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Hollow hierarchical structure Co0.85Se as efficient electrocatalyst for the triiodide reduction in dye-sensitized solar cells
摘要： The exploration of nonprecious metal-based electrocatalysts with high efficiency for the triiodide reduction is critical for the practical applications of the dye-sensitized solar cells. Herein, we develop a facile one-step hydrothermal method to synthesize hollow hierarchical structure Co0.85Se. Under the methanol-water reaction system, the product named as hollow hierarchical structure Co0.85Se-M has the largest specific surface area (215.36 m2 g?1) and the best crystallinity than other products obtained from other alcohol-water reaction systems. When this electrocatalyst is applied as a counter electrode for the dye-sensitized solar cells, it exhibits a small peak-to-peak separation (Epp, 97 mV) for the reduction of I3?/I? redox couple. It is found that the catalytic activity of Co0.85Se is closely dependent on the crystallinity. Moreover, the reactivity pathway is identified by density functional theory, which confirms that triiodide is reduced to iodide ion on Co0.85Se with a smaller energy barrier (～0.65 eV) than on Pt (～1.18 eV). Both experimental and theoretical results demonstrate Co0.85Se-M as an ideal counter electrode material for the dye-sensitized solar cells with a higher power conversion efficiency (8.76%) than Pt counter electrode (7.20%).
关键词： Dye-sensitized solar cells,Hollow hierarchical structure,Cobalt selenides,Electrocatalytic activity,Triiodide reduction
更新于2025-11-21 11:03:13
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Facile ultrasonic synthesized NH2-carbon quantum dots for ultrasensitive Co2+ ion detection and cell imaging
摘要： The amine decorated carbon quantum dots (NH2-CQDs) were synthesized through ultrasonic method from graphite rods derived CQDs and ammonia hydroxide and utilized as the sensing probes for cobalt (II) ions and nucleic acids. The sensing technique was investigated to be the fluorescence quenching effect, which demonstrated linear relationship between cobalt (II) ions concentration and the emission intensity deviation ratio in the concentration range of 50 nM to 40 μM with the detection limit of 12 nM. In brief, this sensitive and selective detection method was confirmed to demonstrate high potential in cobalt (II) ions detection in real samples and nucleic acid sensing in biological cells.
关键词： Nucleic acid sensing,Carbon quantum dots (CQDs),Cobalt sensor
更新于2025-11-19 16:56:42
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Sensitive spectrophotometric determination of trace-level Co2+ in water based on acetate enhanced catalysis of Co2+
摘要： A sensitive spectrophotometric method was developed for the determination of trace-level Co2+ in water based on the acetate enhanced catalytic decolorization of methylene blue (MB) with Co2+ as a catalyst and peroxymonosulfate (PMS) as an oxidizing agent. This indirect spectrophotometric method was easy to operate due to the strong absorption of MB at a maximum absorption wavelength of 664 nm with a molar absorptivity of 5.88 × 104 L mol?1 cm?1. Under the selected reaction conditions of 10.0 mg L?1 MB, 60.0 mg L?1 PMS and 100.0 mg L?1 Ac?, the depletion extent of MB was linearly correlated with the concentration of Co2+ from 0.20 to 7.0 μg L?1 (R2 = 0.986) and then from 7.0 to 50.0 μg L?1 (R2 = 0.991), with a detection limit (3 s/k) of 0.10 μg L?1. It was found that this method possessed excellent anti-interference capability to various coexisting ions including similar transitional metals. The developed method was used to determine the Co2+ concentration in practical samples with satisfactory results.
关键词： Spectrophotometry,Methylene blue,Catalytic decolorization,Acetate,Trace-level Cobalt
更新于2025-11-19 16:56:35
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Formation of CoTe2 embedded in nitrogen-doped carbon nanotubes-grafted polyhedrons with boosted electrocatalytic properties in dye-sensitized solar cells
摘要： Developing high active and earth-abundant electrocatalysts is a challenge for commercialization of dye-sensitized solar cells (DSSCs). Herein, a designed synthesis of CoTe2 nanoparticles embedded in nitrogen-doped carbon nanotubes-grafted polyhedron (CoTe2@NCNTs) using zeolitic imidazolate framework-67 (ZIF-67) as template is reported. Benefiting from the high surface area induced by the in situ growth of CNTs and the synergistic effect between CoTe2 and the N-doped nanostructured carbon, CoTe2@NCNTs hybrids exhibit remarkable catalytic activity toward the reduction of I3? ions. When employed as counter electrode (CE) of DSSCs, CoTe2@NCNTs hybrids deliver overwhelming power conversion efficiency (PCE) of 9.02%, possessing ~12% improvement compared with the Pt CE (8.03%). This study provides an emerging substitute for traditional Pt CE and a strategy to synthesize efficient electrocatalysts via rational surface engineering.
