Electrochemical process for the reduction of molecular oxygen

Abstract

The present invention relates to an electrochemical process for the reduction of molecular oxygen in alkaline solutions in the presence of nitrogen-doped carbon nanotubes, in which no hydrogen peroxide forms as a by-product of the reduction.

1 - 8 . (canceled) 
     
     
         9 . Process for the electrochemical reduction of molecular oxygen to oxygen ions having a double negative charge in solutions having a pH greater than or equal to 8, which comprises contacting said molecular oxygen in said solutions with nitrogen-doped carbon nanotubes containing pyridinic and quaternary nitrogen, and which are free of metal and semimetal constituents, under the influence of an applied electrical voltage. 
     
     
         10 . Process according to  claim 9 , wherein the nitrogen-doped carbon nanotubes have a diameter of 3 to 150 nm. 
     
     
         11 . Process according to  claim 9 , wherein the nitrogen-doped carbon nanotubes have an aspect ratio of at least 2. 
     
     
         12 . Process of  claim 9 , wherein the nitrogen-doped carbon nanotubes have ratios of pyridinic to quaternary nitrogen of greater than or equal to 1. 
     
     
         13 . Process according to  claim 9 , wherein the nitrogen content of the nitrogen-doped carbon nanotubes is greater than or equal to 1 atom %. 
     
     
         14 . Process according to  claim 9 , wherein said voltage is +0.2 V to −0.8 V, measured against an Ag/AgCl reference electrode. 
     
     
         15 . Electrolysis apparatus for the electrochemical reduction of molecular oxygen to oxygen ions having a double negative charge, comprising a first electrode space ( 1 ) filled with a solution having a pH greater than or equal to 8, in which an electrode ( 1   a ) comprising nitrogen-doped carbon nanotubes having pyridinic and quaternary nitrogen and being free of metal and semimetal constituents is present, which electrode has an electrically conductive connection via a voltage source ( 3 ) to a further electrode ( 2   a ) in a further electrode space ( 2 ), a membrane ( 4 ) being present between the first and the further electrode spaces. 
     
     
         16 . The process of  claim 10 , wherein said diameter is 4 to 100 nm. 
     
     
         17 . The process of  claim 16 , wherein said diameter is 5 to 50 nm. 
     
     
         18 . The process of  claim 11 , wherein said aspect ratio is at least 5. 
     
     
         19 . The process of  claim 18 , wherein said aspect ratio is at least 10. 
     
     
         20 . The process of  claim 12 , wherein said ratio of pyridinic nitrogen to quaternary nitrogen is greater than or equal to 1.5. 
     
     
         21 . The process of  claim 21 , wherein said ratio of pyridinic nitrogen to quaternary nitrogen is greater than or equal to 2. 
     
     
         22 . Process according to  claim 9 , wherein the nitrogen-doped carbon nanotubes have a diameter of 5 to 50 nm, wherein said aspect ratio is at least 10, wherein the nitrogen content of the nitrogen-doped carbon nanotubes is greater than or equal to 1 atom %, and wherein said ratio of pyridinic nitrogen to quaternary nitrogen is greater than or equal to 2.