In summary, IRR mechanism computation reveals that the electron-donating ability of the electro-catalysts is the key to increase IRR rate. In addition, AFG is screened from the volcano plot owing to the optimal iodine binding energy and the higher catalytic activity. AFGs are of great potential as carbon-based CE candidates, implying the importance of introduction of ethylamine group on the surface of graphene that can help to reduce ionization energy and lower the activation energy barrier of IRR. Finally, the PCE of the DSCs using AFG as CE is close to that based on Pt CE. Our present work provides an efficient strategy and good example for rational design of highly efficient CEs for DSCs.