It sounds like a magic trick: you put a special device in contact with air, let sunlight fall on it, and it produces free fuel. Yet this is the basic idea of researcher Mihalis Tsampas (NWO Institute DIFFER - Dutch Institute for Fundamental Energy Research) in collaboration with Toyota Motor Europe (TME).

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The research partners want to develop a system that absorbs water vapor and uses solar energy to subsequently split that vapor into hydrogen and oxygen. The research project is made possible by a grant from the NWO ENW PPS fund

Common goals

In this project, DIFFER and Toyota explore an innovative way to produce hydrogen directly from humid air. The motivation for this research project is twofold. We need new sustainable fuels to reduce both our dependence on fossil fuels as well as greenhouse gas emissions. One of these sustainable fuels is hydrogen, which can be used to store solar energy directly. If you combine hydrogen with oxygen, energy is released in the form of electricity while the only byproduct is clean water.

In their search for solutions, Toyota stumbled upon DIFFER's Catalytic and Electrochemical Processes for Energy Applications group, led by Mihalis Tsampas. The group worked on a method to split water in its vapor phase, which occurs much more frequently than its liquid phase. Working with gas instead of liquid has several advantages explains Tsampas. There are a few technical problems with liquids, such as undesired bubbles, also there is no need for expensive installations to purify the water by using water in the gaseous phase instead of the liquid phase. And finally by using the water that is present in the surrounding air, their technology can also be used in remote places where no water is available.

Proven principle

Over the past year, DIFFER and Toyota have already demonstrated in a joint feasibility study that the intended principle does indeed work. The researchers developed a new solid photoelectrochemical cell that was able to first capture water from ambient air and then produce hydrogen under the influence of sunlight. This first prototype immediately took 60 to 70 percent of the amount of hydrogen you can make from liquid water. The system is a membrane reactor in which polymer electrolyte membranes, porous photoelectrodes and materials that absorb water are combined.

Toyota’s approach

According to Isotta Cerri (General Manager, Advanced Material Research), Toyota is actively contributing to ways to produce hydrogen without fossil fuels with their pioneering work on the first mass-produced sedan on hydrogen. It fits within the Toyota Environmental Challenge 2050, in which they aim for zero CO2 emissions during all life phases of their vehicles. Hydrogen from sustainable sources significantly helps to reduce greenhouse gas emissions With this kind of fundamental research, they work towards a society where affordable, easy-to-use hydrogen technology is available for their own activities as well as for their customers.

Improving and scaling up

In the new project, partners will significantly improve their existing system. Tsampas explains that in their first prototype they used model photo electrodes, that are known to be very stable. But the material they used only absorbs UV light which accounts for less than five percent of all the sunlight that reaches the earth. In a next step the researchers will use more innovative materials and optimize the system architecture to increase both the water intake and the amount of sunlight absorbed.

Once that hurdle has been taken, the focus shifts to scaling up the technology. The current photoelectrochemical cells for hydrogen production are very small, approximately a square centimeter. In order to be economically viable their size must be scaled up at least two to three orders of magnitude.

Tsampas expects that in the end you will see these types of systems in homes where they produce the hydrogen needed to fuel a car for daily commute.

Further reading: NWO press release / DIFFER - Dutch Institute for Fundamental Energy Research

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