Abstract
Ion leaching from pure-phase oxygen-evolving electrocatalysts generally exists, leading to the collapse and loss of catalyst crystalline matrix. Here, different from previous design ...methodologies of pure-phase perovskites, we introduce soluble BaCl
2
and SrCl
2
into perovskites through a self-assembly process aimed at simultaneously tuning dual cation/anion leaching effects and optimizing ion match in perovskites to protect the crystalline matrix. As a proof-of-concept, self-assembled hybrid Ba
0.35
Sr
0.65
Co
0.8
Fe
0.2
O
3-
δ
(BSCF) nanocomposite (with BaCl
2
and SrCl
2
) exhibits the low overpotential of 260 mV at 10 mA cm
-2
in 0.1 M KOH. Multiple
operando
spectroscopic techniques reveal that the pre-leaching of soluble compounds lowers the difference of interfacial ion concentrations and thus endows the host phase in hybrid BSCF with abundant time and space to form stable edge/face-sharing surface structures. These self-optimized crystalline structures show stable lattice oxygen active sites and short reaction pathways between Co–Co/Fe metal active sites to trigger favorable adsorption of OH
−
species.
As a reliable indicator of human physiological health, respiratory rate has been utilized in more and more cases for prediction and diagnosis of potential respiratory diseases and the respiratory ...dysfunction caused by cystic fibrosis. However, compared with smart mobile electronics, traditional clinical respiration monitoring systems is not convenient to work as a household wearable device for real-time respiration monitoring in daily life due to its cumbersome structure, complex operability, and reliance on external power sources. Thus, we propose a wearable wireless respiration sensor based on lateral sliding mode triboelectric nanogenerator (TENG) to monitor respiratory rates by sensing the variation of the abdominal circumference. In this paper, we validate the possibility of the device as a respiration monitoring sensor via an established theoretical model and investigate the output performance of the sensor via a series of mechanical tests. Furtherly, the applications of the respiration sensor in different individuals, different breathing rhythms, different active states, and wireless transmission have been verified by a lot of volunteer tests. All the results demonstrate the potential of the proposed wearable sensor as a new alternative for detecting and monitoring real-time respiratory rates with general applicability and sensitivity.
Abstract
Electrochemical CO
2
reduction (ECR) is highly attractive to curb global warming. The knowledge on the evolution of catalysts and identification of active sites during the reaction is ...important, but still limited. Here, we report an efficient catalyst (Ag-D) with suitable defect concentration operando formed during ECR within several minutes. Utilizing the powerful fast operando X-ray absorption spectroscopy, the evolving electronic and crystal structures are unraveled under ECR condition. The catalyst exhibits a ~100% faradaic efficiency and negligible performance degradation over a 120-hour test at a moderate overpotential of 0.7 V in an H-cell reactor and a current density of ~180 mA cm
−2
at −1.0 V vs. reversible hydrogen electrode in a flow-cell reactor. Density functional theory calculations indicate that the adsorption of intermediate COOH could be enhanced and the free energy of the reaction pathways could be optimized by an appropriate defect concentration, rationalizing the experimental observation.
In this paper, a kind of green triboelectric nano-generator based on natural degradable cellulose is proposed. Different kinds of regenerated cellulose composite layers are prepared by a blending ...doping method, and then assembled with poly(tetrafluoroethylene) (PTFE) thin films to form tribioelectric nanogenerator (TENG). The results show that the open circuit output voltage and the short circuit output current using a pure cellulose membrane is 7.925 V and 1.095 μA. After adding a certain amount of polyamide (PA6)/polyvinylidene fluoride (PVDF)/barium titanate (BaTiO3), the open circuit output voltage peak and the peak short circuit output current increases by 254.43% (to 20.155 V) and 548.04% (to 6.001 μA). The surface morphology, elemental composition and functional group of different cellulose layers are characterized by Scanning Electronic Microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and tested by the electrochemical analyze. Moreover, after multiple assembly and rectification processing, the electrical output performance shows that the peak value of open-circuit output voltage and the peak value of short circuit output current increases by 132.06% and 116.13%. Within 500 s of the charge-discharge test, the single peak charge reached 3.114 V, and the two peak charges reached 3.840 V. The results demonstrate that the nano-generator based on cellulose showed good stability and reliability, and the application and development of natural biomaterials represented by cellulose are greatly promoted in miniature electronic sensing area.
