Electrocatalytic reduction of trace nitrobenzene using a graphene-oxide@polymerized-manganese-porphyrin composite

A core–shell structure electrocatalyst for trace nitrobenzene reduction was prepared with Mn(ii)[5,10,15,20-tetra(4-aminophenyl)porphyrin] (MnTAPP) and graphene oxide (GO) as raw materials. Firstly, MnTAPP and GO were combined together by covalent bonds, and then the supported MnTAPP was coupled together through p-dibromobenzene, a conjugated bridging agent, to obtain a more stable graphene-oxide@polymerized-manganese-porphyrin composite (GMPP@AMP). The structure and morphology of the GMPP@AMP were characterized by FT-IR, Raman spectroscopy, SEM and TEM. The GMPP@AMP modified glassy carbon electrode (GMPP@AMP/GCE) was prepared and the electrochemical activity of GMPP@AMP towards nitrobenzene reduction was evaluated by cyclic voltammetry (CV). The results showed that GMPP@AMP/GCE had a more positive reduction potential than MnTAPP/GCE and GO/GCE, and the reduction current responded more sensitively. Electrocatalytic reduction currents of nitrobenzene were found to be linearly related to concentration over the range 0.04 to 0.24 mM using a differential pulse voltammogram (DPV) method. Nitrobenzene is easily compatible with polymerized MnTAPP which has rich nitrogen-containing functional groups and porous structure, and the highly conductive GO combined with the polymerized MnTAPP having excellent electron transfer ability. This produced a significant synergistic catalytic effect during the electrocatalytic reaction of trace nitrobenzene. The novel composite has good application prospects in electrochemical detection of trace nitrobenzene compounds in the environment.