Computational modeling of benzyl alcohol oxidation coupled with hydrogen production in a photoelectrochemical reactor

Abstract

In photoelectrochemical (PEC) cells, hydrogen production at the cathode must be coupled with the oxidation reaction at the anode. Selective oxidation of benzyl alcohol into benzaldehyde is an attractive alternative pathway due to its lower overpotential than the traditional oxygen evolution reaction (OER). In this work, simulation of selective oxidation of benzyl alcohol into benzaldehyde paired with hydrogen production in 2 chambers of 2-dimensional PEC reactor was studied using COMSOL Multiphysics (5.6). Charge transport and electrochemical kinetics were simulated using Nernst Planck’s and Butler Volmer's equations, respectively. The results have showed that hydrogen and benzaldehyde concentrations on electrode surfaces increased with the direction of electrolyte flow to the posterior end of the reactor. Moreover, the accumulation of hydrogen and benzaldehyde concentration on electrode surfaces decreased significantly with an increase of electrolyte velocity due to the higher shear force. In addition, the 3-dimensional PEC reactor model was also simulated to obtain the optimal design with the best orientation. The results for all PEC reactor model show streamline as a uniform linear motion which is a characterization of a laminar flow. The horizontal PEC reactor model has shown the best choice for fabrication because of lower pressure drop compared to that of the one with vertical orientation.