Zn Atoms Research Articles

Gram-scale synthesis of Ni-Zn diatomic sites catalyst for efficient electrochemical CO2 reduction

Diatomic catalysts inherit the advantages of single atom catalysts and use the adjacent metal-N sites for functional complementary and synergistic effects in electrochemical CO2 reduction (ECR). However, preparation of diatomic catalysts with high yield, Faradaic efficiency and stability together with low overpotential still remains challenging. In this work, we develop a nitrogen-doped carbon supported Ni-Zn diatomic catalyst, whose CO Faradaic efficiency of is higher than 92.0 % in the wide potential range of −0.57 ∼ −1.07 V vs RHE, and the maximum CO Faradaic efficiency is 97.5 % at −0.77 V vs RHE. And also, CN-NiZn performs an extraordinary stability for 30 h in the long-time durability test. More importantly, large-quantities (around 1.66 g) of Ni-Zn diatomic catalysts with remarkable catalytic performance can be prepared by this method. Synchrotron radiation X-ray absorption spectroscopy was tested to reflect the coordination environment and valence states around Ni and Zn atoms. Theoretical calculations further reveal that the synergistic effect between Ni and Zn binary metal sites largely reduces the energy barrier of the reaction to produce the intermediate *COOH, thus effectively increasing the selectivity of ECR. This work indicates that the introduction of another coordination metal can significantly affect the electronic structure of monatomic catalysts, thus improving the electrocatalytic activity and selectivity of ECR.

Insight on Cu-doping dependent structural, electronic and optical properties of AgZnF3 Fluro-perovskite for solar cell applications: A DFT study

The density function theory (DFT) with GGA and PBE was employed to determine the structural, electrical, and optical characteristics of pure and Cu doped AgZnF3 type Fluro-perovskite. The structural properties of composite are calculated in realistic agreement with those testified in the literature. The band gap of the hybrid AgZnF3 is small and indirect. AgZnF3 contained a calculated band width of 1.52 eV. AgZnF3's total electronic properties were principally controlled by the Zn atom, whereas the Zn-d state and the F-p state had a minor impact on its partial electronic properties and state density. Cu doping modified AgZnF3's electrical band structure by narrowing the band gap. With increasing doping concentrations, the partial densities of states, which are likewise impacted by doping concentrations decreased. This material is appropriate for a variety of applications due to the improvement in optical characteristics and decrease in the band gap.

In-situ constructed solvated carbon quantum dot clusters to achieve uniform Zn plating in aqueous zinc ion batteries

Zinc ion batteries (ZIBs) have become the most competitive candidates for the next-generation energy storage systems due to its low-price, good safety and high theoretical capacity. However, the uncontrollable dendrite growth and parasitic side reactions still hinder the practical application of the zinc ion batteries. Herein, a hybrid functionalized carbon quantum dots (FCQDs)/ZnSO4 electrolyte is in-situ synthesized via a simple one-pot hydrothermal method with glucose as precursor. The created FCQDs possess abundant anionic groups like hydroxyl, carboxyl and sulfonic acid groups, and those anionic groups can strongly absorb Zn2+ ions and then the FCQDs, Zn2+ and water molecules together generate a special solvation structure of solvated carbon quantum dot clusters [FCQDsZnx(H2O)y]2x+. The solvated FCQDs clusters can help to in-situ induce the uniform Zn deposition through a co-plating of Zn atoms and the functionalized FCQDs. Additionally, this unique solvation structure promotes easier dissociation of solvation water molecules, thus decreasing the de-solvation energy. The lower de-solvation energy barrier can help to restrain the water decomposition and the related by-products. Benefiting from the construction of this unique solvated FCQDs clusters, the hybrid electrolyte with FCQDs endows a better performance of both Zn||Zn symmetric cells and full ZIBs.

Ordered planar plating/stripping enables deep cycling zinc metal batteries.

