Shaping hollow spherical assemblies for enhanced Cu⁰/Cu⁺ interface to boost C₂₊ selectivity in CO₂ electroreduction

The creation of Cu⁰/Cu⁺ interface over Cu-based catalysts is known to facilitate the production of multi-carbon (C₂₊) products during CO₂ reduction reaction (CO₂ RR). However, the Cu⁺ moieties exhibit high susceptibility towards reduction into Cu⁰ at a high current density. Thus, a comprehensive understanding and rational shaping strategy for the construction and stabilization of Cu⁰/Cu⁺ interface in Cu-based catalysts is imperative. Herein, we proposed a controllable “nanoparticle assembly” strategy to obtain hollow spherical assemblies (HSA) composed of numerous Cu₂O nanoparticles (HSA-Cu₂O). The HSA-Cu₂O catalysts significantly enhance the selectivity of C₂₊ products, resulting in an impressive overall Faraday efficiency (FE) of 79.2% ± 0.7% at a partial current density of 317.1 mA cm⁻². The HSA-Cu₂O catalysts undergo in-situ electrochemically reconstruction during CO₂RR, achieving Cu⁰/Cu⁺ interfacial sites with a high density. The Auger electron spectra, in-situ Raman, and morphological evolution studies have confirmed that the combination of the Cu⁰/Cu⁺ interface and hollow sphere architecture facilitated the concentration of *CO intermediates, thereby promoting C–C dimerization to boost C₂₊ selectivity in CO₂RR.