Study on Capacitance of Zn-Based Electrode in Redox Electrolyte System

Electrode material is one of the most important factors affecting the performance of supercapacitors, and electrolyte solution is another. In this work, electrochemical properties of hydroxide zinc carbonate composite electrode (HZC) in KOH + K3[Fe(CN)6] electrolyte were studied. It was proved that [Fe(CN)6]3−in electrolyte participated in electrochemical reactions and promoted electron transfer. The specific capacitance of HZC electrode was as high as 920.5 F·g−1 at 1.0 A·g−1 in 1 mol·L−1 KOH and 0.04 mol·L−1 K3[Fe(CN)6] electrolyte, which is 172.9% higher than that in KOH. The combination of HZC electrode and low alkalinity aqueous electrolyte provided the supercapacitor system with good capacitance performance, safety, and environmentally friendly.

Proton-Conducting Polyoxometalates as Redox Electrolytes Synergistically Boosting the Performance of Self-Healing Solid-State Supercapacitors with Polyaniline

Energy storage devices with high volumetric and gravimetric capacitance are in urgent demand due to the booming market of portable and wearable electronics.Using redox-active molecules as electrolytes is a strategy to improve the capacitance and energy density of solid-state supercapacitors(SCs).In this study,polyoxometalates(POMs)are applied as proton conductors and redox mediators in polyvinyl alcohol(PVA)electrolytes,which increase the capacitance of obtained SCs with polyaniline(PANI).H_(3)PMo_(12)O_(40)-loaded PANI electrodes provide pseudocapacitance with an eight-electron Faraday reaction in a charge–discharge cycle.This has rarely been reported in SCs before.The largest capacitance of SCs with H_(3)PMo_(12)O_(40)and H_(3)PW_(12)O_(40)as electrolytes is 7.69 F/cm^(2)(3840 F/g)based on a single electrode at 0.5 mA/cm^(2).In addition,POM electrolytes exhibit excellent self-healing ability,which is attributed to the rich hydrogen-bonding network between POMs and PVA.This study demonstrates that the capacitance of solid-state SCs is improved by using molecular redox-active electrolytes and showcases the potential of applying this strategy to other energy storage devices in the future.

Higher open-circuit voltage set by cobalt redox shuttle in SnO_2 nanofibers-sensitized CdTe quantum dot solar cells

In this study, we report an efficient CdTe-SnOquantum dot（QD） solar cell fabricated by heat-assisted drop-casting of hydrothermally synthesized CdTe QDs on electrospun SnOnanofibers. The as-prepared QDs and SnOnanofibers were characterized by dynamic light scattering（DLS）, UV–Vis spectroscopy,photoluminescence（PL） spectra, X-ray diffraction（XRD） and transmission electron microscopy（TEM）. The SnOnanofibers deposited on fluorine-doped tin oxide（SnO） and sensitized with the CdTe QDs were assembled into a solar cell by sandwiching against a platinum（Pt） counter electrode in presence of cobalt electrolyte. The efficiency of cells was investigated by anchoring QDs of varying sizes on SnO. The best photovoltaic performance of an overall power conversion efficiency of 1.10%, an open-circuit voltage（Voc）of 0.80 V, and a photocurrent density（JSC） of 3.70 m A/cmwere obtained for cells with SnOthickness of5–6 μm and cell area of 0.25 cmunder standard 1 Sun illumination（100 m W/cm）. The efficiency was investigated for the same systems under polysulfide electrolyte as well for a comparison.

Reversible faradaic reactions involving redox mediators and oxygen-containing groups on carbon fiber electrode for high-performance flexible fibrous supercapacitors

Flexible fibrous supercapacitors(FFS)are taking account of as the energy storage devices for wearable electronics owing to their high power density,high safety,long cycle life,and simple manufacturing process.Nevertheless,FFSs have the disadvantage of low specific capacitance that results from the electrochemical characteristics of the electrical double layer on the carbon fiber electrode.In this study,for the first time,an FFS comprising surface-activated carbon fibers as an electrode/current collector and a redox additive gel polymer electrolyte(FFS-SARE)was fabricated for use as a wearable energy storage device.The FFS-SARE showed outstanding electrochemical performance,namely,high specific capacitances of 891 and 399 mF cm^(-2) at current densities of 70.0 and 400 μA cm^(-2),respectively,and remarkable ultrafast cycling stability over 5000 cycles with 92%capacitance retention at a current density of 400.0 μA cm^(-2).Moreover,they exhibited mechanical flexibility and had high feasibility,and they showed good energy storage performance that renders them suitable for use in wearable electronic textiles.

Generalized Electron Balance for Dynamic Redox Systems in Mixed-Solvent Media

A complex example of electrolytic redox system involving 47 species, 3 electron-active elements and five (3 am-phiprotic + 2 aprotic) co-solvents, is presented. Mixed solvates of the species thus formed are admitted in the system considered. It is proved that the Generalized Electron Balance (GEB) in its simplest form obtained according to the Approach II to GEB is identical with the one obtained for aqueous media and binary-solvent system, and is equivalent to the Approach I to GEB.

Compact Formulation of Redox Systems According to GATES/GEB Principles

The Generalized Electron Balance (GEB), together with charge balance and concentration balances, completes the set of equations needed for resolution of electrolytic redox systems. The general formulae for GEB were obtained according to Approach II to GEB, i.e., on the basis of the equation 2?f(O) ? f(H) obtained from elemental balances: f(H) for H, and f(O) for O. Equivalency of the Approach II and the Approach I to GEB was proved for an aqueous solution and a binary-solvent system. On this basis, a compact form of GEB was derived.

Charge Storage Properties of Aqueous Halide Supercapatteries with Activated Carbon and Graphene Nanoplatelets as Active Electrode Materials

Device level performance of aqueous halide supercapatteries fabricated with equal electrode mass of activated carbon or graphene nanoplatelets has been characterized.It was revealed that the surface oxygen groups in the graphitic structures of the nanoplatelets contributed toward a more enhanced charge storage capacity in bromide containing redox electrolytes.Moreover,the rate performance of the devices could be linked to the effect of the pore size of the carbons on the dynamics of the inactive alkali metal counterion of the redox halide salt.Additionally,the charge storage performance of aqueous halide supercapatteries with graphene nanoplatelets as the electrode material may be attributed to the combined effect of the porous structure on the dynamics of the non-active cations and a possible interaction of the Br^(-)/(Br_(2)+Br^(-)_(3))redox triple with the surface oxygen groups within the graphitic layer of the nanoplatelets.Generally,it has been shown that the surface groups and microstructure of electrode materials must be critically correlated with the redox electrolytes in the ongoing efforts to commercialize these devices.