Metal anodes are emerging as culminating solutions for the development of energy-dense batteries in either aprotic, aqueous, or solid battery configurations. However, unlike traditional intercalation electrodes, the low utilization of "hostless" metal anodes due to the intrinsically disordered plating/stripping impedes their practical applications. Herein, we report ordered planar plating/stripping in a bulk zinc (Zn) anode to achieve an extremely high depth of discharge exceeding 90% with negligible thickness fluctuation and long-term stable cycling. The Zn can be plated/stripped with (0001)Zn preferential orientation throughout the consecutive charge/discharge process, assisted by a self-assembled supramolecular bilayer at the Zn anode-electrolyte interface. Through real-time tracking of the Zn atoms migration, we reveal that the ordered planar plating/stripping is driven by the construction of in-plane Zn─N bindings and the gradient energy landscape at the reaction fronts. The breakthrough results provide alternative insights into the ordered plating/stripping of metal anodes toward rechargeable energy-dense batteries.

Highly efficient (V2O5)0.91Zn0.09 powdered catalyst for water organic pollutant elimination

(V2O5)1-x Znx powdered samples with different light doping levels (x = 0.03–0.09) were prepared by a solid-state thermal reaction and studied by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive analysis (EDAX), and optical diffuse reflectance spectroscopies. The prepared samples has been revealed that the increments in Zn-doping levels accompanied by vacuum heat treatment lead to the appearance of an additional V12O26 phase beside the pure V2O5 oxide, resulting not only in more donor vanadium atom liberation but also in multi-heterojunction component formation. Besides, Eg values decrease from 2.38 to 2.2 eV as Zn doping increases from x = 0 to x = 0.09. All previous observations improve the process of purifying water from pollutants by increasing the number of free carriers of V2O5 powder by adding Zn atoms and making vacuum heat treatments. The photocatalytic examination has been carried out using constants of 0.5 g and 0.01 g/L (10 ppm) of the catalyst quantity and MB-dye concentration, respectively, under Vis – irradiations. The acidic solution medium with a pH of 2 strongly motivated the degradation activity. The highest catalytic efficiency of 99.78% was attained by the (V2O5)0.91 Zn 0.09 compound within a time of 70 min and continued invariably for 5 hours in the dark. These catalytic results have proved the possibility of their reusability.

Mechanical response in tension of twin-induced Mg alloys in wide strain rate regimes

Effect of twin boundary with/without segregation of solute atoms on deformation behavior in tension is examined in Mg–3Al–1Zn (AZ31) alloys from low strain rates to high strain rates. Solute atoms (Al and/or Zn atoms) are segregated at {10 1‾ 2} twin boundaries by static annealing at a temperature of 423 K with a holding time of 150 min. The room-temperature tensile mechanical response of the specimens, which have pre-induced twin boundaries, shows detwinning behavior, regardless of the strain rate between 10−5/s and 100/s. The yield strength of these specimens is also unlikely to be affected by strain rate, because twin boundary mobility, i.e., the shrinkage, is an athermal process. On the other hand, the specimen with segregating of solute atoms at twin boundaries exhibits an increased strength and a decreased strain hardening as compared with those in the specimen having non-segregated twin boundaries. Newly formed deformation twins of several types, i.e., the {10 1‾ 2} twins, {101‾ 1} twins and {101‾ 2}-{101‾ 1} double twins, are the origin of fracture in these specimens.

Evolution of bimodal-structure and achieving ultra-high yield strength in the as-extruded ZK70 alloy via Gd addition

