Abstract Our 1D + 1D model of DMFC reveals a new effect. At infinitely small total current in the cell, near the channel inlet forms a “bridge”, a narrow region with finite local current density. The bridge short-circuits the electrodes, thus reducing cell open-circuit voltage. In our previous work the effect is described for the case of equal methanol λ a and oxygen λ c stoichiometries. In this Letter, we analyze the general case of arbitrary λ a and λ c . In the case of λ a > λ c current may occupy finite domain of the cell surface. Asymptotic solution for the case of λ a ≫ λ c shows, that the size of this domain is proportional to oxygen stoichiometry. In the opposite limit of λ a ≪ λ c local current exponentially decreases with the distance along the channel. Asymptotic solutions suggest that the bridge forms regardless of the relationship between λ a and λ c . In all cases local current density in the bridge increases with the rate of methanol crossover and decreases with the growth of the “rate-determining” stoichiometry. The expression for voltage loss at open-circuit is derived.
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