Electrochemical reduction of CO2 on a CoTPP/MWCNT composite: Investigation of operation parameters influence on CH3OH production by differential electrochemical mass spectrometry (DEMS)

Abstract

Renewable electricity-driven electrochemical production of small organic molecules, such as CH3OH, from chemical industry waste CO2 feedstock is highly desirable for circular economy. These reactions proceed via multiple intermediate steps which causes high overpotential and poor selectivity imposing a challenge for designing techno-economically viable systems. Proper understanding of the reaction mechanism is essential to overcome those challenges. Herein, we present a simple qualitative analysis to understand the reaction mechanism during electrochemical reduction of CO2 (eCO2R) on a cobalt tetraphenylporphyrin / multiwalled carbon nanotube (CoTPP/MWCNT) composite in the temperature range of 20–50 °C by employing differential electrochemical mass spectrometry (DEMS) in 0.1 M and 0.5 M KHCO3 electrolytes. Interestingly, temperature is observed to strongly affect the onset potentials for product generation in such a way that with the increase of temperature from 20 °C to 50 °C a decrease in the onset potential specifically for methanol formation is observed. Moreover, formaldehyde (HCHO) formation appears to occur at lower overpotentials before the formation of CH3OH which suggests that on the composite electrocatalyst, HCHO is an important intermediate on a route to CH3OH. This work offers valuable information on reaction routes to CH3OH and temperature effects on the eCO2R selectivity on molecular catalysts.