Investigating and quantifying the effects of catalyst layer gradients, operating conditions, and their interactions on PEMFC performance through global sensitivity analysis

A gradient cathode catalyst layer (CCL) with promoted mass transfer and Pt utilization could enhance the output performance of proton exchange membrane fuel cells (PEMFCs). Since operating conditions affect reaction and mass transfer rate inside the PEMFC, the gradient CCL can only exert its full potential within a narrow operating range. Assessing the impact of gradients, operating conditions, and their interactions on output performance is vital to maximizing the benefits of gradient CCLs. Therefore, a global sensitivity analysis was conducted using Sobol's approach based on a one-dimensional, two-phase, non-isothermal PEMFC model. Five parameters, including Pt gradient (α), ionomer gradient (β), temperature (T), anode relative humidity (RHa), and cathode relative humidity (RHc), were selected as model inputs. The results show that RHc has the most significant impact on output performance among the operating parameters. The advantage provided by the gradient design is presented in mass transport-constrained situations. The impact of α on current density is more significant than β. Meanwhile, regarding the interaction effect of operating conditions and gradients, α and RHc provide the most significant pairwise interaction effect. Finally, the mechanisms underlying these interactions were analyzed, and some options were proposed to maximize the benefits of gradient CCLs.