Simple Hydrothermal Synthesis Research Articles

Efficient recovery of ammonia from digestate by membrane distillation: Nano-FeOOH re-entry structure modification, anti-fouling, and anti-wetting performance

The recovery of resources from wastewater has drawn worldwide attention, and digestate has the potential to produce amino fertilizers as an ammonia-rich carrier. Membrane distillation (MD) is an effective process to recover ammonia from digestate, but membrane fouling and wetting are identified as major challenges faced. However, the research to enhance membrane fouling resistance and ammonia transfer efficiency through membrane modification has seldom been explored. Herein, we fabricated FeOOH grafted membranes with superior resistance to wetting by simple hydrothermal synthesis and fluorination. The grafted re-entrant FeOOH nanoparticles and fluorosilanes were confirmed by SEM, EDS, FTIR, and XRD. The superior hydrophobicity of the modified film was confirmed by contact angle (CA = 152.9 ± 2.8°) analysis. The fouling growth behavior of the membrane surface was monitored in situ by optical coherence tomography (OCT), and the anti-fouling performance was proved to be superior to that of commercial polyvinylidene fluoride membrane (PVDF) (no fouling accumulation was detected for 6 h). The modified membrane achieved ammonia recovery flux of 3.89 ± 0.18 g/m2 h and high ammonia recovery of 95.2 ± 2.3% without wetting occurrence. Our research illustrates that the grafting of nano-FeOOH re-entrant structures facilitates the recovery of ammonia from highly concentrated ammonia wastewater without wetting and fouling, revealing its promising prospect in MD resource recovery.

Multicolor emission-based nitrogen, sulfur and boron co-doped photoluminescent carbon dots for sequential sensing of Fe3+ and cysteine: RGB color sensor and live cell imaging

Herein, a simple hydrothermal synthesis is used to prepare multiple heteroatom-doped photoluminescent carbon dots (CDs) from thiourea (N and S source) and boric acid (B source) as precursors. The optical and physicochemical properties of the as-synthesized NSB-CDs were studied using UV–Vis, photoluminescence, TEM, FT-IR, XRD, Raman, and XPS analyses. The NSB-CDs exhibited excellent stability, high photostability, pH, and ionic strength tolerance; they retained their excellent stability independent of excitation. The NSB-CDs featured small sizes of approximately 3.2 ± 0.4 nm (range: 2.0–5.0 nm) as evidenced using TEM measurements. The NSB-CDs were used as a photoluminescent sensing platform to detect Fe3+ as well as cysteine (Cys) molecules. The competitive binding of Cys to Fe3+ resulted in NSB-CDs that retained their photoluminescence. For the rapid identification and quantification of Fe3+ and Cys, NSB-CDs were developed as a “switch-on” dual-function sensing platform. The linear detection range of Fe3+ was 0–20 μM (limit of detection [LOD]: 54.4 nM) and that of Cys was 0–50 μM (LOD: 4.9 nM). We also introduced a smartphone RGB analysis method for detecting low-concentration solutions based on digital images. The NSB-CDs showed no toxicity at 100 μg/mL. Photoluminescent probes for multicolor live-cell imaging can be used with NSB-CDs at this concentration, suggesting that NSB-CDs may be promising photoluminescent probes.

Hierarchical nanocomposite of cobalt sulfide nanoflakes-decorated reduced graphene oxide for enhancing the electrocatalytic hydrogen evolution reaction

The hydrogen evolution reaction (HER) driven by electrocatalytic water splitting is attaining prevalent attention for the manufacturing of clean and green hydrogen energy. Herein, we report the simple one-step hydrothermal synthesis of cobalt sulfide nanoflakes decorated with reduced graphene oxide (CoS/rGO) nanocomposites as an effective electrode material for HER. The CoS/rGO nanocomposites exhibited the rGO nanosheet-decorated hierarchically interconnected CoS nanoflakes structure. The CoS/rGO nanocomposites exhibited an excellent HER activity with a low overpotential of 371 mV and a small Tafel slope of 103 mV/dec. More interestingly, the catalytic stability of CoS/rGO nanocomposites is comparatively higher than the pristine CoS NFs. These results suggest that the facile nanocomposites of CoS/rGO could be a prominent catalytic material for effective green hydrogen production.

