Development of efficient, earth-abundant and low-cost electrocatalyst for effective water electrolysis is highly demanding for production of sustainable hydrogen energy. In this paper, we report the ...cost-effective synthetic protocol for porous NiO hollow spheres in large scale through a simple spray drying strategy, using aqueous nickel ammonium carbonate complex solution, followed by calcination. The synthesized NiO hollow spheres calcined at 300 °C (NiO-300) are porous, made of nanoparticles in size range of 10–16 nm with a size range of 2.5–4 μm and total surface area of 120 m2/g. The NiO-300 exhibited excellent bifunctional electrocatalytic water splitting characteristic, both OER, and HER, in basic solution. NiO-300 modified glassy carbon electrode showed superior water electrolysis kinetics and to achieve 10 mA cm−2 current density, it required 370 mV overpotential for OER and 424 mV overpotential for HER in 1 M KOH. It is also worked well with cost-effective plastic chip electrode. An assembled two-electrode system by pairing NiO modified plastic chip electrode as both anode and cathode in a 1.0 M KOH electrolyte for overall water splitting exhibit clear bubble formation at 1.6 V potential.
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•Synthesis of porous NiO hollow spheres by spray drying followed by calcination.•Showed efficient bifunctional electrocatalytic behaviour for Overall Water-Splitting.•Reaches 10 mA/cm−2 current density at a overpotential of 370 mV in 1 M KOH for OER.•424 mV overpotential in required to achieve 10 mA cm−2 current density 1 M KOH for HER.•Exhibit clear bubble formation at 1.6 V potential in an assembled two-electrode system.
Here, the synthesis of RuO2 loaded CeO2 with varying amount of Ru loading with enhanced amount of Ce3+ and surface area, through synthesis of CeO2 using cerium ammonium carbonate complex as procure ...followed by Ru loading by impregnation and calcination at 300 °C, is presented. Corresponding characterizations by XRD, SEM, TEM, XPS of all the samples reveal the formation of highly crystalline mesoporous CeO2 nanoparticles with uniformly dispersed RuO2 particles on the CeO2 surface having approximately 45% Ce3+. All the samples were utilized as oxygen evolution reaction (OER) catalyst for electrocatalytic H2 generation through water electrolysis. Electrocatalytic experiments reveal that synthesized 1 wt% RuO2 loaded CeO2 (1-RuO2/CeO2) showed superior OER activity. A quite low over-potential of 350 mV is required to attain a current density of 10 mA/cm2 (ɳ10), with a Tafel slope of 74 mVdec−1 for OER in 1 M KOH solution. The synthesized 1-RuO2/CeO2 electrocatalyst also exhibited superior long term stability in basic medium and redox atmosphere.
•Simple aqueous solution based Chemical Synthesis of RuO2–CeO2 hetero nanostructures.•Synthesis is based on formation of CeO2 spheres followed by Ru impregnation.•1 wt% RuO2–CeO2 showed excellent electrocatalytic OER activity in 1 M KOH solution.•Showed low overpotential of 350 mV for 10 mA/cm2 & Tafel slope of 74 mVdec−1 for OER.•Exhibited superior electrochemical stability in basic as well as redox environment.
As an extremely attractive technology for the efficient generation of O2 and H2, water electrolysis involving oxygen and hydrogen evolution reactions (OER, HER) mainly depends on efficient and ...affordable electrocatalysts. In this work, we initially synthesize silver permanganate, AgMnO4 (AMO), nanoparticles (NPs) with Pd0 through NaBH4 reduction. Subsequently, their surface is further modified using PdO x (x = 1, 1.5, 2) via annealing the AMO/Pd nanocomposite (NComp-1). For the optimization of catalytic properties, the chemical state of oxidic Pdδ+ is modulated by changing the annealing temperature from 160 to 360 °C. The electrocatalytic activity of NComp-1 is observed to improve gradually on increasing the temperature, and it reaches a maximum at 260 °C. This increase in temperature leads to an increase in the chemical state of Pdδ+ species produced at the AMO–Pd interface. Moreover, a temperature of 260 °C provides mixed-valence Pd (0, 2+, 3+), which strongly contributes to excellent OER/HER activities of AMO/PdO x /Pd-260 NComp (NComp-3). However, a temperature of 360 °C converts all Pd to Pd4+, which in turn decreases its activity, implying the intrinsic benefit of mixed-valence Pdδ+ toward OER/HER. The optimized NComp-3 features enhanced bifunctional properties, exhibiting extremely low overpotentials (η10) (160 mV for OER, 58 mV for HER at 10 mA cm–2) with small Tafel slopes (64.9 mV dec–1 for OER, 37.8 mV dec–1 for HER). Inspired by the superior bifunctionality, a symmetric alkaline electrolyzer is assembled with NComp-3, which needs only 1.50 V to reach a water-splitting current of 10 mA cm–2 and exhibits remarkable long-term stability. The enhanced electrocatalytic performance may be due to the synergetic effect among AMO, PdO x , and Pd, which distinctively improves the adsorption of reaction intermediates, surface area, electrical conductivity, charge-mass transport, and also stability. Therefore, our work highlights the importance of surface engineering through regulating the surface electronic status and also offers a feasible strategy for synthesizing efficient bifunctional electrocatalysts for renewable energy applications.
