To achieve high performed zinc metal batteries, it is imperative to address the issues of dendrite growth and the side‐reactions occurring at the Zn anode, particularly when the batteries are ...operated at high current densities and high temperature. Herein, a flexible and dendrite‐free Zn metal anode (AgNPs@CC/Zn), which is prepared by inkjet printing silver nanoparticles on a 3D carbon matrix, is reported. Experimental observations and DFT calculation reveal that the Ag nanoparticles can work as heterometallic seeds for zinc deposition, and thus simultaneously improve the zincophilicity and thermal conductivity of the carbon matrix. This not only lowers the Zn nucleation overpotential and guides the uniform Zn nucleation but also promotes the reversible zinc stripping/plating via AgZn alloying/de‐alloying reactions. As a result, the AgNPs@CC/Zn anode presents low voltage hysteresis of 80 mV and superior cycling over 480 h at a high current density of 10 mA cm−2. The AgNPs@CC/Zn anode can enable full cells with exceptional cyclic stability and enhanced high‐temperature endurance. Furthermore, the foldable pouch cell using the AgNPs@CC/Zn anode exhibits high capacity retention regardless of different deformation status. This work demonstrates the promising potential of inkjet printing technology in developing 3D dendrite‐free zinc anode for foldable and heat‐resistant zinc batteries.
A flexible and dendrite‐free Zn metal anode is prepared by inkjet printing silver nanoparticles on a 3D carbon matrix, boosting electrochemical performance of zinc metal batteries. The Ag nanoparticles as heterometallic seeds can promote reversible zinc stripping/plating via AgZn alloying/de‐alloying reactions and improve the zincophilicity and thermal conductivity of the carbon matrix.
Developing efficient catalysts for the ammonia oxidation reaction (AOR) is crucial for NH3 utilization as a large‐scale energy carrier. This work reports a promising Ni–Cu–Fe–OOH material for ammonia ...oxidation, and density functional theory is used to investigate the AOR mechanism. It is revealed that the oxygen‐atoms bonded with the metal‐atom on the surface of electrode play an important role in AOR. By codoping Cu and Fe, the electron distribution around the oxygen‐atom is affected, which helps to promote the occurrence of ammonia oxidation. The Ni–Cu–Fe–OOH material delivers one of the highest ammonia removal efficiency to date of ≈90% after 12 h. In addition, ≈55% of the initial ammonia is successfully degraded after 24 h in high ammonia concentration. Thus, this work reveals the mechanism of AOR that can provide new ideas to tailor more powerful and updated catalysts in the future.
The paper reports a Ni–Cu–Fe–OOH ternary electrode material for efficient ammonia electrooxidation. The density functional theory calculations determine the mechanism and path of ammonia decomposition, and show that the electron density around OO–Ni is affected by dopants. A 90% NH3 removal efficiency is achieved using Ni–Cu–Fe–OOH ternary electrode. The electrode material can operate under harsh conditions.
Dispersed wind power connected to the weak grid may cause the frequency instability. In this paper, a hierarchical controller applied to a microgrid (MG), including wind turbines (WT) and battery ...units (BU), is proposed to provide a coordinated frequency support to a weak grid by adjusting the tie-line active power flow according to the frequency-grid requirements. The coordination between MG local and central controllers provides the following features.1) In case of required grid-frequency, the MG tie-line power flow will be controlled to be constant in each dispatching time interval. 2) In case of under-frequency, the coordination between WT virtual inertia and BU controllers will be used to participate in primary frequency regulation (PFR). Then, BU supplies power according to the secondary frequency regulation (SFR) commanded by the main-grid dispatch center. 3) In case of over-frequency, BU absorbs power to reduce the tie-line active power for PFR purposes. After that, the SFR uses pitch control coordinated with the battery charge control. A stability analysis model is established to deal with several transitions among different operation modes and the interaction between the weak grid impedance and the MG output impedance. Simulation results are presented to validate the proposed approach.
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Laser melting is known to be capable in initiating thorough evolution in microstructure and bringing novel functional performance in metals. But realization of this potential in ...ceramics only reaches a preliminary stage that needs further investigation. Here we demonstrate zirconia, traditionally an insulative ceramic at low temperature, could be transformed into an electronic conductor with the conductivity on order of 10−3 S⋅cm-1 at room temperature by a simple laser melting process without inducing metallic phases. Transmission electron microscopy and ab-initio simulation show that oversaturated oxygen vacancies, together with their ordered metastable distribution along <001 > , are introduced during this non-equilibrium process, and result in a clear defect level significantly narrowing bandgap to less than 1 eV, leading to the considerable electronic conductivity. These results identify a strategy of utilizing this non-equilibrium method in oxide ceramics to realize some unconventional performances determined by metastable structure thoroughly altered down to atomic level.
•Commercial cellulose separator is modified by two-dimensional porous g-C3N4 nanosheets.•The porous g-C3N4 coating redistributes the zinc ion flux through the separator.•The porous g-C3N4 coating ...improves mechanical strength of separator.•The porous g-C3N4 modified separator enables a dendrite-free zinc anode.