S–CdIn2S4: A novel near-infrared emitter triggered by low potential for constructing a dual-mode immunosensing platform

CdIn2S4 is an interesting ternary metal sulfide whose narrow band gap and tunable optical properties offer new opportunities for the development of novel ECL emitters. Here, we use a simple hydrothermal synthesis to obtain hollow spindle CdIn2S4 (S–CIS), which exhibits strong near-infrared electrochemiluminescence (ECL) emission with K2S2O8 as a coreactant at a low excitation potential (−1.3 V), which is encouraging. The lower excitation potential of S–CIS is probably due to the low band gap energy, which makes the excitation potential positively shift. This lower excitation potential reduces the side-reactions caused by high voltages, effectively avoiding irreversible damage to biomolecules, and protecting the biological activity of antigens and antibodides. In this work, new features of S–CIS in ECL studies are also presented, demonstrating that the ECL emission mechanism of S–CIS is generated by surface state transitions and that S–CIS exhibits excellent near-infrared (NIR) characteristics. Importantly, we introduced S–CIS into electrochemical impedance spectroscopy (EIS) and ECL to the construct a dual-mode sensing platform to achieve AFP detection. The two models with intrinsic reference calibration and high accuracy showed outstanding analytical performance in AFP detection. The detection limits were 0.862 pg mL−1 and 16.8 fg mL−1, respectively. This study demonstrates the key role and great application potential of S–CIS as a novel NIR emitter with easy preparation, low cost and great performance in the development of a simple, efficient and ultrasensitive dual-mode response sensing platform for early clinical use.

Facile fabrication of few-layer nanostructured MoSe2 entrenched on N-doped carbon as a superior anode material for high-performance potassium-ion hybrid capacitors

As an emerging class of advanced capacitor-battery hybrid energy storage and transformation devices, potassium ion hybrid capacitors (PIHCs) have become the next generation of electrochemical energy storage systems owing to their abundant ratio of raw materials and inexpensive potassium resources. However, potassium ions have backward kinetics because of their ionic radius. Therefore, the improvement of applicable materials with powerful capacity and rapid charge and discharge capabilities remains a large challenge. Here, we design simple hydrothermal synthesis methods to anchor MoSe2 nanosheets into a 3-dimensional N-doped porous carbon skeleton as a fast, durable electrode to boost energy storage for PIHCs. Specifically, highly conductive 3-dimensional N-doped porous carbon skeleton materials can efficiently alleviate the accumulation of MoSe2 nanosheets and facilitate electron diffusion. It is demonstrated that MoSe2/NC utilized as potassium ion battery anodes exhibits a reversible capacity (415.1 mA h g−1 at 100 mA g−1) and a superior rate performance (212.4 mAh g−1 at 5000 mA g−1) as a result of its unique nanostructure and powerful chemical interactions between MoSe2 nanosheets and N-doped carbon skeletons. As a result of its use of an anode of MoSe2/NC and a cathode of activated carbon, the PIHCs can provide an extremely high energy density of 136.8 Wh kg−1 accompanied by a power density of 400 W kg−1 excellent rate performance and an exceptionally long-cycle lifespan.

High thermoelectric performance in the n-type Bi2S3/f-MWCNTs nanocomposites prepared by hydrothermal method

In this study, we successfully combined functionalized multi-walled carbon nanotubes (f-MWCNTs) into the Bi2S3 matrix using a simple hydrothermal synthesis technique to optimize its thermoelectric properties. The presence of MWCNTs optimizes the electrical transport properties of the matrix material, resulting in a power factor (PF) of up to 151 μW K−2 m−1 for the Bi2S3/f-MWCNTs (0.5 wt%) nanocomposite, which is nearly 70% higher than that of the pure Bi2S3. In addition, the enhanced phonon scattering effect results in a total thermal conductivity of 0.27W·K−1·m−1 at 589K for Bi2S3/f-MWCNTs nanocomposite, which is close to the lowest value reported for Bi2S3-based materials. Ultimately, the thermoelectric merit (ZT) values of the Bi2S3+xwt%f-MWCNTs (x = 0.5, 1, 1.5, 2) nanocomposites were all improved to varying degrees. We prepared Bi2S3/f-MWCNTs nanocomposites with high thermoelectric properties by simple hydrothermal synthesis technique. The use of composite structure to regulate the thermoelectric optimum value of Bi2S3-based materials will further broaden its application in the thermoelectric field.

