catalytic activity and morphological changes in Ag nanoparticles during the electrochemical CO2 reduction reaction (CO2RR) for CO production by identical location transmission electron microscopy (IL-TEM) measurements. The synthesized Ag/C catalyst with 95.1% CO Faradaic efficiency (FECO) at −0.82 V vs. RHE showed a gradual decrease in the CO production current density and FECO, whereas the H2 production increased during 12 h of CO2RR. IL-TEM images showed that small Ag particles with dimensions of less than 5 nm were newly formed from the original particles within 1 h of reaction, accounting for 80% of the total number of particles, and slowly grew to around 10 nm with multiple domains when the CO2RR was prolonged. These morphological changes were explained in connection with the CO current density gradient, where it was proposed that the formation of small particles causes a sharp decrease in the CO production during the first hour, and subsequent growth of the Ag nanoparticles did not restore the CO2RR activity of the particles. It was confirmed that degradation of the nanoparticles was more severe at a higher cathodic potential, and occurred during the CO2RR, but not in the hydrogen evolution reaction (HER) in N2-purged KHCO3 electrolyte. In this study, we introduce analytical methods for observing morphological changes of nanoparticles in the identical location during CO2RR electrolysis.

Hydrogen Evolution Reaction for Vacancy‐Ordered i‐MXenes and the Impact of Proton Absorption into the Vacancies

AbstractA study of the hydrogen evolution reaction (HER) for Mo‐, W‐, and Nb‐based MXenes is presented, where W1.33C MXene with ordered vacancies is chosen for further investigation. The electrochemical measurements show that if the W1.33C MXene is subjected to high cathodic potentials, it greatly improves the activity and onset potential for the HER. The enhancement continues to improve independent of whether the potential is kept fixed at a certain cathodic potential or if the potential is scanned repeatedly. Interestingly, the improvement disappears if the material is subjected to anodic potential. Based on these observations, the hydrogen interaction with the MXene surface as well as in the vacancies is investigated by means of first‐principles calculations. These show that the adsorption energy of hydrogen is sensitive to both surface coverage and vacancy occupancy, and that, for certain structures with hydrogen in the vacancies, thermoneutral values of hydrogen adsorption can be obtained. Based on the calculations it is argued that under high cathodic potentials, protons can transfer to the vacancies and stay there in a metastable state as hydrogen atoms, while at anodic potential the process is reversed. The first‐principles results provide a rationale for the strongly enhanced HER activity observed experimentally on W1.33C MXene.

Fast Charge Transfer between LLZO Solid Electrolyte and LCO Cathode Thin Films with a Modified Interface

Thin film deposition of solid electrolytes can be useful for the fabrication of better solid-state batteries by reducing the thickness of the electrolyte material to a few hundred nanometers. This facilitates ionic conductance for faster charge-discharge and reduces the total volume of inactive material, therefore increasing energy and power density. Thin film batteries can also be valuable model systems to investigate interface charge dynamics and to serve as playgrounds for interface engineering, without the complexity of bulk systems. Here we investigate the charge transfer properties between the lithium garnet Li7La3Zr2O12 (LLZO) solid electrolyte and the LiCoO2 cathode using a thin-film model system, with the aim of reducing the interface resistance and allowing high charge-discharge rates.Bulk LLZO electrolyte has come under the spotlight owing to its high ionic conductivities (10-4 - 10-3 S/cm) as well as a wide electrochemical stability window (against metallic lithium anode and high potential cathode materials). We developed a method for fabricating crystalline LLZO thin films using magnetron co-sputtering followed by an annealing step at 700°C (significantly below the standard processing temperatures). The resulting 500 nm-thick Ga-doped LLZO thin films show densities and ionic conductivities (2×10-4 S/cm) comparable to the values observed in bulk ceramic pellets.[1]Based on this thin film fabrication process, we fabricated an all-thin-film model system to investigate the LLZO / LCO cathode interface. This architecture provides an easy access to the interface for characterization, allowing one to identify the degradation processes taking place at the interface under high-temperature co-sintering. Introducing an in situ-lithiated Nb2O5 diffusion barrier at the interface, it was possible to lower the LLZO / LCO charge transfer resistance to about 50 Ω cm2, a 3-fold reduction with respect to previously reported values. The low interfacial resistance combined with the high conductance through the LLZO thin-film electrolyte allows charge transfer at high charge–discharge rates up to 40 C (0.9 mA/cm2).[2] References [1] Sastre, Jordi, et al. "Lithium Garnet Li7La3Zr2O12 Electrolyte for All‐Solid‐State Batteries: Closing the Gap between Bulk and Thin Film Li‐Ion Conductivities." Advanced Materials Interfaces (2020): 2000425.[2] Sastre, Jordi, et al. "Fast Charge Transfer across the Li7La3Zr2O12 Solid Electrolyte/LiCoO2 Cathode Interface Enabled by an Interphase-Engineered All-Thin-Film Architecture." ACS Applied Materials & Interfaces 12.32 (2020): 36196-36207.

