Macroscopic multi-dimensional modelling of electrochemically promoted systems

The objective of this work is the construction of macroscopic models for electrochemically promoted catalytic systems, i.e. systems where the catalytic performance is improved by application of potential between the anode and cathode electrodes in the cell. This polarization effect leads to a formation of an effective double layer over the catalytic film due to migration of ‘backspillover’ species from the electrolyte to the working electrode when potential difference is applied in the system. In this paper, we propose a multidimensional, isothermal, dynamic solid oxide single pellet model, which describes the chemical and electrochemical phenomena taking place under polarization conditions. The electrochemically promoted oxidation of CO over Pt/YSZ is used as an illustrative system. The partial differential equation-based 2- and 3-dimensional macroscopic models that describe the simultaneous mass and charge transport in the pellet are constructed and solved in COMSOL Multiphysics. The model predicts species coverage on the catalytic surface, electronic and ionic potential curves across the pellet, gas mixture concentration within the reactor and CO2 production rate. Parameter estimation is undertaken so as to provide us with values of parameters, which are necessary for the simulation of the model. Subsequent sensitivity analysis is performed to investigate the effect of the percentage change of each estimated parameter on the CO2 production rate. As it is shown, the reaction rate curves obtained from the current modelling framework are in good agreement with values found in the literature.