One pot synthesis of carbon decorated NiO nanorods as cathode materials for high-performance asymmetric supercapacitors

The composites of metal oxides and carbons are of research interest for improving the energy density of supercapacitors. In this work, we have demonstrated a simple one-pot hydrothermal synthesis method to prepare NiO nanorods followed by carbon framework decorated NiO nanorods (NiO@C). The NiO@C electrode showed an excellent specific capacitance of 1360 F g−1 compared to pristine NiO of 890 F g−1 at 1 A g−1 in a voltage range of 0.05 to 0.5 V in 1 M KOH electrolyte. The NiO@C electrodes showed excellent cycle stability over 10,000 cycles with 90 % capacitance retention. Asymmetric supercapacitors fabricated using corncob-derived activated carbon anode, and NiO@C cathode delivers a power density of 4574 W kg−1 at an energy density of 21.6 Wh kg−1. The enhanced capacitance of NiO@C material is due to the synergistic effect of the pseudocapacitive of NiO nanorods and the electric double-layer capacitance of the carbon matrix. Besides, the carbon framework facilitates quick charge acceptance, improved cycling stability, and rate capability. The cost-effective one-pot synthesis and eco-friendly NiO nanorods with easy electrode fabrication open opportunities for developing high-energy-density NiO-based supercapacitors.

A novel MoP2@Ni2P nanosheet and an individual kelp-based porous carbon for assembly a unique high performance asymmetric supercapacitor

In order to improve the specific capacity and energy density of the asymmetric supercapacitors, it is necessary to design positive and negative electrode materials with special structure and good electrochemical properties. Herein, a novel MoP2@Ni2P nanosheet material is prepared by one-step simple hydrothermal synthesis and low temperature phosphating method, which exhibits excellent specific capacity of 133.6 mAh g−1 at 0.5 A g−1. In addition, a kelp based porous carbon nanosheet material (AKPC) is prepared via swollen the kelp in a sodium chloride solution and then subjected to an activation and carbonization. Because of its biomaterial unique morphology, the carbon material shows ultra-high specific surface area (1197 m2 g−1) and large pore volume, thus possess a high specific capacitance of 180 F g−1 at 0.5 A g−1. Moreover, the above two materials are assembled into a unique asymmetric supercapacitor with operating voltage of 1.65 V, which has demonstrated a high energy density of 31.5 Wh kg−1 and excellent cycling stability with 81 % capacitance retention after 1500 cycles in aqueous electrolyte. The successful preparation of the asymmetric device provides a new idea for the development of high performance electronic devices.

Nanostructured Ternary Nickel‐Based Mixed Anionic (Telluro)‐Selenide as a Superior Catalyst for Oxygen Evolution Reaction

Developing protocols for designing high‐efficiency, durable, cost‐effective electrocatalysts for oxygen evolution reaction (OER) necessitates deeper understanding of structure–property correlation as a function of composition. Herein, it has been demonstrated that incorporating tellurium into binary nickel chalcogenide (NiSe) and creating a mixed anionic phase perturbs its electronic structure and significantly enhances the OER activity. A series of nanostructured nickel chalcogenides comprising a layer‐by‐layer morphology along with mixed anionic ternary phase are grown in situ on nickel foam with varying morphological textures using simple hydrothermal synthesis route. Comprehensive X‐ray diffraction, X‐ray photoelectron spectroscopy, and in situ Raman spectroscopy analysis confirms the formation of a trigonal single‐phase nanocrystalline nickel (telluro)‐selenide (NiSeTe) as a truly mixed anionic composition. The NiSeTe electrocatalyst exhibits excellent OER performance, with a low overpotential of 300 mV at 50 mA cm−2 and a small Tafel slope of 98 mV dec−1 in 1 m KOH electrolyte. The turnover frequency and mass activity are 0.047 s−1 and 90.3 Ag−1, respectively. Detailed electrochemical measurements also reveal enhanced charge transfer properties of the NiSeTe phase compared to the mixture of binaries. Density functional theory calculations reveal favorable OH adsorption energy in the mixed anionic phase compared to the binary chalcogenides confirming superior electrocatalytic property.

