Have you worried that, with the prospect of global shortages, water would be the oil of the 21st century? Have you worried that with the current energy crunch, oil would be the oil of the 21st century?
The gist - in what reads to me like a twist on photo-voltaic cells, sunlight plus water (fresh or saline) is used to produce oxygen and hydrogen. The yydrogen is then run through a fuel cell and recombined with oxygen to produce fresh water plus energy. The net effect - Florida can convert its abundant salt water and sunlight to fresh water and electricity. So can California, or Saudi Arabia. Very cool. Well, very cool unless this is this generation's cold fusion.
From the Times:
Splitting a water molecule is an experiment familiar to generations of high school chemistry students. In common industrial practice, it involves a container with water at a very high pH and a base like lye. The container is sealed to keep out contaminants like carbon dioxide, which is present in the atmosphere. But in one paper scheduled for publication in the journal Science on Friday, two researchers at the Massachusetts Institute of Technology describe a technique that works at ambient temperatures and pressures in ordinary water.
“Trees don’t grow in base; they grow in regular water,” said one of the researchers, Daniel G. Nocera, a professor of energy at the institute, who compared the process to photosynthesis, nature’s way of storing energy by separating hydrogen and oxygen.
Because the conditions are benign and the chemistry works at a small scale, Dr. Nocera said, this electrolyzer could be incorporated into a solar cell, which would turn out hydrogen rather than electricity.
Dr. Nocera worked with a postdoctoral fellow, Matthew W. Kanan.
The system could use saltwater. When the hydrogen and oxygen recombine in the fuel cell, the result is pure water, raising the possibility that the technology could be used for desalination.
The abstract is here. A flavor:
In Situ Formation of an Oxygen-Evolving Catalyst in Neutral Water Containing Phosphate and Co2+
Matthew W. Kanan 1 and Daniel G. Nocera 1*
The utilization of solar energy on a large scale requires its storage. In natural photosynthesis, energy from sunlight is used to rearrange the bonds of water to O2 and H2-equivalents. The realization of artificial systems that perform similar "water splitting" requires catalysts that produce O2 from water without the need for excessive driving potentials. Here, we report such a catalyst that forms upon the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing Co2+. A variety of analytical techniques indicates the presence of phosphate in an approximate 1:2 ratio with cobalt in this material. The pH dependence of the catalytic activity also implicates HPO42– as the proton acceptor in the O2-producing reaction. This catalyst not only forms in situ from earth-abundant materials but also operates in neutral water under ambient conditions.
Clear as mud.
A PLEA FOR ENGINEERING TALENT: Here is a problem that would be easily ball-parked by someone with the right background (this would take me back to high school chemistry and physics, when I worked to the rhythmic beating of pterodactyl wings):
Obviously it varies by latitude, season, and time of day, but determine the solar energy per square meter striking, for example, Miami.
And even with perfect catalysts and no activation energy it takes a certain amount of energy to separate water into hydrogen and oxygen. Presumably there will be some conversion loss when the elements are recombined to produce fresh water and electricty.
But given the solar energy input it should be possible to estimate the water and energy outputs. And somewhere the water and power usage of Miami ought to be available (or use a per capita guess.)
So, do we need to pave Florida with these conversion cells in order to save it?
HMM: This description clarifies a point to which the Times summary merely alluded - a photovoltaic cell is the starting point providing the electricity to drive the electrolysis:
PORTLAND, Ore. — Researchers at the Massachusetts Institute of Technology have combined a liquid catalyst with photovoltaic cells to achieve what they claim is a solar energy system that could generate electricity around the clock.
A liquid catalyst was added to water before electrolysis to achieve what the researchers claim is almost 100-percent efficiency. When combined with photovoltaic cells to store energy chemically, the resulting solar energy systems could generate electricity around the clock, the MIT team said.
Currently, MIT is working with photovoltaic cell manufacturers to incorporate electrolysis using their catalyst into solar energy systems. By combining the two, excess capacity during the day could be stored as hydrogen and oxygen, then used in fuel cells at night when needed.
"Solar cell makers can add super-cheap electrolyzers to their system so that they work 24/7 -- during the day making hydrogen and oxygen, then at night recombining it in fuel cells to generate electricity," Nocera predicted.
Even if they get 100% efficiency on the electrolysis, there is still a conversion loss when the fuel cell combines hydrogen and oxygen to produce electricity. And peak power demands occur during the day. Still, this could be a great way to produce hydrogen in remote sunny (and wet) locations and transport it elsewhere. And the same dodge could apply to wind power.