Weakening CO poisoning over size- and support-dependent Pt_n/X-graphene catalyst (X = C, B, N, n = 1–6, 13)

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.