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An electrochemical nitrogen reduction reaction (ENRR) is considered a promising alternative for the traditional Haber-Bosch process. In this study, we present a method for improving the ENRR by controlling the wettability of the catalyst surface, suppressing the hydrogen evolution reaction (HER) while facilitating N

The inclusion of trace amounts of Mg and Zn to Al alloys caused the development of β and τ phases at the grain boundary, resulting in the change from pitting corrosion to intergranular corrosion and therefore increased corrosion resistance.

The electrochemical approach for the feasible ammonia production via N2 fixation is well-thought-out to be an eco-friendly strategy to replace the polluting Haber Bosch process. However, the impeding activation barrier of strong N≡N and the competing hydrogen evolution reaction constrain the Faradaic efficiency of the electrochemical nitrogen reduction reaction. Therefore, the implication of innovative strategies for designing an active electrocatalyst remains a crucial criterion to deliver operational efficiencies during electrochemical reactions. This study proposes a unique fabrication of three-dimensional (3D)-architectured electrodes encompassed with cobalt-rich tungsten carbide (Co-WC) as an electrocatalyst using a 3D-printing technique for the efficient electrochemical nitrogen reduction reaction. Here, the cobalt acts as a binder between tungsten carbide particles after sintering, and the particles are bonded to each other. The 3D-printing process generates 3D-architectured Co-WC electrodes with an average particle size of 1–3 µm through precise control of printing parameters. The electrochemical performance of the 3D-architectured Co-WC electrode reveals a better selectivity for N2 reduction under ambient condition. Substantially, the 3D-architectured Co-WC electrodes demonstrate an improved ammonia yield rate of 34.61 μg h−1 cm−2 and Faradaic efficiency of 2.12% at an applied potential − 0.6 V (vs. RHE). 3D-printing techniques can be an effective design method for manufacturing 3D-architectured active material with superior performance and selectivity.

Three novel Zintl phase solid solutions in the Ca11−xGdxSb10−y (0.36(2) ≤ x ≤ 0.58(4), 0.26(1) ≤ y ≤ 0.37(1)) system have been successfully synthesized by arc melting, and their crystal structures were carefully characterized by powder and single-crystal X-ray diffraction analyses. During the synthesis, as we changed the reaction time, we were able to observe the early stages of the crystal growth process for a cubic-shaped single crystal with hummocky-type patterns on it. All three title compounds adopted the tetragonal I4/mmm (Z = 4, Pearson code tI84) space group and crystallized in the Ho11Ge10-type phase. The overall complex crystal structure contained three Ca/Gd mixed sites with particular site preferences and one Sb site with some occupational deficiencies. A series of DFT calculations and detailed structure analyses proved that the observed cationic site preference should be attributed to the size-factor criterion rather than the electronic-factor criterion, and the Gd-containing title compounds became a tipping point for the size factor criterion in the overall Ca11−xRExSb10−y (RE = rare-earth metals) series. Theoretical investigations indicated that the energetically unfavorable antibonding character of the Sb–Sb interaction on the Sb4 tetramers caused ca. 2.6–3.7% (fractional percentage) of Sb deficiencies and eventually resulted in keeping the p-type character of the Ca11−xGdxSb10−y system despite the successful n-type Gd doping. According to the temperature-dependent thermoelectric property measurements, the relatively “heavier” Gd dopants successfully improved the electrical conductivity, Seebeck coefficient, and thermal conductivity of Ca10.63(4)Gd0.37Sb9.74(1) compared to those of two previously reported Ca10.75(3)Nd0.26Sb9.82(1) and Ca10.82(4)Sm0.18Sb9.86(1), which contained the relatively “lighter” Nd and Sm dopants.

A thermoelectric coated grain nanocomposite CuInTe2/SnTe with eco-friendly elements was synthesized. The nanocomposite contains a coating layer of CuInTe2 and SnO2 at the grain boundaries of the SnTe matrix. The coating layer was synthesized using the cation exchange process considering the hard soft acid base (HSAB) concept, the solubility product, and crystal structure. The CuInTe2 coating layer blocks the low energy carriers of the composite resulting in 40% enhancement of the Seebeck coefficient due to energy filtering. The coherent phonon scattering by the coating layer of CuInTe2 effectively reduces the lattice thermal conductivity to almost the minimum theoretical limit. The thermoelectric figure of merit (zT) for the CuInTe2/SnTe nanocomposite was as high as 1.68 at 823 K, which is significantly higher than that of bulk SnTe in the mid-temperature range. The average zT from 373 K to 823 K for the nanocomposite was 0.76, which is promising for utilization in industrial application.

