Copper-decorated nitrogen-doped carbon nanosheets for electrocatalytic reduction of co2

Abstract

A method of making an electrocatalyst, including dissolving a copper salt and an aromatic compound in a solvent to form a first mixture, heating the first mixture to a temperature of 90-120° C. for 1-20 hours (h) to form a copper complex, heating the copper complex under a nitrogen atmosphere at a temperature of 500-1,000° C. to form a nanocomposite; and coating a layer of the nanocomposite on a substrate to form the electrocatalyst. The nanocomposite contains copper nanoparticles (NPs) and nitrogen-doped carbon nanosheets. The copper NPs are uniformly dispersed on a surface of the nitrogen-doped carbon nanosheets, the nitrogen-doped carbon nanosheets have an average thickness of 0.1-10 nm, and the copper NPs are spherical and have an average diameter of 2-10 nm.

1 . A method of making an electrocatalyst comprising:
 dissolving a copper salt and an aromatic compound in a solvent to form a first mixture;   heating the first mixture to a temperature of 90-120° C. for 1-20 hours (h) to form a copper complex;   heating the copper complex under a nitrogen atmosphere at a temperature of 500-1,000° C. to form a nanocomposite; and   coating a layer of the nanocomposite on a substrate to form the electrocatalyst,   wherein the nanocomposite comprises:   copper nanoparticles (NPs); and   nitrogen-doped carbon nanosheets,   wherein the copper NPs are uniformly dispersed on a surface of the nitrogen-doped carbon nanosheets,   wherein the nitrogen-doped carbon nanosheets have an average thickness of 0.1-10 nm, and   wherein the copper NPs are spherical and have an average diameter of 2-10 nm.   
     
     
         2 . The method of  claim 1 , wherein the nanocomposite comprises Cu, C, N, and H. 
     
     
         3 . The method of  claim 1 , wherein the nitrogen-doped carbon nanosheets are directly crosslinked with the copper NPs in the nanocomposite. 
     
     
         4 . The method of  claim 1 , wherein the copper NPs consist of copper. 
     
     
         5 . The method of  claim 1 , wherein the copper NPs are not agglomerated in the nanocomposite. 
     
     
         6 . The method of  claim 1 , wherein the nitrogen-doped carbon nanosheets have a graphitic structure. 
     
     
         7 . The method of  claim 1 , wherein the nitrogen-doped carbon nanosheets have a length of greater than 1 μm and a width greater than 500 nm. 
     
     
         8 . The method of  claim 1 , wherein the copper salt is selected from the group consisting of copper (II) chloride, copper (II) sulfate, copper (II) nitrate, copper (II) acetate, copper (II) bromide, copper (II) phosphate and hydrates thereof. 
     
     
         9 . The method of  claim 1 , wherein the aromatic compound is melamine. 
     
     
         10 . The method of  claim 1 , wherein the heating the copper complex is at about 700° C. 
     
     
         11 . The method of  claim 1 , wherein the substrate is made from at least one material selected from the group consisting of conductive carbon, stainless steel, aluminum, nickel, copper, platinum, zinc, tungsten, and titanium. 
     
     
         12 . A method of reducing carbon dioxide, comprising:
 applying a potential of less than 0 to −2.0 V vs RHE to an electrochemical cell,   wherein the electrochemical cell is at least partially submerged in an aqueous solution comprising carbon dioxide,   wherein on applying the potential the carbon dioxide is reduced,   wherein the electrochemical cell comprises:   the electrocatalyst made by the method of  claim 1 ; and   a counter electrode.   
     
     
         13 . The method of  claim 12 , wherein the aqueous solution further comprises at least one of sodium bicarbonate and potassium bicarbonate. 
     
     
         14 . The method of  claim 12 , wherein the electrocatalyst has a current density at 1.0 V vs RHE of −10 to −3 mA cm −2 . 
     
     
         15 . The method of  claim 14 , wherein the electrocatalyst maintains the current density for at least 12 h. 
     
     
         16 . The method of  claim 12 , wherein reducing the carbon dioxide forms at least one selected from formate and acetate. 
     
     
         17 . The method of  claim 16 , having a faradic efficiency for reducing carbon dioxide to formate of 35-45%. 
     
     
         18 . The method of  claim 16 , having a faradic efficiency for reducing carbon dioxide to acetate of 10-20%. 
     
     
         19 . The method of  claim 12 , wherein the counter electrode is made from at least one material selected from the group consisting of platinum, gold, and carbon. 
     
     
         20 . The method of  claim 12 , wherein the aqueous solution is saturated with the carbon dioxide.