Solar Fuels: Harnessing Energy From the Sun

Our addiction to fossil fuels, like oil and gas, has led to a climate crisis. Fossil fuels are energy-dense and easy to store and transport, but they cause immeasurable harm to our environment. Renewable energy sources like solar panels and wind turbines, while helpful for producing electricity in our homes and industries, can’t supply all of our energy needs. A solar panel can’t, for example, fully power an airplane or a cargo ship. We need an alternative type of carbon-neutral fuel with all the benefits of fossil fuels, and this is where solar fuels step in. 

Solar fuels are generated using energy captured from the sun. This is a major focus of the work carried out at the Dutch Institute for Fundamental Energy Research (DIFFER), which aims to be a frontrunner in the Netherlands and Europe on energy research. Anja Bieberle-Hütter, leader of the Electrochemical Materials and Interfaces group, and Interim Head of the Solar Fuels research theme at DIFFER, is striving to increase the efficiency of solar fuel production. Her group focuses on photoelectrochemical water splitting, where sunlight is used to split water into oxygen and hydrogen. This hydrogen can be stored as compressed or liquefied gas or further processed to higher hydrocarbons and then stored. Unlike fossil fuels, hydrogen doesn’t release any carbon when it’s burned, only water vapour. 

However, this water-splitting process needs to become more efficient before it can be considered commercially viable. In particular, the oxygen formation is complex and slows down hydrogen production. Anja’s group is trying to understand how to accelerate oxygen formation and to remove this bottleneck. Her group focuses on the materials and the electrochemistry. She says, “Our aim is to understand the processes at the surface and the interfaces between the different materials better by combining experiments and simulations. For example, we measure impedance [resistance in an electrical circuit] data, and we simulate the same data. Doing both enables us to identify the limiting processes. Over the long term, these findings can be used to tune the materials and interfaces towards highest performance, and also to predict data that cannot be measured.”

For many years before DIFFER, Anja worked on fuel cells, which convert (solar) fuels into usable energy and so represent the other side of the coin. When she joined DIFFER in 2013, she was interested in seeing things from another angle and looked forward to the challenge of applying her modelling and experimental experience to a different aspect of energy research. She says, “What fascinates me is that it’s all about sustainable energy applications. You can use abundant resources like water so it’s really sustainable. And solar fuels or fuel cells can be realised in the short-to-medium term future.”

DIFFER is located in Eindhoven and is part of Brainport Eindhoven, an area with a high concentration of technology companies and educational institutions. The institute is committed to making infrastructure investments which will help advance energy research and serve the national and international community. As head of DIFFER’s solar fuel theme, Anja, together with collaborators at other Dutch institutions, recently submitted a multimillion-euro research proposal for a large pulsed laser deposition (PLD) facility. The facility will be used for the fabrication and investigation of complex metal oxide thin films for energy applications, such as electrolysers, fuel cells, batteries. Next to the PLD, DIFFER is focusing on other, unique large infrastructure projects, such as using an ion beam facility to study solar fuel processes under operation.

Anja enjoys being part of an institute dedicated to energy research that encourages a multidisciplinary approach. She also collaborates with colleagues working on generating clean energy by plasma processes or by fusion, the type of reaction that occurs in the sun. “It’s all about energy transition and how to get to alternative energy solutions, and also realising that we actually need a mixture of solutions,” she says. “You might wonder, ‘Why do you need solar fuels if you can solve every problem with fusion energy?’ But with fusion, we need at least 50 more years to achieve it so we cannot rely on it alone. I appreciate the value of the institute having a broader view on this topic.” Working at DIFFER has also given Anja the opportunity to be part of EU networks and funded projects that shape the strategy for energy research in Europe. Knowing that your work can make a real difference to society is what makes working at DIFFER so rewarding.