Metal-organic layers induce in situ nano-structuring of Cu surface in electrocatalytic CO₂ reduction

Cu-based catalysts have attracted widespread attention for its capability in electrocatalytically reducing CO₂ to a variety of products. Surface modification of Cu has become an interesting method for tuning the catalytic performance. Here, we use Zr-based metal-organic layers (MOLs) as the additive of the Cu surface, which enhanced the Faradaic efficiency of CH₄ by two times as compared to the untreated polycrystalline Cu foil. Unexpectedly, the MOLs were found to induce in situ nano-structuring of the Cu foil surface within seconds in the electrolysis, as revealed by a combination of scanning electron microscopy (SEM), grazing incidence X-ray diffractometry (GIXRD), and linear sweep voltammetry (LSV) measurements. These surface changes are responsible for the shift of product selectivity. Control experiments suggest that negatively charged µ₃-O⁻ on the Zr-cluster in the MOL might interact with CO-covered Cu surface and induce roughing and nano-structuring. This work reveals a potential role of additive on Cu to induce surface nano-structuring that tunes catalytic activity and selectivity.