Achieving ultra-high tensile yield strength over 400 MPa in RE modified Mg–Zn-based alloys using conventional thermomechanical processing is a challenging task. In this study, we successfully produced a Mg–7Zn–2Gd–0.5Zr (wt. %) alloy with exceptional strength through traditional hot-extrusion techniques. This alloy exhibits a tensile yield strength of 440 MPa and an acceptable ductility of 4.5%, surpassing a majority of previously reported Mg–Zn-RE-based alloys. Our findings demonstrate that the addition of Gd in Mg–Zn-based alloys effectively retards dynamic recrystallization (DRX) during extrusion, leading to the formation of a distinctive bimodal structure comprising approximately 13.8% coarse un-recrystallized (unDRXed) grains and about 86.2% fine DRXed grains. Furthermore, the alloying effect of Gd enhances particle density, including micron-sized particles and dynamic nano-precipitates. These dynamic precipitates play a crucial role in impeding dislocation movement during extrusion, thereby contributing to the formation of bimodal structure. Additionally, both nano-precipitates and segregation of Zn and Gd atoms towards grain boundaries facilitate the formation of fine DRXed grains through pinning effect. Consequently, the significantly increased tensile yield strength observed in our Gd-modified alloy can be attributed to multiple strengthening mechanisms: fine DRXed grains, strong texture exhibited by unDRXed grains, numerous dynamic precipitates, high-density residual dislocations, and co-segregation of solutes. However, the formation of bimodal structure worsens the yield asymmetry of the Gd-modified alloy due to its strong basal texture. These results provide a valuable insight for further development efforts aimed at achieving ultra-high-strength Mg–Zn-RE-based alloys.

Highly dispersed Zn-N, S co-doped carbon for highly efficient electrocatalytic oxygen reduction

Supportive atomic Zn electrocatalysts exhibit excellent stability for oxygen reduction reaction (ORR) due to their fully occupied d orbitals of Zn, but their catalytic activity is not satisfactory. Whereas heteroatom doping can anchor the Zn atoms to achieve higher Zn loading; and additionally serve as auxiliary sites to enhance the catalytic activity of Zn sites. Herein, we present a method for the synthesis of N, S co-doped carbon with highly dispersed Zn (named Zn-NSC). The ORR activity of the Zn-NSC catalysts is optimized by adjusting the pyrolysis temperature and the atomic structure of the dopant molecules. The optimized Zn-NSC demonstrates significantly enhanced ORR electrocatalytic activity, this is attributable to its highly co-doping of N and S heteroatoms that are adjacent to Zn atoms. Specifically, the Zn-NSC3 catalyst exhibits remarkable ORR characteristics with excellent onset voltage (0.97 V vs RHE) and half-wave potential (0.87 V vs RHE), surpassing those of Pt/C (0.97 V and 0.85 V, respectively). Additionally, the Zn-NSC3 can be utilized as efficient cathode for Al-air batteries, achieving a high power density of 119.4 mW cm−2 and satisfactory discharge stability. This work proposes an approach for synthesizing low-cost and efficient ORR electrocatalysts for Al-air battery applications.

Electrolyte Optimization Strategy: Enabling Stable and Eco-Friendly Zinc Adaptive Interfacial Layer in Zinc Ion Batteries.

Aqueous zinc ion batteries (AZIBs) have emerged as a promising battery technology due to their excellent safety, high capacity, low cost, and eco-friendliness. However, the cycle life of AZIBs is limited by severe side reactions and zinc dendrite growth on the zinc electrode surface, hindering large-scale application. Here, an electrolyte optimization strategy utilizing the simplest dipeptide glycylglycine (Gly-Gly) additive is first proposed. Theoretical calculations and spectral analysis revealed that, due to the strong interaction between the amino group and Zn atoms, Gly-Gly preferentially adsorbs on zinc's surface, constructing a stable and adaptive interfacial layer that inhibits zinc side reactions and dendrite growth. Furthermore, Gly-Gly can regulate zinc ion solvation, leading to a deposition mode shift from dendritic to lamellar and limiting two-dimensional dendrite diffusion. The symmetric cell with the addition of a 20 g/L Gly-Gly additive exhibits a cycle life of up to 1100 h. Under a high current density of 10 mA cm-2, a cycle life of 750 cycles further demonstrates the reliable adaptability of the interfacial layer. This work highlights the potential of Gly-Gly as a promising solution for improving the performance of AZIBs.

