1D FeS-FeS
2
@TiO
2
heterojunctions were developed to investigate the photoexcited charge separation and transportation to active sites for improved photocatalytic properties. Morphological, optical, ...and spectroscopic studies on the photoanodes demonstrated excellent interfacial interaction, homogeneity, and wide solar light sequestering. Photoelectrochemical studies optimized the sensitizer loading of the 10-FeS-FeS
2
@TiO
2
heterojunction that possesses the highest photocurrent of 1.74 mA cm
−2
as compared to pure TiO
2
NTs with a photocurrent of 0.30 mA cm
−2
at 0.3 V
versus
Ag/AgCl (1.23 V RHE) under a light intensity of 100 mW cm
−2
. Also, 10-FeS-FeS
2
@TiO
2
NTs showed an excellent charge carrier donor density (
N
D
) of 3.86 × 10
17
cm
−3
and consequently the least electron-hole (e
−
/h
+
) pair recombination was observed. Redox shuttling of FeS-FeS
2
with high surface area TiO
2
NTs resulted in excellent electron-hole pair charge separation and transportation
via
the optimized loading and uniformity of the sensitizer. The current strategy has paved the way for the development of efficient photocatalysts for enhanced photoexcited charge separation and transportation during photocatalysis.
1D FeS-FeS
2
@TiO
2
heterojunctions were developed to investigate the photoexcited charge separation and transportation to active sites for improved photocatalytic properties for the hydrogen production from water splitting.
Pencil graphite electrodes (PGEs) have several advantages over other carbon‐based or commercial metal electrodes, including widespread availability, very low cost, and ease of modification. To make ...the best use of PGEs in electroanalysis, significant recent advances in the development of different nanomaterial‐PGEs have been observed. The literature published up to mid‐2015 is summarized in the present review, with a focus on the various methodologies used to readily modify graphite pencil electrodes using nanomaterials. This review also touches on the surface characterization of these electrodes and their potential applications in a variety of electrochemical detection applications. The review outlines the scope for further research in this area and discusses the importance of surface modifications of conventional PGE electrodes using nanomaterials or a combination of nanomaterials and electroactive polymers.
Non-enzymatic electrochemical detection of catechol (CC) and hydroquinone (HQ), the xenobiotic pollutants, was carried out at the surface of novel carbon nanocoils/zinc-tetraphenylporphyrin ...(CNCs/Zn-TPP) nanocomposite supported on glassy carbon electrode. The synergistic effect of chemoresponsive activity of Zn-TPP and a large surface area and electron transfer ability of CNCs lead to efficient detection of CC and HQ. The nanocomposite was characterized by using FT-IR, UV/vis. spectrophotometer, SEM and energy dispersive X-ray spectroscopy (EDS). Cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy were used for the electrochemical studies. CNCs/Zn-TPP/GCE nanosensor displayed a limit of detection (LOD), limit of quantification (LOQ) and sensitivity for catechol as 0.9 µM, 3.1 µM and 0.48 µA µM
cm
, respectively in a concentration range of 25-1500 µM. Similarly, a linear trend in the concentration of hydroquinone detection was observed between 25 and 1500 µM with an LOD, LOQ and sensitivity of 1.5 µM, 5.1 µM and 0.35 µA µM
cm
, respectively. DPV of binary mixture pictured well resolved peaks with anodic peak potential difference, ∆E
of 110 mV showing efficient sensing of CC and HQ. The developed nanosensor exhibits stability for up to 30 days, better selectivity and good repeatability for eight measurements (4.5% for CC and 5.4% for HQ).
The inorganic nitrate (NO3‾) anion is present under a variety of both natural and artificial environmental conditions. Nitrate is ubiquitous within the environment, food, industrial and physiological ...systems and is mostly present as hydrated anion of a corresponding dissolved salt. Due to the significant environmental and toxicological effects of nitrate, its determination and monitoring in environmental and industrial waters are often necessary. A wide range of analytical techniques are available for nitrate determination in various sample matrices. This review discusses biosensors available for nitrate determination using the enzyme nitrate reductase (NaR). We conclude that nitrate determination using biosensors is an excellent non-toxic alternative to all other available analytical methods. Over the last fifteen years biosensing technology for nitrate analysis has progressed very well, however, there is a need to expedite the development of nitrate biosensors as a suitable alternative to non-enzymatic techniques through the use of different polymers, nanostructures, mediators and strategies to overcome oxygen interference.
