Title: Heterogeneous Molecular Catalysis for Electrochemical Energy Conversion in Neutral Water

Abstract

Electrochemical energy conversion in a neutral aqueous system catalyzed by low-cost molecular catalysts is a viable way for the production of green fuels and chemicals. Due to the low conductivity of molecular catalysts, their immobilization on the electrode surface is a key element of heterogeneous molecular catalysts that can be efficiently and easily recovered and reused in consecutive cycles. Herein we present a concept of “molecular wire”, i.e. connection of the catalyst to electrode via a conductive covalent linker, which has profound effect on the electrocatalytic performances in both CO₂ electrochemical reduction and oxygen evolution reaction compared to the noncovalent counterpart. However, the catalyst experienced a gradual loss of activity. To resolve this issue, a range of detailed mechanistic studies allow us to rational design a new type of catalyst imparting a significantly higher resistance to degradation. The resulting catalyst shows no sign of deactivation and yields a record turnover number (TON) of ~5 million over the course of 150 h long electrolysis while maintaining a faradaic efficiency of CO (FE_CO) over 90 %. The electron transfer from electrode onto the moiety plays an important role in overall redox kinetics. Our recently developed variable frequency square wave voltammetry (VF-SWV) allows direct 2D electrochemical mapping of charge migration and to explore the statistical distribution of the reaction rates. We believe this methodology could also be useful in other areas of electrochemical reactions.