Using microfabrication to explore CO₂ reduction

One promising way to lower atmospheric levels of CO₂ is to convert it to something useful such as CO, a starting material for making valuable hydrocarbons. Researchers have shown that catalysts combining copper and indium can drive that conversion electrochemically, but mechanistic details have remained elusive, thwarting efforts to improve the process.

By using microfabrication techniques to make highly ordered catalytic electrodes, chemists in Switzerland have uncovered new details about the active phase of the catalysts that facilitate the reaction (Nat. Commun. 2018, DOI: 10.1038/s41467-018-03980-9).

Microfabrication methods usually help manufacturers make tiny integrated circuits. Javier Pérez-Ramírez of ETH Zurich and coworkers used the procedures, instead, to make model electrodes patterned with millions of precisely arranged copper and indium catalytic islands.

The team had suspected that some unrecognized synergistic interfacial effect involving the metals and their oxides was key to reducing CO₂. To test that hypothesis, they prepared electrodes consisting of microscopic indium oxide islands on a copper support (denoted In₂O₃/Cu). The researchers also made In₂O₃/Cu₂O and In/Cu₂O electrodes and varied the size of the islands to control the size of the island-support interfaces.

The chemists found that the highest catalytic activity occurs at the interface between copper oxide and indium in regions that are low in indium and that form under reaction conditions.

CO₂ reduction is approaching commercialization, says Brian Seger, a catalysis specialist at Technical University of Denmark, and “this study provides interesting results that should help us better understand the underlying mechanism.”