Zinc metal anode is a promising choice in aqueous zinc ion batteries (ZIBs) due to its high volumetric capacity, low toxicity, and natural abundance. However, zinc dendrite growth severely compromises the practicability of zinc metal anode in large-scale utilizations of ZIBs. As a key component of ZIB, separator plays an important role in regulating zinc ion flux and thus has a direct impact on zinc dendrite growth. However, little attention has been paid on the the effect of separator on dendrite growth. Herein, we report a modified separator by coating a layer of g-C3N4 nanosheets onto commercial cellulose fiber separator via a simple drop casting route. The porous two-dimensional g-C3N4 nanosheets act as ion redistributors to induce homogenous zinc ion flux, thus the g-C3N4 coated separator enables a dendrite-free zinc deposition and improves the reversibility of zinc metal anodes. As a result, the Zn||Zn symmetric cell using the g-C3N4 coated separator exhibits a 300-fold improvement in cycling lifetime of over 590 h at 3 mA cm−2 and the coulombic efficiency of Zn||Cu asymmetric cell with g-C3N4 coated separator maintains at 99.2% at 1 mA cm−2 for over 750 cycles, which are better than most of the reported ZIBs to date.
Zn dendrite growth during repeated plating and stripping of a Zn metal anode often causes short-circuiting by puncturing the separator. Herein, we propose a separator modification strategy to ...regulate the Zn-ion flux and achieve uniform Zn deposition through the OH-terminated SiO2 nanosphere coating. The interspaces between the uniform SiO2 nanospheres construct a network of Zn-ion transport channels, and the negatively charged hydroxyl groups on the surface of SiO2 nanospheres can electrostatically attract the Zn ions to direct the ion migration. The negative charges on SiO2 nanospheres are retained at a higher pH, which enables the SiO2 coating to consistently regulate the Zn-ion flux in the operating pH range of the Zn stripping/plating process. With a uniform Zn deposition guided by the SiO2 coating, the dendrite formation is suppressed and the side reactions are alleviated. As a result, the Zn||Zn symmetric cell achieves a cyclic life of 1000 h at both 3 and 5 mA cm–2. Meanwhile, the Zn||Cu asymmetric cell is able to maintain a Coulombic efficiency of 99.62% at 1 mA cm–2 for 2000 cycles, which outperforms many previously reported strategies.
Abstract
We investigated the effect of vacancy formation on brittle (D0
22
) to ductile (L1
2
-like) transition in Al
3
Ti using DFT calculations. The well-known pseudogap on the density of states of ...Al
3
Ti migrates towards its Fermi level from far above, via a W − M co-doping strategy, where M is Si, Ge, Sn or Pb respectively. In particular, by a W − M co-doping the underline electronic structure of the pseudogap approaches an octahedral (L1
2
: t
2g
, e
g
) from the tetragonal (D0
22
: e
g
, b
2g
, a
1g
, b
1g
) crystal field. Our calculations demonstrated that (1) a W-doping is responsible for the close up of the energy gap between a
1g
and b
1g
so that they tend to merge into an e
g
symmetry, and (2) all M-doping lead to a narrower gap between e
g
and b
2g
(moving towards a t
2g
symmetry). Thus, a brittle to ductile transition in Al
3
Ti is possible by adopting this W − M co-doping strategy. We further recommend the use of W-Pb co-doped Al
3
Ti to replace the less anodic Al electrode in Al-battery, due to its improved ductility and high Al diffusivity. Finally this study opens a new field in physics to tailor mechanical properties by manipulating electron energy level(s) towards higher symmetry via vacancy optimization.
Developing efficient catalysts for the ammonia oxidation reaction (AOR) is crucial for NH
utilization as a large-scale energy carrier. This work reports a promising Ni-Cu-Fe-OOH material for ammonia ...oxidation, and density functional theory is used to investigate the AOR mechanism. It is revealed that the oxygen-atoms bonded with the metal-atom on the surface of electrode play an important role in AOR. By codoping Cu and Fe, the electron distribution around the oxygen-atom is affected, which helps to promote the occurrence of ammonia oxidation. The Ni-Cu-Fe-OOH material delivers one of the highest ammonia removal efficiency to date of ≈90% after 12 h. In addition, ≈55% of the initial ammonia is successfully degraded after 24 h in high ammonia concentration. Thus, this work reveals the mechanism of AOR that can provide new ideas to tailor more powerful and updated catalysts in the future.
