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

• CO 2 reduction is studied in range of temperatures on CoTPP/MWCNT by DEMS. • Formaldehyde formation before CH 3 OH suggest that the former is an intermediate. • Onset potential of CH 3 OH formation declines by 0.2 V upon 30 °C temperature increase. • CH 3 OH is produced electrochemically rather than chemically. Renewable electricity-driven electrochemical production of small organic molecules, such as CH 3 OH, from chemical industry waste CO 2 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 CO 2 (eCO 2 R) 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 KHCO 3 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 CH 3 OH which suggests that on the composite electrocatalyst, HCHO is an important intermediate on a route to CH 3 OH. This work offers valuable information on reaction routes to CH 3 OH and temperature effects on the eCO 2 R selectivity on molecular catalysts.