Heteroatom (N, O, and S)-Based Biomolecule-Functionalized Graphene Oxide: A Bifunctional Electrocatalyst for Enhancing Hydrazine Oxidation and Oxygen Reduction Reactions

Abstract

In this work, a new method is developed to synthesize an l-cysteine-based graphene oxide (l-Cy-rGO) electrocatalyst by a chemical synthesis approach. The electrocatalytic studies of l-Cy-rGO for the oxygen reduction reaction (ORR) and hydrazine oxidation reaction (HOR) have been demonstrated, as important fuel-cell oxidation and reduction reactions confirm its bifunctional nature. The electrochemical ORR performance of l-Cy-rGO is significantly improved with an onset potential of 0.77 V vs reversible hydrogen electrode (RHE) and a current density of −2.32 mA/cm2 in O2-saturated 0.5 M KOH electrolytes. The electrochemical impedance spectroscopy (EIS) and chronoamperometric (i–t) measurements of the electrocatalyst are also carried out toward determining the feasibility of electron transfer and current/potential stability at the interface. The l-Cy-rGO electrocatalyst shows excellent activity toward ORR in alkaline medium. Furthermore, l-Cy-rGO shows better electrocatalytic activity toward HOR at an onset potential of 1.01 V vs RHE and the maximum current density of 65 mA/cm2 at a potential of 1.59 V vs RHE at 35 μM hydrazine hydrate in 0.5 M KOH. The electrochemical studies show that the l-Cy-rGO exhibits the highest electrocatalytic activity toward hydrazine oxidation. Moreover, the l-cysteine-functionalized graphene oxide supporting material plays an excellent role that could be from their synergistic catalytic effect. The l-Cy-rGO electrocatalyst shows excellent electrochemical ORR and HOR performances due to the presence of S- and N-heteroatom-containing surface of GO that enhances the electrocatalytic activity and electron transfer capabilities toward the ORR. Morphological studies based on high-resolution transmission electron microscopy (HRTEM) confirm that the size of l-Cy-rGO is ∼10 nm. X-ray photoelectron spectroscopy (XPS) analysis confirms the surface functionalization of GO by l-cysteine (l-Cy-rGO) from the binding energies of C–S, C–N, C–O, and C–C signals. Based on these findings, we find that the metal-free amino acid-functionalized carbon-based electrocatalyst shows excellent electrochemical ORR and HOR performances and demonstrate its key role toward enhancement in activities.

Palladium-Nickel Electrocatalysts on Nitrogen-Doped Reduced Graphene Oxide Nanosheets for Direct Hydrazine/Hydrogen Peroxide Fuel Cells

“…According to Equation ( 3), H 2 O and N 2 are products of this type of DFC [10,11]. Various chemicals have been designed recently and their performances as catalysts examined in the DHzHPFC [3,5,9,[12][13][14][15][16][17][18]. For example, the accumulation of gas bubbles on the electrode surface is effectively solved by using a nano-hill morphology of vertical graphene, by means of which a superoleophobic electrode was obtained that could accelerate the elimination process of bubbles generated on the anodic electrode surface.…”

Cobalt-modified palladium nanocatalyst on nitrogen-doped reduced graphene oxide for direct hydrazine fuel cell

“…39,40 For instance, a very high positive charge on the carbon atom adjoining to nitrogen atoms and also a positive change of Fermi energy at the apex of the Brillouin zone of rGO are reported in the literature for the nitrogen-doped reduced graphene oxide (NrGO NSs). [39][40][41] NrGO NSs have been widely employed as catalyst support, or as an active material for various main electrochemical processes involving HzOR, H 2 O 2 or O 2 reduction, lithium-ion battery, and supercapacitor. 42,43 Considering to the advantages of NrGO NSs as a catalyst support and good results of alloying Pd with Co transition metal, it is expected that incorporating PdCo bimetallic NPs on the NrGO NSs will be successful for improving performance in DHzHPFC applications.…”

Synthesis of Metal‐Free Nanoporous Carbon with Few‐Layer Graphene Electrocatalyst for Electrochemical NO2− Oxidation

“…Thus, the nanoporous nature of the carbon nanostructures is seen from the above observations along with it confirms its nanoporous nature and is in good agreements with the literature. [30][31][32][33]…”