Cactus membranes address prickly problem

A new type of membrane, inspired by the cactus plant, could significantly boost fuel cell performance.

The Challenge

Keeping fuel cells hydrated

One of the main barriers to the uptake of fuel cell electric vehicles is water management and heat management in fuel cell systems.

Inspired by the humble cactus, a new type of membrane has the potential to significantly boost the performance of fuel cells and transform the electric vehicle industry. © CSIRO, Jesse Hawley

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 their performance, proton exchange membrane fuel cells – or PEMFCs – need to stay constantly hydrated.

This is currently achieved by placing the cells alongside a radiator, water reservoir and a humidifier, but these extra components occupy a large amount of space in a vehicle and consume significant power.

Our Response

New cactus-inspired solution offers an alternative

To solve this issue, our scientists teamed up with Hanyang University in Korea, and looked to the cactus plant for inspiration.

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.

The team developed a membrane that 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, meaning 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.

The Results

Hydrated membranes

Cactus inspired membranes

Show transcript

[Music plays, CSIRO logo appears on bottom right hand corner of screen, and text appears:  Cactus-inspired skin gives fuel cells a boost]  

[Image changes to show various images of cactus growing in a field] 

[Image changes to show Cara] 

Cara:  Hi, I’m Cara.  I’m a material scientist working at CSIRO Manufacturing. 

[Image changes to show Cara working in a laboratory] 

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. 

[Image changes back to Cara] 

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. 

[Image changes to show various images of cactus growing in a field] 

And then in cooler conditions the cracks actually open up so that the water can enter into the membranes and hydrate them. 

[Image changes back to Cara] 

[Image changes to show Cara working in a laboratory] 

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. 

[Image changes back to Cara] 

So by optimising the membrane we can potentially use these fuel cells in cars of the future. 

[Image changes to show a car driving along a road] 

[Image changes to show Aaron] 

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. 

[Image changes to show cactus growing in a field] 

[Image changes to show Aaron writing a formula on a board] 

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. 

[Image changes back to Aaron] 

Fuel cells are a promising technology for the future of the car industry. 

[Image changes to show various images of cars driving along a highway] 

[Image changes back to Aaron] 

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. 

[Image changes to show cactus growing in a field] 

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. 

[Image changes back to Aaron] 

They also increase the performance up to fourfold. 

[Image changes back to Cara] 

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. 

[CSIRO logo appears with text: Big ideas start here]  

Hide transcript

This research addresses the hurdle of fuel cell hydration and brings us a step closer to fuel cell electric vehicles being more widely available.

The technique could also be applied to other existing technologies that require hydrated membranes, including devices for water treatment and gas separation.

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 humidity. The cross-continent team has been working together for over ten years.


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