UK scientists have discovered why combining two different fuel cell technologies can boost cell performance.

The hybrid fuel cell contains both solid oxide and molten carbonate electrolytes

Direct carbon fuel cells run on solid carbon fuel and typically use solid oxide or molten carbonate electrolytes to transport ions between the electrodes. John Irvine at the University of St Andrews and colleagues made a hybrid direct carbon fuel cell containing both types of electrolyte. They found that the binary electrolyte system enhanced carbon oxidation because carbon was oxidised not only on the electrode surface but also in the carbon-electrolyte slurry.

Dianxue Cao, an expert in direct carbon fuel cells at Harbin Engineering University, China, is impressed by the findings. 'This significantly improves understanding of the electrochemical oxidation of solid carbon in molten carbonates,' he says.

Solid carbon, which comes from various sources such as coal or plants, packs a lot of energy into a small volume, making it an attractive fuel. Irvine states that coal will be a major energy source in the future but, unless it can be converted into electricity more efficiently, will lead to an increase in carbon dioxide emissions. Fuel cells could be the answer, he says. 'Carbon fuel cells offer very high efficiency of conversion and, if implemented in the correct way, can yield two to three times the amount of energy for a given amount of coal compared to conventional thermal generation,' he explains.

Madelaine Chapman