▎ 摘　　要

CO poisoning is one of the obstacles for platinum catalysts toward the electro-catalysis process for proton exchange membrane fuel cell (PEMFC) or direct methanol fuel cell (DMFC). Herein, we aim to weaken the CO poisoning on Pt by varying the cluster sizes and supports via doping graphene with B and N based on DFT + D3 calculations. Energetically, the most favorable Pt-n/X-graphene (X = C, B, N; n = 1-6, 13) structures are obtained, and the calculated binding energies between Pt-n and X-graphene are size- and support-dependent on a sequence: Pt-n/B-g > Pt-n/N-g > Pt-n/C-g. The low-coordinated and protruded Pt atoms are identified as the active sites. The medium-sized clusters (n = 4-6) display CO poisoning-free properties with an excellent CO oxidation performance, resulting from the moderate locations of d-band center and electronic transfer via the interface. Furthermore, E-R mechanism is revealed to dominate the reaction route with a rate-limiting step of the second CO2 desorption. The corresponding activation energy barriers are 0.53, 0.61 and 0.56 eV for Pt-n/B-g (n = 4, 5, 6), respectively. This work provides insights into the theoretical design of CO poisoning-free catalyst Pt-n/X-g in the applications of DMFC/PEMFC.