Selective synthesis of carbon-nanotubes/graphite or carbon-nanotubes/multi-graphene composites on 3-D nickel foam prepared with different nickel catalyst and pre-treatment

Abstract

The research is to deposit carbon on porous 3-D nickel foam (NiF) as a gas diffusion electrode (GDE) by chemical vapor deposition (CVD). Effects of three different preparations of the nickel (Ni) catalyst and two pre-treatments of oxidation and reduction for carbon deposition were investigated. In the first method, the carbon was deposited on NiF with and without sputtering a Ni seed layer before the CVD. In the second method, the NiF was oxidized, then reduced by hydrogen into Ni particle as a catalyst and the carbon also was deposited by CVD. In the third method, a thin film of SiO2 was deposited on the NiF as a separation layer, then the Ni catalyst was deposited and finally, carbon was also deposited by CVD. The results exhibited large grain sizes of Ni catalyst cannot grow carbon nanotube (CNTs) during CVD. Pre-treatment of oxidation and the reduction reduce the grain size of the Ni catalyst, and an oxidation temperature equal or higher than the reduction temperature always makes it easy to grow CNTs. A smooth SiO2 thin film was used as a separation layer to deposit the Ni catalyst to grow the SWCNTs and a low area ratio of ID/IG for a non-crystallized sp3 graphite microstructure always creates a graphene microstructure. A suitable hydrogen gas could help the amount of growth of CNTs. Anyway, the specified Ni catalysis could promise strategy the selective synthesis of CNTs/graphite or CNTs/multi-graphene composites on NiF.