Hydrogen purification can be simplified by using a pump equipped with membrane materials developed by Chris Arges, an associate professor of chemical engineering at Penn State.
For the first time, researchers have achieved a recovery rate of 98.8% from a conventional water-cooled water gas shift reactor’s exit stream of 98.8% hydrogen, which is the highest value ever recorded. In ACS Energy Letters, the team explained their strategy in detail.
A water gas shift reactor is used in traditional hydrogen separation methods, which necessitates an additional step. Carbon monoxide is first converted to carbon dioxide in the water gas shift reactor, and then an absorption process is used to separate the hydrogen from the carbon dioxide. For immediate use or storage, a compressor is used to pressurize the purified hydrogen.
In order to quickly and economically separate hydrogen from other gas molecules like carbon dioxide and carbon monoxide, it is necessary to use high-temperature proton-selective polymer electrolyte membranes, or PEMs. Using Arges’ PEM and other newly developed materials, the electrochemical pump separates and compresses hydrogen from gas mixtures, making it more efficient than traditional methods. It is also capable of operating at higher temperatures than other high-temperature-PEM-type electrochemical pumps, which enhances its ability to separate hydrogen from the unwanted gasses.
The team used an electrode “sandwich,” in which electrodes with opposing charges form the “bread” and a membrane serves as the “deli meat,” to accomplish the separation. The electrode ionomer binder materials, like the gluten in bread, are designed to hold the electrodes together.
Protons and electrons are released from the hydrogen as a result of the bread slice, or positively charged electrode, in the pump. The electrons travel through the pump via a wire that touches a positively charged electrode while the protons travel through the membrane. There, the protons and electrons combine to form hydrogen again after they travel through the membrane toward the negatively charged electrode.
Carbon monoxide, carbon dioxide, methane and nitrogen gas cannot pass through the PEM because it only allows protons to pass through. An adhesive phosphonic acid ionomer binder was developed by the team to hold electrode particles together in the hydrogen pump so they could function properly.
Hydrogen purification in natural gas pipelines will be investigated by researchers using their approach and tools. This method of transporting and storing hydrogen has yet to be successfully implemented, but it holds great promise. Using a fuel cell or turbine generator, hydrogen could help support solar or wind energy systems and a variety of more environmentally friendly applications.
The Office of Energy Efficiency and Renewable Energy at the U.S. Department of Energy provided the funding for this project.
