Abstract
Hybrid systems composed of the reduced graphene oxide-supported platinum and multiwalled carbon nanotube-supported iridium (both noble metals utilized at low loadings on the level of 15 and ≤2 µg cm−2, respectively) were considered as catalytic materials for the reduction of oxygen in acid media (0.5-mol dm−3 H2SO4). The electrocatalytic activity toward reduction of oxygen and formation of hydrogen peroxide intermediate are tested using rotating ring–disk electrode (RRDE) voltammetric experiments. The efficiency of the proposed catalytic systems was also addressed by performing galvanodynamic measurements with gas diffusion electrode (GDE) half-cell at 80 °C. The role of carbon nanotubes is to improve charge distribution at the electrocatalytic interface and facilitate the transport of oxygen and electrolyte in the catalytic systems by lowering the extent of reduced graphene oxide restacking during solvent evaporation. The diagnostic electrochemical experiments revealed that—in iridium-containing systems—not only higher disk currents, but also somehow smaller ring currents are produced (when compared to the Ir-free reduced graphene oxide-supported platinum), clearly implying formation of lower amounts of the undesirable hydrogen peroxide intermediate. The enhancement effect originating from the addition of traces of iridium (supported onto carbon nanotubes) to platinum, utilized at low loading, may originate from high ability of iridium to induce decomposition of the undesirable hydrogen peroxide intermediate.
Highlights
Despite appreciable progress in the development of proton exchange membrane fuel cells, their commercialization still requires the lowering of the costs and more durable materials
We propose and describe a hybrid system composed of the reduced graphene oxide-supported platinum aligned with multiwalled-carbon-nanotube-supported iridium as catalytic materials for the reduction of oxygen in acid medium (0.5-mol dm−3 H2 SO4 )
The role of carbon nanotubes is to improve charge distribution at the electrocatalytic interface and facilitate the transport of oxygen and electrolyte in the catalytic systems by lowering the extent of reduced graphene oxide restacking during slow solvent evaporation. Another important issue is the ability of the proposed carrier to act as an efficient system for the decomposition of the hydrogen peroxide intermediate generated when a Pt catalyst is utilized at low loading
Summary
Despite appreciable progress in the development of proton exchange membrane fuel cells, their commercialization still requires the lowering of the costs and more durable materials. The role of carbon nanotubes is to improve charge distribution at the electrocatalytic interface and facilitate the transport of oxygen and electrolyte in the catalytic systems by lowering the extent of reduced graphene oxide restacking during slow solvent evaporation. Another important issue is the ability of the proposed carrier (carbon nanotubes decorated with Ir) to act as an efficient system for the decomposition of the hydrogen peroxide intermediate generated when a Pt catalyst is utilized at low loading. The rotating ring–disk voltammetric (RRDE) diagnostic experiments reveal that in iridium-containing systems, higher disk currents, and somehow smaller ring currents have been produced (compared to reduced graphene oxide-supported platinum), clearly implying formation of lower amounts of the undesirable hydrogen peroxide intermediate
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