Electrolyzer and method of use
Provided herein are methods for operating carbon oxide (CO x ) reduction reactors (CRR) and related apparatus. In some embodiments, the methods involve shutting off, reducing, or otherwise controlling current during various operation stages including hydration, break-in, normal operation, planned shut-offs, and extended shutoff or storage periods.
1. A method of operating a membrane electrode assembly (MEA) for CO x reduction, the MEA comprising a cathode, an anode, and a membrane between the cathode and the anode, and the method comprising:
inletting a gas comprising CO x to the cathode of the MEA and applying a current to the MEA at a first current density, to thereby reduce CO x and produce a CO x reduction product; and
during operation to produce the CO x reduction product for a downstream process, automatically pausing applied current according to a current pause schedule.
2. The method of claim 1 , wherein automatically pausing the applied current comprises reducing the applied current to a non-zero level.
3. The method of claim 1 , wherein the current pause schedule comprises current-on periods at the first current density separated by current pause periods, wherein the applied current during at least a portion of a current pause period is zero or at a second current density lower than the first current density.
4. The method of claim 3 , wherein the duration of a current-on period is between 10 hours and 1000 hours.
5. The method of claim 4 , wherein the duration of a current pause period is between 5 minutes and 10 hours.
6. The method of claim 3 , wherein the duration of a current-on period between 1 hour and 10 hours.
7. The method of claim 6 , wherein the duration of a current pause period is between 500 microseconds and 20 minutes.
8. The method of claim 3 , wherein the duration of a current-on period between 3 minutes and 1 hour.
9. The method of claim 8 , wherein the duration of a current pause period is between 500 microsecond and 10 minutes.
10. The method of claim 3 , wherein the total current-on period duration is at least three times longer than the total current pause period duration.
11. The method of claim 3 , wherein the current pause period durations are constant and the current-on period durations are constant.
12. The method of claim 1 , wherein one or both of the current pause period duration and the current-on period duration vary.
13. The method of claim 1 , wherein automatically pausing the applied current comprises a single step from the first current density.
14. The method of claim 1 , wherein automatically pausing the applied current comprises multiple steps from the first current density.
15. The method of claim 1 , wherein automatically pausing the applied current comprises a continuous ramp from the first current density.
16. The method of claim 1 , wherein automatically pausing the applied current comprises returning to the first current density using a single step.
17. The method of claim 1 , wherein automatically pausing the applied current comprises returning to the first current density using multiple steps.
18. The method of claim 1 , wherein automatically pausing the applied current comprises returning to the first current density using a continuous ramp.
19. The method of claim 1 , wherein automatically pausing the applied current comprises reducing the applied current to zero.
20. The method of claim 19 , wherein reducing the applied current to zero comprises shorting the MEA.
21. The method of claim 19 , wherein the MEA has an open circuit potential when the applied current is zero.
22. The method of claim 1 , further comprising stopping flow of the gas while pausing current.
23. The method of claim 1 , further comprising maintaining a flow of the gas comprising CO x to the cathode while pausing current.
24. The method of claim 1 , further comprising maintaining a flow of the gas comprising CO x to the cathode at the same flow rate while pausing current.
25. The method of claim 1 , further comprising inletting anode feed material to the anode of the MEA.
26. The method of claim 25 , further comprising stopping flow of the anode feed material while pausing current.
27. The method of claim 25 , further comprising maintaining a flow of the anode feed material to the anode while pausing current.
28. The method of claim 25 , further comprising maintaining a flow of the anode feed material to the anode at the same flow rate while pausing current.
29. The method of claim 1 , further comprising, prior to producing a CO x reduction product for a downstream process, performing a break-in procedure comprising applying current in a multi-step or continuous ramp to the first current density.
30. The method of claim 29 , further comprising, prior to the break-in procedure, performing a hydration operation in which no current is applied and wherein a cathode gas and an anode feed material are inlet to the cathode and anode, respectively, of the MEA.
