Electrochemical detection cell

Abstract

An electrochemical cell comprising an anode, a cathode and a reference electrode operating in an aqueous electrolyte is utilized for detection of noxious gases in air. The gas is oxidized at the anode and detection thereof occurs as a result of the current generated by the reaction. A fixed potential difference is maintained between the anode and the reference electrode to avoid generation of undesired current from reactions involving an oxygen-water redox couple within the cell which would invalidate anode-cathode current for gas detection purposes. The fixed potential is chosen from within the range of about 0.9 to 1.5 volts.

What is claimed is: 
     
       1. An electrochemical cell for quantitatively detecting a .Iadd.noxious .Iaddend.gas .Iadd.in the presence of air .Iaddend.comprising an anode having catalyst bonded to polytetrafluoroethylene to provide a diffusion electrode, a cathode, a reference electrode .Iadd.at which substantially no current flow.Iaddend., and an aqueous electrolyte .[.in contact with.]. .Iadd.within an electrolyte container, each of said anode, cathode and reference electrode having a catalytic surface contacting .Iaddend.said .[.anode, cathode and reference electrode;.]. .Iadd.electrolyte, and said reference electrode contacting air, .Iaddend.means for exposing said anode to a .[.gaseous substance.]. .Iadd.gas containing a noxious gas .Iaddend.to be detected; .Iadd.said anode being arranged in said cell so that one surface of said anode contacts said gas exposing means and the opposite surface contacts said electrolyte whereby the noxious gas to be detected migrates from the surface contacting said gas exposing means to the internal surface of said anode to interface with the electrolyte for reaction in the presence of the catalyst, .Iaddend.means connecting said anode and reference electrode, said latter means being a potentiostat .[.for.]. maintaining a fixed potential on said anode relative to said reference electrode of from about 0.9 to 1.5 volts with respect to the potential of the reversible hydrogen couple in the electrolyte of said cell which potential is independent of the concentration of the .Iadd.noxious .Iaddend.gas to be detected and means for measuring said current flowing between sad anode and cathode of said cell, said measured current being a measure of the concentration of the gas being detected. 
     
     
       2. The electrochemical cell of claim 1 wherein the anode comprises a material selected from the group consisting of platinum, rhodium, iridium, ruthenium, palladium, osmium, tungsten oxide, tungsten carbide, molybdenum oxide, molybdenum sulphide, gold, and alloys or mixtures thereof. 
     
     
       3. The electrochemical cell of claim 2 wherein the anode includes platinum. 
     
     
       4. The electrochemical cell of claim 2 wherein the anode includes gold. 
     
     
       5. The electrochemical cell of claim 1 wherein the electrolyte is potassium hydroxide. 
     
     
       6. The electrochemical cell of claim 1 wherein the electrolyte is phosphoric acid. 
     
     
       7. The electrochemical cell of claim 1 wherein the electrolyte is sulfuric acid. 
     
     
       8. The electrochemical cell of claim 1 wherein the electrolyte is contained in a matrix. 
     
     
       9. The electrochemical cell of claim 1 wherein the electrolyte is free flowing. .[.10. An electrochemical cell for quantitatively detecting a gas comprising an anode, a cathode, a reference electrode, and an aqueous electrolyte in contact with said anode, cathode and reference electrode; means for exposing said anode to a gaseous substance to be detected including a chamber behind said anode, said chamber defining a labyrinthine path; means connecting said anode and reference electrode, said latter means being a potentiostat for maintaining a fixed potential on said anode relative to said reference electrode of from about 0.9 to 1.5 volts with respect to the potential of the reversible hydrogen couple in the electrolyte of said cell which potential is independent of the concentration of the gas to be detected, and means for measuring said current flowing between said anode and cathode of said cell, said measured current being a measure of the concentration of the gas being detected..].