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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.

We report here non‐enzymatic electrochemical biosensing of H2O2 using a highly stable, metal‐free, tyramine functionalized graphene (T‐GO) based electrocatalytic system. The surface functionalization of tyramine on graphene was carried out chemically. The obtained sheets were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) as well as X‐ray photoelectron (XP), Raman, FT‐IR and UV‐visible spectroscopy. More significantly, the combined results from morphological and structural studies show the formation of a few layers of graphene with effective large‐scale functionalization by tyramine. As a metal‐free electrocatalyst, the as‐synthesized T‐GO shown good electrocatalytic activity towards reduction of H2O2 with a sensitivity of 0.105 mM/cm2 confirmed by combined results from cyclic voltammetric (CV) and linear sweep voltammetric (LSV), and amperometric (i–t) measurements. The lower onset potential (−0.23 mV vs SCE), lower detection limit, wider concentration range (10 mM to 60 mM) with higher electrochemical current and potential stability demonstrated the potential of our non‐enzymatic and cost‐effective T‐GO based electrocatalytic system towards reduction of hydrogen peroxide.

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As functional molecules, amino acids have attracted great attention in the field of material sciences due to their interactive sites. New studies have shown the electrocatalytic activity capability of amino-acid-functionalized graphene oxide (GO) toward the oxygen evolution reaction (OER). The improved active sites and further tunable and huge surface area after l-lysine functionalization on reduced graphene oxide (Ly-rGO) offer significant opportunities for further enhancement in the OER activity. Herein, the functionalization of GO with terminal nitrogen-containing groups (l-lysine) results in efficient and stable electrocatalytic activity for OER with a lower overpotential of 0.33 V at 10 mA cm–2 and a lower Tafel slope of 80 mV dec–1. Electrochemical impedance spectroscopic of Ly-rGO also shows a lower R ct = 29.58 Ω and an excellent current stability for 5000 s at an onset potential of 1.29 V vs SCE in 0.5 M KOH. Morphological studies based on high-resolution transmission electron microscopy confirm that the size of Ly-rGO is ∼5 nm. X-ray photoelectron spectroscopic analysis confirms the surface functionalization of GO by lysine (Ly-rGO) from the binding energies of C–N, C–O, and C–C. From this perspective, our findings emphasize the usefulness of metal-free amino-acid-functionalized carbon-based electrocatalysts for OER, which is an important water-splitting reaction, and demonstrates that they may be keys toward enhancement in activities.

Direct ethanol fuel cells (DEFCs) are one of the resourceful and sustainable technologies for energy applications. Ethanol oxidation has been used to construct cost-effective and proficient electrocatalysts to substitute noble-based electrocatalysts like Rh, Pd, Ir, and Ag. Here in, we have presented a surface modification approach of doping a crucial oxophilic character metal onto a transition metal with carbon support. Noble metal-free cobalt−bismuth bimetallic nanoparticledecorated reduced graphene oxide (Co−Bi@rGO) electrocatalysts were fabricated for enhanced ethanol oxidation reaction from their synergetic effect of rGO, Co, and Bi. A highly active, cost-effective, and efficient approach has been developed for the preparation of Co−Bi@rGO (Co NPs; ∼2 nm), initially Bi@rGO (Bi NPs@rGO; ∼50 nm), by a simple reduction method followed by Co, by Galvanic exchange of Bi atoms with Co. The as-synthesized nanocomposites were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and BET surface area measurement studies. Cyclic voltammetric studies show an ultralow onset potential of 0.28 V with a high current density of 10.25 mA/cm 2 , having a higher enhancement factor for Co−Bi@rGO compared to other individuals, including Bi NPs, Bi@rGO, and rGO under similar electrolyte conditions, which could be due to their synergetic cooperative interactions at electrified interfaces. Combined results from chronoamperometry (i−t) and electrochemical impedance spectroscopy show that Co−Bi@rGO is highly durable and sensitive toward the ethanol oxidation reaction compared to individual counterparts. This work also provides the noble metal-free bimetallic electrocatalysts for ethanol oxidation and assists in hydrogen production from an agricultural base.

Ethylenediamine functionalized C60 (EDA@C60) based electrocatalyst demonstrated for hydrazine oxidation and it shows more than double current density i.e. 20 mA cm−2 at an ultralow onset potential of 0.2 V vs. SCE with better stability over oxidized C60.

Herein, we focused on the one pot synthesis of ZnO nanoplates (NP edge thickness of ∼100 nm) using a chemical emulsion approach for chemical (direct) and electrochemical (indirect) determination of NO2.