To enhance the efficiency of hydrogen production, bimetallic oxides with spinel structures, M2GeO4 (M = Fe, Co), were synthesized via a facile one-pot hydrothermal method and were used as electrocatalysts for urea-assisted water electrolysis. In alkaline electrolyte with urea, Fe2GeO4, which was used as the anode in the electrolysis cell, exhibited a lower potential (1.53 V (vs. RHE)) and a smaller Tafel slope (76 mV dec−1) Co2GeO4 (1.65 V (vs. RHE), 79 mV dec−1), indicating that Fe2GeO4 reduced the overall input potential to produce H2. The superior performance of Fe2GeO4 in the urea-added water electrolysis was attributed to the higher oxidation state of its metal cations, larger electrochemical active surface area, and lower charge transfer resistance than those of Co2GeO4. Hence, Fe2GeO4 showed 5.49 times higher H2 peak intensity than Co2GeO4, indicating higher efficiency of H2 production.

One promising approach to improving thermoelectric energy conversion is to use nanostructured interfaces that enhance Seebeck coefficient while reducing thermal conductivity. Here, we synthesized A...

The integration of energy conversion and storage systems such as electrochemical water splitting (EWS) and rechargeable zinc-air battery (ZAB) is on the vision to provide a sustainable future with green energy resources. Herein, a unique strategy for decorating 3D tetragonal CoMn

In thermoelectric energy conversions, thermal conductivity reduction is essential for enhancing thermoelectric performance while maintaining a high power factor. Herein, we propose an approach based on coated-grain structures to effectively reduce the thermal conductivity to a much greater degree when compared to that done by conventional nanodot nanocomposite. By incorporating CdTe coated layers on the surface of SnTe grains, the thermal conductivity is as low as 1.16 W/m-K at 929 K, resulting in a thermoelectric figure of merit, i.e., zT, of 1.90. According to our developed theory, phonons scatter coherently due to the phase lag between phonons passing through and around the coated grain. Such scattering is induced by the acoustic impedance mismatch between the coated layer and the grain, resulting in a gigantic phonon-scattering cross section. The phonon-scattering cross section of the coated grains is several orders of magnitude larger than that of the nanodots with the same impurity concentration. Th...

Heavily Cu-doped Bi2Te3 nanoparticles were prepared by intercalating copper metal into flower-like Bi2Te3 nanoparticles using the disproportionation redox reaction of Cu(I) salt. The phase, chemical composition, and morphology of the Bi2Te3 nanoflowers were analyzed by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The synthesized Cu-doped Bi2Te3 nanopowders were consolidated by spark-plasma sintering into bulk pellets, and the effects of Cu-doping on the transport properties (electrical resistivity, Seebeck coefficient, and thermal conductivity) of these materials were investigated. Superstoichiometric amounts of Cu (up to ∼28 at%) can be incorporated into flower-like Bi2Te3 nanoparticles, which have large accessible surface area for diffusion of Cu ions. The flower-like morphologies did not change despite high Cu incorporation. Variation in carrier concentration was achieved by changing Cu precursor concentration. Cu-doping in Bi2Te3 can enhance the Seebeck coefficient due to a decrease in carrier concentration, thus the power factors increased compared with that of the un-doped sample. Furthermore, the thermal conductivity of Cu-doped Bi2Te3 is substantially reduced. As a result, Cu-doped Bi2Te3 sample with 15.6 at% Cu exhibited the best thermoelectric performance with a figure of merit of 0.67 at 415 K, which is more than two times higher than that of undoped Bi2Te3 nanopowder.

Most bike sharing system has an imbalance problem in certain time zones and certain rental stations where bicycles are insufficient or overloaded. So, a demand forecasting model is required to solve this problem. In this paper, we evaluate the performance applying the machine learning, neural network model with the bicycle demand dataset collected from the bicycle sharing system in actual operation in order to develop a model that predicts bicycle demand information for choosing a proper demand forecasting model. From the results, the neural network models outperform the machine learning models.

One promising approach to improving thermoelectric energy conversion is to use nanostructured interfaces that enhance Seebeck coefficient while reducing thermal conductivity. Here, we synthesized Au-Cu

Charge storage in supercapacitors is strongly related to the bond characteristics and electronic structure of electrode materials. Graphene-based materials are widely used in a supercapacitor due to the easily tunable properties and high surface/volume ratios. However, we claim that the typical covalent bond characteristics of 2D carbon materials originating from this 2pπ orbital is not very suitable to the application in supercapacitor. Here, we suggest an efficient way to improve the supercapacitor performance by tuning the covalency of bonding between the graphene-based electrode and potassium ion. We, for the first time, also introduce a simple solvent-free scale-up doping technique to prepare fluorine-doped graphene oxide (FGO) by direct plasma treatment on graphene oxide (GO) powder at ambient pressure. The FGO enabled fast electrochemical charge transfer and provided a large number of active sites for redox reactions during supercapacitor operation, and those mechanisms were thoroughly studied by various electrochemical analyses. As a result, the fabricated symmetric supercapacitor using FGO electrodes exhibited a maximum power density (~3200 W/kg) and energy density (~25.87 Wh/kg) with superior cycle stability (20000 cycles) without capacitance loss. Furthermore, the computational calculation results clarified the roles of semi-ionic C–F bonding of FGO: huge charge accumulation on the electrodes and superior electrical conductivity. Thus, our study demonstrates a facile strategy to develop promising functionalized materials, which can enhance the viability of supercapacitor for the next generation of energy storage systems.

