Like Straw into Gold
Syngas, or synthesis gas, is a fuel blend usually made up of carbon monoxide, hydrogen, and carbon dioxide. It is a vital precursor in the production of synthetic fuels and various chemicals. Now, a team of researchers has developed a new process for creating syngas using just water and carbon dioxide, using a tiny number of copper atoms on a gold surface. This nanomaterial supports an electrochemical reaction at room temperature.
Syngas can already be converted into small molecules, such as ethanol, or larger hydrocarbons like those found in gasoline, via thermochemistry or fermentation. However, designing a process and material that could easily control syngas composition would be a major advancement, reducing the environmental effects inherent to those industrial processes. This was the impetus for the work in this study.
“We know of no other single electrocatalyst that combines high production rates with such wide-ranging syngas composition control,” said study leader Peidong Yang, Department of Energy Lawrence Berkeley National Laboratory Materials Sciences Division senior faculty scientist, in a press release. “Many processes that utilize syngas require different compositions of gas, so we wanted to create a family of electrocatalysts that can be easily tunable.”
Flexible, Sustainable Outcomes
The team discovered that changing the number of copper atoms on the nanostructured gold surface was the key to controlling how much hydrogen and carbon monoxide are generated; more hydrogen-rich fuels are more powerful, and produce fewer emissions. The researchers quantified the copper atoms using X-ray photoelectron spectroscopy, which measures the elemental composition and chemical state of a material.
“The copper changes the strength with which CO2 binds with the surface,” postdoctoral researcher and study lead author Michael Ross said in the press release. “A nanostructured surface that is primarily gold yields mostly carbon monoxide. To produce a mixture that is more hydrogen-rich, we add more copper.”
The team's design allows for a wide range of syngas mixes and a flexible outcome. Without any copper atoms, the process creates a 1 to 10 hydrogen to carbon monoxide mix. In contrast, when the copper layer is 1-atom thick, a 2 to 1 result is obtained.
“If these electrocatalysts could be scaled up to work in industrial reactors, we could make syngas using renewably generated electricity and CO2,” Ross said in the release. “Syngas is currently being converted into methanol, diesel fuel, and other useful chemicals all over the world. This could make the production of these chemicals much more sustainable.”