Cornell University researchers discovered that a nitrogen doped carbon-coated nickel anode can catalyze an important reaction in hydrogen fuel cells for a fraction of the cost of the precious metals currently used.
The new discovery could hasten the adoption of hydrogen fuel cells, which hold great promise as efficient and environmentally friendly energy sources for vehicles and other applications.
The Héctor D. Abrua lab has made a series of breakthroughs in their ongoing search for active, inexpensive, and long-lasting catalysts for use in alkaline fuel cells.
Platinum and other expensive precious metals are currently required in hydrogen fuel cells to efficiently catalyze the reactions that generate electricity. Although alkaline polymer electrolyte membrane fuel cells (APEMFCs) allow nonprecious metal electrocatalysts to be used, they lack the performance and durability required to replace precious metal-based systems.
The hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) produce electricity in a fuel cell (OOR). Platinum is a model catalyst for both reactions because it efficiently catalyzes them and is durable in the acidic environment of a PEM fuel cell.
According to the researchers, recent experiments with nonprecious-metal HOR electrocatalysts had to overcome two major challenges: low intrinsic activity due to a high hydrogen binding energy and poor durability due to metal oxide formation.
The researchers devised a nickel-based electrocatalyst with a 2 nanometer nitrogen-doped carbon shell to overcome these obstacles.
The anode (where hydrogen is oxidized) catalyst in their hydrogen fuel cell is made up of a solid nickel core surrounded by a carbon shell. The resulting completely precious-metal-free hydrogen fuel cell outputs more than 200 milliwatts per square centimeter when paired with a cobalt-manganese cathode (where oxygen is reduced).
According to Abrua, the presence of nickel oxide species on the nickel electrode’s surface dramatically slows the hydrogen oxidation reaction. The nitrogen-doped carbon coating acts as a barrier and improves HOR kinetics, making the reaction faster and more efficient.
Furthermore, the graphene coating on the nickel electrode prevents the formation of nickel oxides, resulting in electrodes with significantly longer lifespans. Carbon monoxide poisons platinum quickly, so these electrodes are much more resistant to it.
The Center for Alkaline-Based Energy Solutions, an Energy Frontier Research Center funded by the US Department of Energy’s Office of Science, Basic Energy Sciences, and the Zhuang research group at Wuhan University, China, were both involved in this study, with funding from the Chinese National Natural Science Foundation.
