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Cara: Hi, I’m Cara. I’m a material scientist working at CSIRO Manufacturing.
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I look at porous materials for a range of applications for the environment.
CSIRO and Hanyang University have been collaborating together for about ten years now, looking at the porosity at the molecular level in membranes.
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So these membranes are inspired by the cactus, where in hot, arid conditions the cracks on the surface actually close up to prevent the water from evaporating out.
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And then in cooler conditions the cracks actually open up so that the water can enter into the membranes and hydrate them.
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So here at CSIRO we were able to characterise these membranes and investigate these small pore sizes to tailor the materials for a range of applications, such as in fuel cells, where they need to be working at high temperatures and in dry conditions.
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So by optimising the membrane we can potentially use these fuel cells in cars of the future.
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Aaron: Hi, I’m Aaron. I’m a mathematician here at CSIRO, and I was able to model these membranes to explain why they perform so well.
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We were able to probe the pore size as well as develop the modelling to understand how water transports through these pores so that the fuel cells can remain hydrated in drier conditions.
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Fuel cells are a promising technology for the future of the car industry.
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One of the technical challenges preventing fuel cell powered vehicles entering the market is that the fuel cells don’t last very long because they dry out.
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These membranes are able to self humidify the fuel cells so that you don’t need a humidifier onboard, and so that they’re less expensive and they last a lot longer.
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They also increase the performance up to fourfold.
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Cara: The technique that we use, we can measure the size and the number of pores at the molecular level to optimise these materials. And this can only be done in a handful of labs around the world.
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The membrane, developed by scientists from CSIRO and Hanyang University in Korea, was described today in the journal Nature. The paper shows that in hot conditions the membrane, which features a water repellent skin, can improve the efficiency of fuel cells by a factor of four.
According to CSIRO researcher and co-author Dr Aaron Thornton, the skin works in a similar way to a cactus plant, which thrives by retaining water in harsh and arid environments.
“Fuel cells, like the ones used in electric vehicles, generate energy by mixing together simple gases, like hydrogen and oxygen. However, in order to maintain performance, proton exchange membrane fuel cells – or PEMFCs – need to stay constantly hydrated,” Dr Thornton said.
“At the moment this is achieved by placing the cells alongside a radiator, water reservoir and a humidifier. The downside is that when used in a vehicle, these occupy a large amount of space and consume significant power,” he said.
According to CSIRO researcher and co-author Dr Cara Doherty, the team’s new cactus-inspired solution offers an alternative.
“A cactus plant has tiny cracks, called stomatal pores, which open at night when it is cool and humid, and close during the day when the conditions are hot and arid. This helps it retain water,” Dr Doherty said.
“This membrane works in a similar way. Water is generated by an electrochemical reaction, which is then regulated through nano-cracks within the skin. The cracks widen when exposed to humidifying conditions, and close up when it is drier.
“This means that fuel cells can remain hydrated without the need for bulky external humidifier equipment. We also found that the skin made the fuel cells up to four times as efficient in hot and dry conditions,” she said.
Professor Young Moo Lee from Hanyang University, who led the research, said that this could have major implications for many industries, including the development of electric vehicles.
“At the moment, one of the main barriers to the uptake of fuel cell electric vehicles is water management and heat management in fuel cell systems. This research addresses this hurdle, bringing us a step closer to fuel cell electric vehicles being more widely available.
“This technique could also be applied to other existing technologies that require hydrated membranes, including devices for water treatment and gas separation,” he said.
The cross-continent team has been working together for over ten years. For this study, Hanyang University conceived and designed the experiments. Using characterisation and modelling expertise, CSIRO researchers were then able to determine how the membranes behaved under changing humidities.
