LAUSR

Recent advances in electrocatalysts for the CO2 reduction reaction (CO2RR) have led to several promising results, including the large‐scale production of low‐carbon fuels. One of the next steps in this route is the generation of economically and scientifically valuable multicarbon (e.g., C4) chemicals. However, this process has rarely been reported to‐date and has generally suffered from a low production rate (jpartial ≤ 0.097 mA cm−2) and Faradaic efficiency (FE) of ≤ 1%. This is largely due to the lack of efficient electrocatalysts for the complicated and interconnected reaction pathway of C4 generation. Herein, CuxIr1–x alloy nanoparticles (NPs) are shown to convert CO2 into (CH3)3COH (t‐BuOH) with a jpartial of 0.207 mA cm–2 at a FE of 14.8%, which is the best performance toward C4 production demonstrated so far. Furthermore, this study proposes a probable mechanism of C4 formation based on density functional theory (DFT) calculations. The findings suggest that the C4 production is facilitated by the strong electronic interaction between Cu and Ir and the high oxophilicity of the Ir‐rich surface, which enhances the binding strength of oxygen‐bound intermediates. This work opens the potential of Ir‐based alloys for the CO2RR and highlights the production of C4 chemicals beyond the currently available C1–C3 products.