ELECTROCHEMICAL METHOD FOR REDUCING MOLECULAR OXYGEN
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 . 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 under the influence of an applied electrical voltage.
2 . Process according to claim 1 , wherein the nitrogen-doped carbon nanotubes have a diameter of 3 to 150 nm.
3 . Process according to claim 1 or 2 , wherein the nitrogen-doped carbon nanotubes have an aspect ratio of at least 2.
4 . Process of claim 1 , wherein the nitrogen-doped carbon nanotubes have pyridinic and quaternary nitrogen in a ratio greater than or equal to 1.
5 . Process according to claim 1 , wherein the nitrogen content of the nitrogen-doped carbon nanotubes is greater than or equal to 1 atom %.
6 . Process according to claim 1 , wherein said voltage is +0.2 V to −0.8 V, measured against an Ag/AgCl reference electrode.
7 . (canceled)
8 . 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 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.
9 . The process of claim 2 , wherein said diameter is 4 to 100 nm.
10 . The process of claim 9 , wherein said diameter is 5 to 50 nm.
11 . The process of claim 3 , wherein said aspect ratio is at least 5.
12 . The process of claim 11 , wherein said aspect ratio is at least 10.
13 . The process of claim 4 , wherein said ratio of pyridinic nitrogen to quaternary nitrogen is greater than or equal to 1.5.
14 . The process of claim 13 , wherein said ratio of pyridinic nitrogen to quaternary nitrogen is greater than or equal to 2.