Process and high surface area electrodes for the electrochemical reduction of carbon dioxide
View Patent ↗Methods and systems for electrochemical conversion of carbon dioxide to organic products including formate and formic acid are provided. A method may include, but is not limited to, steps (A) to (C). Step (A) may introduce an acidic anolyte to a first compartment of an electrochemical cell. The first compartment may include an anode. Step (B) may introduce a bicarbonate-based catholyte saturated with carbon dioxide to a second compartment of the electrochemical cell. The second compartment may include a high surface area cathode including indium and having a void volume of between about 30% to 98%. At least a portion of the bicarbonate-based catholyte is recycled. Step (C) may apply an electrical potential between the anode and the cathode sufficient to reduce the carbon dioxide to at least one of a single-carbon based product or a multi-carbon based product.
1. A method for electrochemical reduction of carbon dioxide into products, comprising:
(A) introducing an acidic anolyte to a first compartment of a first electrochemical cell, the first compartment including an anode;
(B) introducing a catholyte including an alkali metal bicarbonate to a second compartment of the first electrochemical cell, the catholyte saturated with carbon dioxide, the second compartment including a high surface area cathode, the high surface area cathode including a coating containing indium and having a void volume of between about 30% to 98%, at least a portion of the catholyte including the alkali metal bicarbonate being recycled;
(C) applying an electrical potential between the anode and the cathode sufficient to reduce the carbon dioxide to an alkali metal formate;
(D) introducing the alkali metal formate to an ion exchange compartment of a second electrochemical cell;
(E) applying an electrical potential between an anode of the second electrochemical cell and a cathode of the second electrochemical cell sufficient to produce at least formic acid and an alkali metal hydroxide;
(F) introducing the alkali metal hydroxide with carbon dioxide to generate at least a portion of the alkali metal bicarbonate introduced to the second compartment of the first electrochemical cell; and
(G) separating the alkali metal formate from the alkali metal bicarbonate of the catholyte of the first electrochemical cell with a nano-filtration system, wherein the nano-filtration system separates monovalent anions from divalent anions.
2. The method of claim 1 , wherein separating the alkali metal formate from the alkali metal bicarbonate of the catholyte of the first electrochemical cell with a nano-filtration system comprises:
introducing the alkali metal bicarbonate of the catholyte to an alkali metal hydroxide to convert at least a portion of the alkali metal bicarbonate to an alkali metal carbonate; and
separating the alkali metal carbonate from the alkali metal formate with a nano-filtration unit.
3. The method of claim 2 , further comprising:
introducing the alkali metal carbonate with the alkali metal hydroxide and with carbon dioxide to generate at least a portion of the alkali metal bicarbonate introduced to the second compartment of the first electrochemical cell.
4. The method of claim 1 , wherein at least a portion of the alkali metal hydroxide is generated by one or more of the first electrochemical cell and the second electrochemical cell.
5. The method of claim 1 , wherein the formic acid is generated in the ion exchange compartment of the second electrochemical cell.
6. The method of claim 1 , wherein the alkali metal hydroxide is generated in a cathode compartment of the second electrochemical cell.
7. The method of claim 1 , wherein the high surface area cathode has a specific surface area of greater than 2 cm 2 /cm 3 .
8. The method of claim 1 , wherein the acidic anolyte includes sulfuric acid.
9. The method of claim 1 , further comprising:
generating a halogen selected from the group consisting of F 2 , Cl 2 , Br 2 , and I 2 in at least one of the first compartment of the first electrochemical cell and the first compartment of the second electrochemical cell.
10. The method of claim 9 , further comprising:
reacting the halogen with an organic compound to produce a halogenated product.
11. The method of claim 10 , wherein the halogen is bromine.
12. The method of claim 9 , wherein the halogen is bromine.
13. The method of claim 1 , wherein the high surface area cathode includes from 5% to 99% as indium in alloy with bismuth.