A collaboration of researchers from various institutes in China has developed a novel approach that allows proton exchange membrane (PEM) electrolyzers to work with impure water, thereby helping reduce costs and allowing easier deployment of infrastructure in real-world settings.
This opens up larger possibilities of applications and increases sustainable approaches to meeting our energy demands.
As countries shifted their focus to cleaner sources of energy to fuel their economies, the solar and wind power sectors got a major boost. While electricity generated using these sources is clean and sustainable, it cannot meet high-power applications like heavy vehicles or supply backup power to data centers or hospitals.
Hydrogen generated by splitting water molecules can be used in fuel cells to generate high power electricity without combustion. This is achieved through electrolyzers, where water is electrolyzed into hydrogen (H2) and oxygen (O2) molecules. The process called electrolysis can be made greener by using energy from a wind or solar power plant as well. But the technology isn’t easily deployable.
Hurdles with electrolyzers
Electrolysis technologies have been around for centuries, but it is only in recent years that attempts are being made to use them to produce hydrogen. Alkaline electrolyzers are the most popular approach used and are widely deployed. However, in hydrogen production, the purity of the final product is not close to what is needed for a fuel cell.
Proton Exchange Membrane (PEM) electrolyzers offer better purity hydrogen since they only allow protons (H+ ions) to pass through them while blocking other gases. The purer hydrogen yield also comes at a higher cost since PEMs require ultrapure water to work. Impurities like differently charged ions or contaminants can rapidly degrade the PEM infrastructure.
Researchers at Tianjin University and other institutes in China came up with a novel approach to creating an acidic microenvironment in PEM electrolyzers that allows them to work even with impure water.
“Developing PEM electrolyzers that can withstand lower-purity water could minimize water pretreatment, lower maintenance costs, and extend system lifetime,” the researchers wrote in their research paper.
Creating acidic microenvironments
The researchers added Bronsted acid oxide (MoO3-x) to the PEM’s cathode made from platinum and carbon to achieve this. The acid oxide works as a catalyst during the electrolysis reaction and helps lower the pH locally, thereby increasing the performance of the electrolyzer.
This was confirmed using technologies that combined pH ultramicroelectrode with scanning electrochemical microscopy and confirmed that the PEM did not degrade rapidly even when using impure water.
“PEM electrolyzers typically use ultrapure water as a feedstock because trace contaminants in feedwater, especially cationic impurities, can cause their failure,” the researchers added in their paper.
Using their approach, where the electrode’s microenvironment is pH-regulated, the researchers successfully operated the PEM electrolyzer with tap water for more than 3,000 hours at a current density of 1.0 A per sq. cm. The performance was comparable to state-of-the-art PEM electrolyzers that work with ultrapure water, the researchers claimed.
The research opens up possibilities for wider deployment of PEM electrolyzers to produce green hydrogen at lower costs in the future.
The research findings were published in the journal Nature Energy.
