ABSTRACT
A wide spectrum of electrode potentials of minerals that compose sulfide ores enables the latter, when in contact with hydrothermal solutions, to form galvanic pairs with cathode potentials sufficient for electrochemical reduction of CO2. The experiments performed demonstrated the increase of cathode current on the rotating pyrite disc electrode in a range of potentials more negative than -800 mV in presence of CO2. In high-pressure experiments performed in a specially designed electrochemical cell equipped with a pyrite cathode and placed into autoclave, accumulation of formate was demonstrated after 24 hr passing of CO2 (50 atm, room temperature) through electrolyte solution. The formation of this product started on increasing the cathode potential to -800 mV (with respect to saturated silver chloride electrode). The yield grew exponentially upon cathode potential increase up to -1200 mV. The maximum current efficiency (0.12%) was registered at cathode potentials of about -1000 mV. No formate production was registered under normal atmospheric pressure and in the absence of imposed cathode potential. Neither in experiments, nor in control was formaldehyde found. It is proposed that the electrochemical reduction of CO2 takes part in the formation of organic molecules in hydrothermal solutions accompanying sulfide ore deposits and in 'black smokers' on the ocean floor.
Subject(s)
Carbon Dioxide/chemistry , Electrochemistry , Iron/chemistry , Organic Chemicals/metabolism , Sulfides/chemistry , Electrochemistry/instrumentation , Electrochemistry/methods , Electrodes , Formates/chemistry , Organic Chemicals/chemistry , Oxidation-Reduction , Pressure , TemperatureSubject(s)
Carbon Dioxide/chemistry , Carbon Dioxide/pharmacology , Iron/chemistry , Sulfides/chemistry , Electrochemistry , Electrodes , Environment , Formates/chemistry , Geologic Sediments , Hydrogen-Ion Concentration , Models, Biological , Models, Chemical , Physical Phenomena , Physics , TemperatureABSTRACT
The effect of concentration of ethanol and dimethyl sulfoxide on the catalytic activity of laccase is studied for the enzymatic reaction of catechol oxidation and bioelectrocatalytic reaction of oxygen reduction under the conditions of direct electron transfer. Laccase-Nafion composite is elaborated ensuring the enzyme stability in a wide potential range and a content of organic solvents. Based on the STM measurements, the structure of composite layer is proposed. It is shown that the mechanism of oxygen reduction reaction by laccase in organo-aqueous mixtures is similar to that earlier proposed for aqueous solutions. A decrease in the electrocatalytic activity of laccase in the oxygen reduction correlates with a decrease in the laccase enzymatic activity in the substrate oxidation. However, a decrease in the laccase activity in the composite is observed at a higher content of organic solvent in the mixture. The mechanism of laccase inactivation by organic solvents is proposed.
Subject(s)
Biosensing Techniques/methods , Dimethyl Sulfoxide/chemistry , Electrochemistry/methods , Ethanol/chemistry , Oxidoreductases/chemistry , Water/chemistry , Biosensing Techniques/instrumentation , Catalysis , Catechols/chemistry , Electrodes , Enzyme Activation , Enzyme Inhibitors , Enzyme Stability , Enzymes, Immobilized/chemistry , Fluorocarbon Polymers , Laccase , Organic Chemicals/chemistry , Oxidation-Reduction , Oxidoreductases/antagonists & inhibitors , Oxygen/chemistry , Sensitivity and Specificity , Solvents/chemistryABSTRACT
Research results obtained in the last 3 years in the area of electrochemical amperometric biosensors are presented. Selective electrochemical biosensors are proposed on the basis of investigations of electrode materials, electrolyte content, selective properties of polymer materials and mediators influence. Biosensor parameters for determination of glucose, phenol and biological oxygen demand are described.
Subject(s)
Biosensing Techniques , Glucose/analysis , Water Supply/standards , Blood Glucose/analysis , Electrochemistry , Phenol , Phenols/analysisABSTRACT
The influence of temperature, oxygen pressure and inhibitors of laccase on the dioxygen electroreduction reaction has been examined at different solution pH. On the basis of obtained data, a reaction mechanism including electron transfer from the enzyme active site to the oxygen molecule is suggested as the slow step.
