Scientists at CalTech are perfecting a technique that converts water, air, and sunlight into different kinds of fuel that could power everything from car engines to fuel cells in cell phones. It sounds almost too good to be true, from an environmental stand-point.
The technique for converting water and carbon dioxide into hydrogen gas and carbon monoxide—gasses that can be then recombined in different ongoing processes into useful fuel—has been known for some while. But the conversion processes tend to rely on expensive materials to aid in the chemical reactions, including rare and expensive metals like platinum.
The new technique being championed by CalTech and the Swiss Federal Institute of Technology uses ceria to catalyze the conversion instead. This is oxidized cerium, and you're likely to have already encountered it in the form of self-cleaning oven linings. Since cerium is much more abundant than the typical metals used for catalysis (100,000 times more so than platinum, for example) then the cost of the conversion process is potentially much, much lower. The raw material components are so cheap that the ultimate fuel creation process could thus be very powerful for future eco power systems.
The trick involves collecting sunlight to heat a reactor vessel up to 3,000 degrees Fahrenheit which causes the ceria to naturally release oxygen from its structure—leaving an oxygen "vacancy" that the material would prefer to be filled up when it's cooled back down. At this point water and CO2 is injected into the system and the mix is heated up again, only not so much. The hydrogen atoms in water and the carbon atoms in CO2 really want to retain their partner oxygen atoms (it's why water and CO2 are stable materials) but the cerium's reactivity is higher—it successfully scavenges oxygen from water and carbon dioxide, giving an output of re-oxygenated ceria, hydrogen gas and carbon monoxide. Then the process is repeated, to generate more fuel gasses.
The byproducts can be used to power hydrogen fuel cells for portable devices or cars—thanks to the high purity of the H2 the reactor spits out—or combined to make methane gas that can be burned in engines in a similar way to gasoline-powered engines run. Since the hydrogen and oxygen in these fuels are "harvested" from the environment, and the conversion process requires very little input apart from sun, then the carbon footprint of producing and burning the fuels is potentially very low.
In its first iteration, the experimental reactor converts just 1% of the inbound solar energy into useful fuel gasses—but the team is confident this figure can be boosted. And because sunlight is ubiquitous, as are the component input gasses, the ultimate levels of solar efficiency aren't too crucial to the ultimate outcome.
Image via Flickr user hvnly.