Progress in fuel cell technology

The power beneath the bonnet of the green, efficient car of the future will most likely be the fuel cell. Yet the technology needed to convert chemical energy directly into electrical energy has so far fallen short of the scientific and practical requirements of the electric motor vehicle.

Now a team of chemical engineers and materials scientists at the University of Edinburgh, together with colleagues at Imperial College, London, believe they have made significant strides towards solving some of the major problems that keep fuel cells from replacing the internal combustion engine.

Mortaza Sahibzada and Ian Metcalfe have devised new electrode catalysts and techniques for depositing thin layers of novel electrolyte materials to generate power from "intermediate temperature" solid oxide fuel cells.

"Fuel cells generate electrical power very efficiently with a lot less fuel consumption and a lot less gas emission - and if you could use a liquid fuel like methanol, vehicles could utilise the existing petrol pumps. It is far more flexible than other related technologies," said Dr Sahibzada.

Two types of fuel cell are already at an advanced stage of development. Solid oxide devices similar to Dr Sahibzada's are being made to operate at about 900° C to generate electric power for buildings while some cars and buses are being fitted with low temperature fuel cells that use hydrogen.

However, the ideal motor vehicle fuel cell would both run at a temperature low enough not to melt metallic engine components and use a more practical, liquid fuel, such as methanol, rather than hydrogen.

In a paper to appear in the journal Chemical Engineering Science, Dr Sahibzada and colleagues outline a method to cut the thickness of cerium gadolinium oxide for the fuel cell electrolyte to just a few microns - which keeps its ionic resistance low. He also describes the use of zinc and palladium as effective catalytic promoters for the anode and cathode of the cell.

The experimental fuel cell his team was able to fabricate with the new catalysts produced power at temperatures around

600° C, low enough to be practical, though the research has still not reached high enough power densities to run a vehicle.

He has already started work on a new electrolyte material, lanthanum gallate, which he believes will prove even better at accommodating the electrochemical reactions that generate power.