The atomic structural descriptor based on cluster expansion method and superior performance of oxygen reduction on PtTi surface alloys from theoretical perspective

Although alloying Pt with Ti is a feasible routine to improve oxygen reduction activity and stability, the atomic configuration of surface alloys on PtTi is still lacking deep understanding. Herein, the effect of Ti concentrations (x) in sublayer on ORR activity of PtTi surface alloys (Pt@Pt1-xTix@) with FCC or HCP Ti substrate, are systematically studied by first -principles calculations. The accurate atomic structural descriptor based on cluster expansion method is proposed to describe local atomic environment effect on intermediate (OH/OOH) adsorption ability. Different from b = 3.20 eV in traditional linear scaling relationship Delta GOOH = Delta GOH + b, the b values vary from 3.15 to 3.53 eV on PtTi surface alloys. Among surfaces alloys with different Ti concentrations, FCC- and HCP-Pt@Pt1-xTix(Pt)@ displayed the highest stability and catalytic activity at x = 3/9, and possessed a threefold and fivefold times of catalytic activity with a benchmark Pt(111) according to the calculated exchange current rate constants. Importantly, the FCC-Pt@Pt1-xTix(Pt)@ could be promising ORR catalyst as its high ORR activity at larger range of Ti concentration (x = 1/9-3/9), strong stability, and low Pt usage.