Electro-Carboxylation of Furfural By CO2 in γ-Valerolactone

The continuous rise of global warming and depletion of fossil fuel resources has led to the development of new ways of valorization of non petro-sourced chemicals. In this objective, it is important to develop electrochemical valorization processes of CO2, a greenhouse gas, for the synthesis of valuable molecules. When the CO2 electroreduction is performed in aqueous media, the competitive HER will decrease the energetic efficiency and the rapid deactivation of reaction intermediates will lead to side products such as CO, formic acid, oxalic acid and small chain hydrocarbons [1]. To circumvent these issues and create value added chemicals, reductive electro-carboxylation reactions can be performed in polar aprotic solvents (DMF, DMSO, acetonitrile or NMP) in the presence of tetraalkylammonim bromide or chloride as electrolytes [2].In this work, we focused on non-aqueous bio-sourced solvent, the γ-valerolactone (GVL), to perform a carboxylation reaction of bio-sourced molecules like furfural by electroreduction of CO2. The reductive electro-carboxylation of furfural was studied at a Pt/C electrode was studied in a bio-sourced GVL with tributylmethylammonium chloride (TBMACl) as electrolyte. The solvent behavior in the CO2 reduction potential range was studied by in situ FTIRS measurements which indicated that GVL reacted at the electrode in the absence of furfural and/or of CO2, while the presence of furfural and/or of CO2 made the solvent much less reactive. The electrochemical study showed that the CO2 electroreduction started at from the high cathodic potential of −0.8 V vs SCE (saturated calomel electrode) and the coupling of electrochemistry with in situ FTIRS demonstrated that it reacted with furfural.The reductive electro-carboxylation was then performed in an electrolysis cell. The cell voltage was maintained at 2.0 V (corresponding to a cathode potential of -1.9 V vs. SCE) for 24 h. In absence of furfural, gas chromatography coupled with mass spectroscopy (GC–MS) analyses revealed the formation of oxalic acid (coupling reaction of CO2) as main reaction product. In the presence of furfural in the reaction medium, a new carboxylated specie, 2-furyl(hydroxy)acetic acid, was identified as the main reaction product. 1H NMR and LC-MS analyses further confirmed the formation of this compound, demonstrating the potentialities of bio-sourced solvents for reduction electro-carboxylation of a bio-sourced molecule by reduction of CO2[3].[1] Y. Hori, Electrochemical CO2 reduction on metal electrodes, in: C. Vayenas, R. White, M. Gamboa-Aldeco (Eds.), Modern Aspects of Electrochemistry, 42, Springer, NewYork 2008, pp. 89–189[2] R. Matthesses, J. Fransaer, K. Binnemans, D.E. De Vos, Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids, Beilstein J. Org.Chem. 10 (2004) 2484–2500.[3] Florent Boissou, S. Baranton, M. Tarighi, K. De Oliveira Vigier, C. Coutanceau, The potency of γ-valerolactone as bio-sourced polar aprotic organic medium for the electrocarboxlation of furfural by CO2. J. Electroanal. Chem. 848 (2019) 113257

Achieving long-cycling sodium-ion full cells in ether-based electrolyte with vinylene carbonate additive

The sodium-ion full cell can be employed in the ether-based electrolyte by the addition of VC and exhibits long term cycling stability and high capacity retention. • NaCF 3 SO 3 -DGM + 5wt% VC electrolyte could make sodium-ion full cells applicable. • The sodium-ion full cell with the electrolyte exhibits long term cycling stability. • VC can be synergistically oxidized with DGM to form integrity CEI layers. Application of sodium-ion batteries is suppressed due to the lack of appropriate electrolytes matching cathode and anode simultaneously. Ether-based electrolytes, preference of anode materials, cannot match with high-potential cathodes failing to apply in full cells. Herein, vinylene carbonate (VC) as an additive into NaCF 3 SO 3 -Diglyme (DGM) could make sodium-ion full cells applicable without pre-activation of cathode and anode. The assembled FeS@C || Na 3 V 2 (PO 4 ) 3 @C full cell with this electrolyte exhibits long term cycling stability and high capacity retention. The deduced reason is additive VC, whose HOMO level value is close to that of DGM, not only change the solvent sheath structure of Na + , but also is synergistically oxidized with DGM to form integrity and consecutive cathode electrolyte interphase on Na 3 V 2 (PO 4 ) 3 @C cathode, which could effectively improve the oxidative stability of electrolyte and prevent the electrolyte decomposition. This work displays a new way to optimize the sodium-ion full cells easily with bright practical application potential.

