In this study, a new solid embeddable Ag/AgCl reference electrode (RE) was electrochemically investigated for corrosion monitoring in reinforced concrete. The electrode was fabricated by applying the cement mortar as the bottom layer, and the polymer gel as electrolyte. Several electrochemical methods were applied. The experiments were carried out in simulated concrete solutions and concrete. Furthermore, an exposure period over 1 year was used to evaluate the stability of the electrodes embedded in concrete. It has been found that the electrode potential was not obviously affected by the chloride concentration, but affected by the pH value of solution. The Ag/AgCl RE had uniformity in concrete environments. The reversibility of Ag/AgCl RE in all solutions is only within ±4 mV. Besides, potentiodynamic tests revealed that the Ag/AgCl RE had a high exchange current density, which was advantageous when using Ag/AgCl RE to conduct resistance tests. Galvanostatic application of 0.2 µA/cm2 caused little variation of potential with time (∼30 mV in several days), indicating the presence of a finite polarization resistance. As a result, the new solid Ag/AgCl RE was suitable as a sensor electrode for concrete structures.
The equilibrium constant, Kc, of the reaction 3Ti2+ = 2Ti3+ + Ti was studied in the molten binary mixtures of LiCl. The accurate values of Kc were calculated by the best-fitting method under consideration of the TiOCl(s) dissolution at temperature of 973 K, 1023 K and 1073 K, respectively. The fitted concentration of O2− was verified by emf method with yttria-stabilized zirconia electrode (YSZE). The influence of the cation radius of electrolyte on the equilibrium constant was studied in molten binary mixtures of LiCl at 1023 K on the basis of the reliable method for obtaining accurate value of Kc. It was found that the Kc values decreased from 0.59 to 0.27 with the concentration of LiCl increasing at 1023 K. More importantly, results disclosed that the values of Kc correspond with polarizing power no matter in CsCl-LiCl or KCl-LiCl system.
The performance of the Li/LiNi0.5Mn1.5O4 cells cycled to 5.0 V (vs. Li/Li+) using 1.0 M LiPF6-EC/DMC (1/1, v/v) with and without dimethoxydiphenylsilane (DDS) at 25°C has been investigated. Cells with 1% DDS added deliver slightly lower initial discharge capacity than the cells with baseline electrolyte, 115.3 vs. 120.9 mAh g−1. Electrochemical methods and ex-situ analytical techniques, including TGA and SEM, are employed to conduct the interfacial chemistry of LiNi0.5Mn1.5O4/electrolyte to better understand the improved electrochemical performances of the cells with introduction of DDS. The results indicate that DDS can be electro-oxidized and participates in the formation of the surface layer on cathode electrode, which prevents electrolyte from further decomposition and promotes Li+ conduction of the cathode/electrolyte interphase, thus improves the electrochemical performances of Li/LiNi0.5Mn1.5O4 cells.
In this paper, a novel packed-bed electrocatalysis reactor (PBECR) composed of titanium dioxide coated activated carbon (TiO2/AC) was presented for efficient wastewater treatment. The TiO2/AC in the PBECR could provide numerous convergent-divergent access tubes for organic compounds (OC) that can eliminate AC plugging to ensure operation permanence in electrochemical oxidation. Further, the employment of TiO2/AC is beneficial to shorten phenol degradation pathway and decrease poisonous intermediate accumulation. In addition, the PBECR show perfect electrode performance in treating landfill leachate, validating the broad applicability of the proposed process. It was found that the electrode area expansion and short-circuit avoidance by TiO2 are the main factors in enhancement of OC oxidation kinetics, which are different from mechanisms of those photoprocesses. These observations can be of considerable technological and theoretical values and facilitate to be extended to wide applicable ranges of TiO2.
A simple method for direct and quantitative determination of carbendazim using electrochemically reduced graphene oxide modified glassy carbon electrode (ERGO/GCE) has been developed. The obtained electrode was characterized using scanning electron microscopy, Raman spectroscopy, cyclic voltammetry and differential pulse voltammetry. Compared to bare and graphene oxide modified electrodes (GO/GCE), the ERGO/GCE not only significantly shifted to a lower positive potential, but also noticeably enhanced the current response. The resulting carbendazim sensor showed a wide linear range (2.0 nM to 400 nM) and a low detection limit (1.0 nM). In addition, the proposed sensor has excellent selectivity, good stability and can be successfully applied in soil sample. The ERGO, which was obtained by facile, cost-effective method, could provide a promising platform to develop excellent electrochemical sensors for detecting carbendazim.
The porous carbon material was prepared from sawdust impregnated with a 0.1 M FeCl3 aqueous solution with CO2 activation at 800°C. Pores were found to develop with increasing activation time. The BET surface area, average pore diameter and volume of the mesopores also became greater with increasing activation time. The ratio of the mesopore to total pore volume in the activated carbon was more than 90% after 5 min of activation. Precise control of the pore size distribution is possible by finely tuning the activation time. The porous carbonized material was examined for use in electric double layer capacitor (EDLC) electrodes. The charge and discharge characteristics of EDLC electrodes using these carbonized materials were studied. Cyclic voltammetry and rate performance indicated good correlation between the pore structure of the carbonaceous materials and the magnitude of the electrolyte. These relationships were in good agreement with the Nyquist plot obtained by measuring the impedance. These results were also in accordance with pore structure analysis obtained using the nitrogen adsorption method. It is suggested that the Nyquist diagram characterizes the pore structure of porous carbon from the viewpoint of ion transfer.
The electrochemical behavior of carbonate ion at a Ni electrode in LiF–NaF–Li2CO3 molten salt was investigated using cyclic voltammetry, square wave voltammetry, and chronopotentiometry. The results show that the electrochemical reduction of carbonate ion to carbon is a simple four-electron transfer that occurs in a one-step process. The reduction of carbonate ion at a Ni-wire working electrode is an irreversible process with diffusion-controlled mass transfer. The diffusion coefficient of carbonate ion at 973, 993, 1023, 1043, and 1063 K is 4.46 × 10−5, 4.82 × 10−5, 5.31 × 10−5, 5.90 × 10−5, and 6.54 × 10−5 cm2 s−1, respectively, and the results obey the Arrhenius law, with an activation energy of 35.8 kJ mol−1. The X-ray diffraction results show that hexagonally structured graphitized carbon can be obtained by potentiostatic electrolysis. Scanning electron microscopy images show that the deposits exhibit a spherical morphology.