Fast recycling process for ruthenium, gold and titanium coatings from hydrophilic PEM fuel cell bipolar plates
A method for recovering ruthenium oxide or gold and titanium or titanium oxide from a bipolar plate at the end of the life of a fuel cell stack so as to use these materials in other fuel cell stacks thereafter. The bipolar plate is immersed in a solution including a suitable acid that dissolves the titanium or titanium oxide. The ruthenium oxide or gold will be released from the plate and will float on the solution from which it can be removed. The solution is then heated to evaporate the acid solution leaving a powder of the titanium oxide. The stainless steel of the bipolar plate is thus cleaned of the titanium or titanium oxide, and can be reused.
1. A method for recycling a bipolar plate including a titanium or titanium oxide layer and a conductive layer deposited on the titanium or titanium oxide layer, said method comprising:
soaking the bipolar plate in a container including an acid solution that dissolves the titanium or titanium oxide layer;
skimming conductive material from the conductive layer that is floating on the acid solution to remove it from the container after the titanium or titanium oxide layer has dissolved;
heating the acid solution to evaporate the acid solution; and
removing titanium oxide from the container after the acid solution has evaporated.
2. The method according to claim 1 wherein the acid solution is a solution including water, 25% HNO 3 and 2% HF.
3. The method according to claim 1 wherein the acid solution is a solution including water, 1M H 2 SO 4 and 0.1M HF.
4. The method according to claim 1 wherein the conductive material is ruthenium oxide.
5. The method according to claim 1 wherein the conductive material is iridium oxide.
6. The method according to claim 1 wherein the conductive material is gold.
7. The method according to claim 1 wherein the conductive material is platinum.
8. The method according to claim 1 wherein the bipolar plate is a stainless steel bipolar plate.
9. The method according to claim 1 further comprising using the bipolar plate in another fuel cell stack after it has been recycled.
10. The method according to claim 1 wherein removing the titanium oxide from the container includes removing the titanium oxide as a powder from the container.
11. A method for recycling a stainless steel bipolar plate including a titanium oxide/ruthenium oxide layer deposited on a titanium or titanium oxide layer, said method comprising:
soaking the bipolar plate in a container including an acid solution that dissolves the titanium or titanium oxide in the titanium or titanium oxide layer on which the titanium oxide/ruthenium oxide layer is deposited;
skimming the ruthenium oxide floating on the acid solution to remove it from the container after the titanium or titanium oxide in the titanium or titanium oxide layer on which the titanium oxide/ruthenium oxide layer is deposited has dissolved;
heating the acid solution to evaporate the acid solution; and
removing the titanium oxide from the container after the acid solution has evaporated.
12. The method according to claim 11 further comprising converting the ruthenium oxide to ruthenium chloride to be applied to a titanium or titanium oxide layer of another bipolar plate.
13. The method according to claim 11 wherein the acid solution is a solution including water, 25% HNO 3 and 2% HF.
14. The method according to claim 11 wherein the acid solution is a solution including water, 1M H 2 SO 4 and 0.1M HF.
15. The method according to claim 11 further comprising using the bipolar plate in another fuel cell stack after it has been recycled.
16. The method according to claim 11 wherein removing the titanium oxide from the container includes removing the titanium oxide as a powder from the container.
17. A method for recycling a stainless steel bipolar plate including a titanium or titanium oxide layer and a gold layer deposited on the titanium or titanium oxide layer, said method comprising:
soaking the bipolar plate in a container including an acid solution that dissolves the titanium or titanium oxide layer;
skimming the gold floating on the acid solution to remove it from the container after the titanium or titanium oxide layer has dissolved;
heating the acid solution to evaporate the acid solution; and
removing the titanium oxide from the container after the acid solution has evaporated.
18. The method according to claim 17 wherein the acid solution is a solution including water, 25% HNO 3 and 2% HF.
19. The method according to claim 17 wherein the acid solution is a solution including water, 1M H 2 SO 4 and 0.1M HF.
20. The method according to claim 17 further comprising using the bipolar plate in another fuel cell stack after it has been recycled.