Gold-containing catalyst with porous structure

Abstract

The invention relates to a gold-containing catalyst with porous structure that is obtainable through a process that comprises the following steps: melting together of gold and at least one less noble metal that is selected from the group consisting of silver, copper, rhodium, palladium, and platinum, and at least partial removal by dissolving the at least one less noble metal out of the starting alloy thus obtained. The catalyst has high activity and great long-term stability, despite the fact that it does not contain a support material or a compound that serves as a support material. The catalyst can be used to accelerate and/or to influence the product selectivity of oxidation and reduction reactions. The catalyst is suitable, for example, for the oxidization of carbon monoxide to carbon dioxide, which makes it usable, among other things, in a fuel cell, in particular a polymer electrolyte membrane fuel cell (PEM), for protection of the anode catalyst against blocking by carbon monoxide.

1 . Gold-containing catalyst with porous structure, prepared by a method that comprises the following steps: producing a starting alloy by melting together of gold and at least one less noble metal that is selected from the group consisting of silver, copper, rhodium, palladium, and platinum; and a dealloying step comprising at least partial removal of the less noble metal by dissolving the at least one less noble metal out of the starting alloy.  
     
     
         2 . The catalyst defined in  claim 1 , comprising a ratio of gold to the less noble metal(s) in the starting alloy is in the range from 50 atom %: 50 atom % to 10 atom %: 90 atom % liegt.  
     
     
         3 . The catalyst defined in  claim 1  or  2 , comprising an Au—Ag-starting alloy, the ratio of gold to silver in the starting alloy is within the range from 45 atom %: 55 atom % to 20 atom %: 80 atom %.  
     
     
         4 . The catalyst defined in one of the preceding claims, wherein the process further comprises a step of homogenization, in which the starting alloy is held for an adequate time at a temperature just below the melting point.  
     
     
         5 . The catalyst defined in one of the preceding claims, wherein the process also comprises at least one shaping step with which the starting alloy is given a desired shape.  
     
     
         6 . The catalyst defined in  claim 5 , comprising the shaping of the starting alloy by at least one of the shaping methods of pressing, stamping, rolling, bending, boring, hammering, cutting, and milling is used.  
     
     
         7 . The catalyst defined in one of claims  5  or  6 , further comprising, after the at least one shaping step, a step of annealing the shaped starting alloy.  
     
     
         8 . The catalyst defined in one of the preceding claims, comprising the dealloying step and the creation of the porous structure occur with the use of at least one wet-chemical and/or one electrochemical process.  
     
     
         9 . The catalyst defined in one of the preceding claims, comprising after the dealloying step, the ratio of gold to the at least one less noble metal in the porous structure is in the range from 100 atom %: 0 atom % to 95 atom %: 5 atom %, determined using AAS.  
     
     
         10 . The catalyst defined in one of the preceding claims, further comprising a step of activation of the material obtained after the at least partial dealloying at a temperature of roughly +40° C. to +80° C. in an oxygen-containing atmosphere, optionally in the presence of carbon monoxide.  
     
     
         11 . The catalyst defined in one of the preceding claims, comprising a pore structure with diameters of roughly 30 to 100 nm determined with scanning electron microscopy and a surface in the range of 2 to 8 m 2 /g determined with the BET process.  
     
     
         12 . The catalyst defined in one of the preceding claims comprises of a powder, pellets, or a membrane-type structure, with the membrane-type structure having a thickness of as little as about 100 mm.  
     
     
         13 . The catalyst defined in one of claims  1  through  12  is used in a process to accelerate and/or influence the product selectivity of oxidation and reduction reactions.  
     
     
         14 . The process defined in  claim 13  comprises oxidation of carbon monoxide contained in a medium to carbon dioxide.  
     
     
         15 . The process defined in  claim 14 , wherein the temperature of the carbon monoxide-containing medium is in the range from roughly −50° C. to +150° C.  
     
     
         16 . A fuel cell that contains a catalyst defined in one of claims  1  through  12 .  
     
     
         17 . The fuel cell defined in  claim 16 , comprises a polymer electrolyte membrane fuel cell, preferably a low temperature polymer electrolyte membrane fuel cell.  
     
     
         18 . The fuel cell defined in  claim 16  or  17 , wherein the catalyst comprises a framed or frameless membrane catalyst or a catalyst charge that is arranged upstream relative to the anode catalyst in the gas stream.  
     
     
         19 . The catalyst defined in  claim 5 , wherein said resulting gold-containing catalyst with porous structure contains no support structure for said gold.  
     
     
         20 . The catalyst defined in  claim 1 , where said less noble metals are selected from the group consisting of silver, copper and palladium.