Phase engineering of Pt-Mn intermetallics for durable oxygen reduction reaction electrocatalysis

Controlling the crystal phase of intermetallic has been demonstrated as a promising strategy for enhancing oxygen reduction reaction (ORR) performance. However, the controlled synthesis of intermetallic with specific crystal phases remains a formidable challenge. Herein, structure ordered Pt-Mn intermetallics with face-centered cubic Pt3Mn (fcc-Pt3Mn/C) and face-centered tetragonal PtMn (fct-PtMn/C) are synthesized via an impregnation-reduction method. Benefiting from the rational control of crystal phase, fct-PtMn/C with optimal surface atomic arrangement and binding environment exhibits higher activity than fcc-Pt3Mn/C and Pt/C. Moreover, fct-PtMn/C exhibits a superior mass activity retention rate of 90.3 % after 50,000 potential cycles from 0.6 to 1.0 V compared to significantly lower rate of 56.0 % and 34.8 % for fcc-Pt3Mn/C and Pt/C, respectively. Structural analysis reveals that fct-PtMn/C maintains its crystal phase, particle size, and morphology exceptionally well during the durability test, demonstrating its outstanding structural stability. Theoretical calculations indicate that phase engineering can lower the reaction energy barrier, weaken the adsorption energy of reaction intermediates on fct-PtMn/C, and thus enhance the ORR performance.