报告题目：Electrochemical reduction of CO2 on immobilized Cobalt protoporphyrin
CO2 is the most notorious greenhouse gas, which has caused and will continue to cause climate change. The abundance of the CO2 resulting from the excessive combustion of fossil fuels makes it a perfect raw material to produce valuable fuels. Among diverse methods, electrocatalytic reduction of CO2 using renewable energies seems to be a promising long-term objective.
Herein, we report on electrochemical reduction of CO2 on a simple, cheap and commonly available molecular catalyst to 8-electron transferred product methane. The catalytic system is a pyrolytic graphite (PG) electrode coated with cobalt protoporphyrin (Co-PP), turning over CO2 to methane in an aqueous acidic solution (pH=1-3) with a moderate overpotential (~ 0.5-1V). In the absence of buffer anions, the catalytic system shows higher activity and different selectivity. At pH=1, methane and H2, which is a competing product, are the only gas products. The CO formation is observed at pH=2 together with the methane and H2 as products. The most important aspect of the pH effect is that there is a potential range at which the CO and methane is formed while there is no sign of the formation of H2. This means that we can control the selectivity of the electrochemical reduction of CO2 by tuning the experimental conditions. The role of proton is understood by comparing the voltammetry of H2 evolution reaction on Co-PP at different pH (1-3). Besides, in order to get an insight of the mechanism, electrochemical reduction of potential intermediates was also conducted.