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•Nitrate determination is important in environmental materials.•Microbial Nitrate reduction coupled with spectrophotometry and chromatography.•Electrochemical determination of Nitrate allows real time analysis.•Nitrate reductase is used for fabrication of Nitrate biosensors.•Immobilization of Nitrate reductase using conducting or non-conducting polymers.
There is an overwhelming desire to discover new catalytic materials for efficient water oxidation that perform at low overpotentials (below 1.50 V vs. RHE), and which exhibit tremendous stability ...along with high oxygen evolution reaction (OER) current density over a small potential window. However, it remains a challenge to establish a competent solar to fuel conversion system. We present here the first example of a nanoscale nanoporous Pd-derived benchmark material used as a highly stable and low overpotential electrocatalyst for water oxidation. The Pd electrocatalyst executes water oxidation at an onset potential of just 1.43 V vs. RHE; η = 200 mV. The catalyst also exhibits remarkable performance for OER, reaching a current density of 10 mA cm −2 at 1.47 V ( η = 240 mV), and with a current density of 100 mA cm −2 achieved at only 1.63 V ( η = 400 mV), which represents better OER activity than that of the benchmark IrO 2 electrocatalyst (301 mV and 313 mV required to drive a current density of 10 mA cm −2 ). Furthermore, the catalyst demonstrates a Tafel slope of 40 mV dec −1 , a high mass activity of 560 mA mg −1 (MA) and a large TOF value of 0.2 s −1 , and exhibits remarkable long-term stability for use in oxygen evolution experiments. A thin-film Pd electrocatalyst was obtained via the Aerosol-Assisted Chemical Vapor Deposition (AACVD) method on conducting surfaces. XRD and XPS analyses showed a phase-pure crystalline metallic Pd deposit. A surface morphology study revealed a nanoparticulate highly porous nanostructure. Our study reveals a straightforward method for the development of the first example of a Pd-derived nanoporous electrocatalyst for high-efficiency water oxidation and for chemical energy conversion.
In this study, a facile and potentially scalable synthesis of AgBiS2 (schapbachite) using melts of metal xanthates is presented; AgBiS2 is both a significant mineral and a technologically important ...material. This ternary material was synthesized by a novel and low-cost solventless route using simple ethyl xanthate complexes of silver and bismuth. p-XRD analysis indicates that the synthesized ternary material is highly crystalline and belongs to the cubic phase (schapbachite). The electrochemical properties of the material were tested; the potential of the synthesized material for application in charge storage shows a high specific capacitance of 460 F g−1 at 2 mV s−1. A capacitance retention of 83% with a 100% coulombic efficiency was observed after 3000 cycles. The charge storage potential, analysed by fabricating actual symmetrical devices, shows a specific capacitance of 14 F g−1 at 2 mV s−1. An energy density of 26 W h kg−1 and a power density of 3.6 kW kg−1 were observed. Besides, the potential for the oxygen evolution reaction was also studied. An overpotential of 414 mV and a Tafel slope of 134 mV dec−1 were obtained for water oxidation. The fabrication of an electrolyzer cell using the synthesized material as the cathode indicates that a current of 10 mA cm−2 can be achieved at a potential of 1.63 V.
