Nanotechnology

Extracts clean fuel from water

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May 30, 2023

(Nanowerk News) An abundant supply of clean energy lurks in plain sight. It is hydrogen that we can extract from water (H2O) using renewable energy. Scientists are looking for low-cost methods to produce clean hydrogen from water to replace fossil fuels, as part of efforts to fight climate change.

Hydrogen can propel vehicles while emitting nothing but water. Hydrogen is also an important chemical for many industrial processes, especially in steelmaking and ammonia production. Using cleaner hydrogen is highly desirable in the industry.

A multi-agency team led by Argonne National Laboratory has developed a low-cost catalyst for a process that produces clean hydrogen from water. Other contributors include DOE’s Sandia National Laboratories and Lawrence Berkeley National Laboratory, and Giner Inc.

This research was published in Science (“La and Mn doped cobalt spinel oxygen evolution catalyst for proton exchange membrane electrolysis”). Oxygen bubbles evolve from the fibers, the interconnected catalyst particles (right) during the electrocatalytic reaction with water.  The lattice structure for the cobalt-based catalyst is on the left. Oxygen bubbles evolve from the fibers, the interconnected catalyst particles (right) during the electrocatalytic reaction with water. The lattice structure for the cobalt-based catalyst is on the left. (Image: Argonne National Laboratory/Lina Chong and Longsheng Wu using Shutterstock background)

“A process called electrolysis produces hydrogen and oxygen from water and has been around for more than a century,” said Di-Jia Liu, senior chemist at Argonne. He also holds joint appointments at the Pritzker School of Molecular Engineering at the University of Chicago.

The proton exchange membrane electrolyzer (PEM) represents a new generation of technology for this process. They can split water into hydrogen and oxygen with higher efficiency near room temperature. Reduced energy demand makes it an ideal choice for producing clean hydrogen using renewable but intermittent sources, such as solar and wind.

This electrolyzer runs with a separate catalyst for each of its electrodes (cathode and anode). The cathode catalyst produces hydrogen, while the anode catalyst forms oxygen. The problem is that the anode catalyst uses iridium, which has a current market price of around $5,000 per ounce. Insufficient supply and high cost of iridium pose major barriers to the widespread adoption of PEM electrolyzers.

The main ingredient of this new catalyst is cobalt, which is much cheaper than iridium. “We are trying to develop a low-cost anode catalyst in a PEM electrolyzer that generates hydrogen at a high output while consuming minimal energy,” said Liu. “By using the cobalt-based catalyst prepared by our method, one can remove the major cost barrier to producing clean hydrogen in electrolyzers.”

Giner Inc., a leading research and development company working towards the commercialization of electrolyzers and fuel cells, evaluated the new catalyst using a PEM electrolyzer test station under industrial operating conditions. Performance and durability far outperform competitors’ catalysts.

Crucial to advancing catalyst performance further is understanding the reaction mechanism on the atomic scale under electrolyzer operating conditions. The team deciphered the critical structural changes that occur to the catalyst under operating conditions using X-ray analysis at the Advanced Photon Source (APS) at Argonne. They also identified key catalyst features using electron microscopy at Sandia Labs and at Argonne’s Center for Nanoscale Materials (CNM). APS and CNM are both user facilities of the DOE Office of Science.

“We imaged the atomic structure on the surface of the new catalyst at various stages of preparation,” said Jianguo Wen, materials scientist at Argonne.

In addition, computational modeling at the Berkeley Lab reveals important insights about the durability of catalysts under reaction conditions.

The team’s achievement is another step forward in DOE’s Hydrogen Energy Earthshot initiative, modeled on the US space program’s “Moon Shot” of the 1960s. Its ambitious goal is to bring down the cost of producing green hydrogen to one dollar per kilogram within a decade. Green hydrogen production at that cost could reshape the country’s economy. Applications include power grids, manufacturing, transportation and residential and commercial heating.

“More generally, our results set a promising path forward in replacing catalysts made of expensive precious metals with much cheaper and more abundant elements,” Liu notes.



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