Nanocrystalline FeS and FeSe compounds were prepared by solvothermal decomposition of a precursor complex Fe3(μ3-O)(μ2-O2CCH2Cl)6(H2O)3NO3·H2O in the presence of thiourea and sodium selenite, ...respectively. The as-obtained products were characterized by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and UV–vis spectroscopic techniques. Structural analyses revealed that the FeS and FeSe nanoparticles (NPs) are composed of needle-like and spherical particles, respectively. The FeS and FeSe NPs showed photocatalytic activity for the decomposition of rose bengal (RB) and methylene blue (MB) dyes under white light illumination. They also showed good catalytic activity toward oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 and followed Michaelis–Menten kinetics. In addition, both FeS and FeSe NPs exhibited electrocatalytic activity toward reduction of hydrogen peroxide, which on immobilization on glassy carbon (GC) electrodes perform as amperometric sensors for detection of H2O2. At pH 7.0, the FeS/GC showed a linear range for detection of H2O2 from 5 to 140 μM, while for FeSe/GC the range was 5 to 100 μM.
A luminescent nanoprobe (NP), MnO2-modified Er3+/Yb3+-codoped Ag2MoO4 upconversion nanoparticles (UCNPs; cod-AMO-3/MnO2), was constructed for rapid, sensitive, and selective “turn-on” detection of ...trace As3+. Herein, two kinds of luminescent NPs were developed based on luminescence resonance energy transfer (LRET) between cod-AMO-3 as the energy donor and MnO2 as the energy acceptor. By using MnO2 as the matrix in cod-AMO-3/MnO2 fluorometric assay, the upconversion luminescence (UCL) intensity (I UCL) of the cod-AMO-3 probe was quenched significantly through LRET, illustrating MnO2 as an efficient quencher for UCL. With the addition of As3+, a stable bidentate binuclear (BB) corner-sharing bridged complex (As5+-MnO2) was probably formed, which alters the surface of the upconversion NP, leading to gradual separation between UCNPs and MnO2 and subsequent recovery of I UCL. Interestingly, it possessed superior sensitivity, reaction kinetics, and also high selectivity toward As3+ in aqueous solution. Our optimized cod-AMO-3/MnO2 nanocomposite (NComp) demonstrated a linear range of 0–150 ppb and an ultrasensitive detection limit of 0.028 ppb for As3+, which is extremely below the regulatory level, signifying the promising practical usage of this system. To the best of our knowledge, such a surface-modified Ln3+-codoped Ag-based nanosensor being applied for As3+ detection probably has not been reported yet, and it is rather unexplored. In a nutshell, the ability to monitor the As3+ concentration may enable the rational design of a convenient platform for a diverse range of environmental monitoring applications.
•Nitrogen Rich Ordered Mesoporous carbon (NOMC) and NiS nanoparticles nanocomposites (NiS/NOMC).•Highly efficient and stable as an electrocatalyst for the oxidation of urea and low over ...potential.•High electrochemically active surface area (ECSA).•Synergy between NiS and nitrogen rich mesoporous NOMC.