关键词： Carbon nanotubes,Counter electrode,Dye-sensitized solar cells,Cobalt telluride
更新于2025-11-14 17:04:02
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Grafting cobalt sulfide on graphene nanosheets as a counterelectrode for dye-sensitized solar cells
摘要： In the present work a composite counter electrode of graphene nanosheets grafted cobalt sulfide was fabricated through a facile synthetic route, in which cobalt sulfide nanoparticles were successfully grafted on the surface of graphene nanosheets. Used as a counter electrode in DSSC, a power conversion efficiency of 7.28% can be achieved. Such a result might be contributed to the facts that this counter electrode composed of graphene nanosheets grafted cobalt sulfide has a good stability and electrochemical catalytic performance toward triiodide reduction reaction.
关键词： photovoltaic performance,graphene nanosheets,cobalt sulfide,counterelectrode,Dye-sensitized solar cell
更新于2025-11-14 17:04:02
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Direct Observation of Structural Evolution of Metal Chalcogenide in Electrocatalytic Water Oxidation
摘要： As one of the most remarkable oxygen evolution reaction (OER) electrocatalysts, metal chalcogenides have been intensively reported due to their high OER activities during the past few decades. It has been reported that electron-chemical conversion of metal chalcogenides into oxides/hydroxides would take place after OER. However, the transition mechanism of such unstable structures, as well as the real active sites and catalytic activity during OER for these electrocatalysts, has not been understood yet, which urgently needs a direct observation for the electrocatalytic water oxidation process, especially at nano or even angstrom scale. In this research, by employing advanced Cs-corrected transmission electron microscopy (TEM), a step by step oxidational evolution of amorphous electrocatalyst CoSx into crystallized CoOOH in OER has been in situ captured: irreversible conversion of CoSx to crystallized CoOOH is initiated on the surface of electrocatalysts with a morphology change via Co(OH)2 intermediate during OER measurement, where CoOOH is confirmed as the real active species. Besides, this transition process has also been confirmed by multiple applications of X-ray photoelectron spectroscopy (XPS), in situ Fourier-transform infrared spectroscopy (FTIR) and other ex situ technologies. Moreover, based on this discovery, a high-efficiency electrocatalyst of a nitrogen-doped graphene foam (NGF) coated by CoSx has been explored through a thorough structure transformation of CoOOH. We believe this in situ and in-depth observation of structural evolution in OER measurement can provide insights into the fundamental understanding of the mechanism for OER catalysts, thus enabling the more rational design of low-cost and high-efficient electrocatalysts for water splitting.
关键词： structural evolution,XPS,in situ TEM,water oxidation,cobalt chalcogenide
更新于2025-11-14 15:27:09
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Gold doping induced strong enhancement of carbon quantum dots fluorescence and oxygen evolution reaction catalytic activity of amorphous cobalt hydroxide
摘要： Gold doping induced strong enhancement of carbon quantum dots fluorescence and oxygen evolution reaction catalytic activity of amorphous cobalt hydroxide. Water splitting using electrocatalysts is expected to provide an alternative green energy source to meet increasing energy demands as well as addressing environmental concerns related to fossil fuels. Herein, we report one-step synthesis of sulfur, nitrogen and Au-doped carbon quantum dots (Au-SCQDs) and strong enhancement of fluorescence intensity and oxygen evolution reaction (OER) catalytic activity of amorphous Co(OH)2 nanoparticles compared to pure Co(OH)2 as well as commercial RuO2 and Pt/C catalysts. Au doping into sulfur and nitrogen co-doped CQDs showed over seventy times enhanced fluorescence. OER studies of amorphous-Co(OH)2 incorporated Au-SCQDs produced current density of 178 mA cm?2 at the applied potential of 2.07 V whereas un-doped Co(OH)2 showed current density of 59 mA cm?2. To produce geometric current density of 10 mA cm?2, amorphous Co(OH)2-Au-SCQDs (CSA) required 388–456 mV overpotential depending on the Au ion concentration used for preparing the Au-SCQDs, which is equal to or lower than overpotential required by commercial electrocatalysts. The strongly enhanced OER activity of Co(OH)2-Au-SCQDs (CSA) was attributed to the presence of electronegative metallic conducting Au atoms along with the high catalytic surface area of amorphous Co(OH)2. The present studies demonstrate a new method of exploiting amorphous Co(OH)2NPs electrocatalysts that could provide more catalytically active sites by integrating an electronegative conducting Au atom doped SCQDs matrix.
