Modeling of spontaneous hydrogen evolution in a direct methanol fuel cell

Hydrogen evolution takes place in the negative electrode of a direct methanol fuel cell with insufficient oxygen supply. In this work, we developed a two-dimensional computational model to investigate the formation and evolution of the galvanic region (GR) and the coupled electrolytic region (ER) where this spontaneous hydrogen evolution occurs. Special attention is paid to the species, potential and current distributions at different air flow rates (AFRs), and the effect of water flooding is highlighted. The open-circuit potential (OCP) of the cell is found to be quite sensitive to the AFR, especially just after the emergence of the abnormal ER. It is also demonstrated that the extent of cathode flooding has dramatic impacts on the cell behavior, which may be the major reason for the observed uncertainties of experimentally measured OCPs and current distributions.