A system developed at the Technion shows unprecedented efficiency in producing hydrogen from water using solar energy
The journal Nano Letters reports on a dramatic turn in the field of hydrogen fuel production: 100% efficiency in the production process. The breakthrough took place in the laboratory of Associate Professor Lilach Amirav from the Shulich Faculty of Chemistry, and its essence: a significant jump from 60% to 100% - in the production of hydrogen fuel by breaking down water using solar energy.
Hydrogen fuel is considered a promising energy source mainly because it is produced from water, which is always available, and therefore does not involve the political and economic problems that characterize the traditional energy market; And because, unlike fossil fuels (gasoline, etc.), its use is non-polluting. This is why the US alone invests billions of dollars in programs such as the Hydrogen Fuel Initiative, which encourage the development of hydrogen production technologies. Furthermore, these photocatalytic processes, in which water is broken down into hydrogen and oxygen, are also relevant to other areas, including energy conversion and wastewater purification.
However, many constraints make it difficult to develop efficient photocatalysis processes that meet the following basic conditions: optimal absorption of solar radiation by the catalytic material; Effective decomposition of the water into oxygen and hydrogen without meeting them (which may lead to an explosion), and stability of the system so that it does not lose its effectiveness over time.
Now, as mentioned, the journal Nano Letters reports on a breakthrough achieved in the laboratory of Associate Professor Lilach Amirav, a faculty member in the Shulich Faculty of Chemistry and a member of the Russell Berry Nanotechnology Institute and the Grand Energy Program at the Technion. While most of the research effort in the world is done on the empirical path - trial and error with different materials and testing their effectiveness - in the laboratory of Prof. Mishna Amirav, catalytic materials are developed based on a precise characterization of the material at the individual particle level. This is how advanced artificial materials have been developed over the years that are optimally suited to the photocatalytic task. The new system presented in the current article proves that the effort paid off; This system, centered on a nanometer photocatalyst operating in a very basic environment, breaks all previous conventions regarding maximum utilization and produces 360,000 moles of hydrogen per hour per mole of catalyst.
The system is built from two semiconductors, arranged as a tiny nanometer particle (quantum dot) of one material, planted asymmetrically inside the other material which is shaped like a nanometer rod, and at the end of the rod is a platinum particle. The quantum dot has the ability to attract and store positive charges. When the system is immersed in water and exposed to sunlight, the nanorod absorbs photons (light) and releases charges. The electrons (negative charge) accumulate in the platinum particle, while the positive charges accumulate in the quantum dot. The physical separation between these charges is the key to the success of the system. The electrons are responsible for redox, the reaction that produces hydrogen from water. When a water molecule breaks, a positively charged hydrogen ion is released. When two such ions react with two electrons, on top of the platinum, they join together to form a hydrogen molecule. The efficiency of the result, as mentioned, is 100% efficiency in this process, which means that every two photons created a hydrogen molecule, without losses, a goal that was considered impossible to achieve until now.