In direct methanol fuel cell technology, highly stable electrochemical catalysts are critically important for their practical utilization at the commercial scale. In this study, sub ~10 nm hollow ...Pt-Ni (1:1 at. ratio) nanoboxes supported on functionalized Vulcan carbon (Pt-Ni/C-R2) were synthesized through a facile method for the efficient electrooxidation of methanol. Two reaction procedures, namely, a simultaneous reduction and a modified sequential reduction method using a reverse microemulsion (RME) method, were adopted to synthesize solid Pt-Ni NPs and hollow nanoboxes, respectively. To correlate the alloy composition and surface structure with the enhanced catalytic activity, the results were compared with the nanocatalyst synthesized using a conventional NaBH
reduction method. The calculated electroactive surface area for the Pt-Ni/C-R2 nanoboxes was 190.8 m
.g
, which is significantly higher compared to that of the Pt-Ni nanocatalyst (96.4 m
.g
) synthesized by a conventional reduction method. Hollow nanoboxes showed 34% and 44% increases in mass activity and rate of methanol oxidation reaction, respectively, compared to solid NPs. These results support the nanoreactor confinement effect of the hollow nanoboxes. The experimental results were supported by Density Functional Theory (DFT) studies, which revealed that the lowest CO poisoning of the Pt
Ni
catalyst among all Pt
-Ni
mixing ratios may account for the enhanced methanol oxidation. The synthesized hollow Pt-Ni/C (R2) nanoboxes may prove to be a valuable and highly efficient catalysts for the electrochemical oxidation of methanol due to their low cost, numerous catalytically active sites, low carbon monoxide poisoning, large electroactive surface area and long-term stability.
A new organo-tin complex has been synthesized and used as a single source precursor for the synthesis of SnSe nanosheets by the hot injection method and thin films by the aerosol assisted chemical ...vapor deposition (AACVD) method. The films were deposited on glass substrates at three different temperatures. The textural quality and preferential growth were found to be significantly altered by changes in the deposition temperature. Oleylamine capped nanosheets and the as-deposited thin films by AACVD were characterized by powder X-ray diffraction (p-XRD) and microscopic techniques. The thin films were also studied by Raman spectroscopy. The stoichiometry is marginally affected by temperature, and all films were slightly selenium deficient. The synthesized material was also evaluated for the photoelectrochemical (PEC) splitting of water. The PEC study revealed the bifunctional nature of the material, which can be applied for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), by switching the applied potential.
A new organo tin complex has been synthesized and used as a single source precursor for the synthesis of tin selenide nanosheets and deposition of thin films.
The development of efficient and selective nanostructured catalysts for industrially relevant hydrogenation reactions continues to be an actual goal of chemical research. In particular, the ...hydrogenation of nitriles and nitroarenes is of importance for the production of primary amines, which constitute essential feedstocks and key intermediates for advanced chemicals, life science molecules and materials. Herein, we report the preparation of graphene shell encapsulated Co
O
- and Co-nanoparticles supported on carbon by the template synthesis of cobalt-terephthalic acid MOF on carbon and subsequent pyrolysis. The resulting nanoparticles create stable and reusable catalysts for selective hydrogenation of functionalized and structurally diverse aromatic, heterocyclic and aliphatic nitriles, and as well as nitro compounds to primary amines (>65 examples). The synthetic and practical utility of this novel non-noble metal-based hydrogenation protocol is demonstrated by upscaling several reactions to multigram-scale and recycling of the catalyst.
This work presents a comparative study on the structural, optical and electrochemical characteristics of visible light driven (VLD) reduced titanium dioxide (TiO2−x) nanocatalysts synthesized via ...inorganic and organic synthetic routes. X-ray diffraction (XRD) patterns, Raman spectra and X-ray absorption fine structure (XAFS) analyses reflected anatase phase titania. Whereas, the quantitative EXAFS fit and XANES analysis revealed structural distortion due to the presence of oxygen and titanium vacancies with low valent Ti states in anatase lattices of certain nanocatalysts, which subsequently leads to better electrochemical and photocatalytic activities. Moreover, owing to the large surface area and mesoporous structures, the Mg–TiO2−x nanocatalysts exhibited enhanced water adsorption and ultimately increased overall water splitting with an OER overpotential equal to 420 mV vs. RHE at a current density of 10 mA cm−2 (Tafel slope = 62 mV dec−1), extended visible light absorbance, decreased photoluminescence (PL) intensity and increased carrier lifetime in comparison with commercial titania.
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