Stabilizing Copper for CO₂ Reduction in Low-Grade Electrolyte

We demonstrate herein a CO₂ reduction electrocatalyst regeneration strategy based on the manipulation of the Cu(0)/Cu²⁺ equilibrium with high concentrations of ethylenediaminetetraacetic acid (EDTA). This strategy enables the sustained performance of copper catalysts in distilled and tap water electrolytes for over 12 h. The deposition of common electrolyte impurities such as iron, nickel, and zinc is blocked because EDTA can effectively bind the metal ions and negatively shift the electrode potential of M/M ⁿ⁺. The Cu/Cu²⁺ redox couple is >600 mV more positive than the other metal ions and therefore participates in an equilibrium of dissolution and redeposition from and to the electrode in high concentrations of EDTA. These dynamic equilibria serve to further regenerate the surface copper catalyst to prevent the deactivation of catalytic sites. On the basis of this strategy, we show that >95% of initial hydrocarbon production activity can be maintained for 12 h in KHCO₃ (99% purity) enriched distilled water and 6 h in KHCO₃ (99% purity) enriched tap water.