In this report, CuI and Sn co-doped n-type Bi2Te3 samples have been prepared by a high-temperature solid-state reaction, and the effect of co-doping on the thermoelectric properties was investigated from room temperature to 525 K. Sn single-doped and undoped Bi2Te3 were prepared for comparison. Detailed charge transport data including electrical conductivity, Seebeck coefficient, Hall coefficient, and thermal conductivity are presented. Microscopic observation of CuI/Sn co-doped samples revealed that numerous distinctive microstructures such as nanoprecipitates of the Cu and SnI-rich phase were generated in the matrix. The lattice thermal conductivity of CuI/Sn co-doped Bi2Te3 was substantially reduced compared to those of undoped and single doped Bi2Te3. Benefiting from the improved electrical transport properties by doping and the reduced lattice thermal conductivity by numerous microstructures, the ZT value of the Bi2Te3 doped with 1 at.% CuI/Sn is distinctly enhanced to 1.24 at 425 K. The average ZT value (ZTave ~ 1.02) at 300–525 K was clearly higher than those of Sn-doped Bi2Te3 (ZTave ~ 0.54) and CuI-doped Bi2Te3 (ZTave ~ 0.98). This work indicates that the average ZT can be improved over a broad temperature range using a co-doping approach.

The integration of energy conversion and storage systems such as electrochemical water splitting (EWS) and rechargeable zinc-air battery (ZAB) is on the vision to provide a sustainable future with green energy resources. Herein, a unique strategy for decorating 3D tetragonal CoMn2 O4 on carbon cloth (CMO-U@CC) via a facile one-pot in situ hydrothermal process, is reported. The highly exposed morphology of 3D tetragons enhances the electrocatalytic activity of CMO-U@CC. This is the first demonstration of such a bifunctional activity of CMO-U@CC in an EWS system; it achieves a nominal cell voltage of 1.610 V @ 10 mA cm-2 . Similarly, the fabricated rechargeable ZAB delivers a specific capacity of 641.6 mAh gzn-1 , a power density of 135 mW cm-2 , and excellent cyclic stability (50 h @ 10 mA cm-2 ). Additionally, a series of flexible solid-state ZABs are fabricated and employed to power the assembled CMO-U@CC-based water electrolyzer. To the best of the authors' knowledge, this is the first demonstration of an in situ-grown binder-free CMO-U@CC as a flexible multifunctional electrocatalyst for a built-in integrated rechargeable ZAB-powered EWS system.

In this study, a series of bismuth telluride (Bi2Te3) samples doped with a metal iodide (MI; M = Cu, Cs, K) were successfully prepared by the conventional solid-state reaction. The electron and thermal transport properties, i.e., electrical conductivity, carrier concentration, Hall mobility, Seebeck coefficient, and thermal conductivity, of MI-doped Bi2Te3 were measured in the temperature range of 300–650 K to understand the effect of metal iodide doping on the thermoelectric performance of Bi2Te3. The microstructure and morphologies of MI-doped Bi2Te3 were investigated by powder X-ray diffraction and high resolution transmission electron microscopy. The electrical conductivity increases with increasing MI contents due to the co-doping effect of metal and iodide. This value is much higher than that of Bi2Te3 doped with Cu prepared under the same experimental conditions. All the MI doped samples exhibit n-type conduction. The HR-TEM images of MI-doped Bi2Te3 samples reveal that all systems contain compositional fluctuations at the nanoscopic level, which suppress the thermal conductivity. Among metal iodides, the CuI dopant was very effective in improving the electrical conductivity and Seebeck coefficient, and suppressing the thermal conductivity, thus enhancing ZT. A significant increase in power factor (43 μW cm−1 K−2 at 368 K) accompanied by the reduction in thermal conductivity (1.23 W m−1 K−1 at 368 K) resulted in a higher ZT of (CuI)0.01Bi2Te3 than those of undoped Bi2Te3 and Cu0.07Bi2Te3.

