Copper catalysts work better when they gain and lose oxygen atoms

The secret to renewable solar fuels Is an off-and-on again relationship.

Numerous scientists have demonstrated that oxide-derived copper catalysts are better at making fuel items from CO2; nonetheless, there is banter concerning why this happens. Under operating conditions for fuel generation – which involves first converting the CO2 into carbon monoxide then building hydrocarbon chains – the copper-bound oxygen is naturally depleted in the catalyst.

However, some researchers believe that small amounts of oxygen remain in the metal structure and that this is the source of the increased efficiency.

By performing X-ray spectroscopy on working solar fuel generator prototypes, scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) and Caltech have demonstrated that catalysts made from copper oxide are superior to purely metallic-origin catalysts when it comes to producing ethylene, a two-carbon gas with a vast range of industrial applications – even after there are no detectable oxygen atoms left in the catalyst.

For the study, scientists brought a gas chromatography (GC) system to the X-ray beamline so they could detect ethylene production in real-time.

Soo Hong Lee, a postdoctoral researcher at Berkeley Lab and co-lead author of the study, said, “Our collaborators from Caltech drove the GC from Pasadena and installed it at the X-ray facility in Palo Alto. With it, we showed that there is no correlation between the amount of oxygen (‘oxide’) in the catalyst and the amount of ethylene produced. So, we think that oxide-derived catalysts are good, not because they have oxygen remaining while they reduce carbon monoxide, but because the process of removing the oxygen creates a metallic copper structure that is better at forming ethylene.”

Scientists noted“Although oxide-derived catalysts’ efficiency wanes over time, it can be regularly “reactivated” by re-adding and re-removing oxygen during a simple maintenance process. Their next step is to design a fuel-generating cell that can operate with X-ray scattering instruments, allowing them to map the changing structure of the catalyst directly. At the same time, it converts carbon monoxide into ethylene.”

Journal Reference:
  1. Soo Hong Lee et al. Correlating Oxidation State and Surface Area to Activity from Operando Studies of Copper CO Electroreduction Catalysts in a Gas-Fed Device. DOI: 10.1021/acscatal.0c01670

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