Energy from the Field

Interdisciplinary development at the Technion: a cell that uses sunlight to produce electricity and hydrogen from spinach leaves

Technion researchers have developed an innovative cell that produces electricity and hydrogen from water using sunlight – the journal Nature Communications reports. The bio-photo-electro-chemical (BPEC) device is based on membranes from spinach leaves. The raw material of the device is water, and its products are electric current, hydrogen and oxygen.

The cell developed by the researchers is based on the system of photosynthesis in plants, which was developed and improved over millions of years by the forces of evolution, and led to the creation of life on Earth. This system breaks down water molecules into oxygen and protons, which are used to create ATP molecules, the basic energy carriers in the animal and plant worlds (the cell’s “fuel”).

Photosynthesis occurs naturally in plant membranes. In order to utilize it for producing electric current, the researchers added iron ions to the solution. Iron ions mediate the transfer of electrons from the membranes to the electrical circuit, enabling the creation of an electric current in the cell.

Alternatively, the electric current can be channeled to form hydrogen gas through the addition of electric power from a rear photovoltaic cell. Thus it is possible to convert solar energy into chemical energy that is stored in the hydrogen gas formed inside the cell. This energy can be converted when necessary into heat and electricity by burning the hydrogen, like burning hydrocarbon fuel; However, unlike the combustion of hydrocarbon fuels, which emits greenhouse gases (carbon dioxide) into the atmosphere and pollutes the environment, the product of hydrogen combustion is clean water. Therefore, this is a closed cycle that begins with water and ends with water, allowing the conversion and storage of solar energy in hydrogen gas, which could be a clean and sustainable substitute for hydrocarbon fuel.

The unique combination of a man-made photovoltaic cell and plant membranes, which absorb sunlight and convert it into to a flow of electrons highly efficiently, paves the way for the development of new technologies for the creation of clean green synthetic fuels from renewable sources: water and solar energy.

The study was conducted by doctoral students Roy I.  Pinhassi, Dan Kallmann and Gadiel Saper, under the guidance of Prof. Noam Adir of the Schulich Faculty of Chemistry, Prof. Gadi Schuster of the Faculty of Biology and Prof. Avner Rothschild of the Faculty of Material Science and Engineering. Prof. Rothschild said: “The study is unique in that it combines leading experts from three different faculties, namely three disciplines: biology, chemistry and materials engineering. The combination of natural (leaves) and artificial (photovoltaic cell and electronic components), and the need to make these components communicate with each other, are complex engineering challenges that required us to join forces.”

The study was conducted at the Nancy and Stephen Grand Technion Energy Program and carried out at the Technion’s hydrogen lab, which was established under the auspices of the Adlis Foundation and the Energy Program. It was funded by the I-CORE (Israeli Centers of Research Excellence) program of the Council for Higher Education’s Planning and Budgeting Committee, the National Science Foundation (Grant No. 152/11), a special grant from the United States – Israel Binational Science Foundation (BSF), and the German-Israeli Project Cooperation Program (DIP).

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Figure: Schematic description of the bio-photo-electro-chemical cell

The study was published in the journal- Nature Communications-

http://dx.doi.org/10.1038/NCOMMS12552