Gas diffusion electrode for reducing carbon dioxide

Abstract

The invention relates to a gas diffusion electrode for reducing carbon dioxide, having a special catalyst morphology (silver in the form of agglomerated nanoparticles having a BET surface area of at least 2 m2/g), and to an electrolysis device. The gas diffusion electrode comprises at least one carrier and a porous coating on the basis of an electrochemically active porous silver catalyst and a hydrophobic material. The invention further relates to a production method for the gas diffusion electrode and to the use thereof as a carbon dioxide GDE in e.g. chlorine electrolysis.

1 .- 14 . (canceled) 
     
     
         15 . A gas diffusion electrode for reducing carbon dioxide, comprising at least one sheet-like, electrically conductive support and a gas diffusion layer and electrocatalyst applied to the support, wherein the gas diffusion layer consists at least of a mixture of electrocatalyst and a hydrophobic polymer and silver acts as electrocatalyst, and wherein the electrocatalyst contains silver in the form of highly porous agglomerated nanoparticles and said nanoparticles have a surface area measured by the BET method of at least 2 m 2 /g. 
     
     
         16 . The gas diffusion electrode as claimed in  claim 15 , wherein the proportion of electrocatalyst is from 80 to 97% by weight, based on the total weight of electrocatalyst and hydrophobic polymer. 
     
     
         17 . The gas diffusion electrode as claimed in  claim 15 , wherein the proportion of hydrophobic polymer is from 20 to 3% by weight, based on the total weight of electrocatalyst and hydrophobic polymer. 
     
     
         18 . The gas diffusion electrode as claimed in  claim 15 , wherein the silver particles are present as agglomerate having an average agglomerate diameter in the range from 1 to 100 μm. 
     
     
         19 . The gas diffusion electrode as claimed in  claim 15 , wherein the silver nanoparticles have an average diameter in the range from 50 to 150 nm. 
     
     
         20 . The gas diffusion electrode as claimed in  claim 15 , wherein electrocatalyst and hydrophobic polymer have been applied in powder form to the support and compacted and form the gas diffusion layer. 
     
     
         21 . The gas diffusion electrode as claimed in  claim 15 , wherein the hydrophobic polymer is a fluorine-substituted polymer. 
     
     
         22 . The gas diffusion electrode as claimed in  claim 15 , wherein the electrode has a total loading of catalytically active component in the range from 5 mg/cm 2  to 300 mg/cm 2 . 
     
     
         23 . The gas diffusion electrode as claimed in  claim 15 , wherein the support is based on nickel, silver or a combination of nickel and silver. 
     
     
         24 . The gas diffusion electrode as claimed in  claim 15 , wherein the support is present in the form of a gauze, woven mesh, formed-loop knit, drawn-loop knit, nonwoven, expanded metal or foam. 
     
     
         25 . The use of the gas diffusion electrode as claimed in  claim 15  for the electrolysis of carbon dioxide to give carbon monoxide. 
     
     
         26 . A process for the electrochemical conversion of carbon dioxide into carbon monoxide, wherein the carbon dioxide is reacted cathodically at a gas diffusion electrode as claimed in  claim 15  to form carbon monoxide, and chlorine or oxygen is simultaneously produced on the anode side. 
     
     
         27 . The process as claimed in  claim 26 , wherein the current density in the reaction is at least 2 kA/m 2 . 
     
     
         28 . An electrolysis apparatus comprising a gas diffusion electrode as claimed in  claim 15  as carbon dioxide depolarized cathode.