Experimental and theoretical insights into colossal supercapacitive performance of graphene quantum dots incorporated Ni3S2/CoS2/MoS2 electrode

Transition metal sulfides (TMS) are promising electrode materials for supercapacitor applications due to their unmatchable advantages. To overcome the deficiency of individual metal sulfides, the combination of one or more pseudocapacitive transition metals with conductive carbon material can be a plausible solution. In this work, a simple and one-step hydrothermal synthesis method is used to fabricate the flower-like Ni3S2/CoS2/MoS2 (NCMS) and Ni3S2/CoS2/MoS2-GQDs (NCMS-G) directly on Ni foam and used it as a binder-free electrode for high-performance supercapacitor applications. The NCMS-G-2.5 electrode possessed colossal specific capacitance (2364 Fg−1 at the current density of 2 Ag−1), excellent rate capability (55 % at the current density of 10 Ag−1), as well as good cycling stability (93 % retention after 10,000 cycles at the current density of 20 Ag−1). Furthermore, assembled NCMS-G-2.5//rGO asymmetric supercapacitor (ASC) device delivered an excellent energy density of 84.8 Wh kg−1 and superior cycling performance (98 % capacitance retention after 10,000 cycles). We have investigated the interactions between Ni3S2/CoS2/MoS2 and carbon based nanostructure GQDs employing state-of-the-art Density Functional Theory (DFT) simulations. The interactions between Ni3S2/CoS2/MoS2 and GQDs is not only long range van der Waals interactions, but also chemical interactions involving charge transfer from metal 3d orbital to C 2p orbital of GQDs are also present. Due to this synergic effect, there is enhancement in electronic states near Fermi level which may improve the conductivity of the hybrid structure. Enhanced quantum capacitance, improved conductivity and increased surface area for the hybrid structure may attribute towards superior charge storage performance for the hybrid structures which support experimental data. It is expected that the fabricated, unique, 3D flower NCMS-G-2.5 has potential prospects for developing advanced and high-performance energy storage devices.

Cobalt‐Nickel Ultrathin Hexagonal Nanosheets for High‐performance Asymmetric Supercapacitors

AbstractIn this work, uniform ultrathin hexagonal nanosheets of Co−Ni bimetallic hydroxides are synthesized using a simple green hydrothermal synthesis method. By tuning a Co/Ni mole ratio of 1 : 2, a special nanosheet structure of Co0.32Ni0.68(OH)2 was obtained with high interlayer spacing and large pore size. This nanosheet exhibits an enhanced specific capacity as high as 1021.96 C/g at 0.5 A/g, 12 times higher than Co(OH)2 (83.23 C/g). The high electrochemical performance is attributed to the interfacial interaction between Co2+ and Ni2+, as well as its special nanosheet structure. The advantages of the composition and structure are further confirmed by density functional theory (DFT) calculations. Besides, the energy storage process was visually observed by in situ Fourier transform infrared (FTIR) spectroscopy. Furthermore, an asymmetric supercapacitor (ASC) is assembled by Co0.32Ni0.68(OH)2 and activated carbon electrodes. The ASC delivers a high energy density of 54.97 W h/kg at a power density of 1.68 kW/kg and maintains 33.52 W h/kg at 32.66 kW/kg. These results highlight the promising applications of ultrathin Co0.32Ni0.68(OH)2 nanosheets as a high‐performance electrode material in supercapacitors.

