Wednesday, June 19, 2013

Breakthroughs open door to Hydrogen Economy

MIT's cheap catalyst in action. (Credit: MIT/NSF)
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.
[originally posted August 1, 2008]
Water Refineries? - National Science Foundation
Currently, most hydrogen is produced from natural gas. Eventually, I foresee most hydrogen to be produced from water with solar and wind energy. As more wind turbines become operational, there will be a growing surplus of electricity at night, when there's plenty of wind but little demand for electricity. It makes sense to use this electricity surplus for the production of hydrogen. Since off-shore wind turbines can produce twice as much electricity as land-based turbines, I expect the Hydrogen Economy to take off at seaports, supplying hydrogen to ships, cars, buses and trucks in the area.
Many see hydrogen power cars first, but there's also a huge potential for ships to be powered by hydrogen, Gary. The hydrogen can be produced at relatively low prices by wind turbines at night. As I said, offshore wind turbines can produce twice as much electricity as land-based wind turbines, so I expect seaports to start supplying hydrogen to ships, cars, buses, trucks, etc, and this development should start within years, rather than decades.

The main 'breakthrough' we're waiting for is not a technological one, but a global commitment to reduce emissions in the most effective way, which IMO is through a framework of feebates, specifically by adding fees to fossil fuel and using the proceeds to fund local rebates on better ways to power, say, ships.
Hydrogen storage is another research area. Palladium can absorb up to 900 times its own volume of hydrogen, at room temperature and atmospheric pressure, but it's scarce. 

A UK team including scientists from the Universities of Birmingham and Oxford, and the Rutherford Appleton Laboratory in Oxfordshire has been testing thousands of solid-state compounds in search of a light, cheap, readily available material which would absorption/desorpt hydrogen rapidly and safely at typical fuel cell operating temperatures. 

In May 2007, they reported to have produced a variety of lithium hydride (specifically Li4BN3H10) that could offer the right blend of properties.
study published in April 2011 looks at using bimetallic borohydride borate, or LiCa3(BH4)(BO3)2, to store hydrogen.
The Nov/Dec issue of Technology Review contains an article about Daniel Nocera's catalyst, also describing that initial tests show that the catalyst also performs well in the presence of salt, and is now being tested to see how it handles other compounds found in the sea. If it works, Nocera's system could produce hydrogen from seawater, which could apart from provide cheap energy on demand also help solve the world's growing shortage of fresh water.
ITM Power makes a home electrolyzer that uses no platinum. According to an article in New Scientist, the home unit can be connected to mains water. ITM Power expects that with mass production it will cost about $15,000 per unit. ITM Power have also developed a fuel cell using their technology, but the fuel cell is still some time away from mass production.
We all need to pull together to facilitate the shift to clean and safe energy. As I described in the article Four Cycles of a Sustainable Economy, wind turbines can generate plenty of surplus energy that can be used to produce hydrogen.
At a meeting of the American Chemical Society, Daniel Nocera reported on his team's work on a catalyst that boosts oxygen production by 200-fold. It eliminates the need for expensive platinum catalysts and potentially toxic chemicals used in making them. Prototype water-splitting systems have been built at a cost of $30 each, operating at power levels of 100 watts

Catalysts are used inside electrolyzers to jump start chemical reactions that break water down into hydrogen and oxygen, as electricity is fed into the electrolyzer. "Owing to the self-healing properties of the catalysts, these electrolyzers can use any water source," including seawater, waste water or water from the Charles River in Boston, the researchers say

Electrolyzers can be powered by surplus electricity at off-peak times, producing hydrogen and oxygen that is stored into tanks. When needed, the stored hydrogen and oxygen can then be recombined in a fuel cell to produce electricity (and clean drinking water as a byproduct). 

The new catalyst has been licensed to Sun Catalytix, founded by Dan Nocera, to develop safe, super-efficient versions of the electrolyzer that are suitable for homes and small businesses within two years. Sun Catalytix mentions that just 3 gallons of water contains enough energy to satisfy the daily energy needs of a large American home.
A team of MIT researchers has engineered a virus to help splitting water into its two atomic components - hydrogen and oxygen - using sunlight. In plants, chlorophyll absorbs sunlight in a process called photosynthetis, while catalysts promote the water-splitting reaction. The team engineered a virus with a wire-like structure allowing the light-absorbing pigments and catalysts to line up with the right spacing to trigger the water-splitting reaction.
Sandia has for years worked on using concentrating solar power (CSP) plants to produce temperatures high enough to split water vapor into hydrogen and oxygen, and ambient carbon dioxide into carbon monoxide and oxygen. 

Sandia's work and the work at at the Swiss Federal Institute of Technology, Zurich, are described recently in New Scientist.

Producing hydrogen in this way has been done for years. In further work in Europe, a team led by Athanasios Konstandopoulos has successfully managed to split carbon dioxide into carbon monoxide and oxygen in this way

Hydrogen and carbon monoxide can subsequently be combined into hydrocarbons, i.e. synthetic oil.
At a Meeting of the American Chemical Society, a team of scientists described the artificial leaf that mimics photosynthesis, the process that plants use to convert sunlight and water into energy.

Daniel Nocera, Ph.D. described an advanced solar cell the size of a poker card but thinner. The device is fashioned from silicon, electronics and catalysts, substances that accelerate chemical reactions that otherwise would not occur, or would run slowly. Placed in a single gallon of water in a bright sunlight, the device could produce enough electricity to supply a house in a developing country with electricity for a day, Nocera said. It does so by splitting water into its two components, hydrogen and oxygen.

The hydrogen and oxygen gases would be stored in a fuel cell, which uses those two materials to produce electricity, located either on top of the house or beside it.

Nocera’s new leaf is made of inexpensive materials that are widely available, works under simple conditions and is highly stable. In laboratory studies, he showed that an artificial leaf prototype could operate continuously for at least 45 hours without a drop in activity.

The key to this breakthrough is Nocera's recent discovery of several powerful new, inexpensive catalysts, made of nickel and cobalt, that are capable of efficiently splitting water into its two components, hydrogen and oxygen, under simple conditions. Right now, Nocera’s leaf is about 10 times more efficient at carrying out photosynthesis than a natural leaf. However, he is optimistic that he can boost the efficiency of the artificial leaf much higher in the future.
paper by Daniel Nocera et al. describes devices that can split water into hydrogen and oxygen, using solar cells comprising earth-abundant elements that operate in near-neutral pH conditions, both with and without connecting wires. The cells consist of a triple junction, amorphous silicon photovoltaic interfaced to hydrogen and oxygen evolving catalysts made from an alloy of earth-abundant metals and a cobalt|borate catalyst, respectively. The devices can carry out the solar-driven water-splitting reaction at efficiencies of 4.7% for a wired configuration and 2.5% for a wireless configuration when illuminated with 1 sun of AM 1.5 simulated sunlight. Fuel-forming catalysts interfaced with light-harvesting semiconductors afford a pathway to direct solar-to-fuels conversion that captures many of the basic functional elements of a leaf.
Researchers from the Department of Chemistry at the Royal Institute of Technology in Stockholm, Sweden, have made a molecular ruthenium catalyzer that can oxidize water to oxygen at over 300 turnovers per seconds, a speed that rivals natural photosynthesis which takes place at speeds of 100 to 400 turnovers per seconds.

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