Today, pure hydrogen (or H2) is a major chemical product derived generally from natural gas. Tens of millions of tons of hydrogen are produced each year; industrial hydrogen is important in petroleum refining and the production of fertilizers.
Thomas Jaramillo, professor of chemical engineering and associate researcher Jakob Kibsgaard want to use electrolysis to produce H2 from water and, in this process, store solar energy, all shown on the University website.
Electrolysis learned in school is simple: introduce two metal electrodes in water, and when electricity is passed through these electrodes, they as a catalyst, transforming the molecules in water in bubbles of hydrogen and oxygen gas.
Platinum is the best catalyst for hydrogen production by water electrolysis. But to do electrolysis industrially to be found first electrode cheaper. "We tried to make pure hydrogen in the most efficient way possible without using precious metals," said Jaramillo.
In the German scientific journal – Angewandte Chemie, Jaramillo and Kibsgaard describe a inexpensive catalyst, durable and effective, which could take the platinum place.
Their ambitions go beyond just using electrolysis to replace current market demand of hydrogen.
Currently, there is no effective way to store solar energy on a large scale. Researchers at Stanford believe that electrolysis could turn water tanks in batteries for storing solar energy.
During the daytime, electricity from solar cells may be used to convert water into hydrogen and oxygen, and the recombination of these gases would generate electricity that may be used during the night.
Electrolysis uses electricity to separate forming chemical bonds with water.
Separation of chemical bonds of water produces a hydrogen ion – a proton with an electron to balance it. A good H2proton catalyst give space to stick until it joins with an electron to form a hydrogen on the catalyst surface, and later to merge with a neighboring hydrogen atom, forming eventually pure hydrogen.
The secret is to find a catalyst with a good viscosity.
"If the binding is too weak, the ions do not stick," says Thomas Jaramillo. "And if the binding is too strong, they are not free."
Platinum is perfect, but expensive. Last year, engineers have discovered that an alternative Stanford molybdenum sulphide, a catalyst widely used in petrochemical processing, some of the sulfide with the appropriate properties to serve as a cheap solution, but effective.
The teacher explained that petrochemical processing has similarities with electrolysis. That's because oil feed stocks such as oil sands contain a significant proportion of heavy molecules. Oil refineries use of catalytic reactions involving hydrogen to separate the heavy molecules into lighter molecules, such as gasoline.
Similarly, electrolysis involves the separation of molecules of water or breakage of chemical bonds thereof. As the engineers at Stanford have tried to improve their discovery, they found a better way to produce hydrogen from water inspiration from the petrochemical industry.
Oil processing often involves cleaning sulfur from fuels to reduce acid rain. During this cleaning process, a portion of the sulfur atoms are incorporated in the composition of the catalysts involved in the processing of petroleum, increasing the activity of these catalysts.
Thus, engineers have been added to the sulfur atom of molybdenum phosphide called a catalyst known to speed up the production property of hydrogen.
Adding sulfur atom created a new catalyst – molybdenum phosphosulfide, which was more effective at producing hydrogen than its predecessor.
The new catalyst is more durable, extremely important quality in an industrial process in which the electrode must work out daily without spoiling, like platinum.
Catalysts developed by Kibsgaard and Jaramillo have a major advantage. As the electrodes are very stable, with a yield close to that of platinum.
Now, the research team is trying to improve the new catalyst. For example, want to bring metal to small, nano-scale to efficiently catalyze the reaction.
Other initiatives include its integration into prototypes for future energy storage systems. The idea would be to use electrolysis of water to store solar energy during the day, as pure hydrogen and then, at night, to recombine hydrogen and oxygen into water, producing electricity in this process.
Jaramillo said the preliminary results of the experiment and scientific paper can be implemented in clean energy strategies, but they are based on ideas borrowed from the petrochemical industry.
"It is interesting to make such connections between these areas totally different," concludes Professor.