RGO‐Wrapped Hexagonal WO3 Nanorod as Advanced Electrode Material for Asymmetric Electrochemical Supercapacitors

The multiple oxidation states of redox‐active materials enable them to store high‐energy better than the commonly used carbon‐based electrode materials. Accounting for these advantages, designing asymmetric supercapacitors by coupling redox‐active materials as positive electrodes with carbon‐based negative electrodes becomes a very attractive strategy. Herein, reduced graphene oxide‐wrapped hexagonal WO3 nanorod (rGO‐WO3 NR) by simple hydrothermal synthesis method is synthesized. Because of improved reaction kinetics resulting from the close contact between rGO and WO3 NRs, rGO‐WO3 NR demonstrates superior electrochemical properties than pure WO3. Motivated by the very high areal capacitance (2.5 F cm−3 at the applied current of 30 mA cm−2), an asymmetric SC device by combining rGO‐WO3 NR with activated carbon is assembled. The as‐assembled rGO‐WO3 NR//activated carbon asymmetric supercapacitor device demonstrates outstanding electrochemical performance in an operating voltage window of 1.2 V, admirable cycling stability of ≈95% (even after 14 000 cycles), with an energy density of 24.1 Wh Kg−1 at a power density of 1532.6 W Kg−1. These demonstrate the combination of redox‐active materials with high energy density can importantly boost the energy storage capacity of a supercapacitor.

Graphene oxide embedded in Bi2S3 nanosheets by hydrothermal method to enhance thermoelectric performance

Bi2S3 is an inexpensive and non-toxic thermoelectric material with high Seebeck coefficient and low thermal conductivity, which makes it have broad development prospects in the field of thermoelectric materials. In this work, we successfully synthesized Bi2S3/graphene oxide (GO) hybrid nanosheets by a simple hydrothermal synthesis method. Due to the unique structure of the two-dimensional nanomaterial GO, it can be uniformly embedded in the Bi2S3nanosheet matrix. The total thermal conductivity of Bi2S3/GO hybrid nanosheets is astonishingly low as 0.32Wm−1K−1 at 619K, which is 13% lower than that of pure Bi2S3. In addition, the thermoelectric performance of Bi2S3/GO hybrid nanostructures were further improved by changing the doping amount of GO. At 300–650K, the maximum thermoelectric figure of merit (ZT) of Bi2S3/GO(0.5 wt%) is 0.17, and its ZT below 550K is higher than that of pure phase Bi2S3. Bi2S3/GO composites were synthesized by an inexpensive and simple experimental method, which provides a new strategy for optimizing the thermoelectric properties of Bi2S3.

Sharp-edged pencil type ZnO flowers and BiOI flakes combined with carbon nanofibers as heterostructured hybrid photocatalysts for the removal of hazardous pollutants from contaminated water

The growth of advanced micro-and nanostructures with metal oxides has consistently generated extraordinary interest in energy and environmental applications. Cutting-edge nanostructures exhibit superior reactive sites and surface areas, thus improving the performance in crucial domains. In this study, sharp-edged pencil-type ZnO flowers and BiOI flakes as pristine materials, and their composition with carbon nanofibers (CNFs) (ZnO–BiOI@CNFs) as a hetero hybrid catalyst as well as binary compositions such as ZnO–BiOI, ZnO@CNFs, and BiOI@CNFs catalysts were fabricated using a simple and convenient hydrothermal synthesis process. The composition of newly produced innovative nanostructures was examined for azo dye degradation under solar simulator exposure. Dye degradation of ∼95% was achieved by the hybrid catalyst (ZnO–BiOI@CNFs) during 120 min of irradiation, which was ∼1.8 and 2.1-times higher than pristine ZnO and BiOI nanostructures, respectively.The improved hybrid catalysts were able to degrade methyl orange (MO) and rhodamine B (RhB) dyes. Importantly, mixed dyes RhB, MO, and azo dye demonstrated 47% dye degradation using a hybrid catalyst. These mixed dye-scalable hybrid catalyst performances offer additional insights into commercialization/industrialization. The outstanding performance of the hybrid catalyst is attributed to the unidirectional electron flow with pencil-like ZnO, a catalyst with a larger absorption zone, high surface area, and reactive sites, particularly ZnO and BiOI nanostructures, and decreased recombination rate with a heterojunction interface. In addition, CNFs can operate as electron traps and sinks, providing very quick redox reactions. To produce the sophisticated nanostructures with homogeneous morphologies, this work presents new insights into energy and environmental applications.

