Structure-activity relationship of small organic molecule functionalized Bi-based heterogeneous catalysts for electrocatalytic reduction of CO to formate.

Ligand engineering has proven to be an effective strategy for tuning and controlling the microenvironment of coordinated metal centers, highlighting the critical bridge between the activity and structural features of catalysts during electrocatalytic CO reduction reactions (eCORR). However, the limited availability of diverse organic ligands has hindered the development of novel high-performing electrocatalysts. In contrast, small organic molecules have been widely used in the fabrication of metal complexes due to their well-defined functionalities, low cost, and easy accessibility. Herein, functionalized small organic molecules were employed to prepare a new type of Bi-based heterogeneous molecular catalyst. These molecular catalysts enhance both electrical conductivity and catalytic activity for converting CO to formate in the eCORR. The relationship between the structure and electrochemical performance of organic-functionalized Bi-based heterogeneous catalysts was thoroughly investigated. Comprehensive characterization and kinetic studies demonstrated that the functional groups of the organic molecules construct bond pathways for electron transfer and promote the transformation of the active phase from Bi to BiOCO. In-situ Raman spectroscopy reveal that the organic molecules remain intact during the structural reorganization, which is beneficial for the sustained generation of BiOCO active site during the eCORR process. Consequently, the organic functionalized Bi-based catalysts achieved a high formate Faradaic efficiency (FE) of 89.8 % and a high current density (j) of 40.0 mA cm at a potential of -0.95 V vs. RHE in an H-type cell. This work establishes a novel strategy for creating active heterogeneous catalysts using small organic molecules, opening new avenues for the development of efficient electrocatalysts for CO reduction.