In an effort to discover new thermoelectric materials, p-type Co2Ge3-xMxS3 (M ​= ​Zn, Cd, Bi; x ​= ​0, 0.01, 0.03, 0.05) skutterudite-based chalcogenides are prepared using a traditional solid-state reaction. The samples are then compacted into pellets by hot pressing for thermoelectric characterization. A comparative investigation is performed by partial substitution of Ge sites with various dopants to assess the influence of substitution on the thermoelectric properties of Co2Ge3S3. Electrical and thermal transport properties, i.e., electrical conductivity, carrier concentration, Seebeck coefficient, and thermal conductivity, of the substituted Co2Ge3S3 samples are measured. Substitution has a moderate positive effect on the transport properties of these ternary skutterudites. All samples exhibit p-type behavior. A maximum power factor value of 10.3 ​μW ​cm−1 ​K−2 is obtained at approximately 518 ​K for Co2Ge2.99Zn0.01S3. Compared to Co2Ge3S3, the lattice thermal conductivity of substituted Co2Ge3S3 is substantially reduced due to the atomic disorder at the Ge sites, and a minimum lattice thermal conductivity value of 2.19 ​W ​m−1 ​K−1 is obtained at approximately 675 ​K for Co2Ge2.95Cd0.05S3. Compared with the referred Co2Ge3S3 sample, the Bi-substituted skutterudite obtained the 21% reduction of the lattice thermal conductivity and 38% enhancement of power factor, resulting in a peak ZT value of ~0.22 ​at 763 ​K of Co2Ge2.97Bi0.03S3.

The phase/microstructure, mechanical properties and corrosion behavior of a series of binary Ti Mn alloys with 5, 10, 15 and 20 wt% Mn were investigated in order to understand the effects of Mn content on mechanical properties, oxidation behavior, and electrochemical corrosion properties of Ti Mn alloys. The phase/microstructure of Ti-xMn alloys was analyzed using X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. All examined properties of the Ti Mn alloys were sensitive to the Mn content. The tested Ti-xMn alloys had α-Ti, β-Ti, and α-TiMn phases. Ti Mn alloy containing 5 wt% Mn composed of α-Ti, β-Ti, α-TiMn, and isothermal ω phases. The proportion of α-Ti phase decreased and precipitation of β-Ti phase increased with increasing wt% of Mn. Cast Ti Mn exhibited higher hardness and better oxidation protection than commercially pure Ti (cp-Ti). The tested Ti-xMn alloys showed better corrosion resistance than the cp-Ti. Ti Mn alloy containing 5 wt% Mn had the highest hardness and lowest modulus, and is a good candidate for dental implant alloy.

The effects of S doping at the oxygen site on the thermoelectric properties of BiOCuSe have been investigated. The partial substitution of S ions at the O sites of BiOCuSe was achieved by sulfurization using CS2 gas. Analysis of the powder X-ray diffraction data indicates that the ZrCuSiAs structure of BiOCuSe is retained after sulfurization. Substitution of O with S leads to an increase in the lattice parameters and a decrease in the band gap. The electrical conductivity rises due to the increase of the electronic contribution with doping. S-doped BiOCuSe materials behave as a p-type semiconductor. The thermoelectric properties of S-doped BiOCuSe materials can be understood through the analysis of the electronic band structure and the density of states close to the Fermi level. The substitution of O sites with S provides possible directions toward the enhancement of the thermoelectric figure of merit of oxide materials with low electrical conductivity.

[Purpose] This study was conducted to determine whether acute aerobic exercise (climbing) is associated with changes in the dietary intake pattern. [Subjects and Methods] Food intake and physical activity data for 15 female college students were sampled for 3 days and categorized according to routine activity or high-intensity activity such as hiking. Nutrient intake based on the data was analyzed using a nutrition program. [Results] Carbohydrate and protein intake was significantly decreased after exercise compared to before acute aerobic exercise, but lipid intake showed no significant difference. Calorie intake was significantly decreased after exercise compared to before exercise; however, calorie consumption was significantly increased after exercise. [Conclusion] Aerobic exercise causes a decrease in total calories by inducing reduction in carbohydrate and protein intake. Therefore, aerobic exercise is very important for weight (body fat) control since it causes positive changes in the food intake pattern in female students.

Single-atom catalysts (SACs), as the name suggests, indicate that only one element participates in the catalytic reaction. The characteristic feature of SACs is that it has immobilized active sites with specific properties, such as unexpected catalytic activity, high product selectivity, and reduced energy barrier. SACs for electrochemical CO2 reduction reactions (CO2RR) should have isolated metal atoms acting as active sites to maximize the efficiency of metal use. Conventional metal catalysts with nano-sized metal particles, however, contain a variety of inactive sites showing inferior efficiency of metal use. Therefore, systematic synthesis and analysis of high-efficiency SACs have been an interesting challenge in the CO2RR. To address these issues, many researchers have attempted to synthesize SACs through various methods and employed numerous characterization techniques to identify single atoms and their electrochemical properties. In this review, we discuss recent trends in the synthesis strategies and analyzing techniques of SACs and explain the influence of SACs on electrochemical CO2RR mechanisms of various C1 and C2 products.