Fabrication of hierarchical MnxOy@SiO2@C-Ni nanowires for enhanced catalytic performance

A novel structure of hierarchical SiO2@C-Ni nanoflakes on MnxOy nanowires is designed, in which Ni nanoparticles (NPs) are highly-density embedded in the carbon layer derived from polydopamine(PDA). MnO2 nanowires are started as carriers and SiO2 layer is used as scarifying template coating on the nanowires, which is further chemically reacted with nickel source to forming nickel silicate (NS) nanoflakes on MnO2 nanowires (MnO2@NS). The formed hierarchical nanoflakes of MnO2@NS are further coated by PDA, serving as a reductive agent to form Ni particles in the following N-2 carbonization process. The calcination temperature has a great impact on the sizes of reduced Ni NPs, and 500 degrees C yields samples with ultrafine magnetic Ni NPs, while higher temperatures destroy the layer structure of graphene-like carbon and cause agglomerations of Ni NPs. MnxOy@ SiO2@C-Ni/500 shows the best catalytic performance on the reduction of 4-nitrophenol due to the ultrafine and highly dispersed Ni NPs.