Transplantation of mesenchymal stem cells (MSCs) holds promise to repair severe traumatic injuries. However, current transplantation practices limit the potential of this technique, either by losing ...the viable MSCs or reducing the performance of resident MSCs. Herein, we design a "bead-jet" printer, specialized for high-throughput intra-operative formulation and printing of MSCs-laden Matrigel beads. We show that high-density encapsulation of MSCs in Matrigel beads is able to augment MSC function, increasing MSC proliferation, migration, and extracellular vesicle production, compared with low-density bead or high-density bulk encapsulation of the equivalent number of MSCs. We find that the high-density MSCs-laden beads in sparse patterns demonstrate significantly improved therapeutic performance, by regenerating skeletal muscles approaching native-like cell density with reduced fibrosis, and regenerating skin with hair follicle growth and increased dermis thickness. MSC proliferation within 1-week post-transplantation and differentiation at 3 - 4 weeks post-transplantation are suggested to contribute therapy augmentation. We expect this "bead-jet" printing system to strengthen the potential of MSC transplantation.
Abstract
Designing well-ordered nanocrystal arrays with subnanometre distances can provide promising materials for future nanoscale applications. However, the fabrication of aligned arrays with ...controllable accuracy in the subnanometre range with conventional lithography, template or self-assembly strategies faces many challenges. Here, we report a two-dimensional layered metastable oxide, trigonal phase rhodium oxide (space group, P-3m1 (164)), which provides a platform from which to construct well-ordered face-centred cubic rhodium nanocrystal arrays in a hexagonal pattern with an intersurface distance of only 0.5 nm. The coupling of the well-ordered rhodium array and metastable substrate in this catalyst triggers and improves hydrogen spillover, enhancing the acidic hydrogen evolution for H
2
production, which is essential for various clean energy-related devices. The catalyst achieves a low overpotential of only 9.8 mV at a current density of −10 mA cm
−
2
, a low Tafel slope of 24.0 mV dec
−
1
, and high stability under a high potential (vs. RHE) of −0.4 V (current density of ~750 mA cm
−
2
). This work highlights the important role of metastable materials in the design of advanced materials to achieve high-performance catalysis.
Display omitted
•A preparation method of CoFe alloy carbide catalyst was proposed.•Co-Fe interdiffusion happened in reduction and affect the alloy carbide formation.•ε'-(CoxFe1-x)2.2C facilitated the ...synergy between CO insertion and dissociation.•0.25 wt% Na promoted ε'-(CoxFe1-x)2.2C formation and enhanced STY of higher alcohols.
Higher alcohols synthesis (HAS) from syngas is quite attractive but still challenging due to the unsatisfied product selectivity and stability. Here, we prepared a series of CoFe bimetallic carbide catalysts and investigated the evolution of active species. The catalysts reduced above 300 °C could ensure an adequate interdiffusion between Co and Fe species to form CoFe alloy and then achieved a high fraction of ε'-(CoxFe1-x)2.2C species during HAS reaction, which exhibited excellent catalytic performance and stability over 200 h. The ε'-(CoxFe1-x)2.2C, acting as uniformly atomic neighboring CoxC-FexC dual sites, facilitated the synergy between CO nondissociative adsorption and CO dissociation, thus boosting the selective production of higher alcohols. It is also demonstrated that adding proper content of Na (0.25 wt%) can enhance the formation of ε'-(CoxFe1-x)2.2C as well as modulate the surface concentration of intermediates. These results may provide new idea for the design of high-performance catalysts for HAS.
