Electrochemical gas sensors and methods for sensing electrochemical active gases in gas mixtures

An electrochemical, galvanic sensing cell for sensing concentrations of an electrochemically active gas in a gas mixture and providing an output electrical current flow from the sensing cell representative of the concentrations of the sensed electrochemically active gas wherein the sensing cell has a gas sensing cathode means and an anode electrode means immersed in an alkaline or basic liquid electrolyte for causing reactions at the anode and cathode electrodes with an electrochemical active gas applied to the gas sensing electrode and providing an output external electrical current flow representative of the sensed gases between gas sensing cathode electrode and the anode electrodes the improvement comprising an electrolyte storage medium in the sensing cell having said liquid electrolyte entrapped therein and said storage medium comprises a microporous silicon dioxide polymer.

An electrochemical, galvanic sensing cell for sensing concentrations of an electrochemical active gas in a gas mixture and providing an output electrical current flow from the sensing cell representative of the concentrations of the sensed electrochemically active gas wherein the sensing cell has a gas sensing cathode electrode means and an anode electrode means immersed in an alkaline or basic liquid electrolyte for causing reactions at the anode and cathode electrodes with an electrochemical active gas applied to the gas sensing electrode and providing an output external electrical current flow representative of the sensed gases between gas sensing cathode electrode and the anode electrodes wherein the improvement comprises a liquid electrolyte stored in a semi-solid having voids therein with said electrolyte immobilized in said voids.

A method of sensing concentrations of an electrochemically active gas in a gas mixture by means of a galvanic sensing cell which senses electrochemically active gases in the sub-parts per billion range including the steps of providing a gas sensing cell which produces electrical output signals representative of the concentrations of an active gas in a gas mixture applied to said gas sensing cell by galvanic action of the cell sensing electrodes wet by an electrolyte, and

• continuously removing any reactive gases in said electrolyte of the cell wherein the cell senses and accurately provides output signals representative of the concentrations of an active gas in a gas mixture including down to sub-parts per billion, 1-10 ppb without resorting to purging the reactive gases from the electrolyte by using a plurality of scavenger electrode means.

A method for sensing concentrations of an electrochemical active gas in a gas mixture by means of a galvanic gas sensor capable of sensing active gases up to parts per billions in a gas mixture including sub-parts per billion,

• providing a galvanic gas sensor having a gas sensing cathode electrode having a preselected area, an anode electrode and an electrolyte for wetting said electrodes, all selected for sensing a preselected active gas or gases and all contained in a single sensor container, and
• continuously removing any unreacted or partially reacted gases in the electrolyte so that the gas sensor senses and signals accurate concentrations of active gases including in a range of 0-10 parts per billion and more in a gas mixture by using scavenger electrode means being at least the same size in area as the sensing electrode.

A method for sensing the concentrations of an electrochemically active gas in a gas mixture by means of an electrochemical, galvanic sensing cell providing an electrical output current representative of the concentrations of the sensed electrochemically active gases including in sub-parts per billion range, said method including the steps of

• providing an electrochemical, galvanic sensing cell which senses concentrations of such an active gas in the parts per billion range,
• said sensing cell having a gas sensing cathode electrode, anode electrode and an electrolyte wherein the electrolyte has a dissolved active gas such as oxygen in the electrolyte in relatively high quantities relative to the quantities of the gas undergoing sensing, and
• continuously removing any dissolved active gas or partially reacted electrochemical gas from the electrolyte before being dissolved in the bulk electrolyte where said sensing cell continuously detects sub-parts per billion of the sensed active gas in a gas mixture without external sparging of the electrolyte.

A method of measuring the concentration of oxygen in parts per billion range in an electrochemical cell without loss of accuracy due to dissolved oxygen concentrations in the electrolyte,

• providing an electrochemical sensing cell which senses oxygen in the parts per billion range by a oxygen sensing electrode and an anode electrode immersed in a preselected electrolyte,
• positioning first scavenger electrode means in the electrolyte in a spaced relationship with the oxygen sensing electrode wherein said first scavenger electrode is at least the same size as said oxygen sensing electrode, positioning an insulative, porous barrier in close relationship with said sensing electrode and said scavenger electrode, said barrier permits the diffusion of electrolyte therethrough and protects the integrity of the oxygen sensing electrode, the scavenger electrode means being effective to react any electrochemical gas not completely reacted at said oxygen sensing electrode,
• removing any dissolved electrochemically active gases such as oxygen from the bulk electrolyte to permit accurate measurements in the sub-parts per billion level by positioning second scavenger electrode means in the electrolyte in a spaced relationship with the first scavenger electrode.

A method of sensing concentrations of an electrochemically active gas in a gas mixture by means of a galvanic sensing cell,

• providing a galvanic sensing cell having a gas sensing electrode and an anode electrode immersed in a basic electrolyte stored in a container for functioning as a galvanic sensing cell for sensing a preselected electrochemical active gas in a gas mixture and providing an electrical output current representative of the concentration of the sensed electrochemical active gas in the gas mixture,
• removing or minimizing the concentration of dissolved electrochemical gases in the electrolyte by sensing the electrochemical active gas that is not completely reacted at the gas sensing electrode for preventing its dissolution into the electrolyte and producing a more accurate representation of the sensed gas, by arranging a scavenging electrode spaced within the electrolyte.

An electrochemical, galvanic sensing cell for sensing concentrations of an electrochemical active gas in a gas mixture applied to said sensing cell and providing an output electrical current flow from the sensing cell accurately reresentative of the concentrations of the sensed electrochemically active gas, comprising

• an insulative container, a gas sensing cathode electrode that has a composite structure with an electrically conductive support having a gas diffusion hydrophobic surface, wherein the gas sensing cathode electrode is mounted to the container for sensing active gases applied thereto, an anode electrode mounted to the container and an electrolyte in said container for wetting the cathode and anode electrodes and providing an external current flow signalling the concentration of an active gas applied to the cathode electrode as a result of electrogalvanic action occuring at the electrodes,
• scavenger electrode means mounted to the insulative container and functioning with the anode electrode for reacting any active gases dissolved in the electrolyte for more accurately electrically signalling the concentration of the sensed active gases applied to the cathode electrode, and
• electrical insulative means secured to said container between said sensing cathode electrode and said scavenger electrode means.