Method of water oxidation with a coated photoanode

Abstract

A method of preparing a photocatalyst. The method includes a sulfone-containing conjugated polyimide obtained by solvothermally imidizing 3-sulfonyldianiline 1,4,5,8-naphthalenetetracarboxylic dianhydride with poly (amic acid) (PAA). The photocatalyst of the present disclosure can be used in an electrochemical cell for water oxidation processes.

1 : The method of  claim 15 , wherein the sulfone-containing conjugated polyimide obtained by solvothermally imidizing 3′-sulfonyldianiline 1,4,5,8-naphthalenetetracarboxylic dianhydride with poly (amic acid) (PAA). 
     
     
         2 : The method of  claim 15 , wherein
 the sulfone-containing conjugated polyimide is in the form of nanosheets having an average length of 100-600 nm and an average thickness of 1-6 nm.   
     
     
         3 : The method of  claim 15 ,
 wherein the sulfone-containing conjugated polyimide is semicrystalline.   
     
     
         4 : The method of  claim 2 , wherein the nanosheets are in the form of microparticles having an average diameter of 1-2 m. 
     
     
         5 : The method of  claim 4 , wherein within each microparticle the nanosheets are stacked together. 
     
     
         6 : The method of  claim 4 , wherein the nanosheets on an exterior surface of each microparticle are curled. 
     
     
         7 : The method of  claim 2 , wherein the nanosheets of sulfone-containing conjugated polyimide has a Brunauer Emmett-Teller (BET) surface area of 100-140 m 2 g −1 . 
     
     
         8 : The method of  claim 15 , wherein the photocatalyst is substantially free of metal. 
     
     
         9 : The method of  claim 15 , wherein the photocatalyst has a band gap of 2.40-2.60 eV. 
     
     
         10 . (canceled) 
     
     
         11 : The method of  claim 15 , wherein the photocatalyst has thermal stability up to 500° C. from thermogravimetric analysis. 
     
     
         12 . (canceled) 
     
     
         13 : The photo method of  claim 15 , wherein the photoanode is formed by depositing an aqueous mixture of the photocatalyst, an organic solvent, and a fluoropolymer on a conductive substrate and drying. 
     
     
         14 : The method of  claim 13 , wherein the photoanode does not have surface passivation or doping. 
     
     
         15 : A method of water oxidation, comprising:
 irradiating a photo-electrochemical cell containing a photoanode having a photocatalyst, a reference electrode, a counter electrode, and an aqueous electrolyte in contact with the photoanode, the reference electrode and the counter electrode with solar illumination,   wherein the photoanode comprises a substrate coated with a thin film comprising a sulfone-containing conjugated polyimide containing reacted units of 3,3′-sulfonyldianiline and 1,4,5,8-naphthalenetetracarboxylic dianhydride, and a sulfonated tetrafluoroethylene based fluoropolymer-copolymer,   wherein the sulfone-containing conjugated polyimide has the following formula:   
       
         
           
           
               
               
           
         
       
     
     
         16 : The method of  claim 15 , wherein:
 the electrolyte is a 0.1-1 M Na 2 SO 4  solution having a neutral pH, the photocatalyst has a current density of 15-25 ρA cm −2  at 0 V vs. a saturated calomel electrode;   and the electrolyte does not contain a sacrificial agent.   
     
     
         17 : The method of  claim 15 , wherein:
 the photocatalyst has a photostability retention under solar irradiation of 70-90 00 after 1000-1800 s.   
     
     
         18 - 20 . (canceled) 
     
     
         21 . The method of  claim 15 , wherein photoanode comprises a fluorine-doped tin oxide (FTO) glass substrate coated with the thin film. 
     
     
         15 : A method of water oxidation, comprising:
 irradiating the photo-electrochemical cell of  claim 12  with solar illumination.   
     
     
         16 : The method of  claim 15 , wherein:
 the electrolyte is a 0.1-1 M Na 2 SO 4  solution having a neutral pH,   the photocatalyst has a current density of 15-25 ρA cm −2  at 0 V vs. a saturated calomel electrode;   and the electrolyte does not contain a sacrificial agent.   
     
     
         17 : The method of  claim 15 , wherein:
 the photocatalyst has a photostability retention under solar irradiation of 70-90% after 1000-1800 s.   
     
     
         18 : A method of synthesizing the photocatalyst of  claim 1 , comprising:
 reacting 3-sulfonyldianiline with 1,4,5,8-naphthalenetetracarboxylic dianhydride to form a poly(amic acid) precursor; and   heating the poly(amic acid) precursor to form the photocatalyst.   
     
     
         19 : The method of  claim 18 , wherein the poly(amic acid) precursor is heated at a temperature of 160-200° C. for 6-15 hours. 
     
     
         20 : The method of  claim 18 , wherein the poly(amic acid) precursor undergoes an imidization reaction during the heating.