Simulation of photoelectrochemical CO2 conversion to useful chemicals

Abstract

Photoelectrochemical (PEC) CO2 reduction reaction (CO2 RR) is one of the possible solutions to reduce CO2 emissions. Among a variety of products derived from CO2 RR, CO, and HCOO- are found to be interesting chemicals. The geometry and arrangement of the main components of PEC cells play important roles in the cell performance of CO2 RR. In this study, a correlation of hydrodynamics and kinetics on the TiO2-photoanode and SnO2-GDE, used as a cathode, was investigated by COMSOL Multiphysics by controlling operating conditions for 2-dimensional different PEC cell configurations. The Microfluidic flow cell (MFC) with a zero-gap anode with a zero-gap anode provided selectivity of 0.62 HCOO-, faradaic efficiency of 68.6% HCOO-, and energy efficiency of 60.4% HCOO- which were achieved with applied absolute cell voltage at 1.5 V and 1.0 mA•cm-2 photocurrent density on the TiO2 photoanode. Therefore, MFC with a zero-gap anode was chosen as the optimal design overcoming the limitation of mass transfer and ohmic overpotential loss by integrating half-cells of the MFC and membrane electrode assembly flow cell (MEAFC) configurations. Moreover, the results showed 1.0 mA•cm-2 of current density, 1.5 cm of cell length (Lcell), 1.5 mm of gas channel width (Wg), and 2.0 mm of electrolyte channel width (Wl) which were the optimum values for this system.