Development of highly sensitive cadmium iondashselective electrodes by titration method and its application to cadmium ion determination in industrial waste water.
Characteristics of cadmium iondashselective electrode made cadmium sulphide (CdS)-silver sulphide (Ag(2)S) mixture were studied. CdS-Ag(2)S mixtures were obtained by gas/solid-phase reaction between silver-cadmium mixed powder and hydrogen sulphide gas (dry method) and by ionic reaction between cadmium-silver mixed ions and sulphide ion (wet method). As a result, it was found that the CdS-Ag(2)S mixture had to be made in the condition of excess existence of sulfur and had better regulate the excess sulfur quantity minimum, for the CdS-Ag(2)S pressed membrane gave a good Nernstian response against the cadmium ion concentration change. As the best way, CdS-Ag(2)S mixture was obtained by adding sulphide ion solution to 5 mol% cadmium ion and 95 mol% silver ion mixed solution while measuring silver sulphide (Ag(2)S) electrode potential as an indicator electrode. According to the reaction was stopped when the potential variation from the initial potential in the sulphide ion solution reached at 87-116 mV which the sulphide ion concentration became 10(-3) - 10(-4) of the initial concentration, the cadmium ion membrane pressed diameter of 8 mm and thickness of 2 mm showed a Nernstian response from 10(-8) to 10(-1) M of cadmium ion concentration. Furthermore, aiming to its application for industrial waste water, masking buffer for interfering metal ions such as lead ion (Pb(2+)) and copper ion (Cu(2+)), which were possibly coexisted and to adjust total ionic strength and pH of sample was developed. The present Cd(2+) iondashselective electrode was applied to the determination of Cd(2+) in the industrial waste water. The good regression line with correlation factor of 0.984 was obtained compared with the conventional atomic absorption spectroscopy.
Synthesis and characterization of silver diethyldithiocarbamate cluster for the deposition of acanthite (Ag2S) thin films for photoelectrochemical applications
Abstract Acanthite (Ag2S) thin films were fabricated on fluorine doped tin oxide coated conducting glass substrates by aerosol assisted chemical vapor deposition (AACVD) using silver cluster [Ag4{S2CN(C2H5)2}3(C5H5N)2]n·nNO3·2nH2O (1) [where (S2CN(C2H5)2) = diethyldithiocarbamate, C5H5N = pyridine] as a single source precursor. Cluster (1) was synthesized by the reaction of sodium diethyldithiocarbamate with silver nitrate in a mixture of acetone and pyridine. (1) was analyzed by melting point, elemental analysis, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, thermogravimetry and single crystal X-ray studies. Single crystal X-ray studies showed that (1) crystallizes in the triclinic crystal system with a = 11.4372(3), b = 11.6768(3), and c = 16.3672(4) A and α = 105.817(3), β = 97.891(3), and γ = 93.274(3)° in the space group P-1. Thermogravimetric analysis revealed that (1) undergoes facile thermal decomposition at 400 °C to give a stable residual mass consistent with the formation of Ag2S. Thin films grown from a 0.02 M solution of (1) in pyridine at 350 and 400 °C using AACVD technique were characterized by powder X-ray diffraction, field emission scanning electron microscopy (FESEM), energy dispersive X-ray and ultraviolet-visible spectrophotometry. FESEM images of the films exhibited well-defined nanorods with length > 1000 nm and diameter 100–150 nm grown without any cracks, fractures or directional preference. A band gap of 1.05 eV was estimated by extrapolating the linear part of a Tauc plot recorded for the films. The photoelectrochemical (PEC) characteristics recorded under Air Mass 1.5 illumination indicated a photocurrent density of 220 μA cm− 2 at 0.0 V vs Ag/AgCl/3 M KCl. The optical and PEC characteristics of the deposited thin films proved their suitability for PEC applications.
A Critical Assessment on Functional Attributes and Degradation Mechanism of Membrane Electrode Assembly Components in Direct Methanol Fuel Cells
Direct methanol fuel cells (DMFC) are typically a subset of polymer electrolyte membrane fuel cells (PEMFC) that possess benefits such as fuel flexibility, reduction in plant balance, and benign operation. Due to their benefits, DMFCs could play a substantial role in the future, specifically in replacing Li-ion batteries for portable and military applications. However, the critical concern with DMFCs is the degradation and inadequate reliability that affect the overall value chain and can potentially impede the commercialization of DMFCs. As a consequence, a reliability assessment can provide more insight into a DMFC component’s attributes. The membrane electrode assembly (MEA) is the integral component of the DMFC stack. A comprehensive understanding of its functional attributes and degradation mechanism plays a significant role in its commercialization. The methanol crossover through the membrane, carbon monoxide poisoning, high anode polarization by methanol oxidation, and operating parameters such as temperature, humidity, and others are significant contributions to MEA degradation. In addition, inadequate reliability of the MEA impacts the failure mechanism of DMFC, resulting in poor efficiency. Consequently, this paper provides a comprehensive assessment of several factors leading to the MEA degradation mechanism in order to develop a holistic understanding.