Electrocatalyst formed from activated vacuum residue and method of electrocatalytically producing hydrogen peroxide

Abstract

An electrocatalyst that includes a microporous network of carbon that includes phosphorus, sulfur, and nitrogen dopant atoms. A portion of the phosphorous is present as isolated phosphorous atoms doped into the microporous network of carbon. A method of forming the electrocatalyst including mixing petroleum vacuum residue and phosphoric acid to form a crude mixture, annealing the crude mixture at 375 to 525° C. in a first inert atmosphere for 1 to 5 hours to form an intermediate product, and heating the intermediate product at 400 to 900° C. in a second inert atmosphere for 1 to 5 hours to form the electrocatalyst. A method of forming hydrogen peroxide using the electrocatalyst.

1 . An electrocatalyst, comprising
 a microporous network of carbon comprising phosphorus, sulfur, and nitrogen dopant atoms, wherein   a portion of the phosphorous is present as isolated phosphorous atoms doped into the microporous network of carbon.   
     
     
         2 . The electrocatalyst of  claim 1 , wherein microporous network of carbon comprises 70.0 to 78 wt % carbon, 11 to 19 wt % oxygen; 3.50 to 8.0 wt % phosphorus, 2.0 to 5.0 wt % sulfur, and 0.25 to 1.5 wt % nitrogen based on a total weight of electrocatalyst by XPS. 
     
     
         3 . The electrocatalyst of  claim 1 , wherein the microporous network of carbon has a BET surface area of 300 to 4000 m 2 /g, a pore volume of 0.2 to 2.4 cm 3 /g, and a micropore volume of 0.1 to 2.3 cm 3 /g. 
     
     
         4 . The electrocatalyst of  claim 1 , wherein a surface of the microporous network of carbon includes carboxylate functional groups and phosphate functional groups. 
     
     
         5 . The electrocatalyst of  claim 1 , wherein the microporous network of carbon has a ratio of a D band intensity to a G band intensity I D /I G  of 0.75 to 1.25 by Raman spectroscopy. 
     
     
         6 . A method of producing the electrocatalyst of  claim 1 , the method comprising mixing petroleum vacuum residue and phosphoric acid to form a crude mixture;
 annealing the crude mixture at 375 to 525° C. in a first inert atmosphere for 1 to 5 hours to form an intermediate product; and   heating the intermediate product at 400 to 900° C. in a second inert atmosphere for 1 to 5 hours to form the electrocatalyst.   
     
     
         7 . The method of  claim 6 , wherein the petroleum vacuum residue and phosphoric acid are present in the crude mixture in a ratio of 1.5:1 to 1:1.5 by weight. 
     
     
         8 . The method of  claim 6 , wherein the petroleum vacuum residue comprises 80.0 to 85 wt % carbon, 7 to 9 wt % hydrogen, 3.0 to 5.0 wt % sulfur, and 0.25 to 1.0 wt % nitrogen based on a total weight of petroleum vacuum residue. 
     
     
         9 . The method of  claim 6 , wherein the phosphoric acid has a concentration of 50 to 99% in water. 
     
     
         10 . The method of  claim 6 , wherein the first and second inert atmosphere are flowing nitrogen gas. 
     
     
         11 . The method of  claim 6 , wherein the annealing and heating are performed with a temperature increase rate of 5 to 10° C./min. 
     
     
         12 . The method of  claim 6 , wherein the method does not involve reduction with hydrogen gas. 
     
     
         13 . The method of  claim 6 , further comprising washing the electrocatalyst with water and drying at 25 to 100° C. 
     
     
         14 . A method of producing hydrogen peroxide, the method comprising
 applying a potential between a counter and a working electrode in an electrochemical cell containing an electrolyte to form hydrogen peroxide; and   collecting the hydrogen peroxide, wherein   the working electrode includes the electrocatalyst of  claim 1 ; and   wherein the electrolyte including an aqueous solution of a base at a concentration of 0.001 to 5 M.   
     
     
         15 . The method of  claim 14 , wherein the method has an onset potential of 0.750 to 0.875 V vs RHE. 
     
     
         16 . The method of  claim 14 , wherein the working electrode has a Tafel slope of 80 to 115 mV/dec. 
     
     
         17 . The method of  claim 14 , wherein the method has an electron transfer number of 1.75 to 3. 
     
     
         18 . The method of  claim 14 , wherein the method has a yield of 80 to 95% OH 2   −  at a potential of 0.5 to 0.65 V vs RHE. 
     
     
         19 . The method of  claim 15 , wherein the aqueous solution of a base at a concentration of 0.001 to 5 M is 0.1 M KOH is saturated with oxygen. 
     
     
         20 . The method of  claim 15 . wherein the working electrode further comprises glassy carbon and a sulfonated fluoropolymer, and
 the electrocatalyst is disposed on the surface of the glassy carbon.