In a study published in Nature Energy, researchers led by Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) describe how nanodiamond-reinforced composite membranes can purify hydrogen from its humid mixtures, making the hydrogen generation processes more efficient and cost-effective.
This image offers an abstract visual representation of graphene oxide sheets (black layers) embedded with nanodiamonds (bright white points). The nanodiamonds exert long range electrostatic forces (nebulous white circles) which stabilize the sheets even in humid conditions creating a promising membrane material for hydrogen purification. Yasuhiro Chida (Brocken 5) and Toru Tsuji (Photograph)
There are several scalable methodologies to produce hydrogen, but hydrogen generally comes as humid mixtures and their purification is a challenge. Membrane technology allows for energy-efficient and economical separation processes. But we need to have the right membrane materials to make it work.—Professor Easan Sivaniah, who led the iCeMS team
Graphene oxide (GO), a water-soluble derivative of graphite, can be assembled to form a membrane that can be used for hydrogen purification. Hydrogen gas easily passes through these filters, while larger molecules get stuck.
Hydrogen is typically separated from CO2 or O2 in very humid conditions. GO sheets are negatively charged, which causes them to repel each other. When exposed to humidity, the negatively charged sheets repel each other even more, allowing water molecules to accumulate in the spaces between the GO sheets, which eventually dissolves the membrane.
Dr Behnam Ghalei, who co-supervised the research, explained that adding nanodiamonds to the GO sheets resolves the humidity-induced disintegration problem.
Positively charged nanodiamonds can cancel out the membrane’s negative repulsions, making the GO sheets more compact and water-resistant.—Dr Behnam Ghalei
The team also included other research groups from Japan and abroad. The researchers at Japan Synchrotron Radiation Research Institute (SPring-8 / JASRI) conducted advanced X-ray studies. The Institute for Quantum Life Science (QST) helped with materials development. ShanghaiTech University (China) and National Central University (Taiwan) were involved in state-of-the-art materials characterizations.
Sivaniah says that nanodiamonds have potential uses beyond hydrogen production. Humidity control is also vital in a number of other fields, including pharmaceuticals, semiconductors, and lithium-ion battery production. Membrane technology could also revolutionize air conditioning by efficiently removing humidity. Air conditioners are among the most inefficient ways to cool, as a significant amount of the electricity used to power them is used to remove humidity, generating more CO2 emissions.
Sivaniah is the founder of OOYOO, a start-up which aims to be instrumental in commercializing membrane technology for a zero-carbon future.
In November, OOYOO signed a memorandum of understanding (MOU) with CAPTICO2, a company formed in Norway in January 2020 with the purpose of developing and commercializing high-capacity and cost-effective Carbon Capture, Utilization and Storage (CCUS) modules.
Under the agreement, OOYOO and CAPTICO2 will explore opportunities to capture and convert up to 99% of the CO2 emission from the shipping industry.
Huang, G., Ghalei, B., Pournaghshband Isfahani, A. et al. (2021) “Overcoming humidity-induced swelling of graphene oxide-based hydrogen membranes using charge-compensating nanodiamonds.” Nat Energy 6, 1176–1187 doi: 10.1038/s41560-021-00946-y