Electrochemical sulfur sensor and the method of making the same

• US 9,097,661 B2
• Filed: 01/27/2011
• Issued: 08/04/2015
• Est. Priority Date: 01/27/2011
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Rebinsky, Douglas A., Liu, Xiaodong, Zemskova, Svetlana M.
• Primary Examiner(s): Hendricks, Keith
• Assistant Examiner(s): CARLSON, KOURTNEY SALZMAN
• Application Number:
  US13/015,144
• Publication Number:
  US 20120193230A1
• Time in Patent Office: 1,650 Days
• Field of Search: 204400-435, 205775-7945, 73 5301- 6456
• US Class Current: 1/1
• CPC Class Codes: G01N 27/4166 measuring a particular property of an electrolyte
• CPC Class Codes: G01N 33/287 Sulfur content

Abstract

This disclosure relates to sulfur sensors that utilize sensing materials that can be used to detect a wide range of concentrations including ultra low concentrations of sulfur in liquids, such as below even 15 ppm. The sulfur sensors comprise a sensing electrode having a material that contributes an electronic output to the analysis and a material that contributes an ionic output to the analysis.

Claims

1. An electrochemical sulfur sensor for determining a concentration of sulfur compounds in a liquid, the electrochemical sulfur sensor comprising:

a reference electrode; and

a sensing electrode including a sensing material including an electronic conductive material wet impregnated with a metal cation, wherein the wet impregnation of the electronic conductive material includes dissolving the metal cation in water and adding the electronic conductive material to the resulting aqueous solution prior to formation of the sensing electrode;

wherein the sensing material exhibits both electronic and ionic conductivity in the presence of the liquid.

2. The electrochemical sulfur sensor of claim 1 wherein the form of the electronic conductive material is selected from the group consisting of graphite foam, metal coupons, tape, fiber, fiber mesh, powder, sintered powder, and thick and thin film depositions.

3. The electrochemical sulfur sensor of claim 1 wherein the electronic conductive material is a graphite foam.

4. The electrochemical sulfur sensor of claim 1 wherein the metal cation is selected from the group consisting of Fe²⁺, Cu²⁺, Ag⁺, Au³⁺, Ni²⁺, Zn²⁺, Pb²⁺, Mo⁴⁺ and combinations thereof.

5. The electrochemical sulfur sensor of claim 1 wherein the reference electrode is a wire comprising Ag, Au, Pt, and combinations thereof.

6. The electrochemical sulfur sensor of claim 1 wherein the electronic conductive material is affixed to a copper-based metal tape.

7. The electrochemical sulfur sensor of claim 6 further including an insulating layer between the reference electrode and the sensing electrode affixed to a copper-based metal tape.

8. The electrochemical sulfur sensor of claim 7 wherein the insulating layer includes PTFE.

9. The electrochemical sulfur sensor of claim 1 wherein the sensing electrode includes a metal composite matrix with graphite, wherein graphite particles are dispersed with metal particles in the metal composite matrix.

10. An electrochemical sulfur sensor for determining a concentration of sulfur compounds in a liquid, comprising;

a reference electrode;

a sensing electrode including a composite material of graphite wet impregnated with a metal cation, wherein the wet impregnation of the graphite includes dissolving the metal cation in water and adding the graphite in powdered form to the resulting aqueous solution prior to formation of the sensing electrode; and

an insulating layer between the reference electrode and the sensing electrode.

11. The sensor of claim 10, wherein the metal cation is selected from the group consisting of Fe²⁺, Cu²⁺, Ag⁺, Au³⁺, Ni²⁺, Zn²⁺, Pb²⁺, Mo⁴⁺, and combinations thereof.

12. A method for forming an electrochemical sulfur sensor for determining a sulfur concentration in a liquid, the electrochemical sulfur sensor including a reference electrode and a sensing material including an electronic conductive material and a metal cation, wherein the sensing material is in association with a sensing electrode, the method comprising:

forming the sensing material by wet impregnating the electronic conductive material with the metal cation, wherein the wet impregnating includes dissolving the metal cation in water and adding the electronic conductive material to the resulting aqueous solution prior to formation of the sensing electrode.

13. The method of claim 12 wherein the metal cation is Fe²⁺.

14. The method of claim 12 wherein the conductive material is in powder form.

15. The method of claim 14 wherein the powder is a graphite powder.

16. The method of claim 14, further including;

combining the aqueous solution with the powdered conductive material to form a composite slurry;

aging the composite slurry for at least about 24 hours;

curing the aged slurry for at least about 10 hours; and

drying the cured slurry.

17. The method of claim 12 wherein the conductive material is a foamed material.

18. The method of claim 17 wherein the foamed material is graphite foam.

19. The method of claim 17, further including;

combining the aqueous solution with the graphite foamed material;

aging the combined solution and foamed material for at least about 12 hours;

curing the aged foamed material for at least about 30 minutes; and

drying the cured slurry.

20. The method of claim 12 wherein the solution is a sol-gel solution;

the method further including;

combining the sol-gel solution with a graphite foam;

applying the combined sol-gel solution and graphite foam to a conductive metal tape.