Slurry of activated carbon particles mixed with an aqueous electrolyte solution has been used as "flowable electrode" in a few recent electrochemical systems, e.g., electrochemical flow capacitors (EFCs) for energy storage, and flow-electrode capacitive deionization (FCDI) for water treatment. In these applications, the porous carbon particles with very large specific surface area adsorb ions from the electrolyte and meanwhile store electrical charges when a voltage source is added in the charging process. Under the flow condition, the motion of the particles and their mutual contact form a dynamically varying electrical network for the charge transport through the bulk material. We introduce a novel particle-based computational model using the Stokesian dynamics to simulate the hydrodynamic interaction of the carbon particles and the charge transport. An analogous electrical circuit model is developed by approximating the particles with many interconnected resistor-capacitor units, and the circuit's topology is temporally changing depending on the instantaneous particle configuration. The Stokesian model and the circuit model are solved simultaneously to study how the hydrodynamic interaction and cluster formation affect the charge transport process of the slurry. The presence of the stationary current collector can be included to incorporate the near-wall effects on particle mobility. In the simulation, we vary the particle concentration as well as the ratio of the particle charging time to the hydrodynamic interaction time. The results shows that the charge transport in the carbon slurry is enhanced by increasing the concentration of the particles and faster particle charging. In addition, cluster formation of the particles plays an important role for the electronic transport process. After scaling, the transient electrical current from the present study generally agrees with that from previous experimental and modeling studies. (c) 2019 The Electrochemical Society.
High cost and limited natural reserves of precious metals as oxygen reduction reduction (ORR) catalysts have hindered the practical application of microbial fuel cells (MFCs). Herein, the cost-effective catalysts were synthesized by co-doping binuclear-cobalt-phthalocyanine (Bi-CoPc) and cerium oxide (CeO2) on ordered mesoporous carbon (OMC). The catalysts Bi-CoPc/x%CeO2/OMC (x = 3, 6 and 12) with different CeO2 loading were physically characterized by Nitrogen physisorption, X-ray Diffraction, Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy, and chemically characterized by Rotary Disk Electrode analysis. The relationship between the CeO2 content and ORR activity was investigated. The optimum CeO2 loading in the Bi-CoPc/6%CeO2/OMC catalyst provided the highest Ce3+ content that are favorable for the chemisorbed oxygen. Bi-CoPc/6%CeO2/OMC led to an increased half wave potential and limiting current density and to the further decreased over-potential. It also displayed a higher electron transfer number in comparison with Bi-CoPc/3%CeO2/OMC and Bi-CoPc/12%CeO2/OMC. The electrochemical results were closely related with the voltage generation obtained in single chamber MFC (SCMFCs) with air cathode. Bi-CoPc/6%CeO2/OMC-based SCMFC generated the highest power density of 486 +/- 6 mW/m(2) and achieved chemical oxygen demand removal of 79.3 +/- 1.5%. The voltage generation for Bi-CoPc/6%CeO2/OMC decreased only by 3.7% after 1300 h of operation, indicating its good stability in MFCs large scale application. (C) 2019 The Electrochemical Society.
The nanoporous microspheres of Co-Zn-S were synthesized by a solvothermal method. The as-obtained Co-Zn-S microspheres, as a non-noble metal catalyst, exhibited highly electrocatalytic activity for oxygen evolution reaction (OER) in alkaline electrolyte. It showed a low overpotential of only 320 mV to afford a current density of 10 mA cm(-2) and a Tafel slope of 80.43 mV dec(-1). Furthermore, the nanoporous microspheres of Co-Zn-S retained excellent electrocatalytic stability within a period of 36000 s. The catalyst also showed good catalytic performance toward the hydrolysis of ammonia borane to produce around 70 mL of H-2 within the time of 30 minutes at room temperature. The nanoporous microspheres of Co-Zn-S exhibits the potential applications for hydrogen/oxygen production by water splitting or ammonia borane hydrolysis. (C) 2019 The Electrochemical Society.
