Electrolysis and fuel production

Electrolysis is a technique that can be used to convert CO2 into fuels and other useful products. To do this efficiently and on a large scale, however, we need to understand exactly how electrolysis works. Professor Marc Koper is an expert in this field.

An ‘electrified’ future looks likely now we have found clean, sustainable methods for generating electricity, such as solar panels and wind turbines. But if we are going to use these new methods on a large scale, we must also be able to store and transport electricity. We will probably store it in chemical bonds that are produced in chemical reactions in sources such as CO₂ and water. Hydrogen looks particularly promising because it can be used in many different ways. It can serve as fuel for cars, for instance, and is also an important raw material in the chemical industry. Another benefit is that burning hydrogen with oxygen results in a ‘clean’ waste product: water. This could be one way of instantly eliminating a major cause of global warming – emissions from fossil fuels.

Marc Koper is Professor of Catalysis and Surface Chemistry at Leiden University and is researching the most efficient way to use electrolysis to produce hydrogen from water, and other fuels from water and CO₂. He is also researching how exactly this process works at the atomic level.

Understanding electrolysis

Koper wants to gain a better understanding of this process of electrochemical reduction of sources such as CO₂ and water. What kind of catalysts – substances that enable the reaction – are needed? And why and how do those catalysts work? We still don’t understand precisely how electrolysis works. For example: when you make hydrogen by electrolysing water, you can do so in different aqueous environments; this environment is called the electrolyte. Koper: ‘You can make hydrogen in an acidic or in a basic electrolyte. We know that it is less efficient in a basic electrolyte than in an acidic one, but we still don’t really know why. Once we understand that, we may be able to make further improvements to the electrolysis.’

In addition, many electrolysis processes depend not only on the catalyst but also on the environment in which the catalyst is situated – the electrode in the aqueous environment, to which you add salt to cause the reaction. Koper: ‘This environment contributes to the outcome of the reaction, but we don’t know exactly how. In fact, when you electrolyse CO₂, the environment itself affects what product you make. For instance, certain salts in the electrolyte promote the formation of longer carbon chains. These are more interesting because they have a higher energy density and are more valuable as a raw material. This is an important factor: people often look for new materials to use for electrolysis, while the environment can have just as much effect on the outcome. It is to be hoped that the knowledge gained from my research will ultimately contribute to a complete and better system for performing electrolysis.’

This research is still at a very early stage; there is much uncertainty about the results and when they will be available. Nevertheless, large companies such as Shell are very interested in Koper’s work. If efficient and affordable techniques can be developed for the electrochemical reduction of CO₂, these companies will be able to offer new types of fuel, such as hydrogen and ethanol, on a large scale: this would represent a revolution of truly unprecedented proportions.

Making platinum more durable

Koper is also researching the production of hydrogen on platinum, via the electrolysis of water. ‘As far as we know at the moment, this method of producing hydrogen works best on a platinum surface. But even platinum degrades, so that after a while the electrolysis produces less and less of the desired end product. For industrial use, it’s important to find ways to extend platinum’s lifespan to the maximum. You therefore want to look at what determines the platinum’s stability and whether you can control it. We’re doing a lot of research into this: how does platinum behave at the atomic level?’

Koper’s group is taking measurements of small pieces of platinum using scanning tunnelling microscopy. ‘While a reaction is taking place, we look at what the platinum atoms are doing and how they arrange themselves. All kinds of things are happening with these atoms: they dissolve, and they arrange themselves in new positions. This behaviour has a big effect on the catalyst’s lifespan. You want to be able to use platinum for as long as possible, and to keep the amount you need to a minimum. At the fundamental level I want to understand: when does platinum start to move, why, and can we control it?’

Koper’s research group is gradually finding out more about how platinum behaves. The group has discovered, for example, that the surface of platinum electrodes that are exposed to varying electrical voltages becomes rough much sooner than was previously imagined. This is important information because this progressive roughening has an adverse effect on the outcome of the electrolysis. By conducting further research, Koper hopes to be able to explain this roughening process.