­New Process Cuts Costs of Green Hydrogen

Hydrogen has often been suggested as a way to fill in the gaps in renewable generation and even replace fossil fuels in some applications, for example, heavy industrial plant and in aircraft. However, the techniques we currently use for extracting hydrogen tend to be as environmentally unfriendly as the fossil fuels that it replaces. The most common method of extracting hydrogen today is by steam-methane reforming to separate hydrogen atoms from carbon atoms in methane (CH4). This requires high temperature steam to react with methane in the presence of a catalyst to produce hydrogen, carbon monoxide, and carbon dioxide (CO2). The methane can come from natural gas, or biogas. The method of heating the steam also usually relies on using fossil fuels being used to create the high temperatures.

A much better way of extracting hydrogen would be to use renewable energy to separate the hydrogen and oxygen in water. This ‘green hydrogen’ extraction method is much cleaner as it doesn’t release carbon like the steam-methane process, and no fossil fuels would be burned in its generation. However, actually getting sustainable hydrogen to market has been a tough task, especially as steam-methane extraction is normally done in refineries, where methane is a by-product and the natural fuel gas is basically free. Nevertheless, that’s not stopped researchers from trying to solve the problem, after all renewable energy is cheap and water can be found in many places. One of the technological challenges that is holding back green hydrogen is the requirement for expensive membranes, gaskets and sealing components to separate the cathodic and anodic compartments.

The latest group to make the attempt are researchers from Israel’s Technion Faculty of Materials Science and Engineering. They claim that their new technology has significant advantages compared to other processes for producing green hydrogen, and its development could reduce costs and accelerate its use. Several years ago, researchers from the same facility developed the E-TAC electrolysis technique that doesn’t require a membrane and sealing to separate the anode and cathode, since the hydrogen and the oxygen are produced at different stages of the process.

Now, a new group under one of the original supervisors, Prof. Rothschild has developed a new process where hydrogen and oxygen are produced simultaneously in two separate cells, unlike E-TAC where they are produced in the same cell but at different stages. The new process was developed by Ilia Slobodkin, with the help of Senior Researcher Dr. Elena Davydova and Dr. Anna Breytus and master’s student Matan Sananis.

In the new research, the solid electrode the oxygen is produced in the E-TAC technique is replaced by NaBr aqueous electrolyte in water. This allows a continuous process (as opposed to a E-TAC’s batch process) and gets rid of the need to swing cold and hot electrolytes alternately through the cell. The bromide anions are oxidized to bromate while producing hydrogen in a cathode, and they then flow with the aqueous electrolyte to a different cell, where they are turned back into their original state while at the same time producing oxygen. Hydrogen and oxygen are produced at the same time in two separate cells in a continuous process without temperature change. The oxygen is produced in the aqueous electrolyte and not in a solid electrode as used in E-TAC. It is therefore not dependent on the rate and capacity limitations typical of those types of electrodes.

The findings of the research were published in Nature Materials, where the researchers describe their basic experiments which prove the preliminary feasibility of the process, and present results that demonstrate its high efficiency and ability to work at high electric current.

https://materials.technion.ac.il/en/faculty/