Lead-free galvanic oxygen sensor

Abstract

A lead-free galvanic oxygen sensor having an aqueous electrolyte and a bismuth anode is disclosed. The electrolyte contains a polyol in addition to water and a salt. Surprisingly, a sensor with such an electrolyte has an increased resistance to passivation.

1 . An oxygen sensor comprising: a housing, a cathode, a bismuth anode, and an aqueous electrolyte comprising a polyol and a salt wherein the anode is substantially free of lead. 
     
     
         2 . The oxygen sensor of  claim 1  wherein the cathode comprises an electrically conductive material selected from the group consisting of platinum, gold, silver, palladium, rhodium, iridium and carbon plated with platinum, gold, silver, palladium, rhodium, or iridium. 
     
     
         3 . The oxygen sensor of  claim 1  wherein the cathode is carbon plated with platinum. 
     
     
         4 . The oxygen sensor of  claim 1  wherein the salt is an alkaline salt. 
     
     
         5 . The oxygen sensor of  claim 1  wherein the salt is selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium acetate, and sodium acetate. 
     
     
         6 . The oxygen sensor of  claim 1  wherein the salt is potassium hydroxide. 
     
     
         7 . The oxygen sensor of  claim 1  wherein the salt is an ammonium quaternary hydroxide, R 4 N + OH − . 
     
     
         8 . The oxygen sensor of  claim 7  wherein R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl, and mixtures thereof. 
     
     
         9 . The oxygen sensor of  claim 1  wherein the polyol is selected from the group consisting of glycerol, erythritol, sorbitol, ethylene glycol, and mixtures thereof. 
     
     
         10 . The oxygen sensor of  claim 1  wherein the polyol is glycerol. 
     
     
         11 . The oxygen sensor of  claim 1  wherein the polyol comprises about 20% to about 30% by volume. 
     
     
         12 . An oxygen sensor comprising: a housing, a cathode, a bismuth anode, and an aqueous electrolyte that includes a salt and a polyol, wherein the anode is substantially free of lead. 
     
     
         13 . The oxygen sensor of  claim 12  wherein the cathode comprises an electrically conductive material selected from the group consisting of platinum, gold, silver, palladium, rhodium, iridium and carbon plated with platinum, gold, silver, palladium, rhodium, or iridium. 
     
     
         14 . The oxygen sensor of  claim 12  wherein the salt is selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium acetate, and sodium acetate. 
     
     
         15 . The oxygen sensor of  claim 12  wherein the salt is potassium hydroxide. 
     
     
         16 . The oxygen sensor of  claim 12  wherein the salt is an ammonium quaternary hydroxide, R 4 N + OH − . 
     
     
         17 . The oxygen sensor of  claim 16  wherein R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl, and mixtures thereof. 
     
     
         18 . The oxygen sensor of  claim 12  wherein the polyol is selected from the group consisting of glycerol, erythritol, sorbitol and ethylene glycol. 
     
     
         19 . The oxygen sensor of  claim 12  wherein the polyol is glycerol. 
     
     
         20 . An electrochemical sensor comprising a bismuth anode and aqueous electrolyte comprising a polyol and a salt.