A "green nano" strategy was extended to prepare monodisperse polypyrrole (PPy) nanospheres with tunable sizes via simply adjusting pyrrole monomer's concentration. And a linear model was obtained and used to predict the diameter of PPy nanosphere. Nitrogen-doped carbon nanospheres (NCSs) with well-controlled diameters were further synthesized through direct carbonzilation of harvested PPy nanospheres, which demonstrated a facile route for the preparation of highly dispersible NCSs with controlled sizes. Then the potential electrochemical response of as-fabricated NCSs toward food additive-Sunset yellow (SY) was explored. NCSs with medium size (M-NCSs) showed the best electrochemical performance and an ultra-high sensitivity of 679.16 A M-1 cm(-2) and lower detection limit of 0.95 nM were gained. This study therefore provides a facile route to high quality, uniform, and size-controlled PPy nanospheres and NCSs, which are promising to be applied to electrochemical and other fields. (C) 2019 The Electrochemical Society.
P2-type Na0.65Mn0.6Ni0.35Cu0.05O2 microspheres assembled irregularly with massive primary nanoparticles are prepared via hydrothermal method and subsequent two-step calcination process. As expected, the P2-type Na0.65Mn0.6Ni0.35Cu0.05O2 microspheres show superior electrochemical performance in terms of high-rate capability and long-period cycling stability. This material exhibits a reversible capacity of 81 mA h g(-1) and exceptional capacity retention up to 79% over 150 cycles even at the high current density of 1 A g(-1). The distinctive spherical structure with high specific surface area can be accountable to the excellent electrochemical properties, which offers abundant surface sodium storage sites and shortened diffusion paths of sodium ions. Therefore, this work puts forward a feasible method to design nanoparticles assembled microspheres for layered oxides with high-rate performance as a promising cathode material for sodium ion batteries. (C) 2019 The Electrochemical Society.
Indium oxide (In2O3) doped zinc oxide (ZnO) nanocomposites were successfully synthesized through a facile microwave hydrothermal method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N-2 adsorption-desorption isotherms (BET) and UV-Vis diffuse reflectance spectroscopy. The morphology of In2O3-ZnO composites was observed to be like flowers, and the diameter of particles constituting the porous petal was about 30 nm. The photoelectrocatalytic test results showed that the photoelectrocatalytic methylene blue (MB) degradation efficiency using In2O3-ZnO nanocomposites as photocatalysts under visible light irradiation and a certain voltage could reached above 95.3% after 60 min, much higher than that of In2O3 particles and ZnO particles. The enhanced photoelectrocatalytic activity was attributed to the doping of In2O3 and applied voltage, which beneficially reduced the recombination of electrons and holes in the photoelectrocatalytic process, therefore, it promoted the production of active species (center dot OH and center dot O-2(-)). (C) The Author(s) 2019. Published by ECS.
In this work molecularly imprinted polymer (MIP)-aptamer (Apt) hybrid recognition sensor based on nanocomposites of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) was reported. The glassy carbon electrode (GCE) was first modified with rGO and AuNPs. Then thrombin-Apt composites were obtained by the incubation of thiolated thrombin aptamer and template thrombin. Subsequently thrombin-aptamer composites were immobilized onto AuNPs/rGO/GCE through the Au-S bond between AuNPs and thiol group at the terminal of aptamer. Finally MIP-Apt hybrid recognition sensor was prepared by the electropolymerization of thionine. Using the polythionine as the probe, cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry were performed to characterize the MIP-Apt sensor. Adsorption kinetic model was established to obtain kinetic binding constants and equilibrium current. Due to hybrid recognition of MIP and Apt, MIP-Apt sensor has faster rebinding rate, better selectivity and sensitivity, comparing with non-molecularly imprinted sensor and non-aptamer molecularly imprinted sensor. The MIP-Apt sensor exhibited good linear response from 2.5 x 10(-9) mg/mL to 1.3 x 10(-6) mg/mL for thrombin with a detection limit of 1.6 x 10(-10) mg/mL. (C) 2019 The Electrochemical Society.