Objective. To investigate the different efficacy of proximal femoral nail antirotation (PFNA) combined with or without a microexternal fixator in the treatment of coral-plane femoral ...intertrochanteric fractures. Methods. 120 patients with intertrochanteric coronal fractures who received treatment in four hospitals from February 2020 to February 2021 were retrospectively included in this study. They were divided into control (PFNA alone, n = 60) and combined treatment group (a microexternal fixator + PFNA, n = 60) according to different surgery methods. All patients were followed up for 6 months. Operative time, amount of intraoperative blood loss, postoperative length of hospital stays, fracture healing time, Harris hip score, modified Barthel index, hip function excellent and good rate, and incidence of complications were compared between the two groups. Results. There were no significant differences in operative time, amount of intraoperative blood loss, postoperative length of hospital stay, and incidence of complications between the two groups (all P > 0.05). Fracture healing time in the combined treatment group was significantly shorter than that in the control group (P < 0.05). After surgery, Harris hip score and modified Barthel index in each group were significantly increased compared with before surgery (both P < 0.05). The increases in Harris hip score and modified Barthel index in the combined treatment group were significantly greater than those in the control group (both P < 0.05). After surgery, Harris hip function excellent and good rate in the combined treatment group was significantly higher than that in the control group (83.33% > 66.67%, P < 0.05). Conclusion. Compared with PFNA alone, a microexternal fixator combined with PFNA for the treatment of coronal plane femoral intertrochanteric fractures can greatly shorten fracture healing time and improve postoperative hip function and activities of living ability, but it cannot greatly increase operative time, the amount of intraoperative blood loss, or the risk of postoperative complications.
The future of a carbon-free society counts on the consistency of intermittent production of renewable energy with our continuous and increasing energy demands. By the Haber-Bosch process developed in ...1909, the large-scale of production of ammonia became possible. Since then, ammonia has been extensively used in the manufacture of fertilizers enabling the rapidly growth of the population over the last century. Moreover, ammonia is currently being explored as a portable long-term (days to months) energy storage vector. On-demand hydrogen production from ammonia (17.6 wt.% hydrogen) enables energy delivery to end users in combination with fuel cells, comparing with other molecules, such as alcohol, formic acid and hydrides, ammonia is the only carbon-free compound which fulfils the requirements of high density. In the nitrogen cycle, ammonia oxidation reaction (AOR) is an important reaction step to realize the conversion of ammonia into clean energy (hydrogen). Therefore, there is an urgent need to develop efficient and cost-effective ammonia electrooxidation catalysts.In recent years, intensive research efforts have been devoted to developing efficient ammonia electrooxidation catalysts, there still exists quite a number of challenges towards catalytic materials with excellent activity, stability, and selectivity. The existing issues mainly lie in two aspects: active species and rate-determining step. Firstly, the species of active sites have not been well explored. During the electrooxidation process, both AOR and OER will occur, whether there is a competitive active site between these two reactions is not clear. Secondly, since ammonia oxidation is a six-electron reaction, the reaction mechanism of AOR remains confused.The main objectives of this project are to design and develop high performance catalysts materials for ammonia oxidation, to investigate the reaction mechanism of certain active materials, as well as to build a frame about how to tailoring Ni-based catalysts for a promising AOR performance.In Chapter 3, Fe/Cu/Ag is doped into Ni(OH)2 by hydrothermal method respectively, and is tested for their AOR performance. The results show that the AOR performance of the composite material increases with the decrease of the doping element valence. We propose that the internal mechanism is because the stable Ni has a six-coordinate structure of NiO6, while the doping of low-valent elements will cause the O-atom that bond with it to form dangling bonds. Hence, the electron around Oatom become more delocalized, and make the AOR reaction easier to occur. In Chapter 4, in order to further understand the synergistic effect of dopants, we introduce Fe-Cu co-doping into the Ni(OH)2 system. The designed catalyst material delivers one of the highest ammonia removal efficiency to date of ~90% after 24 h operation. Combined with the DFT calculation results, we determine the reaction path of the AOR process on the surface of the nickel-based material, and confirm that NH3 tends to be adsorbed on the OO-M on the surface of the material by forming a weak electrostatic attraction. The dangling bonds on OO-M are particularly conducive to NH3 adsorption due to their high electron density, effectively reducing the energy barrier in the AOR reaction, which may be the basic principle behind the enhancement of AOR performance.In Chapter 5, a new strategy to improve the AOR performance of NiFe electrode materials through a magnetic field is introduced. According to previous research, it is important to manipulate the electron density around OO-M to improve its AOR performance. For Ni and Fe, the 3d orbital band structure can be polarized by the magnetic field to adjust the electron distribution. Therefore, this chapter mainly discusses the influence of the external static magnetic field (MF intensity, MF direction, application step) on NiFe electrode material in the AOR reaction.In Chapter 6, after studying the macroscopic effect of the external magnetic field on NiFe material, we have conducted an in-depth study of its internal mechanism. During the electrodeposition process, the reduced NiFe nanoparticles can be aligned by placing the magnet at certain location outside the electrolytic cell. The magnetostriction phenomenon is smartly introduced into the microstructure of the system, and will not be eliminated with further electrooxidation. Theoretical calculations show that the band structure of the 3d orbital of NiFe undergoes an intrinsic change under the action of a magnetic field, which significantly improves the conductivity and enhances the electron delocalization, thereby effectively reducing the energy barrier of the AOR reaction and accelerating the speed of the kinetic reaction.Overall, the strategies proposed in this thesis are effective in the design of highperformance AOR catalysts that is crucial towards future energy revolution.
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