Tailoring rGO-Cu-Cu2O as a three-dimensional catalytic system in boosting of methanol electro-oxidation reaction

Abstract

Tailoring a reduced graphene oxide-Cu-Cu2O (rGO-Cu-Cu2O) as a three-dimensional (3D) integrated catalytic system via an in-situ potential-controlled electrodeposition approach is a feasible pathway to boost methanol oxidation reaction (MOR) for direct methanol fuel cell. The enhancement in catalytic functionality and performances is due to the synergistic interaction between the in-situ electroreduced graphene oxide (rGO) and copper metal ions over it. The sequential and synergistic effect of the co-deposition potential, optimized time, and probable corrosion-promotion effect (formation of a galvanic cell between rGO and copper due to entrapped dissolved oxygen) is believed to be responsible for the structural growth of as-developed 3D catalytic systems. The MOR results suggest that the composite material deposited at the higher cathodic deposition potential (-1.2 V vs SCE), i.e., rGO-Cu (c) featured the remarkable lowest onset oxidation potential (i.e., +0.37 V), peak potential (i.e., +0.73 V), peak current density (135.76 mAcm(-2)), potentiostatic durability at +0.6 V after 3.5 h (similar to 65.85 mAcm(-2)) and outstanding cyclic stability (similar to 97.7 % current retention after 500 cycles), which is superior to the other modified composite electrodes. The enhanced performances are due to the effective dissociative adsorption of methanol from the available active catalytic site's and the presence of hydroxyl groups which has probably improved the oxidation of adsorbed intermediates from the surface. Further, Fourier- transform infrared (FT-IR) experiments revealed that formate as an active intermediate is being generated on all three rGO-Cu-Cu2O modified electrodes and follows the non-CO reaction pathway for direct oxidation of methanol.