About the theoretical capacitance I'm not sure. But you can simply determine the specific capacitance of a material by first taking a CV and second, measure the curve area which is proportional to charge stored.
Thanks for your answer, But every pseudocapacitive material should have a constant theoretical capacitance. It depends on number of charge transfer, Faradaic constant, potential....now I want to know the exact equation, how to calculate it.
You can calculte by following equation Theortical capacitance =n*Faraday constant/Molar mass*Potential window.n is number of electrons invloved in redox reaction
you can calculate the theoretical specific capacitance by using the formula, Cs = (n * F)/(m * V) where n = electron number, F = Faraday constant (96485 C mol-1), m= molecular weight and V = redox potential. value of n you will have to find from literature.