Restructuring and integrity of molecular catalysts in electrochemical CO2 reduction

Abstract

Abstract Electrocatalysts that start a reaction as molecules do not always end the reaction as molecules, and even when they do, they might not be molecules during catalysis. In this Perspective, we discuss knowledge learned from the study of Cu‐based molecularly structured electrocatalysts––including metal coordination complexes, metal‐organic frameworks, single‐atom catalysts, and polymeric materials––that restructure under electrochemical CO2 reduction reactions. Recent reports are summarized with an emphasis on the nature and significance of post‐mortem and in situ characterization for the proper identification of active sites. We demonstrate that molecular and material structures determine whether electrocatalysts restructure and how they restructure, that understanding of restructuring processes can help us identify active sites for catalysis, and that this knowledge can be leveraged to design precatalysts that generate highly active catalysts under reaction conditions. In addition, we provide recommended practices for studying the integrity of heterogeneous molecular catalysts during and after CO2 reduction reactions. Key Points Heterogeneous molecular Cu catalysts have been observed to restructure to metallic Cu clusters under reaction conditions. Dynamic or reversible restructuring confounds identification of real active sites. Both ex situ and in situ techniques are recommended for robust catalyst characterization.

Keywords

• active sites
• CO2 reduction
• electrocatalysis
• molecular catalysts
• restructuring