A research team from the University of Tsukuba, Japan, has identified the active nitrogen atoms in the carbon catalyst of a fuel cell that will optimise renewable energy storage for transport applications.
Proton-exchange membrane (PEM) fuel cells are a proposed renewable energy storage device for transport applications. These fuel cells make use of a chemical reaction known as oxygen reduction, which needs a low-cost catalyst for widespread commercial applications. Nitrogen-doped carbon is one such catalyst, but the chemical details of how nitrogen doping works are controversial.
In an academic paper recently published in Angewandte Chemie, researchers from the University of Tsukuba reported chemical details for optimising the oxygen reduction reaction in PEM fuel cells in acidic conditions. This configuration helps the carbon catalyst adsorb oxygen in a way that enables the fuel cell to function.
Lead author Professor Kotaro Takeyasu said: “We deposited seven nitrogenous molecules onto a paracrystalline carbon black catalyst to make model catalysts with homogeneous structures. We found that 1,10-phenanthroline, with two pyridinic nitrogen atoms at the armchair edges of the catalyst, had the highest activity with reference to current density.”
The team of researchers used sulfuric acid to fully acidify the nitrogen atoms in the catalyst. Upon applying an appropriate voltage under oxygen-saturated conditions, the protonated nitrogen atoms in the catalyst were reduced. This was attributable to the simultaneous oxygen adsorption because there was no reduction in nitrogen-saturated conditions.
Current PEM fuel cells use platinum catalysts, however, because the metal is rare, it is not a realistic option for long-term commercial applications. Thus, platinum catalysts will not enable PEM fuel cells to contribute to a low-carbon economy. The findings described here will help researchers improve the performance o|0f carbon-based catalysts for PEM fuel cells and improve the sustainability of transportation.