Iron Quantum Dots Electro-Assembling on Vulcan XC-72R: Hydrogen Peroxide Generation for Space Applications

Abstract

Highly dispersed iron-based quantum dots (QDs) onto powdered Vulcan XC-72R substrate were successfully electrodeposited by the rotating disk slurry electrodeposition (RoDSE) technique. Our findings through chemical physics characterization revealed that the continuous electron pathway interaction between the interface metal–carbon is controlled. The rotating ring-disk electrode (RRDE) and the prototype generation unit (PGU) of in-situ H2O2 generation in fuel cell experiments revealed a high activity for the oxygen reduction reaction (ORR) via two-electron pathway. These results establish the Fe/Vulcan catalyst at a competitive level for space and terrestrial new materials carriers, specifically for the in-situ H2O2 production. Transmission electron microscopy (TEM) analysis reveals the well-dispersed Fe-based quantum dots with a particle size of 4 nm. The structural and chemical-physical characterization through induced coupled plasma-optical emission spectroscopy (ICP-OES), transmission scanning electron microscopy (STEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS); reveals that, under atmospheric conditions, our quantum dots system is a Fe2+/3+/Fe3+ combination. The QDs oxidation state tunability was showed by the applied potential. The obtention of H2O2 under the compatibility conditions of the drinking water resources available in the International Space Station (ISS) enhances the applicability of this iron- and carbon-based materials for in-situ H2O2 production in future space scenarios. Terrestrial and space abundance of iron and carbon, combined with its low toxicity and high stability, consolidates this present work to be further extended for the large-scale production of Fe-based nanoparticles for several applications.

Ex Situ and In Situ Analyses of the Mechanism of Electrocatalytic Hydrogen Peroxide Production by CoxZn1–xO (0 < x < 0.018) Materials in Alkaline Media

“…I ring is associated with the H 2 O 2 formation–degradation process. The H 2 O 2 selectivity (% H 2 O 2 ) and the electron transfer number ( n ) were calculated as follows , where I ring is the ring current, I disk is the disk current, and N is the collection efficiency.…”

“…Hydrogen peroxide (H 2 O 2 ) is an alternative energy carrier to oil, natural gas, and hydrogen fuel for sustainable energy applications. − However, current H 2 O 2 production is energy-intensive, as it is manufactured by the catalytic oxidation of hydrogen with atmospheric oxygen using anthraquinone as the catalyst. The four-step process includes hydrogenation on a palladium catalyst between hydrogen and anthraquinone, which produces anthrahydroquinone as an intermediate.…”

“…This multistep process involving a Pd catalyst could be improved by performing direct electrocatalytic production. The direct electrochemical production of H 2 O 2 provides a cost-effective in-house generation alternative , but requires a high performing catalyst with good selectivity and stability.…”

“…I ring is associated with the H 2 O 2 formation− degradation process. The H 2 O 2 selectivity (% H 2 O 2 ) and the electron transfer number (n) were calculated as follows5,31…”

Combined Rotating Disk Slurry Electrodeposition–Spontaneous Galvanic Displacement for Pt-M (M = Co, Ni, and Cu) Catalyst Synthesis for the Oxygen Reduction Reaction in Alkaline Media

“…Different synthesis methods, such as hydrothermal, sol–gel, and chemical reduction methods, could be used to obtain ORR electrocatalysts. Electrodeposition is another alternative where the rotating disk slurry electrodeposition (RoDSE) methodology has been studied for over 10 years for catalyst preparation on unsupported carbon materials, for example, Vulcan XC-72R (CBV), single wall carbon nanotubes, reduced graphene oxide, and carbon nano-onions. − Some of the benefits of this method are the fact that no heat treatment is required and scale-up synthesis can be obtained, providing a fluent transition from the rotating disk electrode (RDE) to the membrane electrode assembly (MEA). RoDSE has been successfully used to synthesize Pt, Pd, , Au, Ag, , and Fe nanoparticles supported on different carbon supports for energy conversion applications.…”