Efficient electrolysis promises mass storage for wind power

Sun Catalytix ja 2010 013344 0002 300x124

Finding artificial systems that "split water" requires catalysts that produce oxygen from water without need for excessive driving potentials. The company has found such a catalyst that forms on the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions.

Startup Sun Catalytix is commercializing active, versatile, and affordable catalysts that split water into oxygen and hydrogen in a way that mimicks photosynthesis. Its technology uses catalysts made of abundant elements that split water in a benign and simple operation. By eliminating expensive precious metals and substantially reducing balance of plant costs, the technology promises to convert electrical, solar, or wind energy to storable energy at transformative cost targets. Sun Catalytix systems target the generation of hydrogen from water at significantly lower costs for industrial applications, for energy storage, and for use as a renewable fuel through internal combustion engines or fuel cells.

Research for the technology comes from the MIT lab of Professor Daniel Nocera. The company says H2 from three gallons of water would provide enough energy for the daily needs of an American home.

An abstract of one of the developer’s technical papers describes its development this way: “A thin-film water oxidation catalysts (Co−Pi) (Cobalt and prepared by electrodeposition from phosphate electrolyte and Co(NO3)2 has been characterized by electron paramagnetic resonance (EPR) spectroscopy. Co−Pi catalyst films exhibit EPR signals corresponding to populations of both Co(II) and Co(IV). As the deposition voltage increases to a region where water oxidation prevails, the population of Co(IV) rises and the population of Co(II) decreases. The changes in the redox speciation of the film can also be induced, in part, by prolonged water oxidation catalysis in the absence of additional catalyst deposition. These results provide spectroscopic evidence for the formation of Co(IV) species during water oxidation catalysis at neutral pH.”

Using solar energy on a large scale requires storing it. In natural photosynthesis, energy from sunlight is used to rearrange the bonds of water to oxygen and hydrogen equivalents. Finding artificial systems that “split water” requires catalysts that produce oxygen from water without need for excessive driving potentials. The company has found such a catalyst that forms on the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions. A variety of analytical techniques indicates the presence of phosphate in about a 1:2 ratio with cobalt in this material. The pH dependence of the catalytic activity also implicates the hydrogen phosphate ion as the proton acceptor in the oxygen-producing reaction. This catalyst forms in situ from earth-abundant materials and operates in neutral water under ambient conditions.

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