Nickel-Based Single-Atom Alloys for Methane Dehydrogenation and the Effect of Subsurface Carbon: First-Principles Investigations

Using ab initio calculations, the reaction path for methane dehydrogenation over a series of Ni-based single-atom alloys (Cu, Fe, Pt, Pd, Zn, Al) and the effect that subsurface carbon at the Ni(111) surface has on the reaction barriers are investigated. Due to the well-known problem of coking for Ni-based catalysts, the adsorption and associated physical properties of 0.25 ML, 1.0 ML, and 2 ML of carbon on the Ni(111) surface of various sites are first studied. It is found that the presence of subsurface carbon reduces the stability of the intermediates and increases the reaction barriers, thus reducing the performance of the Ni(111) catalyst. The presence of Al, Zn, and Pt is found to reduce the barriers for the CH4 → CH3 + H and CH3 → CH2 + H (Pt); and CH → C + H (Al, Zn) reactions, while Ni(111) yields the lowest barriers for the CH2 → CH + H reaction. These results thus suggest that doping the Ni surface with both Al or Zn atoms and Pt atoms, functioning as distinct active sites, may bring about an improved reactivity and/or selectivity for methane decomposition. Furthermore, the results show that there can be significant adparticle–adparticle interactions in the simulation cell, which affect the reaction energy diagram and thus highlight the importance of ensuring a common reference energy for all steps.

Electronic and magnetic properties of ZnSeS solid solution modified by Mn impurity, Zn vacancy and pressure

The spin-polarized electronic energy spectra of the ZnSeS solid solution were obtained based on calculations for the supercell, which contains 64 atoms. At the first stage, the properties of the material based on the Mn:ZnSeS supercell, in which Mn replaces the Zn atom, were calculated. The calculation results reveal that the material is a semiconductor for both spin orientations. The second stage is based on the simultaneous presence of a Mn impurity and a cation vacancy. Comparing the results of the first two stages allows us to reveal significant changes in the electronic energy structure caused by the cation vacancy. The material with a vacancy exhibits metallic properties for both spin orientations. The third stage is implemented for the supercell without a vacancy, but under the action of hydrostatic pressure. The material exhibits semiconducting properties for both values of the spin moment. At the fourth stage, the Mn:ZnSeS supercell with a vacancy and under pressure is considered. In the presence of pressure and a VZn vacancy, the ZnMnSeS material exhibits metallic properties for both spin orientations. A material with a vacancy and under pressure can be characterized as a magnetic metal.

Modulation of the microstructure, optical properties and electrical properties of zinc-doped nickel oxide films via direct current sputtering power

Zinc-doped NiO (NiO:Zn) films were direct-current-magnetron sputtered on the glass substrates. The modulation of the properties of the films via sputtering powers (Pspu) was especially studied. The conducting transition from p to n type was also proposed in mechanism. The NiO:Zn films are all preferentially 〈111〉 oriented. The films with high Pspu almost have small lattice distortion due to the improved crystallization caused by the thermal effect and the Zn element doping. The films begin to exhibit the n-type conduction at 90 W Pspu. The conducting transition from p to n type is mainly attributed to the occupation of Ni vacancies by Zn2+ and the interstitial Zn, and the improved n-type conduction in Pspu range of 140 W through 160 W to the increase in content of the interstitial Zn atoms. The absorption edge of the NiO:Zn films remaining at about 3.7 eV is slightly affected by the increase in Pspu, showing that the doping of the Zn element in the NiO is not mainly in the form of the Ni vacancies occupying ions.

Surface Patterning of Metal Zinc Electrode with an In-Region Zincophilic Interface for High-Rate and Long-Cycle-Life Zinc Metal Anode

HighlightsA stable Zn anode was obtained by patterning Zn foil surfaces and endowing a zincphilic interface in microchannels.The accumulation of electrons in the microchannel and the zincphilic interface promoted preferential heteroepitaxial Zn deposition in the microchannel region and subsequent homoepitaxial Zn deposition on the array surface.The Zn symmetrical cells could undergo repeated plating/stripping for more than 25,000 cycles at the current densities of 10 and 20 mA cm−2.

