Effects of complex agents on the anodic deposition and electrochemical characteristics of cobalt oxides

One-step electrochemical elaboration of SnO2 modified electrode for lead ion trace detection in drinking water using SWASV

A facile method was proposed for the elaboration of an electrochemical sensor for heavy metal's trace detection by using square wave anodic stripping voltammetry (SWASV); this method is based on a simple anodic conversion of tin electrode into Sn/SnO₂ modified electrode. Both electrochemical and physico-chemical techniques were used to confirm the modification process and better understand the electrode's behavior. Then, depending on the operating conditions, the response signal was studied and adjusted in order to obtain optimal sensor performance. When optimized, the proposed method reached a lowest detection limit (LOD) of 2.15 μg L^-1 (0.0104 μM), and quantification limit (LOQ) of 5.36 μg L^-1 (0.0259 μM), in linearity range between from 6.2 and 20.7 μg L^-1. Additionally, after having used the elaborated electrode for ten successive measurements, the repeatability remains very high with an RSD of approximately 5.3%; furthermore, ten other species appear to have very slight effect on Pb(II) detection. Finally, for the method validation, the proposed electrode was able to sense different lead concentration integrated in a local bottled spring water by showing recovery levels ranging from 103.8 to 108.4%.

One-step process to form a nickel-based/carbon nanofoam composite supercapacitor electrode using Na2SO4 as an eco-friendly electrolyte

Anodic electrodeposition of NiO_x (NiO + NiOOH) onto carbon nanofoam forming a supercapacitor electrode. The resulting composite electrode operates at 2.2 V in Na₂SO₄ aqueous medium.

Preparation-morphology-performance relationships in cobalt aerogels as supercapacitors

The ability to direct the morphology of cobalt sol-gel materials by using the simple synthetic parameters in epoxide-driven polycondensations has been dramatically demonstrated, and the influence of such morphological differences upon the supercapacity of the materials has been explored. Precursor salt, epoxide, and solvent all influence the speed of the sol-gel transition and the size and shape of the features observed in the as-prepared materials, thereby leading to highly varied microstructures including spheres, sponge-like networks, and plate assemblies of varied size. These morphological features of the as-prepared cobalt aerogels were observed for the first time by high resolution scanning electron microscopy (HRSEM). The as-prepared aerogel materials were identified by powder X-ray diffraction and thermogravimetry as weakly crystalline or amorphous cobalt basic salts with the general formula Co(OH)(2-n)X(n) where X = Cl or NO3 according to the precursor salt used in the synthesis. For all samples, the morphology was preserved through mild calcining to afford spinel phase Co3O4 in a variety of microstructures. Wide-ranging specific surface areas were determined for the as-prepared and calcined phases by physisorption analysis in agreement with the morphologies observed by HRSEM. The Co3O4 aerogels were evaluated for their supercapacitive performance by cyclic voltammetry. The various specimens exhibit capacitances ranging from 110 to 550 F g(-1) depending upon the attributes of the particular aerogel material, and the best specimen was found to have good cycle stability. These results highlight the epoxide-driven sol-gel condensation as a versatile preparative route that provides wide scope in materials' properties and enables the analysis of structure-performance relationships in metal oxide materials.

An entirely electrochemical preparation of a nano-structured cobalt oxide electrode with superior redox activity

A nano-structured Co oxide electrode (with a Ni substrate) was successfully prepared using an entirely electrochemical process, which included the co-deposition of a Ni-Cu alloy film, selective etching of Cu from the film, and anodic deposition of Co oxide on the obtained nano-porous Ni substrate which had an average pore size of approximately 100 nm and a pore density of about 10(13) m(-2). The excellent electrochemical activity of the prepared electrode was demonstrated in terms of its pseudocapacitive performance, which was evaluated using cyclic voltammetry (CV) in 1 M KOH solution. The specific capacitance of the nano-structured Co oxide measured at a potential scan rate of 10 mV s(-1) was as high as 2200 F g(-1), which is over ten times higher than that of a flat oxide electrode (209 F g(-1)). The highly porous Co oxide also had superior kinetic performance as compared to a flat electrode. At a high CV scan rate of 50 mV s(-1), the two electrodes retained 94% and 59%, respectively, of their specific capacitances measured at 5 mV s(-1).

Multifunctional 3D nanoarchitectures for energy storage and conversion

The design and fabrication of three-dimensional multifunctional architectures from the appropriate nanoscale building blocks, including the strategic use of void space and deliberate disorder as design components, permits a re-examination of devices that produce or store energy as discussed in this critical review. The appropriate electronic, ionic, and electrochemical requirements for such devices may now be assembled into nanoarchitectures on the bench-top through the synthesis of low density, ultraporous nanoarchitectures that meld high surface area for heterogeneous reactions with a continuous, porous network for rapid molecular flux. Such nanoarchitectures amplify the nature of electrified interfaces and challenge the standard ways in which electrochemically active materials are both understood and used for energy storage. An architectural viewpoint provides a powerful metaphor to guide chemists and materials scientists in the design of energy-storing nanoarchitectures that depart from the hegemony of periodicity and order with the promise--and demonstration--of even higher performance (265 references).