31. The method of claim 30 , further comprising ramping a MEA temperature to operating temperature during the hydration operation.
32. A method of operating an electrochemical cell comprising a membrane electrode assembly (MEA) for CO x reduction, the MEA comprising a cathode, an anode, and a membrane between the cathode and the anode, and the method comprising:
inletting a gas comprising CO x to the cathode of the MEA and applying a cell voltage to the MEA to thereby reduce CO x and produce a CO x reduction product; and
during operation of the cell to produce the CO x reduction product, cycling the cell voltage.
33. The method of claim 32 , wherein cycling the cell voltage comprises reducing the cell voltage to zero.
34. The method of claim 32 , wherein cycling the cell voltage comprises reducing the cell voltage to a non-zero level.
35. The method of claim 32 , wherein the CO x reduction product is produced for a downstream process.
36. A system comprising:
a CO x reduction reactor comprising an electrochemical cell, the electrochemical cell comprising a membrane electrode assembly (MEA) comprising a (i) cathode comprising a CO x reduction catalyst that promotes reduction of a carbon oxide, (ii) an anode comprising a catalyst that promotes oxidation, and (iii) a polymer electrolyte membrane (PEM) layer disposed between the cathode and the anode; and
an electrical power source controller configured to control voltage applied to the electrochemical cell, wherein the electrical power source controller is configured to, during operation of the CO x reduction reactor, cycle the voltage applied to the cell.
37. The system of claim 36 , further comprising a cathode subsystem configured to interact with the cathode and comprising a carbon oxide flow controller configured to control flow of a carbon oxide feed stream to the cathode of the CO x reduction reactor.
38. The system of claim 37 , wherein the electrical power source controller acts in concert with the carbon oxide flow controller.
39. The system of claim 36 , further comprising an anode subsystem configured to interact with an anode of the CO x reduction reactor and comprising an anode water flow controller configured to control flow an anode feed stream to an anode of the CO x reduction reactor.
40. The system of claim 39 , wherein the electrical power source controller acts in concert with the anode water flow controller.
41. The system of claim 36 , further comprising a backpressure controller configured to maintain pressure at the cathode side of the MEA.
42. The system of claim 37 , wherein the cathode subsystem is configured to controllably recycle unreacted carbon oxide.
43. The system of claim 36 , further comprising an anode water recirculation loop.
44. The system of claim 36 , wherein cycling voltage applied to the cell comprises reducing the voltage to zero.
45. The system of claim 36 , wherein cycling the voltage applied to the cell comprises reducing the voltage to a non-zero level.
46. The system of claim 36 , wherein the electrical power source controller is configured to, during operation of the CO x reduction reactor, cycle the voltage applied to the cell according to a schedule.
47. A method of operating a membrane electrode assembly (MEA) for CO x reduction, the MEA comprising a cathode, an anode, and a membrane between the cathode and the anode, the method comprising:
inletting a gas comprising CO x to the cathode of the MEA and applying a current to the MEA at a first current density, to thereby reduce CO x and produce a CO x reduction product; and
during operation to produce the CO x reduction product for a downstream process, cycling the applied current.
48. The method of claim 47 , wherein cycling the applied current comprises reducing the current to zero.
49. The method of claim 47 , wherein cycling the applied current comprises reducing the current to a non-zero level.
50. A method of operating a membrane electrode assembly (MEA) for CO x reduction, the MEA comprising a cathode, an anode, and a membrane between the anode and the cathode, the method comprising:
inletting a gas comprising CO x to the cathode of the MEA and applying a current to the MEA at a first current density, to thereby reduce CO x and produce a CO x reduction product; and
during operation to produce the CO x reduction product for a downstream process, automatically varying applied current according to a schedule.
51. The method of claim 50 , wherein automatically varying applied current according to a schedule comprises reducing applied current to zero.
52. The method of claim 50 , wherein automatically varying applied current according to a schedule comprises reducing applied current to a non-zero level.