Optimization of high potential cathode materials and lithium conducting hybrid solid electrolyte for high-voltage all-solid-state batteries

LiMn0.8Fe0.2PO4 (LMFP) as high potential cathode is synthesized by a modified mechanical activation method and tested for use in all-solid-state high-voltage rechargeable lithium ion batteries. The influence of synthesis condition on the atomic structure, particle size, morphology, surface area, and electrochemical performance of the active material is investigated. A high dielectric constant ceramic (Al2O3) is composited in Li1.3Al0.3Ge1.7P3O12 (LAGP)-based lithium conducting hybrid solid electrolyte, and a higher lithium ion transference number is observed owing to the anion scavenging effect of Al2O3. An all-solid-state LMFP battery is constructed with a graphite anode and the hybrid solid electrolyte. At current densities of 0.1, 1, 3, and 10 C, initial discharge capacities of 156.3, 133.7, 111.8, and 71.4 mAh g−1 (91.9, 78.6, 65.8, and 42% of theoretical capacity) are obtained with low corresponding capacity fade of 0.001, 0.02, 0.01, and 0.013% per cycle evaluated over 300 cycles, even after charging to 4.5 V.

Extraordinary Stability of IrO2(110) Ultrathin Films Supported on TiO2(110) under Cathodic Polarization

Down to a cathodic potentials of -1.20 V versus the reversible hydrogen electrode, the structure of IrO2(110) electrodes supported by TiO2(110) is found to be stable by in situ synchrotron-based X-ray diffraction. Such high cathodic potentials should lead to reduction to metallic Ir (Pourbaix diagram). From the IrO2 lattice parameters, determined during cathodic polarization in a H2SO4 electrolyte solution (pH 0.4), it is estimated that the unit cell volume increases by 1% due likely to proton incorporation, which is supported by the lack of significant swelling of the IrO2(110) film derived from X-ray reflectivity experiments. Ex situ X-ray photoelectron spectroscopy suggests that protons are incorporated into the IrO2(110) lattice below -1.0 V, although Ir remains exclusively in the IV+ oxidation state down to -1.20 V. Obviously, further hydrogenation of the lattice oxygen of IrO2(110) toward water is suppressed for kinetic reasons and hints at a rate-determining chemical step that cannot be controlled by the electrode potential.

Electrodeposition of ZnO/Cu2O Heterojunctions on Ni-Mo-P Electroless Coating

Electroless Ni-Mo-P coatings were deposited onto ceramic tiles in order to be employed as electrodes for the electrodeposition of ZnO and Cu2O heterojunction layers. Varying conditions, such as duration, annealing of the electroless coating and applied potential, and duration for ZnO electrodeposition were studied in order to optimize the properties of the ZnO/Cu2O heterojunctions toward improved photoelectrical performance. The coatings were evaluated in terms of morphology, crystalline structure, and by electrochemical and photoelectrical means. The obtained results indicated that a prolonged annealing treatment at low temperature is beneficial to improve the roughness and electrical conductivity of the Ni-Mo-P coating to further enhance the electrodeposition of ZnO. The morphology analysis revealed continuous and homogeneous Ni-Mo-P coatings. The formation of cube-like Cu2O crystals with larger grain size was induced by increasing the deposition duration of ZnO. The properties of ZnO layer are much improved when a higher cathodic potential is applied (−0.8 V) for 1 h, resulting in optimum photoelectric parameters as 1.44 mA·cm−2 for the JSC and 760.23 µV for the VOC value, respectively, for the corresponding heterojunction solar cell.

A high potential biphenol derivative cathode: toward a highly stable air-insensitive aqueous organic flow battery

Aqueous organic flow batteries have attracted dramatic attention for stationary energy storage due to their resource sustainability and low cost. However, the current reported systems can normally be operated stably under a nitrogen or argon atmosphere due to their poor stability. Herein a stable air-insensitive biphenol derivative cathode, 3,3′,5,5′-tetramethylaminemethylene-4,4′-biphenol (TABP), with high solubility (>1.5 mol L−1) and redox potential (0.91 V vs. SHE) is designed and synthesized by a scalable one-step method. Paring with silicotungstic acid (SWO), an SWO/TABP flow battery shows a stable performance of zero capacity decay over 900 cycles under the air atmosphere. Further, an SWO/TABP flow battery manifests a high rate performance with an energy efficiency of 85% at a current density of 60 mA cm−2 and a very high volumetric capacity of more than 47 Ah L−1. This work provides a new and practical option for next-generation practical large-scale energy storage.

Quantifying Electrocatalytic Reduction of CO2 on Twin Boundaries

Summary A protocol relying on the use of silver nanostructures with well-defined dimensions and morphologies (e.g., nanocubes and nanowires) has been developed to differentiate and quantitatively determine the atom-specific activities of different surface atoms toward catalyzing electrochemical CO2 reduction reaction (CO2RR). The atom-specific activity of the twin-boundary edges (TBEs) is comparable to (or slightly higher than) that of the single-crystal edges (SCEs) formed from the crossing of two {100} surfaces, and it is on the order of ∼16 attoampere/atom (aA/atom) toward electrochemical CO2RR. This value is more than two orders higher than the atom-specific activity of the {100} surface atoms, i.e., ∼0.1 aA/atom. The high catalytic activity of the TBEs, which represent a class of commonly existing surface defects in stable metal nanostructures with face-centered cubic lattices, is consistent with the DFT calculations, in which the bridge-type binding configuration of COOH∗ at the TBEs stabilizes this intermediate to promote overall CO2RR.