Oxygen evolution reaction (OER) is a key half‐reaction in many electrochemical transformations, and efficient electrocatalysts are critical to improve its kinetics which is typically sluggish due to ...its multielectron‐transfer nature. Perovskite oxides are a popular category of OER catalysts, while their activity remains insufficient under the conventional adsorbate evolution reaction scheme where scaling relations limit activity enhancement. The lattice oxygen‐mediated mechanism (LOM) has been recently reported to overcome such scaling relations and boost the OER catalysis over several doped perovskite catalysts. However, direct evidence supporting the LOM participation is still very little because the doping strategy applied would introduce additional active sites that may mask the real reaction mechanism. Herein, a dopant‐free, cation deficiency manipulation strategy to tailor the bulk diffusion properties of perovskites without affecting their surface properties is reported, providing a perfect platform for studying the contribution of LOM to OER catalysis. Further optimizing the A‐site deficiency achieves a perovskite candidate with excellent intrinsic OER activity, which also demonstrates outstanding performance in rechargeable Zn–air batteries and water electrolyzers. These findings not only corroborate the key role of LOM in OER electrocatalysis, but also provide an effective way for the rational design of better catalyst materials for clean energy technologies.
A dopant‐free, cation‐deficiency manipulation strategy is reported to regulate the bulk oxygen‐ion diffusion properties of perovskites without altering their surface properties, offering a perfect platform to understand the role of lattice‐oxygen participation in oxygen evolution reaction electrocatalysis. Optimizing the cation deficiency level identifies a perovskite candidate with excellent catalytic activity applicable in Zn–air batteries and water electrolyzers.
Since the report of electrochemical activity of LiFePO4 from Goodenough's group in 1997, it has attracted considerable attention as cathode material of choice for lithium‐ion batteries. It shows ...excellent performance such as the high‐rate capability, long cyclability, and improved safety. Furthermore, the raw materials cost of LiFePO4 are lower and abundant compared with conventional Li‐ion battery oxides compounds. The lithium extraction from LiFePO4 operates as biphase mechanism accompanied by a relatively large volume change of ∼6.8%, even though, nanosized LiFePO4 shows exceptionally high‐rate capability during cycling. In the aim to explain this remarkable feature, recent reports using cutting‐edge techniques, such as in situ high‐resolution synchrotron X‐ray diffraction, explained that the origin of the observed high‐rate performance in nanosized LiFePO4 is the absence of phase separation during battery operation at high current densities. In this review, the importance of understanding lithium insertion mechanisms towards explaining the significantly fast‐charging performance of LiFePO4 electrode is highlighted. In particular, phase separation mechanisms, are unclear and deserve considerable attention. Several proposed models for Li diffusion and phase separation in LiFePO4 are summarized. In addition, the crystallographic aspects, defect structures of LiFePO4 are also reviewed. Finally, the status of development of other olivine‐type LiMPO4 (M = Co, Mn, and Ni) are summarized.
The origin of the observed high‐rate performance in nanosized LiFePO4 is the absence of phase separation during battery operation at high current densities. In this review, the importance of understanding lithium insertion mechanisms towards explaining the significantly fast‐charging performance of LiFePO4 electrode for batteries is highlighted.
This study introduces a novel Unmanned Aerial Vehicle-mounted (UAV-mounted) Laser Doppler Vibrometer (LDV) system for detecting debonding damage in Hidden Frame-Supported Glass Curtain Walls ...(HFSGCW). The established system enables UAVs to transport the LDV to high altitudes for operation. The vibration signals acquired by the UAV-LDV system are decomposed into different energy bands by wavelet packet analysis, and then the occurrence and location of the damage are identified by the Sum of Squared Differences (SSD) of the wavelet packet bands’ energy. This paper investigates the potential factors affecting the performance of the Unmanned Aerial Vehicle-Laser Doppler Vibrometer (UAV-LDV) system, including the arrangement of measuring points, measuring distance, noise level, and wind speed through the first-order natural frequency, the normalized frequency response functions, and the SSD indicator. Experimental and simulation results confirm the effectiveness of the UAV-LDV system, highlighting its advantages over traditional methods by offering remote, non-contact, and efficient debonding detection. This method not only indicates the presence of the damage, as traditional indicators do, but also pinpoints the exact location of it, ensuring safety and cost-effectiveness in high-rise inspections. The proposed method and indicator offer advantages in terms of convenience, visualization, and efficiency. The study discusses the impact of measurement point arrangement, measuring distance, noise levels, and wind speed on the system’s performance. The findings demonstrate that while the UAV-LDV system introduces new capabilities in rapid and reliable structural damage assessment, operational challenges such as wind and noise levels significantly influence its accuracy.
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