A new bifunctional electrochemical sensor for hydrogen peroxide and nitrite based on a bimetallic metalloporphyrinic...

Metalloporphyrinic frameworks have been studied in many fields. However, their electrochemical properties were seldom reported. This work reports the synthesis and the electrochemical application of a new bimetallic metalloporphyrinic framework, [Cu₂-Co[5,10,15,20-(4-carboxyphenyl)porphyrin](H₂O)₂]·0.5DMF·5H₂O (Cu-CoTCPP) in which [5,10,15,20-(4-carboxyphenyl)porphyrin]Co(ii) (CoTCPP) struts are bound by Cu(ii)-carboxylate clusters (Cu₂(COO)₄). Cu-CoTCPP was synthesized by the solvothermal method and characterized by various techniques, including XRD, IR, UV-vis, elemental analysis, TG, and TEM. Cu-CoTCPP showed novel bifunctional electrocatalytic ability toward the reduction/oxidation of H₂O₂ and the oxidation of NaNO₂, which might be due to Cu and Co central ions, respectively. With the assistance of multi-walled carbon nanotubes (MWCNTs), Cu-CoTCPP showed further improved sensing performance toward H₂O₂. The linear detection ranges of the Cu-CoTCPP/MWCNTs/GCE for H₂O₂ and NaNO₂ are 5.0 × 10^-7 to 1.8 × 10^-4 M and 2.5 × 10^-6 to 1.1 × 10^-3 M, respectively, with the detection limits of 2.4 × 10^-7 M and 1.7 × 10^-7 M, and the sensitivity of 168 and 439 mA mol^-1 L cm^-2. The bifunctional electrocatalytic ability and the excellent performance imply that the metalloporphyrinic frameworks are promising candidates for fabricating electrochemical sensors.