Single crystal LiNi1/3Co1/3Mn1/3O2 nanorods cathode material with diameter of about 250 nm have been successfully synthesized via a facile template method followed with heat-treatment, using single crystal beta-MnO2 nanorods as self-template and Mn source. The structural changes of LiNi1/3Co1/3Mn1/3O2 nanorods during phase formation and first charge-discharge process are further explored by ex-situ XRD characterization, demonstrating the excellent structural reversibility for long cycling. The electrochemical measurements reveal that LiNi1/3Co1/3Mn1/3O2 nanorods exhibit excellent rate performance with a high discharge capacity of 100.5 mAh g(-1) at 5 C. Particularly, the materials can deliver an excellent discharge capacity of 170.5 mAh g(-1) with a capacity retention of 90.2% at 0.5 C after 200 cycles. The improved electrochemical properties are ascribed to the short Li-ion transport pathways along diameter direction, large surface-to-volume ratio and excellent strain relaxation of LiNi1/3Co1/3Mn1/3O2 nanorods, which could facilitate the diffusion of Li-ion and structural stability. (C) 2019 The Electrochemical Society.
Particle dispersion behaviors in Lithium Ion Battery (LIB) are clarified by Electrochemical Impedance Spectroscopy (EIS) method based on the dielectric characteristics of cathode slurry, which are Carbon Black (CB) aggregation, CB-bare LiCoO2 particles, CB path and CB-coated LiCoO2 particles. The experimental particle dispersion behaviors are evaluated by numerical simulation. In the experiments, cathode slurry is stirred under different rotational speed n; meanwhile, in the simulation, medium conductivities sigma(m) and particle conductivities sigma(p) in cathode slurry model are changed. Herein, CB aggregation and CB path are verified by sigma(m), while CB-bare LiCoO2 particles and CB-coated LiCoO2 particles are verified by sigma(p). Compared with sigma(p), sigma(m) plays important roles in determining particle dispersion behaviors because sigma(m) has the similar functions as n to change characteristic resistances R-cL and R-cH and characteristic frequencies f(cL) and f(cH). Therefore, compared with CB-coated LiCoO2 particles, CB path dominates the conductivity of cathode slurry in LIB. Furthermore, the dielectric characteristics of NMP solution, CB-NMP slurry and LiCoO2-NMP slurry are investigated to clarify how each component of cathode slurry contribute to the whole Nyquist plot. The results show that the straight line is caused by adding CB, while low frequency semi-circle is caused by CB-bare LiCoO2 particles. Electrical impedance spectroscopy (EIS) method, Lithium ion battery (LIB). (C) 2019 The Electrochemical Society.
The "shuttle effect" of polysulfides and sluggish kinetics of sulfur redox are main problems in Lithium-Sulfur batteries. As a result, the Lithium-Sulfur battery systems are still far from commercialization for practical utilities. In this work, we design and prepare a Lanthanum lithium oxide-based multi-functional interlayer with good electronic and lithium ion conduction as well as efficient for polysulfide blocking. We obtain the multi-functional interlayer combined cathode by coating a composite of Lanthanum lithium oxide on as-prepared sulfur electrode. The modified sulfur cathode with such interlayer configuration gives enhanced electrochemical performance (1458.00 mA h g(-1) capacity at initial cycle and 1004.40 mA h g(-1) during the first cycle with 1C rate) with outstanding cycling stability up to 250th cycle delivering the corresponding discharge capacity of 872.79 mA h g(-1) in Li-S batteries. And, the rate performance has been improved by the facile strategy. (C) The Author(s) 2019. Published by ECS.
A membrane cell model was developed to simulate tin electrodeposition with anion exchange membrane in chloride solutions. A three-factor designed set of boundary conditions was applied to determine the effects of inlet flow rate, current density, and HCl concentration on the deposition process. The concentration profiles of various species, electrolyte density distribution, and fluid velocity field were obtained as simulation results. In addition, the morphology of cathode deposit was quantified in the form of deposit thickness distribution. The simulation results of cathode deposit thickness show a good correlation with measured values from lab-scale experiments. It was found that current density has the most significant effect on the electrodeposition process. Suggestions for the tin electrodeposition process with anion exchange membrane are proposed: the current density should not be too high as large current density has strong negative effect on the morphology of cathode deposit; the inlet flow rate should be increased while HCl concentration should be decreased to improve deposit morphology; the starting sheet should be made with a larger size under high current densities. (C) 2019 The Electrochemical Society.
