Preparation of a nanocomposite photoanode for dye-sensitized solar cells

Abstract

A process for preparing a photoanode of dye-sensitized solar cells (DSSCs) is disclosed, which contains nano TiO 2 and functionalized carbon nanomateiral. The process includes reacting a dispersion of functionalized carbon nanomateiral and a TiO 2 precursor in a liquid organic medium under sol-gel conditions to form a carbon nanomaterial/nano TiO 2 composite colloidal solution; mixing with an aqueous polymer solution, and forming a paste suitable for coating by concentrating the resulting mixture; coating the paste on a conductive glass substrate and calcining the coated layer at 300-520° C. in air for 10-60 minutes to obtain a conductive glass plate having a coating of nanocomposite, which can be used to prepare a photoanode of DSSCs by immersing in a dye solution to adsorb a dye thereon.

1 . A process for preparing a nanocomposite photoanode for dye-sensitized solar cells (DSSCs) comprising the following steps:
 a) dispersing functionalized carbon nanomaterials in a liquid medium;   b) dissolving or dispersing a TiO 2  precursor in a dispersion obtained in step a), wherein a weight ratio between said TiO 2  precursor and said carbon nanomaterials is in the range of 10000:1 to 100:1;   c) reacting said precursor under hydrothermal conditions or sol-gel conditions so as to form a colloidal solution of carbon nanomaterial/nano TiO 2  composite;   d) heating said carbon nanomaterial/nano TiO 2  composite colloidal solution in an autoclave at 140-350° C. for 5-48 hours, so as to result in anatase TiO 2  therein;   e) mixing the colloidal solution having anatase TiO 2  obtained in step d) with a polymer solution;   f) concentrating the resulting mixture of the colloidal solution and the aqueous polymer solution from step e);   g) coating a concentrated paste obtained in step f) on a conductive surface of a conductive substrate;   h) calcining the coated layer obtained in step g) at 300-520° C. in air for 10-60 minutes;   i) immersing the conductive substrate having a coating of carbon nanomaterial/nano TiO 2  composite from step h) in a dye solution, such that the dyes are allowed to adsorb onto the coating of carbon nanomaterial/nano TiO 2  composite; and   j) removing said conductive substrate from the dye solution so as to prepare a nanocomposite photoanode for DSSCs.   
     
     
         2 . The process of  claim 1 , wherein the functionalized carbon nanomaterials in step a) include acidic groups, hydroxyl groups, or amino groups as functional groups thereof. 
     
     
         3 . The process of  claim 2 , wherein the functionalized carbon nanomaterials in step a) are acidified single-wall carbon nanotubes, acidified double-wall carbon nanotubes, acidified multi-wall carbon nanotubes, acidified carbon nanohorns, or acidified carbon nanocapsules. 
     
     
         4 . The process of  claim 3 , wherein the functionalized carbon nanomaterials are acidified single-wall, double-wall, or multi-wall carbon nanotubes. 
     
     
         5 . The process of  claim 4 , wherein the carbon nanotubes are multi-wall carbon nanotubes having a length of 1-25 μm, a diameter of 1-50 nm, a specific surface area of 150-250 m 2 /g, and an aspect ratio of 20-2500. 
     
     
         6 . The process of  claim 1 , wherein the TiO 2  precursor is titanium alkoxide, titanium chloride, titanium oxysulfate, or titanium sulfate. 
     
     
         7 . The process of  claim 1 , wherein the precursor is reacted under sol-gel conditions in step c). 
     
     
         8 . The process of  claim 7 , wherein the TiO 2  precursor is titanium alkoxide. 
     
     
         9 . The process of  claim 8 , wherein the TiO 2  precursor is titanium tetra-isopropoxide (TTIP). 
     
     
         10 . The process of  claim 7 , wherein the liquid medium in step a) is an alcohol. 
     
     
         11 . The process of  claim 10 , wherein the liquid medium in step a) is isopropyl alcohol, and the isopropyl alcohol has a weight that is 200-1200% the weight of carbon nanomaterials, while the dispersing is carried out using supersonic treatment. 
     
     
         12 . The process of  claim 1 , wherein in step b) the dissolving or dispersing of a TiO 2  precursor in a dispersion obtained from step a) is carried out using supersonic treatment. 
     
     
         13 . The process of  claim 8 , wherein the step of reacting the precursor under sol-gel conditions comprises adding water into the mixture obtained in step b), and allowing the titanium alkoxide to undergo hydrolytic and condensation reactions. 
     
     
         14 . The process of  claim 13 , wherein the step of reacting the precursor under sol-gel conditions further comprises adding an acid into the mixture undergoing the hydrolytic and condensation reactions. 
     
     
         15 . The process of  claim 14 , wherein the water added has a weight that is 100-1000% the weight of carbon nanomaterials, and the acid added is of a volume that adjusts pH value of the mixture undergoing the hydrolytic and condensation reactions to 1-5. 
     
     
         16 . The process of  claim 1 , wherein the autoclave in step d) is set at 150-300° C., and the heating time is 10-30 hours. 
     
     
         17 . The process of  claim 1 , wherein the conductive substrate is an electrically conductive glass plate having an electrically conductive layer on a surface thereof. 
     
     
         18 . The process of  claim 1 , wherein the polymer solution in step e) is an aqueous solution of a polymer having a weight average molecular weight of 200-30000 g/mol therein. 
     
     
         19 . The process of  claim 18 , wherein the polymer is polyol, cyclodextrin, or cellulose. 
     
     
         20 . The process of  claim 19 , wherein the polymer is polyethylene glycol, polypropylene glycol, or polybutylene glycol. 
     
     
         21 . The process of  claim 20 , wherein the polymer is polyethylene glycol. 
     
     
         22 . The process of  claim 18 , wherein in step f); the mixture is concentrated into a paste comprising 100-250 g of a solid content per liter. 
     
     
         23 . The process of  claim 1 , wherein the coating in step g) is carried out by using the doctor-blade method.