The structure of a pine branch provided Canadian researchers with the inspiration to create the next-generation of fuel cell electrodes.

In January, Audi launched their first fuel cell concept car at the North American International Auto Show. And they’re not the only ones investing in this technology – Toyota already has a production model on the market. While their performance is impressive, the price is not. The Toyota Mirai comes in at a whopping £66,000. Much of the cost involved is around the development of the car’s polymer electrolyte membrane (PEM) fuel cells, but a paper from a group of Canadian scientists may have found a way to reduce that cost, while still improving the cell’s performance.

There is a considerable research focus around the development of robust, stable electrode materials for fuel cells. They typically comprise a porous carbon structure coated in a layer of platinum catalyst. But even those in commercial systems suffer from issues with chemical (and structural) stability, especially under real-word conditions. So to solve this, Prof. Zhongwei Chen and his team at the University of Waterloo developed a monolithic electrode for PEM fuel cells – one that combined catalytic behaviour with high electrical conductivity into a single structure.

Published in Nano Energy [DOI: 10.1016/j.nanoen.2015.11.033], their solution was inspired by a complex system from the natural world – the pine tree. They wanted to create a hierarchical structure, with features that varied from the macroscale (centimetres) to the nanoscale, in order to maximise surface area. They started by producing a flexible, conductive film made from a net of electrospun carbon fibres – in their analogy, this would represent the tree branch. On top of this mat, they grew a uniform layer of platinum nanowires – the pine ‘needles’. This addition increased the mat’s conductivity by 400 times, which the team believe is due to the high-degree of interconnectivity between the mat and the nanowires. In order to improve the catalytic properties of the electrode, a coating of porous bismuth, just 1–3 atomic layers thick, was added to the nanowires.

The team describe their new, free-standing electrode as being “ready to be incorporated into membrane electrode assembly and feasible for mass production.” They also suggest that the carbon mat could find wider application than simply fuel cells – its properties make it suitable for use in batteries and super-capacitors.


R.Wang, D.C. Higgins, D.U. Lee, S. Prabhudev, F.M. Hassan, V. Chabot, G. Lui, G. Jiang, J.Y. Choi, L. Rasenthiram, J. Fu, G. Botton, Z. Chen, “Biomimetic design of monolithic fuel cell electrodes with hierarchical structures”, Nano Energy (2016) 20, 57–67, DOI: 10.1016/j.nanoen.2015.11.033