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.
In this study, we report a method
for fabrication of rhodium nanoparticles
decorated on graphene oxide (Rh–GO) with high coverage of active
sites of Rh nanospheres (NSs) on GO. It is one of the most pivotal
aspects in the development of novel systems having high electrocatalytic
performance toward overall water splitting reactions and is found
to be better than universally acceptable Pt-based nanoelectrodes.
The synthesis of nanohybrids shows the well-dispersed Rh NSs (∼50
nm) on a few layers of graphene oxide sheets. These as-synthesized
nanomaterials were confirmed by scanning electron microscopy (SEM),
high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron
spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy,
Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface
area measurements, thermogravimetric analysis (TGA), and X-ray diffraction
(XRD) analysis. Furthermore, Rh–GO exhibits significantly improved
electrochemical performance toward electrocatalytic water splitting
reactions, that is, hydrogen evolution reaction (HER) and oxygen evolution
reaction (OER), and it shows exceptionally an ultrasmall overpotential
of 2 mV for the HER, reaching a current density of 10 mA cm–2 with a smaller Tafel slope 10 mV dec–1, and the
OER overpotential reaches 0.23 V at 10 mA cm–2 with
a Tafel slope of 27 mV dec–1. The reduced charge
transfer resistances after Rh NSs decoration on GO which lead to simultaneous
enhancement in feasibility toward interfacial electron transfer, result
in an increase in activity toward overall water splitting reactions
(both HER and OER).
Cu
2
ZnSnS
4
(CZTS) was synthesized by the sonochemical
method using 2-methoxyethanol as the solvent and subsequently decorated
onto graphene oxide (GO synthesized by the modified Hummers’
method) using two different approaches such as in situ growth and
ex situ synthesis followed by deposition. Preliminary characterizations
indicated that the synthesized CZTS belongs to the kesterite structure
with a sphere-like morphology. The in situ-synthesized CZTS/GO (I-CZTS/GO)
composite is used as an efficient electrocatalyst for hydrogen evolution
reaction (HER) which revealed superior electrocatalytic activity with
a reduced overpotential (39.3 mV at 2 mA cm
–2
),
Tafel slope (70 mV dec
–1
), a larger exchange current
density of 908 mA cm
–2
, and charge transfer resistance
(5 Ω), significantly different from pure CZTS. Besides, the
I-CZTS/GO composite exhibits highest HER performance with high current
stability of which shows no noticeable degradation after
i
–
t
amperometry. The catalytic activity demonstrates
that the I-CZTS/GO composite could be a promising electrocatalyst
in hydrogen production from their cooperative interactions.
A simple
one-step chemical
method is employed for the successful synthesis of CuO(50%)–ZnO(50%)
nanocomposites (NCs) and investigation of their gas sensing properties.
The X-ray diffraction studies revealed that these CuO–ZnO NCs
display a hexagonal wurtzite-type crystal structure. The average width
of 50–100 nm and length of 200–600 nm of the NCs were
confirmed by transmission electron microscopic images, and the 1:1
proportion of Cu and Zn composition was confirmed by energy-dispersive
spectra, i.e., CuO(50%)–ZnO(50%) NC studies. The CuO(50%)–ZnO(50%)
NCs exhibit superior gas sensing performance with outstanding selectivity
toward NO2 gas at a working temperature of 200 °C. Moreover, these
NCs were used for the indirect evaluation of NO2 via electrochemical
detection of NO2– (as NO2 converts
into NO2– once it reacts with moisture,
resulting into acid rain, i.e., indirect evaluation of NO2). As compared with other known modified electrodes, CuO(50%)–ZnO(50%)
NCs show an apparent oxidation of NO2– with a larger peak current for a wider linear range of nitrite concentration
from 20 to 100 mM. We thus demonstrate that the as-synthesized CuO(50%)–ZnO(50%)
NCs act as a promising low-cost NO2 sensor and further
confirm their potential toward tunable gas sensors (electrochemical
and solid state) (Scheme 1).
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.
Herein, this work highly efficient and inexpensive metal-free multifunctional electrocatalyst demonstrated for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) effectively for all pH. This current studies presents...
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