Table 1 Kinetic, physiochemical, and transport properties.
DescriptionValueRef.
Exchange current density (i0ref)Anode CL2350 A m−2(47)
Cathode CL6.0 × 10−4 A m−2(47)
Reference H2/O2 molar concentration (Cref)40.88 mol m−3(48)
Transfer coefficients (α)Anode CLαa = αc = 1(48)
Cathode CLαc = 1
Activation energy (Ea)Anode CL10 kJ mol−1(47)
Cathode CL70 kJ mol−1(49)
Reaction order in the electrode (r)Anode CL1/2(48)
Cathode CL3/4
Porosity of the GDL (𝜀GDL)0.6Assumed
Porosity of the anode CL (𝜀CL)0.5Assumed
Porosity and permeability of the dense PtNA (Kna)50%, 1.0 × 10−12 m2Estimated
Porosity and permeability of the sparse PtNA (Ksp)86.9%, 3.0 × 10−11 m2Estimated
Permeability of the anode CL (KaCL)1.0 × 10−13 m2Assumed
Permeability of the GDL (KGDL)5.0 × 10−13 m2Assumed
ECSA per catalyst layer volume of dense PtNA catalyst layer (ana)6.0 × 107/mEstimated
ECSA per catalyst layer volume of sparse PtNA catalyst layer (asp)5.038 × 106/mEstimated
ECSA per catalyst layer volume of multiscale PtNA catalyst layer (amul)1.114 × 107/mEstimated
Dry membrane density (ρdry, mem)2000 kg m−3(50)
Equivalent weight of electrolyte in membrane (EW)1.1 kg mol−1(50)
Faraday constant (F)96,487 C mol−1
Universal gas constant (R)8.314 J mol−1 K−1
Catalyst coverage coefficient (nc)1.5
Effective electronic conductivity in the narrow and sparse PtNA (σPtNA)1.2 × 105 S m−1Estimated
Effective electronic conductivity in the Pt/C (σCL)1000 S m−1(48)
Effective electronic conductivity in the GDL (σGDL)10,000 S m−1(48)
Effective electronic conductivity in the graphite BP (σGraphite)20,000 S m−1(48)
Surface tension (σ)0.0625 N m−1(48)
Contact angle of GDL, CL (θ)92°, 92°
Liquid water density (ρl at 65°C)980 kg m−3
Liquid water viscosity (μl)3.5 × 10−4 N s m−2(48)
Thermal conductivity of the hydrogen (kH2)0.2 W m−1 K−1(50)
Thermal conductivity of the oxygen (kO2)0.0296 W m−1 K−1(50)
Thermal conductivity of the water vapor (kH2O)0.0237 W m−1 K−1(50)
Thermal conductivity of the nitrogen (kN2)0.0293 W m−1 K−1(50)
Thermal conductivity of membrane (kmem)0.95 W m−1 K−1(48)
Thermal conductivity of GDL/CL5.0/1.0 W m−1 K−1(48)
Thermal conductivity of graphite20 W m−1 K−1(48)