To explore the heat and mass transfer processes within the low-temperature
catalyst layer, a coupled heat and mass transfer lattice Boltzmann model and
electrochemical model were established, creating a pore-scale model for heat and
mass transfer in the catalyst layer. The influence of the catalyst layer
parameters was investigated. The results indicate that as time progresses, heat
gradually accumulates at the top of the catalyst layer (CL) and is transmitted
towards the bottom. Once oxygen enters the CL, it quickly fills the pores within
the CL, resulting in a rapid decrease in oxygen concentration within the
ionomer. As the platinum volume fraction increases, there is a significant rise
in temperature across the entire calculation domain. With the increasing
platinum volume fraction, the current density also increases rapidly due to the
larger reaction area. When the carbon volume fraction is 0.15, more oxygen
enters the ionomer to participate in reactions, and the large porosity enhances
thermal convection, leading to the highest temperature at this point. As the
ionomer content increases, the area of the high-temperature red zone within the
CL also expands. However, with a carbon volume fraction of 0.25, the diffusion
of oxygen in the pores is reduced, leading to most of the oxygen entering the
ionomer, resulting in the highest current density among the three cases.
Nonetheless, since thermal convection is stronger when the I/C weight ratios is
relatively small, the overall temperature remains high. As the I/C weight ratios
increases, oxygen diffusion weakens, and the overall current density shows an
upward trend.