Hydrophobic catalyst layer for polymer electrolyte fuel cell and method of producing the same, and polymer electrolyte fuel cell and method of producing the same

Abstract

Provided is a hydrophobic catalyst layer for a polymer electrolyte fuel cell to which hydrophobicity is imparted so that the dissipation property of produced water is improved and which simultaneously has an increased effective surface area and an increased utilization ratio of a catalyst, and a method of producing the same. The catalyst layer for a polymer electrolyte fuel cell includes a catalyst obtained by reducing a platinum oxide, a hydrophobic agent, and a proton conductive electrolyte, wherein the hydrophobic agent is mainly composed of alkylsiloxane. An Si compound containing a hydrophobic substituent is brought into contact with a platinum oxide to subject the Si compound to hydrolysis and a polymerization reaction by the catalytic action of the platinum oxide, and then it is reduced, thereby obtaining a hydrophobic catalyst layer carrying an alkylsiloxane polymer.

1 . A hydrophobic catalyst layer for a polymer electrolyte fuel cell, comprising a catalyst, a hydrophobic agent, and a proton conductive electrolyte, 
 wherein the catalyst is a dendritic-shaped catalyst obtained by reducing a platinum oxide,    wherein the hydrophobic agent comprises a compound having an Si atom, an O atom, and a hydrophobic substituent, and    wherein a ratio Si/Pt of a number of Si atoms in the hydrophobic agent to a number of Pt atoms in the catalyst is in a range of 0.15 or more and 0.25 or less.    
     
     
         2 . A hydrophobic catalyst layer for a polymer electrolyte fuel cell according to  claim 1 , wherein the hydrophobic agent comprises a siloxane polymer having a hydrophobic substituent.  
     
     
         3 . A hydrophobic catalyst layer for a polymer electrolyte fuel cell according to  claim 1 , wherein the hydrophobic agent comprises alkylsiloxane.  
     
     
         4 . A method of producing a hydrophobic catalyst layer for a polymer electrolyte fuel cell, comprising the steps of: 
 bringing an Si compound containing a hydrophobic substituent, which causes a hydrolytic reaction owing to a catalytic action of a platinum oxide to form a polymerizable group, into contact with the platinum oxide;    subjecting the Si compound to a polymerization reaction in a vicinity of the platinum oxide to form a hydrophobic agent on a surface of the platinum oxide; and    then reducing the platinum oxide.    
     
     
         5 . A method of producing a hydrophobic catalyst layer for a polymer electrolyte fuel cell according to  claim 4 , wherein the Si compound containing the hydrophobic substituent comprises at least one or more compounds selected from the group consisting of 2,4,6,8-tetraalkylcyclotetrasiloxane, 1,1,1,3,3,3-hexaalkyl-disilazane, monoalkylsilane, dialkylsilane, and trialkylsilane, or a mixture thereof.  
     
     
         6 . A polymer electrolyte fuel cell, comprising at least the hydrophobic catalyst layer according to  claim 1 , and a solid polymeric electrolyte membrane.  
     
     
         7 . A method of producing a polymer electrolyte fuel cell, comprising a step of forming a hydrophobic catalyst layer by a method of producing a hydrophobic catalyst layer for a polymer electrolyte fuel cell according to  claim 4.