A team of scientists from Taiwan have developed a new method for providing fuel cells with a vitamin catalyst that helps improve their performance, and which could offer a viable and cost-effective alternative to the use of expensive platinum catalysts in existing fuel cell technology.
The researchers, whose study was published in the journal Energy & Environmental Science [Chang et al. Energy Environ. Sci. (2011) DOI: 10.1039/c1ee01962g], have been exploring how to produce efficient, durable and inexpensive non-precious metal catalysts for applications in hydrogen fuel technology, and their breakthrough is timely. The innovative high-performance fuel cells currently used require a great deal of platinum to generate a large power output.
Fuel cells are a clean form of energy that use hydrogen and oxygen as fuel and oxidation, respectively. However, many devices now require an oxygen reduction reaction (ORR) at the cathode of the cell to help them generate electricity. Unfortunately, ORR is also slow and requires complex enzymes to progress at a worthwhile rate. Although previous studies have examined ways of making the ORR process faster, it has proved extremely difficult to develop, so the Taiwanese team resolved the problem by loading a large amount of platinum onto the cathode to generate the required ORR rate.
It was then shown that platinum could be omitted completely through the use of carbon with vitamin B12 dispersed within it to form the cathode of a polymer electrolyte fuel cell. Although this version of the cathode did not offer quite the same level of performance as that of platinum cathodes, it was achieved much more cheaply.
The initial motivation for the research actually came when one of the team was offered milk and a cookie after providing a blood donation, and noticed a sign on the packaging that the cookie contained vitamin B12. After a series of experiments, vitamin B12 was found to be efficient for ORR in a proton exchange membrane fuel cell (PEMFC). The use of this catalyst in the cathode of PEMFC demonstrated high activity and also long-term stability, and was one of the best performers out of the non-noble-metal catalysts (NNMCs) that were tried.
This activity and durability means the B12-based catalyst could offer a new direction for research into NNMCs – as it is possible to modify or functionalize the B12 structure to further enhance the activity of the catalyst. However, although the B12-based catalyst does exhibit good ORR performance, its ORR mechanism is still unclear, so the team now aim to use X-ray techniques to resolve this problem. They also plan to work on modifying the catalytic structure to enhance the ORR activity.