Photocatalyst compositions and methods for making the same

Abstract

Photocatalyst compositions may include a photocatalyst layer formed or disposed on the surface of a porous substrate. A metal may be disposed on the photocatalyst layer. If the metal is present predominantly at the surface of the photocatalyst layer, the metal can be utilized efficiently for photocatalytic reactions. The photocatalyst composition may be preferably formed by disposing the photocatalyst layer on the surface of the porous substrate and depositing the metal predominantly on the surface of the photocatalyst layer. Photocatalytic filter devices may include these photocatalyst compositions.

1 . A photocatalyst composition comprising: 
 a porous substrate having a surface,    a photocatalyst layer disposed on the surface of the porous substrate, the photocatalyst layer primarily containing at least one photocatalytic material and having a surface, and    at least one metal disposed predominantly on or near the surface of the photocatalyst layer.    
     
     
         2 . A photocatalyst composition according to  claim 1 , wherein the at least one metal is selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), copper (Cu) and nickel (Ni).  
     
     
         3 . A photocatalyst composition according to  claim 1 , wherein at least 80 wt % of the metal disposed on or near the surface of the photocatalyst layer is disposed on the surface of the photocatalyst layer.  
     
     
         4 . A pholocatalyst composition according to  claim 1 , wherein the metal comprises metal particles having an average particle size of between 1-100 nm.  
     
     
         5 . A photocatalyst composition according to  claim 4 , wherein at least 70% by number of the metal particles disposed on or near the surface of the photocatalyst layer are disposed on the surface of the photocatalyst layer.  
     
     
         6 . A photocatalyst composition according to  claim 1 , wherein the porous substrate is a ceramic having a three-dimensional network structure.  
     
     
         7 . A photocatalyst composition according to  claim 6 , wherein an average diameter of a backbone of the ceramic is between about 100 μm to 1000 μm.  
     
     
         8 . A photocatalyst composition according to  claim 6 , wherein the porous ceramic substrate exhibits a light transmissivity of at least 10% at a thickness of 5 mm.  
     
     
         9 . A photocatalyst composition according to  claim 6 , further having the following properties: 
 (1) porosity of between about 65% to 99%,    (2) bulk density of about 0.05 g/cm 3  to 60 g/cm 3 , and    (3) between 10-30 cells per 25 mm.    
     
     
         10 . A photocatalytic filter device comprising: 
 the photocatalyst composition according to  claim 1  and    a frame supporting the photocatalyst composition.    
     
     
         11 . A photocatalytic filter device according to  claim 10 , further comprising a light source disposed proximally to the photocatalyst composition and emitting light that activates the photocatalytic material.  
     
     
         12 . A method for making a photocatalyst composition comprising: 
 disposing a photocatalyst layer substantially comprising a photocatalytic material on a surface of a porous substrate and    disposing at least one metal predominantly on a surface of the photocatalyst layer, the metal increasing the photocatalytic activity of the photocatalytic material.    
     
     
         13 . A method according to  claim 12 , wherein the metal disposing step further comprises contacting the photocatalyst layer with a solution containing ions the metal, and irradiating the photocatalyst layer with light having a wavelength that activates the photocatalytic material, thereby reducing and depositing the metal on the surface of the photocatalyst layer.  
     
     
         14 . A method according to  claim 13 , wherein the at least one metal is selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), copper (Cu) and nickel Ni).  
     
     
         15 . A method according to  claim 12 , further comprising preparing a ceramic porous structure having a three-dimensional network structure before the photocatalyst layer disposing step.  
     
     
         16 . A method according to  claim 15 , wherein an average diameter of a backbone of the ceramic is between about 100 μm and 1000 m.  
     
     
         17 . A method according to  claim 16 , further comprising attaching ceramic particles to a surface of the backbone of the ceramic.  
     
     
         18 . A method according to  claim 15 , wherein the prepared ceramic porous substrate satisfies at least one of the following conditions: 
 (1) porosity of between about 65% to 99%,    (2) bulk density of about 0.05 g/cm 3  to 60 g/cm 3 , and    (3) between 10-30 cells per 25 mm.    
     
     
         19 . A method according to  claim 15 , wherein the photocatalyst layer disposing step is performed such that light transmissivity at a thickness of 5 mm is at least 10%.  
     
     
         20 . A composition of matter comprising: 
 a ceramic porous support having three-dimensional network structure with a backbone having an average diameter of between about 100-1000 μm,    a photocatalyst material disposed on the backbone of the ceramic porous support, wherein the ceramic porous support having the photocatalyst material disposed thereon exhibits a light transmissivity of at least 10% at a thickness of 5 mm, and    metal particles disposed substantially only on an outer surface of the photocatalyst material, wherein the metal particles include at least one metal selected from the group consisting of Ag, Au, Pt, Pd, Ru, Rh, Cu and Ni and the metal particles have an average particle size of between about 1-100 nm.    
     
     
         21 . A composition of matter according to  claim 20 , wherein at least 80 wt % of the metal disposed on or near the surface of the photocatalyst layer is disposed on the surface of the photocatalyst layer and the ratio of metal particles to photocatalyst material is between about 0.0005 and 5 wt %.  
     
     
         22 . A composition of matter according to  claim 21 , wherein the metal particles include at least one of Ag or Cu.  
     
     
         23 . A composition of matter according to  claim 22 , wherein the composition of matter exhibits the following properties: 
 (1) porosity of between about 65% to 99%,    (2) bulk density of about 0.05 to 60 g/cm 3 , and    (3) between 10-30 cells per 25 mm.    
     
     
         24 . A photocatalytic filter device comprising: 
 the composition of matter according to  claim 23 ,    a frame supporting the composition of matter and    a light source disposed proximally to the composition of matter according to  claim 23  and emitting light having a wavelength that activates the photocatalytic material.