Regulation the surface chemistry and electronic structure of Fe/Co/N co-doped hollow graphene spheres by different atmosphere plasma to enhance oxygen reduction/hydrogen evolution performance of loaded PtNi alloy nanoparticles

Abstract

In this work, plasma under different atmospheres is used to adjust the surface electronic and chemical structure of Fe/Co/N co-decorated hollow graphene spheres (FCNHGS) in order to create suitable conditions for the deposition of Pt1Ni2 alloy nanoparticles (NPs). The results show that plasma treatment in specific atmospheres has different effects on the surface of FCNHGS, such as O2 plasma is etching and oxidation, N2 plasma and Ar plasma is etching, Ar/H2 plasma is etching and reduction, Ar/NH3 plasma is etching, doping and reduction. Therefore, changing the plasma treatment atmosphere can control the anchoring sites on FCNHGS for the deposition of Pt1Ni2 NPs. When Ar/NH3 plasma is used, the synthesized Pt1Ni2@Ar/NH3-FCNHGS exhibits the best bi-functional catalytic activity and the highest utilization efficiency of Pt in the oxygen reduction and hydrogen evolution reaction (ORR/HER) due to the strong interaction between loaded Pt1Ni2 NPs and the Ar/NH3-FCNHGS. Moreover, when the Pt1Ni2@Ar/NH3-FCNHGS is used as cathode catalyst for direct methanol fuel cell, it exhibits superior open-circuit voltage (OCV = 730 mV) and similar peak power density (PPD = 62.8 mW cm−2) to 20 wt% Pt/C from 25 to 80 °C. More importantly, it showed better stability compared with 20 wt% Pt/C after about 72 h of stability testing.