High-quality Cu–Al nanocrystals for enhanced CO₂ electroreduction

In the quest to optimise the catalytic activity and selectivity of the CO₂ reduction reaction (CO₂RR), various imperfections—such as defects, grain boundaries, and vacancies—pose significant challenges. In a groundbreaking approach, we present the synthesis of well-structured CuAl nanocrystals featuring a preferential (111) crystal facet, a first in the field. This innovative structure not only enhances selectivity but also establishes a clear structure–activity relationship for the CO₂RR. The unique properties of CuAl nanocrystals stem from their ability to finely control bonding interactions with CO₂RR intermediates, driven by the synergistic effects of the (111) facet. Utilising a straightforward chemical vapour deposition (CVD) method, we prepared these nanocrystals, revealing the atomic distribution of Cu and Al on this dominant surface, which crucially influences CO₂RR performance. Among them, Cu₉₆Al₄ achieves the highest Faraday efficiency (FE) for HCOOH (77.71%) and CO (18.01%), attributed to the synergistic effects of Cu and Al arising from the optimal d-band centre of Cu active sites and the strong electron-donating ability of Al. This interaction facilitates the electron transfer from Cu to *COOH, resulting in a high FE for C₁ product. Our findings provide a foundation for the systematic investigation of the effect of defects, vacancies, and lattice strain on CO₂RR performance. This work also paves the way for advanced catalytic designs that can significantly increase CO₂ conversion efficiencies.