Laura I. Wagner

Control over product selectivity of the electrocatalytic CO 2 reduction reaction (CO 2 RR) is a crucial challenge for the sustainable production of carbon‐based chemical feedstocks. In this regard, single‐atom catalysts (SACs) are promising materials due to their tunable coordination environments, which could enable tailored catalytic activities and selectivities, as well as new insights into structure‐activity relationships. However, direct evidence for selectivity control via systematic tuning of the SAC coordination environment is scarce. In this work, we have synthesized two differently coordinated Bi SACs anchored to the same host material (carbon black) and characterized their CO 2 RR activities and selectivities. We find that oxophilic, oxygen‐coordinated Bi atoms produce HCOOH, while nitrogen‐coordinated Bi atoms generate CO. Importantly, use of the same support material assured that alternation of the coordination environment is the dominant factor for controlling the CO 2 RR product selectivity. Overall, this work demonstrates the structure‐activity relationship of Bi SACs, which can be utilized to establish control over CO 2 RR product distributions, and highlights the promise for engineering atomic coordination environments of SACs to tune reaction pathways.