Cation Incorporation into Copper Oxide Lattice at Highly Oxidizing Potentials

Area of Science:

• Electrochemistry
• Materials Science
• Surface Science

Background:

• Electrolyte cations influence electrocatalytic reaction kinetics and selectivity.
• Understanding cation-electrolyte interactions is crucial for optimizing electrocatalyst performance.

Purpose of the Study:

• To investigate the atypical mechanism of direct electrolyte cation incorporation into an oxide electrocatalyst lattice.
• To explore the transformations of copper electrodes in alkaline electrochemistry using different electrolytes.

Main Methods:

• Operando X-ray absorption spectroscopy (XAS) in KOH and Ba(OH)2 electrolytes.
• Electronic structure modeling and near-edge XAS simulations.
• Post-reaction characterization of copper electrodes.

Main Results:

• X-ray absorption spectra differed significantly between KOH and Ba(OH)2 electrolytes.
• Barium cations (Ba2+) were directly incorporated into the copper oxide lattice, forming BaCuO2 at oxidizing potentials.
• Further oxidation led to a Cu3+-like Ba-Cu-O phase, with Cu-Ba bonds persisting even at reducing potentials.

Conclusions:

• This study provides the first evidence of direct oxidative incorporation of an electrolyte cation into a bulk lattice to form a mixed oxide electrode.
• This mechanism opens a new pathway for in situ formation of active and selective oxidation electrocatalysts.