Electrocatalyst Supports for Fuel Cells

Abstract

Titanium oxide (usually titanium dioxide) catalyst support particles are doped for electronic conductivity and formed with surface area-enhancing pores for use, for example, in electro-catalyzed electrodes on proton exchange membrane electrodes in hydrogen/oxygen fuel cells. Suitable compounds of titanium and a dopant are dispersed with pore-forming particles in a liquid medium. The compounds are deposited as a precipitate or sol on the pore-forming particles and heated to transform the deposit into crystals of dopant-containing titanium dioxide. If the heating has not decomposed the pore-forming particles, they are chemically removed from the, now pore-enhanced, the titanium dioxide particles.

1 . A porous catalyst support comprising particles of titanium oxide, the particles of titanium oxide containing a dopant element for enhanced electron conductivity and the particles having surface area-increasing pores resulting from vacated pore-forming particles.  
     
     
         2 . A catalyst support as recited in  claim 1  in which the dopant element comprises one or more elements selected from the group consisting of lanthanum, manganese, molybdenum, niobium, tantalum, tungsten, strontium, vanadium, and yttrium.  
     
     
         3 . A catalyst support as recited in  claim 1  in which the dopant element comprises niobium.  
     
     
         4 . An electrode for a fuel cell, the electrode comprising catalyst particles dispersed on catalyst support particles of titanium oxide, the titanium oxide containing a dopant element for enhanced electronic conductivity and the particles having surface area-increasing pores resulting from vacated pore-forming particles.  
     
     
         5 . An electrode for a fuel cell as recited in  claim 4  in which the electrode is formed on a surface of with a proton exchange membrane and comprises noble metal catalyst particles.  
     
     
         6 . An electrode for a fuel cell as recited in  claim 4  in which the electrode is a cathode for reduction of oxygen in a stream of air.  
     
     
         7 . An electrode for a fuel cell as recited in  claim 5  in which the electrode is a cathode for reduction of oxygen in a stream of air.  
     
     
         8 . An electrode for a fuel cell as recited in claims  4  in which the catalyst comprises platinum and the dopant element is niobium.  
     
     
         9 . An electrode for a fuel cell as recited in claims  5  in which the catalyst comprises platinum and the dopant element is niobium.  
     
     
         10 . A method of making titanium dioxide particles for supporting particles of a catalyst comprising: 
 co-dispersing compounds of titanium and a dopant element as solutes or an sol in a liquid medium;    dispersing insoluble particles for pore-forming in the liquid medium, the particles being no larger than about twenty nanometers in largest dimension;    precipitating the dispersed compounds of titanium and dopant on the pore-forming particles;    separating the titanium compound and dopant compound coated particles from the liquid medium;    heating the coated particles in an atmosphere to form crystalline, dopant element-containing titanium oxide; and if necessary after the heating,    removing the embedded template particles from the crystalline, dopant element-containing titanium oxide particles to leave template particle-vacated pores in the titanium oxide particles.    
     
     
         11 . A method as recited in  claim 10  in which the titanium compounds are titanium (IV) alkoxide compounds and the liquid medium comprises an alcohol and/ or water.  
     
     
         12 . A method as recited in  claim 10  in which the template particles are silica particles.  
     
     
         13 . A method as recited in  claim 10  in which the dopant element comprises one or more elements selected from the group consisting of lanthanum, manganese, molybdenum, niobium, tantalum, tungsten, strontium, vanadium, and yttrium.  
     
     
         14 . A method as recited in  claim 10  in which the dopant element comprises niobium.