Acetylene Black Carbon Research Articles

The electrochemical properties of Fe 2O 3-loaded carbon electrodes for iron–air battery anodes

The redox efficiency of iron has been improved by increasing the distribution of iron on the carbon surface with Fe 2O 3-loaded carbon materials. The Fe 2O 3-loaded carbon material was prepared by loading Fe 2O 3 on carbon by a chemical method. Fe(NO 3) 3 was impregnated on carbon with different weight ratios of iron-to-carbon in an aqueous solution, and the mixture was dried and then calcined for 1 h at 400 °C in flowing Ar. The effect of various carbons on the physical and electrochemical properties of Fe 2O 3-loaded carbon electrodes was investigated with the use of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) along with X-ray energy-dispersive spectroscopy (EDS), cyclic voltammetry (CV) and galvanostatic cycling performance. Transmission electron microscopy coupled with X-ray diffraction measurements revealed that small Fe 2O 3 particles were distributed on the carbon surface. Natural graphite and several nano-carbon materials such as acetylene black and tubular carbon nanofibers (tubular CNF) exhibited improved characteristics, such as enhanced capacity and higher redox currents for the Fe 2O 3-loaded carbon electrode. SEM and EDS results suggest that Fe 2O 3-loaded nano-carbon electrodes, due to the large surface area of the nano-carbon, have more Fe 2O 3 dispersed than on Fe 2O 3-coated graphite electrodes.

Nanocomposite material laccase/dispersed carbon carrier for oxygen electrode

The effect of carbon dispersion degree on the effectiveness of oxygen electroreduction by laccase at its immobilization at superdispersed colloid graphite (SCG) or acetylene carbon black (ACB) is studied. A method of synthesizing the highly active composite material based on SCG is suggested providing the optimum orientation of enzyme molecules for the direct bioelectrocatalysis due to the fact that the particles of the carrier (SCG) and laccase molecules are commensurable. The specific current of oxygen reduction per enzyme molecule for the composite of SCG + laccase is five times higher than that at the composite based on ACB. The effect of the specific activity increase is observed only at ultra-thin layers of the composite material at the electrode; for the creation of the gas-diffusion oxygen electrode the active layer structure should be optimized to remove the percolation effects.

Diffusion layer parameters influencing optimal fuel cell performance

The performance of polymer electrolyte fuel cells (PEFCs) is substantially influenced by the morphology of the gas diffusion layer. Cells utilising sintered gas diffusion layers made with a low pore volume Acetylene Black carbon, at an optimised thickness, showed better performance compared with cells containing Vulcan XC-72R carbon. The cells were optimised using both oxygen and air as oxidants showing that different conditions were required in each case to achieve optimum cell performance. A model, in which the hydrophobicity and porosity of the diffusion layer affect water impregnation and gas diffusion through the gas diffusion layer, is presented to explain the influence of the diffusion layer morphology on cell performance.

ToF-SIMS and XPS study of sulphur on carbon black surface

A very broad range of carbon blacks (CB) from different origins and different manufacturing processes (furnace CB, plasma CB, acetylene CB, plasma-treated CB, etc.) were analysed by surface-sensitive techniques: time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS), The data were compared with conventional bulk properties of industrial CB: specific surface area and sulphur titration. Different types of sulphur functional groups were identified at CB surfaces by ToF-SIMS (HS-, SOx-, HSOx-, SCN-, etc.). A linear relationship between the ToF-SIMS intensity of the sulphur-containing ions and the total sulphur bulk quantity was observed. The total intensity of ToF-SIMS spectra was found to be dependent on the specific surface area of the CB samples. The total quantity of sulphur measured by XPS, when detected, was in good agreement with the total sulphur bulk quantity. However, the ToF-SIMS sensitivity for sulphur functional groups was much higher than the XPS sensitivity, Copyright (C) 2000 John Wiley & Sons, Ltd.

Synthesis of carbon/EMD composite from carbon-suspended sulfuric acid and manganese sulfate bath

A study has been made of the electrodeposition of MnO 2 on a titanium anode from a carbon or carbon/MnO 2 composite suspended in a H 2SO 2-MnSO 4 bath. Electrolytic manganese dioxide (EMD) containing acetylene black or vapour-grown carbon fibre shows excellent alkaline battery performance ad good grindability. Nevertheless, passivation of the titanium anode sometimes occurs during electrolysis at a current density of 1 A dm −2. This problem is successfully resolved without loss of battery performance, by using carbon/δ-MnO 2 as suspension particles. Apart from producing EMDs with good grindability and excellent battery performance, this bath has several other advantages, namely: easy maintenance of the dispersion; good reproducibility; low anode potential during electrolysis, and higher carbon content. It is proposed that a close relationship exists between battery performance and the surface characteristics of EMDs such as BET surface area and pore size.