The urea oxidation reaction (UOR), as a feasible alternative for the slow oxygen evolution reaction (OER), is recognized as an encouraging puissant approach for hydrogen generation through water splitting. The route also offers excellent potential for hydrogen production through wastewater remediation. Here, a simple synthetic strategy has been adopted to embed NiS in a nitrogen-rich stable and activated mesoporous carbon matrix (NOMC) that has been successfully exploited for UOR. The NOMC supported nickel sulfide catalyst with high electrochemically active surface area (ECSA) exhibits a very good response towards the electro-catalytic oxidation of urea in an alkaline medium with a low working oxidation potential (potential corresponding to the current density value of 10 mA/cm2 taken as a standard) of 1.34 V (vs. RHE). The introduction of heteroatom (N) to the mesoporous carbon support and subsequent incorporation of metal sulfide rather than metal oxide or metal hydroxide, as reported previously, is done purposefully to increase the electrocatalytic activity of the catalyst through the synergistic effects of charge density with carbon support. The synergism is further supported by the comparative response in urea oxidation reaction (UOR) for NiS/NOMC catalyst compared to other Ni-based catalysts like Ni(OH)2, NiS, and NiS/CMK-3, which indicates that the activity is highest for NiS/NOMC. The catalyst attains good stability in an alkaline medium. The mesoporous carbon framework (NOMC) with considerably high BET surface area, large pore volume, and interconnected ion diffusion channels accelerate the transport of electrons through the porous surface, which makes NiS/NOMC highly efficient and stable as an electrocatalyst for the oxidation of urea in comparison to its other composite catalysts in alkaline medium.
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Composite electrodes are gradually gaining interest due to their versatile applications. plastic chip electrode (PCE) comprising of graphite and Poly(methyl methacrylate) (PMMA) is one such composite ...that can be fabricated by simple solution‐phase mixing followed by solvent evaporation. In this study, we report more than two times enhancement in the bulk conductance of PCE by removing the passivating superficial polymer layer above the filler, through the treatment of cold plasma. Comparative characterization of the pre‐ and posttreated electrode has been performed by scanning electron microscopy (SEM), spreading resistance imaging (SRI), contact angle, and current–voltage characteristics as well as electrochemical impedance spectroscopy (EIS). Improved electroactivity of PCE has been demonstrated through cyclic voltammetry (CV).
The superficial polymer layer over the conducting graphite is removed by cold plasma treatment, in a polymer composite electrode, to improve its bulk electrical properties.
A luminescent nanoprobe (N
), MnO
-modified Er
/Yb
-codoped Ag
MoO
upconversion nanoparticles (UCNPs; cod-AMO-3/MnO
), was constructed for rapid, sensitive, and selective "turn-on" detection of trace ...As
. Herein, two kinds of luminescent N
s were developed based on luminescence resonance energy transfer (LRET) between cod-AMO-3 as the energy donor and MnO
as the energy acceptor. By using MnO
as the matrix in cod-AMO-3/MnO
fluorometric assay, the upconversion luminescence (UCL) intensity (
) of the cod-AMO-3 probe was quenched significantly through LRET, illustrating MnO
as an efficient quencher for UCL. With the addition of As
, a stable bidentate binuclear (BB) corner-sharing bridged complex (As
-MnO
) was probably formed, which alters the surface of the upconversion N
, leading to gradual separation between UCNPs and MnO
and subsequent recovery of
. Interestingly, it possessed superior sensitivity, reaction kinetics, and also high selectivity toward As
in aqueous solution. Our optimized cod-AMO-3/MnO
nanocomposite (NComp) demonstrated a linear range of 0-150 ppb and an ultrasensitive detection limit of 0.028 ppb for As
, which is extremely below the regulatory level, signifying the promising practical usage of this system. To the best of our knowledge, such a surface-modified Ln
-codoped Ag-based nanosensor being applied for As
detection probably has not been reported yet, and it is rather unexplored. In a nutshell, the ability to monitor the As
concentration may enable the rational design of a convenient platform for a diverse range of environmental monitoring applications.
Synthesis of morphologically tuned Bi2S3 NPs with excellent photocatalytic performance towards degradation of DDT and MB dye under visible light irradiation Display omitted
Here in, morphologically ...tuned Bi2S3 NPs were successfully synthesized from a single-source precursor complex Bi(ACDA)3 HACDA=2-aminocyclopentene-1-dithiocarboxylic acid by decomposing in various solvents using a simple solvothermal method. The as-obtained products were characterized by XRD, TEM, UV−vis spectroscopy and BET surface area measurements. Structural analyses revealed that the as-prepared Bi2S3 NPs can be tuned to different morphologies by varying various solvents and surfactants. The interplay of factors that influenced the size and morphology of the nanomaterials has been studied. Moreover, mastery over the morphology of nanoparticles enables control of their properties and enhancement of their usefulness for a given application. These materials emerged as a highly active visible light-driven photocatalyst towards degradation of methylene blue dye and the efficiencies are dependent on size and surface area of the NPs. In addition, photocatalytic degradation of highly toxic dichlorodiphenyltrichloroethane was studied using synthesized Bi2S3 NPs as catalyst and the rate of degradation has been found to be much better compared to that exhibited by commercial WO3. We believe that this new synthesis approach can be extended to the synthesis of other metal sulfide nanostructures and open new opportunities for device applications.
