Efficient Electroreduction of CO₂ to CH₄ Over Amino Acid-Modified Copper Under Acidic Conditions

Electroreduction of CO₂ into CH₄ under acidic conditions is a promising strategy for CO₂ utilization, which allows for high CO₂ conversion efficiency. However, the selectivity of CH₄ is low because the hydrogen evolution reaction is enhanced under acidic conditions. Here, we report that the CO₂ can be efficiently reduced into CH₄ over a Cu catalyst by modifying with a glutamic acid molecule under acidic conditions. The CH₄ Faradaic efficiency can reach 62.9% with a current density of 450 mA cm⁻². Meanwhile, a single-pass carbon efficiency of 48.1% toward CH₄ is achieved. Experiments revealed that the glutamic acid molecule can enhance the concentration of K⁺ on the surface of Cu, which can suppress the HER and promote CO₂ reduction, resulting in high selectivity of CH₄ under acidic conditions.