Studies to improve the Li/SO2Cl2 cell

The performance of the Li/SO2Cl2 primary cell was studied as a function of the type of the carbon cathode, cathode catalysts and electrolyte additives. Solutions of LiAICl4 in S02 are more conductive than those in SO2Cl2 and, consequently, the electrolyte resistance in the Li/SO2Cl2 cell decreases during discharge as one mole of S02 is formed per mole of SO2Cl2. The replacement of the low surface area Chevron acetylene black carbon with the high surface area Ketjenblack carbon cathode increases cell capacity and reduces cathode polarization. The high surface area carbon, however, causes a deterioration in the storability of the cell, manifested as higher self-discharge rate. The use of carefully purified SO2Cl2, and of Ca2+ as an additive to the electrolyte, has been found to reduce the voltage delay of the cells stored at 70°C. The low temperature discharge capacity of the Li/SO2Cl2 cell can be increased with the addition of S02. Furthermore, the added S02 appeared to improve the storability of the cells. Cathodes doped with a catalyst consisting of a mixture of polyacrylonitrile and Co, Ni or Fe-salts, after heat treatment at 800° C, demonstrated 350–500 mV gain in the load voltage at 25 mA cm−2. Catalysed cells stored at 70°C retained their higher cell voltage but, like the uncatalysed cells, showed a loss in capacity.

Effect of carbon dioxide on electrochemical stability of gas diffusion electrodes in alkaline solution

By means of radioisotope (3H and 14C) tracer methods, a study was undertaken to investigate the role of CO2 impurity [10% (m/o)] contained in O2 feed gas on the electrochemical stability of gas diffusion electrodes which performed the oxygen reduction in alkaline solution. The electrodes were prepared by supporting a perovskite oxide catalyst on three kinds of carbon carriers; hydrophilic activated carbon, hydrophobic acetylene black and furnace-type carbon black. For the electrodes with the carriers mixed by activated carbon and acetylene black, a polarization loss of the electrode and a dissolution of CO2 into electrolytic solution were observed during the supply of CO2 to O2 feed gas. Under a low gas flow rate of the feed gas, a reversible polarization responsible to the supply of CO2 was observed in the electrodes with high contents of activated carbon carrier. However, an irreversible fatal polarization loss accompanied with the progressive wetting of the electrode was observed under a high gas flow rate of the feed gas, leading to the decay of three phase equilibrium even when cutting off the supply of CO2. On the other hand, neither the dissolution of CO2 into electrolytic solution nor the wetting of the electrode induced by the introduction of CO2 were detected for the electrode with furnace-type carbon black which was able to construct a compactly packed electrode structure.

The effect of heat treatment atmospheres on the electrocatalytic activity of cobalt tetraazaannulenes: preliminary results

Ambient heat treatment atmospheres have been found to have significant effect on the oxygen reduction catalytic activity of Co tetraazaannulene and its dibromo derivative. Two macrocyclic chelates were absorbed on acetylene black carbon from DMF (dimethyl formamide) solutions, then heat treated in each of the following environments: N 2, Ar, vacuum and nitrogen passed over heated copper turnings. Electrodes were prepared by pasting the catalyst mixed with a Teflon slurry onto a carbon cloth. The catalytic activity was evaluated from steady state current vs voltage measurements for the electrochemical reduction of oxygen in 4 N H 2SO 4. The results indicate that the activity of the two chelates is influenced by the ambient atmospheres of heat treatment. ESCA examination of the adsorbed Co tetraazaannulene dibromide on the acetylene black carbon heat treated in N 2 and vacuum indicated evidence of bonding with the carbon surface for the former and possible polymerization of the catalyst on the surface for the latter.

Preparation of iron phthalocyanine catalyzed carbon electrodes by chemical modification

A technique for chemically bonding and polymerizing organometallic chelate catalysts on a carbon substrate has been developed, with the objective of improving catalyst activity and stability for the reduction of oxygen in acidic electrolytes. Acetylene black carbon was chemically modified by bonding with polymerized iron tetrachlorophthalocyanine catalyst, followed by heat treatment. An electrode made with this catalyst showed significant improvement in activity and stability as compard with a similar unmodified catalytic electrode.