Silver particles deposited onto magnetic carbon nanofibers as highly active catalysts for 4-nitrophenol reduction

We used CO₂ as a carbon source for conversion to carbon nanofibers through the catalytic hydrogenation reaction on a Ni-Na/Al₂O₃ catalyst. The Ag⁺ adsorbed on carbon nanofibers could be spontaneously reduced through the oxidation–reduction reaction Ni + 2Ag⁺ →2Ag + Ni²⁺. The adsorbed Ag⁺ was reduced by the electrons released from Ni, forming Ag particles on the carbon surface. The Ag deposited on the magnetic carbon nanofibers was employed to remove contaminants in water, in which 4-nitrophenol was reduced to 4-aminophenol. The apparent rate of 4-nitrophenol reduction was significantly enhanced with increasing Ag concentration in the range of 0.5–2.6 wt%, from 8.5 × 10^-3 to 1.25 × 10^-1 s^-1. The negative charge on the surface when Ag particles formed was assumed to be an important factor in enhancing the catalytic rate because of the increases in the coverage and adsorption rate of 4-NP on the catalyst surface.