In PEMFCs, the limiting current is associated with gas transport by diffusion $($Fick$$s law$)$ as a fuel cell must continuously be supplied with fuel and oxidant to produce electricity. Products must also be continuously removed to have maximum fuel cell efficiency. The study of mass transfer of uncharged species is important because it can lead to significant fuel cell performance losses if not understood properly. A standard way of calculating fuel cell concentration loss $($or mass transport loss$),$ may be expressed by the equation:

$\backslash$eta conc$=$constant.ln$($ilim$/($ilim$-1))$

constant$=$RT $(1+1/\backslash$alpha $)/$nF

For the PEM fuel cell, the majority of mas transfer loss happens at cathode as diffusivity of oxygen is much smaller than that of hydrogen. Please determine the concentration overpotential at the cathode with a diffusion layer thickness of $0\mathrm{.}001$ cm$.$ The diffusivity of oxygen in the catalyst layer at $80\backslash$deg C is given below:

Do$2=3\mathrm{.}5\backslash$times $105$cm$2/$sIn PEMFCs, the limiting current is associated with gas transport by diffusion $($Fick$\text{'}$s

law$)$ as a fuel cell must continuously be supplied with fuel and oxidant to produce

electricity. Products must also be continuously removed to have maximum fuel cell

efficiency. The study of mass transfer of uncharged species is important because it

can lead to significant fuel cell performance losses if not understood properly. A

standard way of calculating fuel cell concentration loss $($or mass transport loss$),$ may

be expressed by the equation:

${}_{\text{c}\text{o}\text{n}\text{c}}=$ constant $*ln(\frac{i_{lim}}{i_{lim}-i})$

constant $=\frac{RT}{nF}(1+\frac{1}{})$

For the PEM fuel cell, the majority of mas transfer loss happens at cathode as diffusivity

of oxygen is much smaller than that of hydrogen. Please determine the concentration

overpotential at the cathode with a diffusion layer thickness of $0\mathrm{.}001cm(10$ points$).$ The

diffusivity of oxygen in the catalyst layer at $80C$ is given below:

$D_{O_2}=3\mathrm{.}5{10}^{-5}c\frac{m^2}{s}$