* This story originally appeared on Materials Today on 8th September 2015 *
Working with a global car brand, a team of researchers have successfully developed a platinum-free catalyst, for use in automotive fuel cells.
Fuel cell electric vehicles are no longer just a clever idea. Around the world, car manufacturers are developing and commercialising them, with most investing heavily in ongoing research. At the moment, those fuel cells leading the way in the automotive sector utilise platinum-based catalysts on both sides of a membrane electrode assembly (MEA). But cost is a major limiting factor in their widespread use. Together, the platinum (Pt) and the electrodes make up 40-50% of the total price of a fuel cell stack, and Pt alone costs over $32k per kg. And so recently, a considerable research effort has focused on reducing the amount of Pt used in fuel cells.
A paper in a recent issue of Nano Energy [DOI: 10.1016/j.nanoen.2015.07.002] goes one step further – led by Plamen Atanassov from Northeastern University, a team of researchers have developed a completely platinum-free catalyst for use in fuel cell vehicles. Instead they looked to another transition metal – iron. So-called metal-nitrogen-carbon catalysts have been used in energy storage systems for some time, but this material from Atanassov and his team is the first to be produced using nicarbazin, an inexpensive salt widely used in the poultry sector.
The team used a sacrificial support method to synthesise the iron-nicarbazin (Fe-NCB) catalyst. Using a fumed silica material for the template, this approach was found to allow a high level of control of the catalyst’s pore size and therefore, its water management and gas transport properties – both crucial factors in an MEA’s operation. They found that the Fe-NCB displayed its highest activity at 900°C, and durability tests showed its performance to degrade by only 3-4%. Then, working with Nissan’s North America Technical Centre, the catalyst was added to a series of membrane electrode assemblies, and characterised under automotive test conditions.
By optimising the stack structure, they found that high current densities could be obtained with this catalyst, as well as improved durability, a reduction in resistive losses and better water management. The team see this as a promising candidate for future polymer electrolyte membrane fuel cells, and are continuing to work with Nissan to develop it further.
The paper: A. Serov et al, Nano Energy (2015) 16, 293–300, “Nano-structured non-platinum catalysts for automotive fuel cell application.” DOI: 10.1016/j.nanoen.2015.07.002