The first parameter to integral() must be a function handle that expects one input. You are passing a function handle that expects two inputs.
You have assigned C as a constant value so it would seem to make the most sense to use
Vc1 = @(Ic) (1/C)*Ic;
However, you do not need to do a numeric integration to solve that, as it is simple case of constant*x:
integral of Ic/C for Ic = 0 to 1 is Ic^2/(2*C) from 0 to 1 which is 1/(2*C) - 0/(2*C) which is 1/(2*C)
.. though you said Ia1 and Ia2 are inputs. If your integral is over C then the integral would be Ic*(log(upperbound)-log(lowerbound)) which would be Ic*(log(1)-log(0)) which would be Ic*(0-(-infinity)) which would be Ic*infinity which would be sign(Ic)*infinity
