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Using microfabrication to explore CO2 reduction

By analyzing microscopic catalyst structures, chemists shed light on mechanism for reaction that puts the unwanted gas to good use

by Mitch Jacoby
April 26, 2018 | A version of this story appeared in Volume 96, Issue 18

This micrograph shows the structure and composition of microfabricated electrodes.
Credit: Nat. Commun.
Analysis of electrodes featuring 2.5-µm-wide islands of indium oxide (light) on copper oxide (dark) reveals that halos with low indium concentration (outside of white circles) are catalytically active for 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.”


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