Insights into the trigger effect of Pt-N bond on lattice distortions of novel PtCu alloys enabling an unusual pathway in oxygen reduction

Abstract

The precise manipulation of the carbon matrix into a unique hierarchical structure by heteroatoms (N) doping, further applying to load Pt-transition metal (M) nanoparticles (NPs) can enable PtM/NC catalyst with excellent oxygen reduction reaction (ORR) activity. However, the electronic and geometric structure changes of PtM NPs after introducing N, and the corresponding catalytic mechanism during ORR are often neglected. Herein, the N-doped metal organic framework (MOF)-derived carbon loaded PtCu NPs catalyst (PtCu/NC) is prepared to reveal the surface behavior of Pt-N and its modulation mechanism. The Cu and carbon separation property of Cu-MOF pyrolysis supports the preferential N-doping of carbon, followed by PtCu alloying. This lays the structural basis for the formation of Pt-N bond. The density function theory (DFT) proves that N preferentially bonds with Pt to form Pt-N bond to trigger lattice distortions of the subsequently alloyed PtCu NPs. In situ Raman analysis shows the dynamic evolution of OOH* intermediate on distorted PtCu NPs, further proving that there is indeed the electron transfer from N to Pt superior to that of Cu promoting associative pathway for oxygen reduction. These boost PtCu/NC catalyst exhibiting excellent ORR activity with a mass activity (MA) of 0.87 AmgPt−1 (@0.80 V), greater than that of 20 wt% Pt/C. Additionally, a high MA is also obtained in the methanol oxidation reaction (MOR) test, also higher than that of Pt/C.