Characterisation and H2O2 sensing properties of TiO2-CNTs/Pt electro-catalysts

Titania/carbon nanotubes/platinum (TiO2-CNTs/Pt) nanohybrids, prepared by the micro-emulsion method followed by wet impregnation for Pt loading, were synthesized and investigated as active materials for H2O2 oxidation. Steps of preparation method employed were optimized in order to improve the sensing performance of TiO2-CNTs/Pt nanocomposite towards the H2O2 oxidation. By changing the order in which CNTs are added to the solution, hetero-structures with different grain size and crystalline phase of the metal oxide were synthesised. Adding CNTs to the micro-emulsion solution favoured the aggregation between oxide nanoparticles over the interaction with CNTs, leading to the formation of larger anatase titania agglomerates. Instead, smaller-sized rutile particles formed by adding CNTs before the onset of precipitation. The order of CNT addition to the solution was found to influence also Pt particle size, with the smaller metal particles observed on the sample prepared by the latter procedure. The nanocomposite consisting of uniformly distributed TiO2 particles on the surface of CNTs and smaller Pt nanoparticles showed the best performance sensing towards H2O2. An amperometric H2O2 sensor was fabricated by modifying the working electrode surface of a planar screen printed carbon electrode (SPCE) device. The sensor showed excellent sensitivity (120 μA mM-1 cm-1) and linearity in a large range (from 70 μM to 6 mM), and a low detection limit < 5 μM at 3 signal/noise ratio working at a low potential of 0.3 V.