Breakthroughs open door to Hydrogen Economy

Two studies published in the July 31 issue of Science help open the door to the hydrogen economy by eliminating the need for platinum in electrolyzers and fuel cells.

Hydrogen can be produced by means of electrolysis, i.e. running electricity through water in order to split it into its constituent hydrogen and oxygen. Current electrolyzers use a catalyst made of platinum. The same goes for fuel cells that recombine hydrogen with oxygen, in order to (re)produce electricity.

The problem is that platinum is a precious metal that costs about $1,700 to $2,000 per ounce, which until now made the equipment to produce and use hydrogen rather expensive.

Daniel Nocera and Matthew Kanan of the Massachusetts Institute of Technology (MIT) have discovered a cheaper way to produce hydrogen and oxygen from water. To produce oxygen, Nocera and Kanan added cobalt and phosphates to neutral water and then inserted a conductive-glass electrode. As soon as the researchers applied a current, a dark film began to form on the electrode from which tiny pockets of oxygen began to appear, eventually building into a stream of bubbles.

After analyzing the electrode, the researchers concluded that a cobalt-phosphate mixture, possibly combined with phosphate, had deposited as a film. Nocera and Kanan believe the film is the catalyst that helps break apart the water molecules to produce oxygen. The protons (hydrogen nuclei) released from the process pick up electrons and convert back into hydrogen at a partner electrode.

Nocera and Kanan also found evidence that the catalyst seems to refresh itself, a mechanism that would make maintenance of such oxygen-extracting systems far simpler than alternatives, although that finding needs confirmation from additional experiments.

The method works with nothing but abundant, non-toxic natural materials. Cobalt costs about $2.25 an ounce and phosphate costs about $.05 an ounce. "The new catalyst works at room temperature, in neutral pH water, and it's easy to set up", Nocera says. "We figured out a way just using a glass of water at room temperature, under atmospheric pressure."

In a similar development, Chemist Bjorn Winther-Jensen of Monash University in Australia and his colleagues have made a fuel cell that uses electrodes made from a special conducting polymer that costs around $57 per ounce. During experiments, the polymer proved just as effective as platinum at harvesting electricity.

In order for this to work on the grand scale of a fuel cell stack for a hydrogen vehicle or power plant, "we need to develop a more three-dimensional structure to get thicker electrodes and a higher current per square centimeter," says Winther-Jensen.

References:
Hydrogen Power on the Cheap--Or at Least, Cheaper - Scientific American

Water Refineries? - National Science Foundation

'Major Discovery' Primed To Unleash Solar Revolution: Scientists Mimic Essence Of Plants' Energy Storage System - Science Daily