Capture fossil fuel power plant emissions and convert them to fuel. That’s the aim of a team of researchers at the Massachusetts Institute of Technology, who assert that the process they developed in the laboratory demonstrates the fundamental science that can be used for a range of processes.

The researchers were able to get carbon dioxide (CO₂) to react with a silver electrode material to produce carbon monoxide (CO). That is a major step since there are already established methods for converting CO and hydrogen to a variety of liquid fuels, says Assistant Professor of Chemistry Yogesh Surendranath.

A porous silver-based catalyst is the key to the conversion process. Credit: MIT The difficulty was to come up with a system in which the conversion process can be tuned to consistently produce a single end product. The team achieved this by developing a porous silver electrode material. The material is tuned by controlling its pore dimensions.

This is in contrast with previous efforts that focused on varying the surface active site chemistry. The porous material is made by depositing polystyrene beads on a conductive electrode substrate, then electrodepositing silver on the surface. The beads are dissolved, leaving pores whose size is determined by that of the original beads.

The final catalyst contains a honeycomb-like structure of hexagonal cells. Varying the size of the pores “tunes the selectivity and activity of the catalyst, without modifying the surface active site chemistry," says Surendranath.

In addition, increasing the thickness of the catalyst increases the production of CO by up to three times while suppressing the production of hydrogen gas by as much as tenfold. The researchers varied the process to control the CO production to anywhere from 5-85% of the reaction’s output.

Capping off the possible benefits, researchers say that if the process is powered with solar or wind-generated electricity it could be completely carbon neutral. Conversion facilities could be sited at fossil fuel power plants to capture their emissions flows and generate fuels that could still use the existing infrastructure of gas stations, delivery vehicles, and storage tanks.