Photocatalytic degradation of glyphosate using Ce/N co-doped TiO2 with oyster shell powder as carrier under the simulated fluorescent lamp

Glyphosate is currently one of the most used organophosphorus herbicides in the world and its accumulation and translocation in soil and wave causes environmental pollution and biological health problems. A new approach to the problem is provided by the preparation of cerium and nitrogen co-doped titanium dioxide composite nano-photocatalysts loaded on modified oyster shell powder (CeNT@Oys) by a simple hydrothermal synthesis. The physicochemical and optoelectronic properties are analyzed using SEM, BET, XRD, Raman, FTIR, UV-vis DRS, XPS characterization techniques and a range of photoelectrochemical techniques. The results show that the addition of modified oyster shell powder increases its specific surface area, while Ce-N-TiO2 is an anatase crystal composed of Ce doped in the form of interstitial and surface, interstitial form of N, and the co-doping of Ce and N elements gives it the property of being excited by visible light. The photocatalytic activity of the different catalysts was evaluated by degrading 50 mg/L glyphosate solution under simulated sunlight. The catalyst was determined to be reusable by five repeated degradation experiments. Based on quenching experiments and the electron paramagnetic resonance tests, the effective active species of glyphosate degraded by the catalyst was determined and the mechanism of glyphosate degradation by photocatalyst was proposed. Finally, the degradation pathway for the photocatalytic degradation of PMG by CeNT@Oys was determined by HPLC-MS/MS determine of the intermediate products.

Fabrication of ZnWO4/Carbon Black Nanocomposites Modified Glassy Carbon Electrode for Enhanced Electrochemical Determination of Ciprofloxacin in Environmental Water Samples

The major problem facing humanity in the world right now is the sustainable provision of water and electricity. Therefore, it is essential to advance methods for the long-term elimination or removal of organic contaminants in the biosphere. Ciprofloxacin (CIP) is one of the most harmful pollutants affecting human health through improper industrial usage. In this study, a zinc tungsten oxide (ZnWO4) nanomaterial was prepared with a simple hydrothermal synthesis. The ZnWO4/Carbon black nanocomposites were fabricated for the determination of CIP. The nanocomposites were characterized by field emission scanning electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. Electrochemical studies were done using cyclic voltammetry and differential pulse voltammetry methods. Based on the electrode preparation, the electrochemical detection of CIP was carried out, producing exceptional electrocatalytic performance with a limit of detection of 0.02 μM and an excellent sensitivity of (1.71 μA μM-1 cm-2). In addition, the modified electrode displayed great selectivity and acceptable recoveries in an environmental water sample analysis for CIP detection of 97.6% to 99.2%. The technique demonstrated high sensitivity, selectivity, outstanding consistency, and promise for use in ciprofloxacin detection. Ciprofloxacin was discovered using this brand-new voltammetry technique in a water sample analysis.

A simple hydrothermal synthesis of an oxygen vacancy-rich MnMoO4 rod-like material and its highly efficient electrocatalytic nitrogen reduction.

Electrocatalytic nitrogen reduction (NRR) for artificial ammonia synthesis under ambient conditions is considered a promising alternative to the traditional Haber-Bosch process. However, it still faces multiple challenges such as the difficulty of N2 adsorption and activation and limited Faraday efficiency. In this work, a bimetallic oxide MnMoO4 was prepared by a hydrothermal method and low temperature calcination. The influence of the sintering temperature on the microstructure (crystallinity and oxygen vacancies) of the oxide and its NRR properties were systematically explored. The results showed that MnMoO4 sintered at 500 °C had the highest concentration of OVs and showed excellent NRR performance, with the highest NH3 yield (up to 12.28 μg h-1 mgcat-1), high Faraday efficiency (23.04% at -0.30 V vs. RHE), and good stability at -0.40 V vs. RHE, and the catalytic performance was about two times higher than that of Mn2O3 and MoO3. It is also superior to other bimetallic oxide NRR electrocatalysts reported in some cases. In addition, we also explored the ratio between Mn and Mo metals, and the catalytic effect was the best when Mn : Mo = 1 : 1. Due to the synergistic effect between Mn and Mo metals and the large number of OVs present internally, the catalytic activity for the NRR was largely improved. This study suggests that the bimetallic oxide MnMoO4 may be a promising NRR electrocatalyst.

