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A MIT researcher has demonstrated a reaction which resembles the photosynthesis process that plants make each day which means that from now on solar power could be deployed at world scale. Using catalysts developed by the chemist, he showed a video where oxygen was generated from water, just like plants do it in photosynthesis.
“I’m going to show you something I haven’t showed anybody yet,” said Daniel Nocera, the MIT chemist. After the lights were tuned off, he pointed to the video and asked – “Can you see that?” Then he explained – “Oxygen is pouring off of this electrode. This is the future. We’ve got the leaf.” This means that the most difficult obstacle was overcame as from now on we efficiently produce hydrogen gas by splitting water thanks to his catalysts.
This is very important as solar power could be deployed at worldwide and it could remove our dependence on fossil fuels. Solar power cannot replace oil with solar panels as solar cells are not very efficient and the sun doesn’t shine all day long. All this can change now, and we could use the catalysts and light to split water to generate hydrogen fuel which could power our cars. Also, according to Nocera, the catalysts could split seawater and if the hydrogen will be processed in a fuel cell then it will produce fresh water.
During recent history many scientists tried to get energy from the sun by resembling photosynthesis and their attempts were successful. The problem is that this process requires high temperatures, expensive catalysts, and harsh alkaline solutions, so it cannot be deployed at world-scale. Well, this will change as Nocera’s catalysts are cheap and they split water in oxygen and hydrogen at room temperature.
According to Nocera, this process could be used in two ways – one would use solar panels to capture the light coming from the sun and the electricity that will be generated will power an electrolyzer which will split water thanks to these new and cheap catalysts. The other way would require a system that resembles a leaf as the catalysts will be positioned near dye molecules. How will this work? Well, the dye molecules will capture the sunlight and then the catalysts will do their job and split the water to get hydrogen for a later use.
Although there were many scientists and chemists who questioned Nocera’s catalysts, he is very confident of the success of his system.
“With this discovery, I totally change the dialogue. All of the old arguments go out the window,” explained Nocera.
For the moment, solar power provides only 1 percent of the energy demand in the US and if the demand will grow up to 10 percent then utility companies will have to do something when the sun doesn’t shine. According to Ryan Wiser, scientist at the Lawrence Berkeley National Laboratory in Berkeley, CA, utilities could invest a lot of money in energy storage, however, the companies also have a cheaper option in developing natural gas plants that will replace solar power when it’s not available.
“Electrical storage is just too expensive,” concluded Wiser.
The situation changes when we talk about 20 percent of the energy demand as then solar power will contribute to the base load power which is the amount of power required for the minimum energy demand. For the moment, the base load power is supplied by coal power plants. In order to replace coal, solar power needs to be harnessed 24/7 even if the weather is cloudy. As the sun doesn’t shine 24 hours a day, solar power cannot become the most important source of energy in the country.
Another problem is that the solar power-generated electricity cannot be stored efficiently. A good comparison was made by Nathan Lewis from Caltech who said that one kilogram of water pumped uphill, then sent through a turbine would store one kilojoule of energy, meanwhile one kilogram of oil stores 45,000 kilojoules. Lewis added that batteries are also expensive and very inefficient as they store 300 watts per kilogram, meanwhile oil stores 13,000 watts per kilogram.
“The numbers make it obvious that chemical fuels are the only energy-dense way to obtain massive energy storage,” concluded Lewis.
Nocera began studying the process of photosynthesis as of 1984, however, he didn’t start to mimic the process right away. This happened in 2004 when chemists from the Imperial College London discovered a very important protein which was responsible for the release of oxygen from water.
“As soon as we saw this, we could start designing systems,” said Nocera.
In order to fully understand the process, Nocera tried a very different approach – he reversed the reaction and combined oxygen with electrons and protons to get water and he noticed that cobalt-based compounds were the best catalysts so he used them to also split water. When these catalysts failed, he said “let’s forget all the elaborate stuff and just use cobalt directly.”
Nocera was surprised to see that the cobalt worked so good and the success of the experiment made him realize how lucky he was.
“There was no reason for us to expect that just plain cobalt with phosphate, versus cobalt being tied up in one of our complexes, would work this well. I couldn’t have predicted it. The stuff that was falling out of the compounds turned out to be what we needed,” admitted the chemist.
However, Nocera was intrigued by the fact that cobalt worked so well and he wanted to understand why.
“I want to know why the hell cobalt in this thin film is so active. I may be able to improve it or use a different metal that’s better. We were really interested in the basic science. Can we make a catalyst that works efficiently under the conditions of photosynthesis? The answer now is yes, we can do that. Now we’ve really got to get to the technology of designing a cell.”
Despite Nocera’s scientific proof, many scientists questioned his discovery and they said it’s overrated. Even Nocera’s mentor, Thomas Meyer said that “the claim that this is the answer for artificial photosynthesis is crazy” because there is “no guarantee that it can be scaled up or even made practical” and he also added that this is only a “research finding” rather than a breakthrough.
Nocera was also chaffed by John Turner, a researcher at the National Renewable Energy Laboratory in Golden, CO who said that “at least what he’s published so far would never work for a commercial electrolyzer, where the current density is 800 times to 2,000 times greater.” Another fellow researcher who questioned Nocera’s finding, was Ryan Wise who said that “electrolysis is inefficient, so why would you do it?”
One of the scientists who believed in Nocera’s discovery was Michael Grätzel, chemistry and chemical engineering professor at the École Polytechnique Fédérale in Lausanne, Switzerland. Grätzel said that Nocera was very excited and that “he took me to a restaurant and bought a tremendously expensive bottle of wine.”
Grätzel says that he has a way to make Nocera’s discovery practical as in 1991 he developed a futuristic solar cell where the electrons were collected by a titanium-oxide film to generate electricity, instead of setting them off during the electrolysis. Using his cell and Nocera’s catalysts, Grätzel believes that he develop an artificial leaf that would capture sunlight and split water in a process that resembles photosynthesis.
Nocera is very confident that soon we will “make fuels from a glass of water.” Although most of the scientists today don’t agree with Nocera, from where I’m looking this could be possible. Hopefully, the MIT chemist will manage to find a practical use for his catalysts and solar power will replace fossil fuels.