Dynamic First-Principles Molecular-Scale Model for Solid Oxide Fuel Cells

This model for the voltage-current density (V-i) characteristics predicts behavior in both the fuel cell and steam electrolyzer modes. It uses the Stefan-Maxwell equations to find concentrations at the electrode-electrolyte interfaces of hydrogen, oxygen, and steam as functions of i. These concentrations and parameters such as electrode pore characteristics and temperature T are used to calculate "attempt current density" magnitudes a, b, c, d. Here, a and b are the forward and reverse values at the anode, and c and d at the cathode, interfaces with the electrolyte. Multiplying each value by the corresponding "success probability" yields forward and reverse current density magnitudes i(fa) and i(ra) at the anode and i(fc) and i(rc) at the cathode interfaces. The differences at either interface yield i=i(fa)-i(ra)=(a-b)/2+[(a+b)/2]tanh{[-H(a)-2FV(a)]/2RT}, (H=enthalpy change) i=i(fc)-i(rc)=(c-d)/2+[(c+d)/2]tanh{[-H(c)-2FV(c)]/RT}. [H=H(a)+H(c)]