Comparative Study on Electrochemical and Thermochemical Pathways for Carbonaceous Fuel Generation Using Sunlight and Air

A comparative study on the solar-to-fuel (STF) conversion efficiency of electrochemical and thermochemical approaches for methane (CH4), methanol (MeOH), and ethanol (EtOH) generation using sunlight and air was performed. The system level STF conversion efficiency studied herein took into account of both the conversion processes and feedstock capture processes. In particular, the feedstock, CO2 and H2O, in this analysis were assumed to be captured from air. For thermochemical conversion, one and two-step approaches were considered including CH4 generation from the Sabatier reaction, and two-step processes for methanol (MeOH) and ethanol (EtOH) generation from CO and H2 coupled with the reverse water gas shift reaction (rWGS). State-of-the-art electrochemical and hybrid electrochemical-thermochemical processes for CH4, MeOH and EtOH generation, and the corresponding system level STF conversion efficiency were then compared and contrasted to the thermochemical approaches. Target overpotentials and Faradaic efficiency (FE) for the electrochemical CO2 reduction reactions was also presented to compete with thermochemical approaches at different operating scenarios.