Can someone helps me to solve the error in this code?

il = 4; 
R = 8.314; 
F = 96485; 
Alpha = 0.5; 
n = 2; 
Eexc = 53990.065; 
sigma_ref = 0.020; 
Epro = 18912.42; 
delta = 7*2.54*10^-3; 
I = 0:50:350; 
for i = 1:length(I) 
    t=0; 
    for T = [313 333 353]
        t=t+1; 
        % Anode 
        ia = (10^-7)(exp(-(Eexc/R)((1/T)-(1/298)))); 

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

        Eta_Anode(i,t) = ((R*T)/(Alpha*n*F))*(log(I(i)/ia)); 
        % Cathode 
        ic = (10^-3)(exp(-(Eexc/R)((1/T)-(1/353)))); 
        Eta_Cathode(i,t) = -((R*T)/(Alpha*n*F))*(log(I(i)/ic)); 
        %Ohmic 
        sigma(i,T) = sigma_ref*(exp(-(Epro/R)*((1/T)-(1/298)))); 
        Rohm = delta/sigma(i,T); 
        Eta_Ohmic(i,t) = I(i)*Rohm; 
        %Concentration 
        Eta_Conc(i,t) = ((R*T)/(Alpha*n*F))*(log(il/(il-I(i)))); 
        %Voltage 
        H_h2(i,T)=0+(28.84*(T-298)); 
        H_o2(i,T)=0+(28.91*(T-298)); 
        H_h2o(i,T)=-285830+(75.37*(T-298)); 
        H(i,T)=H_h2(i,T)+(0.5*H_o2(i,T))-H_h2o(i,T); 
        S_h2(i,T)=130.68+(28.84*(log(T/298))); 
        S_o2(i,T)=205+(28.91*(log(T/298))); 
        
        S_h2o(i,T)=69.95+(75.37*(log(T/298))); 
        S(i,T)=S_h2(i,T)+(0.5*S_o2(i,T))-S_h2o(i,T); 
        G(i,T)=H(i,T)-(T*S(i,T)); 
        E(i,T)=(G(i,T)/(2*F)); 
        ET(i,t) = 1.5184-(1.5421*10^-3*T)+(9.523*10^-5*T*log(T))+(9.84*10^-8*T^2); 
        EP(i,t)= 1.23+(((R*T)/(n*F))*(log(0.5*0.5^0.5))); 
        VT(i,t) = ET(i,t) + Eta_Anode(i,t) - Eta_Cathode(i,t) + Eta_Ohmic(i,t) + Eta_Conc(i,t); 
        VP(i,t) = EP(i,t) + Eta_Anode(i,t) - Eta_Cathode(i,t) + Eta_Ohmic(i,t) + Eta_Conc(i,t); 
        V(i,t) = E(i,t) + Eta_Anode(i,t) - Eta_Cathode(i,t) + Eta_Ohmic(i,t) + Eta_Conc(i,t); 
        %Mass Flow Rate 
        A(i) = I(i)* 50; 
        M_H2(i) = (A(i)*0.99)/(2*F); 
        M_O2(i) = (A(i)*0.99)/(4*F); 
        M_H2O(i) = (A(i)*0.99)/(2*F); 
        disp (['At Current = ',num2str(I(i)),'A',', Mass Flow Rate of H2 = ', num2str(M_H2(i)),' mol/s',', Mass Flow Rate of O2 = ', num2str(M_O2(i)),' mol/s',', Mass Flow Rate of H2O = ', num2str(M_H2O(i)),' mol/s']); 
    end 
end 
figure(1); 
plot (I,V(:,1),I,V(:,2),I,V(:,3),I,V(:,4),I,V(:,5),I,V(:,6)) 
legend('T=25','T=40','T=56','T=64','T=55','T=48') 
xlabel('Current Density (A/cm2)'); 
ylabel('Cell Voltage (Volt)'); 
title('I-V Curve (General Equation of E reversible)'); 
figure(2); 
plot (I,VP(:,1),I,VP(:,2),I,VP(:,3),I,VP(:,4),I,VP(:,5),I,VP(:,6)) 
legend('T=25','T=40','T=56','T=64','T=55','T=48') 
xlabel('Current Density (A/cm2)'); 
ylabel('Cell Voltage (Volt)'); 
title('I-V Curve (Pressure & Temperature variation)'); 
figure(3); 
plot (I,VT(:,1),I,VT(:,2),I,VT(:,3),I,VT(:,4),I,VT(:,5),I,VT(:,6)) 
legend('T=25','T=40','T=56','T=64','T=55','T=48') 
xlabel('Current Density (A/cm2)'); 
ylabel('Cell Voltage (Volt)'); 
title('I-V Curve (Temperature variation)');