Implanting oxophilic metal in PtRu nanowires for hydrogen oxidation catalysis

Bimetallic PtRu are promising electrocatalysts for hydrogen oxidation reaction in anion exchange membrane fuel cell, where the activity and stability are still unsatisfying. Here, PtRu nanowires were implanted with a series of oxophilic metal atoms (named as i-M-PR), significantly enhancing alkaline hydrogen oxidation reaction (HOR) activity and stability. With the dual doping of In and Zn atoms, the i-ZnIn-PR/C shows mass activity of 10.2 A mgPt+Ru−1 at 50 mV, largely surpassing that of commercial Pt/C (0.27 A mgPt−1) and PtRu/C (1.24 A mgPt+Ru−1). More importantly, the peak power density and specific power density are as high as 1.84 W cm−2 and 18.4 W mgPt+Ru−1 with a low loading (0.1 mg cm−2) anion exchange membrane fuel cell. Advanced experimental characterizations and theoretical calculations collectively suggest that dual doping with In and Zn atoms optimizes the binding strengths of intermediates and promotes CO oxidation, enhancing the HOR performances. This work deepens the understanding of developing novel alloy catalysts, which will attract immediate interest in materials, chemistry, energy and beyond.

Fundamental Understanding of Hydrogen Evolution Reaction on Zinc Anode Surface: A First-Principles Study

HighlightsThe reaction mechanisms of hydrogen evolution reaction (HER) on various crystal surfaces of zinc anode have been systematically investigated by first-principle calculations.Both the thermodynamic and kinetic aspects of HER have been studied to reveal the relative HER activity of several crystal surface of zinc anode.The generalized coordination number of surface Zn atoms are proposed as a key descriptor of HER activity of Zn anode.

Aqueous Zinc Metal Batteries with Anode Stabilized by Plasma Treatment

Aqueous Zn batteries have recently attracted significant attention due to the various benefits offered by Zn metal anodes. However, the formation of dendrites and unwanted side reactions between the Zn anode and the aqueous electrolyte remain challenging problems. Herein, a straightforward plasma treatment that converts the surface of the Zn metal into ZnF2 is proposed. Calculations using density function theory reveal that the diffusion energy barrier for Zn atoms on the ZnF2 surface (0.02 eV) is considerably lower than that on the regular Zn surface (0.25 eV). As a result, the Zn anode treated with plasma (referred to as Plasma‐Zn) exhibits a highly reversible Zn plating/stripping process and significantly suppresses dendrite formation for more than 1300 h. Furthermore, when combined with polyaniline (PANi)‐intercalated V2O5 in a full cell configuration (Plasma‐Zn//PANi‐intercalated V2O5), it demonstrates enhanced rate capability, delivering a discharge capacity of 258 mAh g−1 at 2000 mA g−1, along with improved long‐term stability, retaining 72% of its capacity after 1000 cycles at 1000 mA g−1.

Microstructure Evolution during High-Pressure Torsion in a 7xxx AlZnMgZr Alloy.

A homogenized, supersaturated AlZnMgZr alloy was processed via severe plastic deformation (SPD) using a high-pressure torsion (HPT) technique for different revolutions at room temperature to obtain an ultrafine-grained (UFG) microstructure. The microstructure and mechanical properties of the UFG samples were then studied using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and tensile and hardness measurements. The main purpose was to study the effect of shear strain on the evolution of the microstructure of the investigated alloy. We found a very interesting evolution of the decomposed microstructure in a wide range of shear strains imposed by HPT. While the global properties, such as the average grain size (~200 nm) and hardness (~2200 MPa) appeared unchanged, the local microstructure was continuously transformed. After 1 turn of HPT, the decomposed UFG structure contained relatively large precipitates inside grains. In the sample processed by five turns in HPT, the segregation of Zn atoms into grain boundaries (GBs) was also observed. After 10 turns, more Zn atoms were segregated into GBs and only smaller-sized precipitates were observed inside grains. The intensive solute segregations into GBs may significantly affect the ductility of the material, leading to its ultralow-temperature superplasticity. Our findings pave the way for achieving advanced microstructural and mechanical properties in nanostructured metals and alloys by engineering their precipitation and segregation by means of applying different HPT regimes.

