Dye Diazonium-Modified Carbon Nanotubes with Immobilized Gold Nanoparticles as Nanohybrid Electrocatalyst of Direct Methanol Oxidation

In a world of constant rush towards novel energy sources, hybrid nanomaterials have raised huge interest as their components can synergistically improve the expected performances in terms of power. In this regard, direct methanol oxidation (DMO) is among the most investigated reactions for implementation in portable and other devices. Herein, we report the design of gold-decorated CNT-aryl nanohybrids as electrocatalyst of DMO. In a first step, Azure A (AA), Neutral Red (NR) and Congo Red (CR) dye diazonium salts were reacted with CNTs to provide CNT-Dye nanoscale platforms for the immobilization of gold NPs. This step was conducted with CNT-Dye platforms evenly spread over glassy carbon (GC) electrodes. The CNT-Dye@Au nanohybrid electrode materials served for DMO electrocatalysis. Cyclic voltammograms show that bare CNT-Dye nanohybrids exhibit high electrocatalytic activity, particularly for the CNT-CR nanohybrid which returned a 3-fold improvement. With anchored Au NPs, a further 4 time remarkable increase in the oxidation peak intensity was achieved (i.e. about 12-fold the peak intensity recorded in the absence of any nanocatalyst). The forward to the backward anodic peak current density ratio J_f/J_b was found to be as high as is 1.68.

This work provides a simple, elegant and efficient approach for designing robust, nanohybrid electrocatalyst for DMO, based on the smart combination of CNTs, diazotized dyes and gold NPs.