NanoTin Catalysts for Electrochemical Reduction of Carbon Dioxide to Formate

Abstract

High surface area tin oxide nanoparticles prepared by a facile hydrothermal method followed by electroreduction to tin act as electrocatalysts toward CO 2 reduction to formate, in some embodiments. At certain of these nano-structured tin catalysts, CO 2 reduction occurs selectively to formate at low overpotentials and with high Faradaic efficiencies, with high stability and significant current densities.

We claim: 
     
         1 . A method for reducing carbon dioxide to formate, comprising:
 providing an electrocatalytic electrode in a suitable electrocatalytic cell, wherein the electrocatalytic electrode comprises:
 nanoparticles comprising tin, associated with high surface area carbon; 
   exposing the electrocatalytic electrode to a concentration of carbon dioxide in a fluid composition;   applying a catalyzing potential to the electrocatalytic electrode and allowing at least some of the carbon dioxide to react;   thereby reducing the carbon dioxide to formate.   
     
     
         2 . The method of  claim 1 , wherein the fluid composition comprises potassium bicarbonate, sodium bicarbonate, or a combination thereof. 
     
     
         3 . The method of  claim 1 , wherein the catalyzing potential is about −1.8 V versus SCE. 
     
     
         4 . The method of  claim 1 , wherein the nanoparticles comprising tin, associated with high surface area carbon exhibit a specific current density greater than about 10 A g −1 . 
     
     
         5 . The method of  claim 1 , wherein the nanoparticles comprising tin, associated with high surface are carbon exhibit a specific current density greater than about 100 A g −1 . 
     
     
         6 . An electrocatalytic electrode, comprising:
 an electrically-conductive surface in electrical communication with nanoparticles comprising tin, associated with high surface area carbon.   
     
     
         7 . The electrocatalytic electrode of  claim 6 , wherein the high surface area carbon is chosen from carbon nanotubes, carbon black, mesoporous carbon, graphite, graphene, and combinations of two or more thereof. 
     
     
         8 . The electrocatalytic electrode of  claim 6 , wherein the nanoparticles have an average size of about 200 nm or less. 
     
     
         9 . The electrocatalytic electrode of  claim 6 , wherein the nanoparticles have an average size of about 10 nm or less. 
     
     
         10 . The electrocatalytic electrode of  claim 6 , wherein the nanoparticles have an average size ranging from about 3 nm to about 10 nm. 
     
     
         11 . The electrocatalytic electrode of  claim 6 , wherein the nanoparticles have an average size of about 5 nm. 
     
     
         12 . The electrocatalytic electrode of  claim 6 , wherein the electrically-conductive surface comprises glassy carbon, carbon paper, carbon cloth, or a combination thereof. 
     
     
         13 . The electrocatalytic electrode of  claim 6 , wherein the electrically-conductive surface forms part of a gas diffusion electrode. 
     
     
         14 . A method for making an electrocatalytic electrode, comprising:
 depositing, on an electrically-conductive surface, nanoparticles of tin oxide associated with high surface area carbon;   reducing at least some of the tin oxide to form nanoparticles comprising tin, associated with high surface area carbon,   thereby making the electrocatalytic electrode.   
     
     
         15 . The method of  claim 14 , further comprising:
 reacting tin(II) chloride in the presence of high surface area carbon and water for a time, thereby forming the nanoparticles of tin oxide associated with high surface area carbon.   
     
     
         16 . The method of  claim 15 , wherein the time is at least 30 minutes. 
     
     
         17 . The method of  claim 15 , wherein the time is at least 3 hours. 
     
     
         18 . The method of  claim 15 , wherein the time is no more than about 6 hours. 
     
     
         19 . The method of  claim 14 , wherein the reducing comprises applying a reducing potential to the tin oxide no more positive than about −1 V versus SCE. 
     
     
         20 . The method of  claim 14 , wherein the nanoparticles of tin oxide comprise rutile tin oxide.