Thermoelectric properties of aliovalent Zn doped Cu1.8S polycrystalline materials

Cu1.8S-based materials are regarded as promising thermoelectric materials due to their super ionic nature. The Cu1.8-xZnxS (x = 0, 0.01, 0.03, and 0.09) samples were synthesized by the hydrothermal method followed by cold pressing and sintering. The powder X-ray diffraction pattern has confirmed the phase purity and rhombohedral crystal structure of Cu1.8S. Additionally, FE-SEM micrographs along with the EDX elemental mapping detected the existence of CuS as the secondary phase in the Cu1.8S matrix and uniform distribution of the constituent elements. Upon doping the Zn atom, the Seebeck coefficient subsequently increases owing to the decrement in the carrier concentration, whereas the electrical conductivity gradually reduces. Essentially, the presence of CuS secondary phase and the defects induced by the Zn atom effectively scattered low-mid wavelength phonons, where a very low thermal conductivity of 3.65 W/mK was achieved for Cu1.71Zn0.09S at room temperature. Ultimately, an overall maximum zT of 0.07 at 573 K was observed for Cu1.77Zn0.03S, which is about 3.5 times greater than that of the pristine sample.

Boosted hydrogen evolution kinetics of heteroatom-doped carbons with isolated Zn as an accelerant

Carbon-based single-atom catalysts, a promising candidate in electrocatalysis, offer insights into electron-donating effects of metal center on adjacent atoms. Herein, we present a practical strategy to rationally design a model catalyst with a single zinc (Zn) atom coordinated with nitrogen and sulfur atoms in a multilevel carbon matrix. The Zn site exhibits an atomic interface configuration of ZnN4S1, where Zn's electron injection effect enables thermal-neutral hydrogen adsorption on neighboring atoms, pushing the activity boundaries of carbon electrocatalysts toward electrochemical hydrogen evolution to an unprecedented level. Experimental and theoretical analyses confirm the low-barrier Volmer-Tafel mechanism of proton reduction, while the multishell hollow structures facilitate the hydrogen evolution even at high current intensities. This work provides insights for understanding the actual active species during hydrogen evolution reaction and paves the way for designing high-performance electrocatalysts.

ZIF-8 induced N, P double doped porous molybdenum phosphide hydrogen evolution catalyst

Molybdenum based phosphides have gradually become the investigation frontier of hydrogen evolution catalysts due to the platinum like electronic structure. In this paper, N, P double-doped graphite carbon layers wrapped with MoP nanoparticles (P–MoP@NPC), is directly compounded by one-step high-temperature carboning PMo12-APP@ZIF-8 precursor. P–MoP@NPC possesses splendid hydrogen production reactive, in two kinds of electrolytes, when the overpotentials of P–MoP@NPC are 132 mV and 161 mV, the slope of current density reaching 10 mA cm−2, Tafel slope are 67 and 79 mV dec−1, respectively. In the bargain, P–MoP@NPC displays satisfactory durability in acid and alkaline mediums and can continue to work for more than 24 h. The wonderful hydrogen production ability of P–MoP@NPC is ascribed to the synergistic effect of MoP nanoparticles, hierarchical porous structure as well as N, P double-doped carbon layers. The confinement effect of ZIF-8 makes most of the synthesized MoP nanoparticles evenly distributed. The hierarchical porous structure caused by the volatilization of Zn atoms with high temperature can expose more active centers. The N, P double-doped graphitic carbon layers not only protect the catalyst but also adjust the electronic structure of MoP, promoting the hydrogen production capacity. This work may provide a general way to study molybdenum phosphide catalysts synthesized by APP as a green phosphorus source for energy conversion.