Pt and Au bimetallic and monometallic nanostructured amperometric sensors for direct detection of hydrogen peroxide: Influences of bimetallic effect and silica support

The non-enzyme direct electrochemical sensing of hydrogen peroxide (H₂O₂) by nanostructured electrodes of Pt- and Au-containing bimetallic or monometallic nanocatalysts including paramecium-like nanostructures of PtAu supported on silica nanorods, Pt and Au nanoparticles supported on silica nanorods, and the non-supported Pt and Au nanoparticles (NPs) is reported. The nanocatalysts modified electrodes were fabricated by simple self-assembling on 3-aminopropyl-trimethoxysilane (APTMS) modified glassy carbon. The cyclic voltammetric and amperometric results showed that PtAu supported on silica nanorods has superior performance over the corresponding monometallic counterparts, with a broad linear range from 5.0 µM to 72000 µM for H₂O₂, a detection limit of 2.6 µM, a sensitivity of 46.7 µA mM^-1cm^-2 at a lower working potential of -0.20 V vs SCE, and has good stability and reproducibility. In addition, a systematic test showed that the non-supported Pt NPs sensor has a surprisingly high performance, even better than the paramecium-like nanostructure of PtAu supported on silica nanorods, where the existence of silica nanorod templates in the nanocatalysts retards the electrocatalytic reduction/oxidation of H₂O₂. Among the nanocatalysts tested in this work, the Pt NPs sensor showed fastest response within 3 s, a broad linear response from 5 µM to 58000 µM, a detection limit of 4.2 µM, and the highest sensitivity of 110.3 µA mM^-1cm^-2 at the lowest working potential of -0.08 V vs SCE. Notably, the performance of the Pt NPs sensor is also among the best Pt-containing monometallic or bimetallic nanostructured electrochemical sensors toward H₂O₂ reported so far. This work shows a simple method to fabricate H₂O₂ electrochemical sensors of high performance and indicates the importance of considering not only bimetallic effects but also the influences of the nanostructure of nanocatalysts on the electrocatalytic performance and electrochemical sensing property.