关键词： amorphous cobalt hydroxide,fluorescence,water splitting,Gold doping,carbon quantum dots,oxygen evolution reaction,electrocatalysts
更新于2025-10-22 19:40:53
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Tris(N-methylferrocenyl-N-(2-phenylethyl)dithiocarbamato-S,S′)cobalt(III) for anion sensing and preparation of cobalt-iron sulfide nanoparticles: A new photocatalyst for the degradation of dyes
摘要： Tris(N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S')cobalt(III) (1) and tris(N-methylferrocenyl-N-(2-phenylethyl)dithiocarbamato-S,S')cobalt(III) (2) have been synthesized and characterized by elemental analysis and spectroscopy (IR, UV-vis and NMR). The elemental analysis and IR, 1H and 13C NMR spectra are consistent with the formation of the cobalt(III) complexes with dithiocarbamate ligands. The anion binding properties of 1 and 2 based on host-guest interaction have been examined with the use of cyclic voltammetry.This study showed that both complexes preferred to bind with I- compared to other halides. 2 has been used as precursors for the preparation of cobalt-iron sulfide nanoparticles. TEM image of cobalt-iron sulfide nanoparticles showed that the particles are spherical. The elemental compositions of the nanoparticles were confirmed by energy dispersive X-ray spectroscopy. IR spectral studies on nanoparticles confirm the presence of capping agent (triethylenetetramine). The nanoparticles were explored as photocatalysts to study the degradation of dyes using methylene blue and rhodamine-B in aqueous solution under UV irradiation. The cobalt-iron sulfide works as an efficient photocatalyst for degradation of rhodamine-B.
关键词： cobalt(III) dithiocarbamate,Anion sensing,single source precursors,nanoparticles,cobalt-iron sulfide
更新于2025-09-23 15:23:52
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Formation of Cobalt Impurity Microinclusions in Silicon Single Crystals
摘要： The structure and chemical composition of cobalt impurity microinclusions in silicon have been studied by electron probe microanalysis using n- and p-type Si?Co? samples prepared by diffusion doping and cooled at different rates after diffusion annealing. The cooling rate after diffusion annealing has been shown to have a significant effect on the structural parameters of the samples and the size of the forming impurity microinclusions. The size and shape of the impurity microinclusions determine their distribution over the bulk of the samples.
关键词： cobalt microinclusions,cobalt silicide,cooling rate,electron probe microanalysis
更新于2025-09-23 15:23:52
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Photocatalysis as an advanced reduction process (ARP): the reduction of 4-nitrophenol using titania nanotubes-ferrite nanocomposites
摘要： TiO2 photocatalysis is an advanced process, employed worldwide for the oxidation of organic compounds, that leads to significant technological applications in the fields of health and environment. The use of the photocatalytic approach in reduction reactions seems very promising and can open new horizons for green chemistry synthesis. For this purpose, titanium dioxide nanotubes (TNTs) were developed in autoclave conditions using TiO2 P25 as a precursor material. Based on these nanotubular substrates, TiO2/CoFe2O4 (TCF) nanocomposites were further obtained by wet impregnation method. The materials were thoroughly characterized and their structural, textural, vibrational, optoelectronic and magnetic properties were determined. The composite materials combine absorbance in the visible optical range and high BET surface area values (~100 m2/g), showing extremely high yield in the photocatalytic reduction of 4-nitrophenol (4-NP), exceeding 94% within short illumination time (only 35 min). The developed nanocomposites were successfully reused in consecutive photocatalytic experiments and were easily removed from the reaction medium using magnets. Both remarkable recycling ability and high-performance stability in the photocatalytic reduction of nitrophenol were observed, thus justifying the significant economic potential and industrial perspectives for this advanced reduction process.
关键词： Cobalt ferrite,4-nitrophenol reduction.,Nanocomposite photocatalyst,TiO2 nanotubes
更新于2025-09-23 15:23:52