Tuning the ORR activity of Pt-based Ti₂CO₂ MXenes by varying the atomic cluster size and doping with metals

The rational design of ideal catalysts for the oxygen reduction reaction (ORR) is of great significance for solving the electrocatalytic potential problems in proton exchange membrane fuel cells (PEMFCs). Pt_n (n = 1-4) and Pt₃Au alloy subnanoclusters supported on a defective Ti₂CO₂ monolayer with oxygen vacancies (denoted as v-Ti₂CO₂) are simulated by using density functional theory to investigate their ORR performance. The geometries, energetics, and electronic properties of the different systems are analyzed. It is found that the supported Pt₃Au alloy subnanocluster possesses the best ORR activity. The underlying mechanisms of the improved ORR activity originates from the moderate hybridization between the O 2p and the 5d orbitals of Au and Pt according to the density of states analysis. Our study suggests a facile route for designing low-cost MXene-based electrocatalysts by alloying transition metals with Pt catalysts, which may stimulate realization of suitable alternative catalysts for ORR catalysis.