figure(4); 
plot(I,M_H2(:),I,M_H2(:),I,M_H2(:),I,M_H2(:),I,M_H2(:),I,M_H2(:)) 
xlabel('Current Density (A/cm2)'); 
ylabel('Molar Flow Rate (mol/s)'); 
title('Current vs Molar Flow Rate of H2'); 
figure(5); 
plot(I,Eta_Anode(:,1),I,Eta_Anode(:,2),I,Eta_Anode(:,3),I,Eta_Anode(:,4),I,Eta_Anode(:,5),I,Eta_Anode(:,6),I,Eta_Cathode(:,1),I,Eta_Cathode(:,2),I,Eta_Cathode(:,3),I,Eta_Cathode(:,4),I,Eta_Cathode(:,5),I,Eta_Cathode(:,6),I,Eta_Ohmic(:,1),I,Eta_Ohmic(:,2),I,Eta_Ohmic(:,3),I,Eta_Ohmic(:,4),I,Eta_Ohmic(:,5),I,Eta_Ohmic(:,6),I,Eta_Conc(:,1),I,Eta_Conc(:,2),I,Eta_Conc(:,3),I,Eta_Conc(:,4),I,Eta_Conc(:,5),I,Eta_Conc(:,6)) 
legend('T=25','T=40','T=56','T=64','T=55','T=48') 
xlabel('Current Density (A/cm2)'); 
ylabel('Overpotential (Volt)'); 
title('Different Overpotential'); 
figure(6); 
plot(I,Eta_Anode(:,1),I,Eta_Anode(:,2),I,Eta_Anode(:,3),I,Eta_Anode(:,4),I,Eta_Anode(:,5),I,Eta_Anode(:,6)) 
xlabel('Current Density (A/cm2)'); 
ylabel('Overpotential (Volt)'); 
title('Activation Anode Overpotential'); 
figure(7); plot(I,Eta_Cathode(:,1),I,Eta_Cathode(:,2),I,Eta_Cathode(:,3),I,Eta_Cathode(:,4),I,Eta_Cathode(:,5),I,Eta_Cathode(:,6)) 
xlabel('Current Density (A/cm2)'); 
ylabel('Overpotential (Volt)'); 
title('Activation Cathode Overpotential'); 
figure(8); plot(I,Eta_Ohmic(:,1),I,Eta_Ohmic(:,2),I,Eta_Ohmic(:,3),I,Eta_Ohmic(:,4),I,Eta_Ohmic(:,5),I,Eta_Ohmic(:,6)) 
xlabel('Current Density (A/cm2)'); 
ylabel('Overpotential (Volt)'); 
title('Ohmic Overpotential'); 
figure(9); plot(I,Eta_Conc(:,1),I,Eta_Conc(:,2),I,Eta_Conc(:,3),I,Eta_Conc(:,4),I,Eta_Conc(:,5),I,Eta_Conc(:,6)) 
xlabel('Current Density (A/cm2)'); 
ylabel('Overpotential (Volt)'); 
title('Concentration Overpotential');

Answer 1

[Torsten]

You mean

ia = (10^-7)*(exp(-(Eexc/R)*((1/T)-(1/298)))); 
ic = (10^-3)*(exp(-(Eexc/R)*((1/T)-(1/353))));

instead of

ia = (10^-7)(exp(-(Eexc/R)((1/T)-(1/298)))); 
ic = (10^-3)(exp(-(Eexc/R)((1/T)-(1/353))));

?

And the second dimension of V, VP, VT, Eta_anode,... is only 3, not 6, so that you will get a dimension error in the plots.

Answer 2

[Dyuman Joshi]

There are missing operators at many places in your code, e.g. -

%          vv            vv
ia = (10^-7)(exp(-(Eexc/R)((1/T)-(1/298))));

%          vv            vv 
ic = (10^-3)(exp(-(Eexc/R)((1/T)-(1/353)))); 

Use appropriate operators and this issue will be resolved.

[Dyuman Joshi]

Additionally, V is 8x3 where as you trying to access the 4th, 5th and 6th column of it, which don't exist.

Same for VT and VP.

I suggest you go through your code thoroughly once and check each line.

[Walter Roberson]

MATLAB does not have implied multiplication anywhere