The rhombohedral structure Li2NaV2(PO4)3/C composites were successfully synthesized by a sodium citrate induced sol-gel method. The Li2NaV2(PO4)3/C consists of microplates roughly 80–90 nm in thin. The carbon content in the LNVP/C is approximately 8.29 wt%. As cathode materials for lithium-ion batteries, a cathodic peak at 3.67 V and an anodic peak at 3.82 V can be seen in CV curves, corresponding to the redox couple of V4+/V3+. In addition, the electrode can deliver an initial discharge capacity of 111.4 mAh g−1 at 1 C and about 96.4% of the initial capacity is maintained after 150 cycles. LNVP/C also exhibits high coulomb efficiency and good rate performance.
Binder is one of the key materials which affect the electrochemical performance of the Li-ion batteries. As a promising binder, carboxylmethyl cellulose (CMC) is a derivative of cellulose, in which the hydroxyl (3 per unit) is replaced by the carboxymethyl group. It attaches more and more attention. However, few studies have been carried out on CMC with the degree of substitution (DS). In this study, CMC with different DS was synthesized by a specially designed method. The raw materials and products were characterized with FT-IR, 1H-NMR, 13C-NMR and XRD. A series of CMC with different DS were prepared as silicon-based binder of anode of lithium-ion batteries. Electrical tests, including galvanostatic charge-discharge, cyclic voltammetry, AC impedance and rate capability were performed to evaluate the silicon-based anode. Results showed that the discharging specific capacity of silicon-based anode using CMC of DS = 0.55 in the first and 50th cycle were 2917.0 mAh/g and 1607.6 mAh/g, and the electrochemical performance was superior to those using CMC with lower (0.23 and 0.43) or higher (0.72 and 0.86) DS. The current study confirms that DS of CMC has strongly affected battery performance parameters such as deliverable capacity, power, cycle-life and storage performance etc. The working mechanism is also investigated on why the CMC with the best DS is compatible with the silicon-based anode.
An electrochemical sensor based on a three-dimensional (3D) graphene/carbon nanotube (G/CNT) hybrid was developed for the sensitive detection of olaquindox (OLA). 3D G/CNT hybrid through covalent C-C bonding was fabricated by one-step synthesis using catalytic chemical vapor deposition. To construct the base of the sensor, a novel composite was fabricated by a functionalized 3D G/CNT with poly-(dimethy diallyl ammonium chloride) and Nafion via simple grind and ultrasonication dispersion methods. The electrochemical determination of OLA exhibited an oxidation peak at −0.685 V with a higher current response. Due to the effective surface area and active sites, a good linear relationship was observed between the OLA concentration and peak current over the range of 1.5 × 10−6–2.7 × 10−3 mg mL−1 with a detection limit of 6.12 × 10−8 mg mL−1 (3σ). The proposed electrochemical sensor was used to detect OLA in swine samples at a recovery ranging from 97.78% to 104.25%, which exhibits a broader prospect to supervise animal products and a high potential for food security applications.
A novel method of Ni recovery from the acid leaching solution of electroplating sludge through preparing Ni-Fe alloy with high Fe2+ content (i.e., 0.5 g/L) is proposed in this paper, and the corresponding electrodeposition process was studied using conventional electrochemical techniques and scanning electron microscopy. The obtained results showed that adding saccharin Na at concentrations from 0 to 14 g/L to the deposition bath increased the cathodic polarization potential of Ni-Fe co-deposition, with sensible grain refinement and disappearance of surface cracks observed after the addition of 14 g/L saccharin Na. Two different mathematical models of metal nucleation were tested, and the different morphologies of the deposits formed with and without saccharin Na suggested disparate nucleation mechanisms. The Ni-Fe deposition potential shifted positively in the presence of thiourea, and it should not be added together with saccharin Na during the nucleation stage for the grain refinement of the deposits. The iron contents in the deposits decreased with the increase of thiourea concentration ascribed to the thiourea complex which adsorbed on the cathodic surface preventing Fe2+electrodeposition from the electrolytes.
This paper reports the occurrence of electrochemical oscillations (EOs) in Cu electro-oxidation of phosphoric acid solution, and systematically investigated the effect of potential, electrolyte composition and concentration, temperature, stirring rate, and scanning speed on EOs. The mechanism of EOs occurred as a result of deposition and dissolution effects of CuH2PO4 through electro-oxidation of the Cu anode. The experimental result for amplitude and frequency can be explained by this simplified qualitative analysis, and further verified the previously speculated EO mechanism. This study provides insights into the relevance of micro-chemical mechanisms for the macroscopic non-equilibrium phenomenon and presents novel concepts for highly efficient electrodissolution in metallurgy.
Mechanical attrition (MA) is applied to assist the electroplating Ni-P coating on a magnesium alloy substrate. The influence of MA on the microstructure and electrochemical performance of the coating was studied with SEM, XRD, electrochemical impedance spectroscopy (EIS) and polarization curves. The results show that under MA, the Ni-P electroplating becomes compact and free of cracks and pores, leading to significant improvement in the coating corrosion resistance. MA promote transformation the coating from amorphous state to crystalline one and produce an obvious transition layer at the coating-substrate interface, which is beneficial to enhancing the coating adhesion strength and other mechanical properties.