Cation- and CO₂-assisted electrochemical synthesis of clean, shape-controlled Cu nanocrystals for selective CO₂ reduction to C₂⁺ products

Synthesis of well-controlled faceted metal nanocrystals is important for many applications. It has received much attention in advancing product selectivity of copper-catalyzed CO₂ electrolysis. We developed a facile electrodeposition method that can synthesize shape-controlled copper nanocrystals with ultra-clean surfaces that are difficult to obtain otherwise. Shape control is achieved via the controlled adsorption of CO₂ on copper surfaces by different alkali cations during electrodeposition, with ultra-clean surfaces subsequently obtained upon releasing the electric field. In situ infrared spectroscopy reveals the strong adsorption of CO₂ on copper surfaces in the presence of heavy alkali cations during electrodeposition, yielding well-defined nanocubes. The preferential adsorption of CO₂ on the Cu(100) surface in the presence of cesium cations is explained using constant-potential density functional theory calculations.