Morphological Stability of Copper Surfaces under Reducing Conditions.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Copper is a promising electrocatalyst for CO2 reduction reaction (CO2RR).
• Copper catalysts often deactivate, favoring hydrogen evolution reaction (HER) over CO2RR.
• A prevailing hypothesis suggests potential-induced morphological restructuring causes this deactivation.

Purpose of the Study:

• To investigate the hypothesis of potential-induced morphological restructuring in copper electrocatalysts.
• To study the stability of different copper surfaces under cathodic conditions relevant to CO2RR.
• To identify the root cause of observed morphological changes in copper during CO2RR.

Main Methods:

• Electrochemical voltammetry on principal copper orientations and polycrystalline copper.
• Identical location scanning electron microscopy (ILSEM) to assess morphological changes.
• Controlled exposure to cathodic potentials in alkaline and bicarbonate electrolytes.

Main Results:

• Copper surfaces exhibited high morphological stability under prolonged cathodic potentials in 10 M NaOH.
• ILSEM confirmed no significant morphological changes on nanoparticle-covered copper under CO2RR conditions (-0.75 V for 60 min in 0.5 M KHCO3).
• Observed voltammetric changes were attributed to electrode fouling, not site redistribution.

Conclusions:

• The hypothesis of potential-induced morphological restructuring as the cause of copper deactivation in CO2RR is not supported.
• Accidental oxidation/reduction cycles, leading to minor morphological changes, are likely responsible for reported copper restructuring.
• Electrode fouling is a significant factor affecting voltammetric measurements during CO2RR studies.