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Nanoscale interphase precipitation in microalloyed ferritic steels provides a remarkable (200–400 MPa) strengthening increment, however its origin is unclear. Scanning transmission electron microscopy revealed step formation at the matrix/precipitate interface after both macroscopic uniaxial tension and nanopillar compression testing. Supported by Density Functional Theory modelling, dislocation shearing of nano-sized ( slip–system in the VC nanoparticles.

EBSD in combination with aberration-corrected STEM is used to study the interfacial layer forming at Ni electrode - PbTe thermoelectric material interfaces. Contrary to previous studies, both orthorhombic and monoclinic phases are identified within the interfacial layer. EBSD and STEM data at interphase boundaries demonstrate an approximately smooth transition from orthorhombic to monoclinic phase with almost no crystal defects due to the small differences in lattice parameters and the prevalence of one of two previously unknown orientation relationships between the phases. Moreover, the presence of special boundaries resulting in orientation domains within both phases throughout the interfacial nickel telluride layer needs to be considered when fabricating future thermoelectric devices. Keywords: NiTe, Electron back-scattering diffraction (EBSD), Orientation relationships, High angle annular darkfield, Scanning transmission microscopy (HAADF-STEM)

Abstract To achieve substantial reductions in CO2 emissions, catalysts for the photoreduction of CO2 into value‐added chemicals and fuels will most likely be at the heart of key renewable‐energy technologies. Despite tremendous efforts, developing highly active and selective CO2 reduction photocatalysts remains a great challenge. Herein, a metal oxide heterostructure engineering strategy that enables the gas‐phase, photocatalytic, heterogeneous hydrogenation of CO2 to CO with high performance metrics (i.e., the conversion rate of CO2 to CO reached as high as 1400 µmol g cat−1 h−1) is reported. The catalyst is comprised of indium oxide nanocrystals, In2O3−x(OH)y, nucleated and grown on the surface of niobium pentoxide (Nb2O5) nanorods. The heterostructure between In2O3−x(OH)y nanocrystals and the Nb2O5 nanorod support increases the concentration of oxygen vacancies and prolongs excited state (electron and hole) lifetimes. Together, these effects result in a dramatically improved photocatalytic performance compared to the isolated In2O3−x(OH)y material. The defect optimized heterostructure exhibits a 44‐fold higher conversion rate than pristine In2O3−x(OH)y. It also exhibits selective conversion of CO2 to CO as well as long‐term operational stability.

A metastable-β titanium alloy, Ti-10V-3Fe-3Al (wt. %), was subjected to thermo-mechanical processing including the compression test at 725 °C, which is below the β transus temperature (780 °C), and at strain rate of 10−3 s−1. The presence of phases was determined using transmission electron microscopy and X-ray diffraction. Although the dynamic recovery took place together with slip, both deformation-induced α” martensite and ω were detected as other operating mechanisms for the first time in metastable-β titanium alloy deformed in α + β region. The volume fraction of stress-induced α” was higher than that of the same alloy deformed at room temperature due to a higher strain applied. Stress-induced twinning was not operational, which could be related to the priority of slip mechanism at high temperature resulted from thermally-assisted nucleation and lateral migration of kink-pairs.

Developing a reliable synthesis strategy to concurrently realize electronic structure modulation and two‐dimensionalization of materials is of paramount significance yet still challenging. Herein, a facile and universal strategy is reported to fabricate defect‐abundant atomic‐layered materials with unique electronic structures by mechanical shear‐assisted exfoliation. As a proof‐of‐concept demonstration, atomic‐layered defect‐rich LiCoO2 nanosheets (AD‐LCO) are successfully synthesized, which enable accelerated oxygen evolution kinetics with a substantially decreased oxygen evolution reaction overpotential by 184 and 216 mV at 10 and 50 mA cm–2, respectively. X‐ray absorption spectroscopy suggests that AD‐LCO possesses more d‐band holes and enhanced Co‐O covalency. Density functional theory calculations reveal that the presence of Co lattice vacancies can optimize the adsorption kinetics of intermediates, consequently lowering the energy barrier of the rate‐determining step. Importantly, this method has universal applicability to the fabrication of other ultrathin defect‐rich 2D materials such as BN, WS2, and MoS2. The study has potential implications for offering novel insights into the rational design of ultrathin 2D materials with abundant surface defects for various applications. [ABSTRACT FROM AUTHOR]