Preparation and characterization of nanostructured Fe-doped CoTe2 electrocatalysts for the oxygen evolution reaction.

The key step for hydrogen production through water electrolysis is the development of highly efficient and inexpensive oxygen evolution reaction (OER) catalysts. In this work, we report the successful synthesis of a nanostructured Fe-doped cobalt-based telluride (Fe-doped CoTe2) catalyst on Co foam by a simple one-step hydrothermal synthesis method, which shows excellent OER performance. The influences of Fe doping amounts and reaction temperatures on the morphology, structure, composition, and the OER performance of cobalt-based tellurides have been systematically studied. The optimal sample Co@0.3 g FeCoTe2-200 exhibits a low overpotential of 300 mV at a current density of 10 mA cm-2, and a small Tafel slope of 36.99 mV dec-1, outperforming the undoped cobalt telluride catalysts (Co@CoTe2-200). The Co@0.3 g FeCoTe2-200 electrode also reveals a small overpotential degradation of around 26 mV after an 18-hour continuous OER process. These results unambiguously confirm that Fe doping helps improve the OER activity and long-term catalytic stability. The superior performance of nanostructured Fe-doped CoTe2 can be attributed to the porous structure and the synergistic effect of Co and Fe elements. This study provides a new approach for the preparation of bimetallic telluride catalysts with enhanced OER performance, and Fe-doped CoTe2 holds substantial promise for use as a high-efficiency, cost-effective catalyst for alkaline water electrolysis.

One-Pot Synthesis of Nanostructured Ni@Ni(OH)2 and Co-Doped Ni@Ni(OH)2 via Chemical Reduction Method for Supercapacitor Applications.

Crystalline Ni@Ni(OH)2 (cNNH) and Co-doped cNNH were obtained via a simple one-pot hydrothermal synthesis using a modified chemical reduction method. The effect of each reagent on the synthesis of the nanostructures was investigated concerning the presence or absence of each reagent. The detailed morphology shows that both nanostructures consist of a Ni core and Ni(OH)2 shell layer (~5 nm). Co-doping influences the morphology and suppresses the particle agglomeration of cNNH. Co-doped cNNH showed a specific capacitance of 1238 F g-1 at 1 A g-1 and a capacitance retention of 76%, which are significantly higher than those of cNNH. The enhanced performance of the co-doped cNNH is attributed to the reduced path length of the electrons caused by the decrease in the size of the nanostructure and the increased conductivity due to Co ions substituting Ni ions. The reported synthesis method and electrochemical behaviors of cNNH and Co-doped cNNH affirm their potential as electrochemically active materials for supercapacitor applications.

MoO3/Ti3C2Tx MXene nanocomposites with rapid response for enhanced ethanol-sensing at a low temperature

Ethanol, as one of the most widely used volatile organic compounds (VOCs), can cause serious harm to the human respiratory system when exposed to low concentrations of ethanol gas for a long time. Here, we successfully prepared MoO3/Ti3C2Tx MXene nanocomposites by a simple hydrothermal synthesis method, realizing the effective monitoring of low-concentration ethanol gas (1.61@1 ppm). The specific surface area of MoO3/Ti3C2Tx MXene nanocomposites (61.044 m2/g) is doubled compared with Ti3C2Tx MXene (33.385 m2/g), which provides more reaction centers and active sites for ethanol molecules. Meanwhile, the gas-sensing results revealed that MoO3/Ti3C2Tx MXene nanocomposites show outstanding selectivity and reproducibility, as well as fast response-recovery (10/49 s). Subsequently, the possible sensing mechanism of the composite was further discussed in detail in combination with density functional theory (DFT). This work provides a new sensing design strategy for detecting VOCs at low-temperature.