Abstract
3D and porous reduced graphene oxide (rGO) catalysts have been prepared with sp3-hybridized 1,4-diaminobutane (sp3-DABu, rGO-sp3-rGO) and sp2-hybridized 1,4-diaminobenzene (sp2-DABe, rGO-sp2-rGO) through a covalent amidation and have employed as a metal-free electrocatalyst for oxygen reduction reaction (ORR) in alkaline media. Both compounds have used as a junction between functionalized rGO layers to improve electrical conductivity and impart electrocatalytic activity to the ORR resulting from the interlayer charge transfer. The successful amidation and the subsequent reduction in the process of catalyst preparation have confirmed by X-ray photoelectron spectroscopy. A hierarchical porous structure is also confirmed by surface morphological analysis. Specific surface area and thermal stability have increased after successful the amidation by sp3-DABu. The investigated ORR mechanism reveals that both functionalized rGO is better ORR active than nonfunctionalized rGO due to pyridinic-like N content and rGO-sp3-rGO is better ORR active than rGO-sp2-rGO due to higher pyridinic-like N content and π-electron interaction-free interlayer charge transfer. Thus, the rGO-sp3-rGO has proven as an efficient metal-free electrocatalyst with better electrocatalytic activity, stability, and tolerance to the crossover effect than the commercially available Pt/C for ORR.
Highlights
The charge transfer between multi-layers of rGO (3D type) has not been investigated yet
Both molecules containing amine groups in the terminal positions were used as the junction between rGO layers to impart electrocatalytic activity for the ORR resulting from the net positive charge caused by the N atoms of the adjacent C atoms
Graphene oxide (GO)-COOH showed its poor thermal stability and considerable mass loss (16.4 wt %) at 100 °C were due to the removal of adsorbed water
Summary
The charge transfer between multi-layers of rGO (3D type) has not been investigated yet. Direct ORR8,21,22 catalysis involving four electrons is an interesting research area because of its important role in the application of energy conversion devices, such as FCs and metal-air batteries in alkaline media[18,19,20,21,23] Novel metals, such as platinum (Pt) and its alloy materials are regarded as the most efficient electrocatalysts for ORR in cathodes[24,25]. Both molecules containing amine groups in the terminal positions were used as the junction between rGO layers to impart electrocatalytic activity for the ORR resulting from the net positive charge caused by the N atoms of the adjacent C atoms. The rGO-sp3-rGO showed better electrocatalytic activity, stability, and tolerance to the crossover effect than that of other tested samples including state-of-the-art Pt/C because of its interaction-free interlayer charge transfer
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