Ordering Degree Regulation of Pt<sub>2</sub>NiCo Intermetallics for Efficient Oxygen Reduction Reaction

Alloying transition metals with Pt is an effective strategy for optimizing Pt-based catalysts toward the oxygen reduction reaction (ORR). Atomic ordered intermetallic compounds (IMC) provide unique electronic and geometrical effects as well as stronger intermetallic interactions due to the ordered arrangement of metal atoms, thus exhibiting superior electrocatalytic activity and durability. However, quantitatively analyzing the ordering degree of IMC and exploring the correlation between the ordering degree and ORR activity remains extremely challenging. Herein, a series of ternary Pt2NiCo intermetallic catalysts (o-Pt2NiCo) with different ordering degree were synthesized by annealing temperature modulation. Among them, the o-Pt2NiCo which annealed at 800 °C for two hours exhibits the highest ordering degree and the optimal ORR activity, which the mass activity of o-Pt2NiCo is 1.8 times and 2.8 times higher than that of disordered Pt2NiCo alloy and Pt/C. Furthermore, the o-Pt2NiCo still maintains 70.8% mass activity after 30,000 potential cycles. Additionally, the ORR activity test results for Pt2NiCo IMC with different ordering degree also provide a positive correlation between the ordering degree and ORR activity. This work provides a prospective design direction for ternary Pt-based electrocatalysts.