Cobalt Pyrene‐Quaterpyridine Molecular Complex Immobilized on Functionalized Multi‐Walled Carbon Nanotubes as a Robust Hybrid Catalyst for Efficient Electrochemical Reduction of CO ₂

Molecular complexes immobilized on conductive carbon supports is a promising strategy for designing efficient electrocatalysts of CO₂ reduction reaction (CO₂RR). However, most immobilized catalysts suffer from low catalytic activity and durability due to weak catalyst-support interactions. Herein, modifications of Co quaterpyridine complex (Coqpy) with a pyrene group and multi-walled carbon nanotubes (MWCNT) with carboxyl or amide groups have been made, resulting in a highly efficient and stable hybrid catalyst. The carboxyl groups on MWCNT can effectively bind to Co centers by axial coordination; which allow for loading more electroactive Co complex, facilitate interfacial electron transfer, and lower the energy barrier for CO₂RR. A 2.6-fold increase in CO yield and a higher Faradaic efficiency (97.5% vs 83.6% at 423 mV overpotential) are obtained compared with the hybrid catalyst without carboxyl group. While, the pyrene group induced more substantial π-π interactions, leading to an enhanced electronic coupling between MWCNT and Coqpy, and enhanced hybrid stability, resulting in a ≈ 4.4-fold higher CO turnover frequency than Coqpy. Overall, the outstanding performance of the modified hybrid catalyst (turnover number up to 570000, Faradaic efficiency close to 100%) provides new mechanistic insights and design strategy for efficient and durable CO₂RR based on heterogenized molecular catalysts.