Polyoxometalate-Based Electron Transfer Modulation for Efficient Electrocatalytic Carbon Dioxide Reduction

Electrocatalytic carbon dioxide (CO2) reduction reaction (CO2RR) involves a variety of electron transfer pathways, resulting in poor reaction selectivity, and limiting its use to meet future energy requirements. Polyoxometalates (POMs) can both store and release multiple electrons in the electrochemical process, which is expected to be an ideal “electron switch” to match with catalytically active species, realize the electron transfer modulation and promote the activity and selectivity of electrocatalytic CO2RR. Herein, we report a series new POM-based manganese-carbonyl (MnL) composite CO2 reduction electrocatalysts, thereinto, SiW12-MnL exhibits the most remarkable activity and selectivity for CO2RR to CO, resulting in the Faradaic efficiency (FE) from 65% (MnL) to a record-value of 95% in aqueous electrolyte. A series of control electrochemical experiments, photoluminescence spectroscopy (PL), transient photovoltage (TPV) experiments, and density functional theory (DFT) calculations reveal that POMs act as electronic regulator to control the electron transfer process from POM to MnL units during the electrochemical reaction, enhancing the selectivity of CO2RR to CO and depressing the competitive hydrogen evolution reaction (HER). This work demonstrates the significance of electron transfer modulation in CO2RR and suggests a new idea for the design of efficient electrocatalysts towards CO2RR.