Defective perovskite nanostructured material-based electrode for electrochemical water splitting and method of preparation thereof

Abstract

An electrode includes a transparent substrate, and a layer of a nanostructured material at least partially covering a surface of the transparent substrate. The nanostructured material includes defective perovskite nanostructures (DPNSs) in the form of nanoplates having an average particle size in a range of 10 to 100 nanometers (nm), an interplanar spacing d(101) of the (101) plane in a range of 0.3 to 0.4 nm, and an interplanar spacing d(104) of the (104) plane in a range of 0.2 to 0.3 nm. A method of making the electrode.

1 : An electrode, comprising:
 a transparent substrate; and   a layer of a nanostructured material at least partially covering a surface of the transparent substrate;   wherein the nanostructured material comprises defective perovskite nanostructures (DPNSs) in the form of nanoplates having an average particle size in a range of 10 to 100 nanometers (nm), an interplanar spacing d(101) of the (101) plane in a range of 0.3 to 0.4 nm, and an interplanar spacing d(104) of the (104) plane in a range of 0.2 to 0.3 nm, as determined by X-ray diffraction.   
     
     
         2 : The electrode of  claim 1 , wherein the transparent substrate is a glass substrate, and wherein the glass substrate is at least one selected from the group consisting of a fluorine doped tin oxide (FTO) glass substrate, a tin doped indium oxide (ITO) glass substrate, an aluminum doped zinc oxide (AZO) glass substrate, a niobium doped titanium dioxide (NTO) glass substrate, an indium doped cadmium oxide (ICO) glass substrate, an indium doped zinc oxide (IZO) glass substrate, a fluorine doped zinc oxide (FZO) glass substrate, a gallium doped zinc oxide (GZO) glass substrate, an antimony doped tin oxide (ATO) glass substrate, a phosphorus doped tin oxide (PTO) glass substrate, a zinc antimonate glass substrate, a zinc oxide glass substrate, a ruthenium oxide glass substrate, a rhenium oxide glass substrate, a silver oxide glass substrate, and a nickel oxide glass substrate. 
     
     
         3 : The electrode of  claim 1 , wherein the transparent substrate is a glassy carbon substrate. 
     
     
         4 : The electrode of  claim 1 , wherein the nanostructured material has a formula ATiO 3-x , wherein:
 A is at least one metal selected from the group consisting of Ba, Co, Ni, Pb, Zn, Sr, and La, and 0<x<3.   
     
     
         5 : The electrode of  claim 1 , wherein the nanostructured material has a formula CoTiO 3-x , wherein 0<x<3. 
     
     
         6 : The electrode of  claim 1 , having an overpotential of 0.2 to 0.5 volts (V) in an acidic medium at a current density of 5 to 20 milliamperes per square centimeter (mA/cm 2 ). 
     
     
         7 : The electrode of  claim 1 , having a double layer capacitance of 200 to 280 microfarads per square centimeter (F/cm 2 ) in an acidic medium at an overpotential of 0.352 VRHE. 
     
     
         8 : The electrode of  claim 1 , having an active surface area of 4 to 10 square centimeters (cm 2 ) in an acidic medium at an overpotential of 0.352 VRHE. 
     
     
         9 : The electrode of  claim 1 , having a Tafel slope of 80 to 110 millivolts per decade (mV/decade) in an acidic medium at a scan rate of 5 to 20 millivolts per second (mV/s). 
     
     
         10 : A method of making the electrode of  claim 1 , comprising:
 preparing the nanostructured material having defective perovskite nanostructures by:
 mixing a titanium salt, an alkaline earth metal base and water to form a precipitate in a first mixture; 
 removing the precipitate from the first mixture, drying, and calcining at a temperature of at least 600° C. to form a TiO 2  nanocomposite; 
 mixing the TiO 2  nanocomposite and a borohydride reducing agent to form a second mixture; 
 calcining the second mixture at a temperature of at least 600° C. to form a defective nanocomposite of formula TiO 2-x ; 
 wherein 0<x<2; 
 mixing and sonicating the defective nanocomposite, a cobalt salt, and a solvent to form a suspension; 
 generating a pulsed laser using a laser device and projecting the pulsed laser onto the suspension to form an ablated nanocomposite in the suspension; 
 removing the ablated nanocomposite from the second suspension, washing, and drying to form a nanostructured material precursor; and 
 calcining the nanostructured material precursor at a temperature of at least 600° C. to form the nanostructured material. 
   
     
     
         11 : The method of  claim 10 , wherein the titanium salt comprises titanium tetrachloride, titanium trichloride, titanium potassium fluoride, titanium potassium oxalate, titanium sulfate, titanium tetra iodide, and/or its hydrate. 
     
     
         12 : The method of  claim 10 , wherein the alkaline earth metal base comprises an alkaline earth metal carbonate, and an alkaline earth metal hydroxide. 
     
     
         13 : The method of  claim 10 , wherein the cobalt salt comprises cobalt sulfate, cobalt acetate, cobalt citrate, cobalt iodide, cobalt chloride, cobalt perchlorate, cobalt nitrate, cobalt phosphate, cobalt triflate, cobalt bis(trifluoromethanesulfonyl)imide, cobalt tetrafluoroborate, cobalt bromide, and/or its hydrate. 
     
     
         14 : The method of  claim 10 , wherein the solvent is at least one selected from the group consisting of a ketone solvent, an ester solvent, an alcohol solvent, an amide solvent and an ether solvent, and wherein the alcohol solvent comprises ethylene glycol. 
     
     
         15 : The method of  claim 10 , wherein the pulsed laser has a wavelength of 500 to 560 nm, and a pulse energy of 300 to 400 millijoules (mJ). 
     
     
         16 : The method of  claim 10 , further comprising:
 coating the transparent substrate by:
 mixing the nanostructured material, a sulfonated polymer and a solvent mixture to form a third mixture; 
 sonicating the third mixture to form a coating composition; and 
 drop casting the coating composition onto a surface of the transparent substrate and drying to form the electrode having the layer of the nanostructured material at least partially covered on the surface of the transparent substrate. 
   
     
     
         17 : The method of  claim 16 , wherein the sulfonated polymer comprises at least one of Nafion, sulfonated poly(ether ether ketone) (SPEEK), sulfonated polyimide, sulfonated poly(phenylene oxide) (PPO), sulfonated poly(arylene ether sulfone), and sulfonated poly(4-phenoxybenzoyl-1,4-phenylene). 
     
     
         18 : The method of  claim 16 , wherein the solvent mixture comprises an alcohol solvent and an ester solvent, and wherein a volume ratio of the alcohol solvent and the ester solvent is in a range of 1:50 to 1:10. 
     
     
         19 : A method for electrochemical water splitting, comprising:
 applying a potential between a working electrode and a counter electrode in an electrochemical cell containing an electrolyte to form hydrogen and oxygen;   wherein the working electrode comprises the electrode of  claim 1 ; and   wherein the electrolyte comprising an aqueous solution of an acid having a concentration of 0.001 to 3 molars (M).   
     
     
         20 : The method for  claim 19 , wherein the acid comprises at least one acid selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, boric acid, and citric acid.