Rusting iron makes hydrogen fuel

Iron pellets produced from a reduction-oxidation process could hold key to converting water into hydrogen in cars.

Japanese engineers claimed this week to have found a way to produce hydrogen fuel on board cars by accelerating a process similar to rusting.

Prof Kiyoshi Otsuka at the Tokyo Institute of Technology’s Applied Chemistry Department said that by augmenting natural processes with high temperatures and catalysts, there is potential for ‘a simple, safe and environmentally benign technology for the storage, transport and supply of hydrogen’ to fuel cell-powered vehicles.

Car manufacturers such as General Motors and BMW are vying to take the technological lead in the quest for a new viable clean fuel and to gain government backing for hydrogen in the US and Europe. Existing proposals involve producing the hydrogen outside the vehicle and then delivering it under pressure to the fuel cell. This poses certain technical problems that Otsuka’s system avoids.

‘The iron and iron oxide are non-toxic and quite cheap materials,’ said Otsuka. ‘As the fuel is water, there is no danger of explosion when vehicles collide.’The technology is based on a reduction-oxidation (redox) reaction of magnetite, an iron oxide found in lodestone.

Iron pellets from a redox process could be packed into cassettes mounted on vehicles. Adding water vapour to the cassettes would produce hydrogen, leaving the cassettes full of iron oxide that could be exchanged for recycling at a fuel station.

‘The redox performance of iron oxide was enhanced by the addition of metal elements such as aluminium, gallium, chromium, molybdenum and zirconium,’ explained Otsuka, ‘and the reaction could be operated at a low temperature, say 300 degrees C. The hydrogen could be supplied directly to the fuel cell on board.’

In theory 48g of hydrogen can be produced from 1kg of iron: in laboratory tests at 350 degrees C, from each kilogramme of iron researchers made 0.1g of hydrogen per second. This corresponds to 4,200 litres of hydrogen per litre of iron.

At the moment the technology remains in the laboratory. The catalysing elements are expensive, and to run a car for 500km the weight and volume of iron required are 105 kg and 13.3 litres respectively. However, the Tokyo Institute is working with an industrial partner, Uchiya Thermostat, which hopes to commercialise the research.’We are developing more efficient materials based on iron oxides as well as a unit apparatus with the cassette and water injection equipment,’ said Otsuka.

The iron-based technique is the latest in a series of hydrogen production technologies. In the UK the Hydrogen Solar Production Company plans to commercialise a process using photovoltaic devices for the electrolysis of water, while Warwick University is researching methods exploiting sewage and paper mill waste.