The influence of surface adsorption of benzotriazole (BTAH) and of chloride ions (Cl-) on the kinetics of copper electrodeposition/dissolution in copper sulfate solutions and on copper deposit characteristics have been investigated using electrochemical quartz crystal microbalance (EQCM) combined with cyclic voltammetry (CV). The addition of BTAH alone increases the overpotential of copper deposition, whereas a Cu(I)BTA complex forms at potentials higher than 0.08 V (vs. SCE) accompanied with the occurrence of copper anodic dissolution. With simultaneous addition of BTAH and Cl-, surface adsorption of Cl- competes with that of BTAH during the initial stage of copper nucleation. Different cuprous reaction intermediates form in the examined potential range -0.4 to 0.3 V (vs. SCE), which partly eliminate the favorable effect of BTAH on the deposited copper. A BTAH-containing adsorbed layer formed on the matte side of electrodeposited copper film in the presence of BTAH with or without Cl-, exhibiting a barrier surface property and an improved corrosion resistance compared with the copper film electrodeposited in the electrolyte without addition of BTAH. (C) The Author(s) 2019. Published by ECS.
The vast majority of semiconductors photocatalysts reported for artificial nitrogen fixation have a large bandgap at around 3.0 eV, thus photocatalytic nitrogen reduction is driven mainly by ultraviolet light. In contrast, this report demonstrates for the first time that bismuth iron molybdate (Bi3FeMo2O12) with a bandgap of 2.25 eV exhibits visible-light photocatalytic activity toward nitrogen-to-ammonia conversion. Furthermore, introduction of oxygen vacancy to this photocatalyst increases the ammonia production rate remarkably. Density functional theory (DFT) calculation reveals that the oxygen vacancies help adsorb and stabilize the N-H intermediate species, and lower the energy barrier of intermediate reactions. This work has an implication in design of semiconductor photocatalysts for sustainable ammonia synthesis under the ambient condition using solar energy. (c) The Author(s) 2019. Published by ECS.
Three new 2, 5-di(2-thienyl)-1H-pyrrole(DTP) derivatives, 10-[4-(2,5-Di-thiophen-2-yl-pyrrol-1-yl)-phenyl]-10H-pheno-thiazine (TPPT), 10-[4-(2,5-Di- thiophen-2-yl-pyrrol-1-yl)-phenyl]-10H-phenox azine (TPPO) and 10- [4-(2,5 -Di-thiophen-2-yl-pyrrol-1-yl)-phenyl]-10H-acridin-9-one (TPAO), were synthesized and characterized. TPPT and TPPO showed similar absorption and emission feature owing to similar chemical structure, TPAO displayed bathochromic-shift for both absorption and emission feature due to the existence of ketone group. All the monomers could be electropolymerized to form their polymer film on the electrode surface via oxidative coupling reactions of DTP units. PTPPT film showed yellow-green, green and purple red color upon different applied potentials. PTPPO and PTPAO films exhibited green and yellow at the neutral state, respectively, and turned into the similar violet color for the oxidized state. Moreover, the copolymer P(TPPT/EDOT) and P(TPAO/EDOT) not only showed obvious color change(red, yellow, green and blue), but also possessed better electrochemical stability. (C) 2019 The Electrochemical Society.
The performance of TiCxO1-x solid solutions with different O/C ratio serving as the anode in electrolysis cell was investigated in NaCl-KCl molten salt. It was found that the electrochemical dissolution occurs from the same potential for all the TiCxO1-x. The valance of the dissolved titanium ion depends on the potential applied. Both the dissolution ratio of titanium and the by-product of the anode reaction are dependent on the composition of the anode TiCxO1-x. For high carbon TiCxO1-x (x>0.5), all the titanium in TiCxO1-x dissolves as titanium ions with carbon monoxide (CO) and carbon (C) as the by-products. For low carbon TiCxO1-x (x<0.5), carbon monoxide and carbon dioxide (CO2) were detected in anodic gas, titanium partially dissolves as titanium ion and the remaining forms Ti2O3. The dissolution ratio of titanium decreases with the increase of oxygen in TiCxO1-x. (c) The Author(s) 2019. Published by ECS.