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Hydrogen peroxide (H 2 O 2 ) detection was electrochemically performed using a non-enzymatic cobalt(III) complex ( 2 ) of an amidomacrocyclic ligand ( 1 ). We have characterized the metal complex using analytical techniques such as 1 H NMR and ESI-MS and the composite material of the catalyst supported on multiwalled carbon nanotubes (MWCNTs) with XPS and TEM. Using different carbonaceous nanomaterials, varying catalyst:nanomaterial ratio and changing the pendant groups on the ligand moiety of the complex, we found that a dichloro substituent ( 2a ) supported on MWCNTs as the most effective H 2 O 2 sensor. From these studies, a low detection limit (5.0 × 10 −8 M) and a wide detection range was obtained. Electrochemical studies indicated 2a and MWCNTs worked synergistically to detect the presence of H 2 O 2 . UV/Vis of 2a showed the disappearance of a peak at 500 nm and the emergence of a peak at 395 nm after the addition of H 2 O 2 to 2a indicating formation of an intermediate species. 2a was also able to electrochemically determine the concentration of H 2 O 2 present in several commercial products. Hence, 2a shows promising application as a non-enzymatic H 2 O 2 sensor. [ABSTRACT FROM AUTHOR]