Electrocatalytic nitrogen reduction reaction (eNRR) is a sustainable alternative to the traditional Haber–Bosch process due to its eco‐friendly nature and capability of utilizing renewable energy. However, its low Faradic efficiency (FE), caused by the excessive adsorption and reduction of protons, has been regarded as the main challenge, which leads to low ammonia yield as well. Herein, a carbon‐supported iron electrocatalyst is reported, which is fabricated by low‐temperature (300 °C) potassium vapor reduction of FeF3‐intercalated graphite fluoride, for efficient electrochemical nitrogen reduction. The strategy enables the unique formation of exposed Fe nanoparticles uniformly anchored on graphene and in situ doped with fluorine heteroatoms. These specific features can alter the electronic configuration of the Fe nanoparticles, leading to strong surface polarization that boosts nitrogen absorption capability for eNRR, resulting in high FE (41.6%) and ammonia yield rate (53.3 μg h‐1 mg‐1) simultaneously. First‐principle calculation attributes this enhanced eNRR capability to more empty orbitals carried by the Fe atoms through the electron transfer with F dopant and substrate. As a versatile strategy for synthesizing various ultrafine and highly dispersed metal nanoparticles on the carbon support, this work might shed light on rational designing essential electrocatalysts with effective electronic structure manipulation. [ABSTRACT FROM AUTHOR]

Bismuth telluride‐based materials are already being commercially developed for thermoelectric (TE) cooling devices and power generators. However, the relatively low efficiency, which is characterized by a TE figure of merit, zT, is the main obstacle to more widespread application. Significant advances in the TE performance have been made through boundary engineering via embedding nanoinclusions or nanoscale grains. Herein, an effective approach to greatly enhance the TE performance of p‐type BiSbTe material by incorporating carbon microfibers is reported. A high zT of 1.4 at 375 K and high average zT of 1.25 for temperatures in the range of 300 to 500 K is achieved in the BiSbTe/carbon microfiber (BST/CF) composite materials. Their superior TE performance originates from the low thermal conductivity and the relatively high power factor. A TE unicouple device based on the p‐type BST/CF composite material and the commercially available n‐type bismuth telluride‐based material shows a huge cooling temperature drop in the operating temperature range of 299–375 K, and is greatly superior to the unicouple device made of both commercial p‐type and n‐type bismuth telluride‐based material. The materials demonstrate a high average zT and excellent mechanical properties and are strong candidates for practical applications. [ABSTRACT FROM AUTHOR]

Nanoscale interphase precipitation in microalloyed ferritic steels provides a remarkable (200–400 MPa) strengthening increment, however its origin is unclear. Scanning transmission electron microscopy revealed step formation at the matrix/precipitate interface after both macroscopic uniaxial tension and nanopillar compression testing. Supported by Density Functional Theory modelling, dislocation shearing of nano-sized (<4 nm) VC precipitates was identified as a strengthening mechanism. The findings suggest the operation of an unusual {001}<110> slip–system in the VC nanoparticles. Shearing of VC nanoparticles by dislocations on a non-traditional slip–system was identified as a strengthening mechanism for steels with <4 nm nanoparticles. [ABSTRACT FROM AUTHOR]

Designing cost‐effective and efficient electrocatalysts plays a pivotal role in advancing the development of electrochemical water splitting for hydrogen generation. Herein, multifunctional active‐center‐transferable heterostructured electrocatalysts, platinum/lithium cobalt oxide (Pt/LiCoO2) composites with Pt nanoparticles (Pt NPs) anchored on LiCoO2 nanosheets, are designed towards highly efficient water splitting. In this electrocatalyst system, the active center can be alternatively switched between Pt species and LiCoO2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Specifically, Pt species are the active centers and LiCoO2 acts as the co‐catalyst for HER, whereas the active center transfers to LiCoO2 and Pt turns into the co‐catalyst for OER. The unique architecture of Pt/LiCoO2 heterostructure provides abundant interfaces with favorable electronic structure and coordination environment towards optimal adsorption behavior of reaction intermediates. The 30 % Pt/LiCoO2 heterostructured electrocatalyst delivers low overpotentials of 61 and 285 mV to achieve 10 mA cm−2 for HER and OER in alkaline medium, respectively. [ABSTRACT FROM AUTHOR]

Titanium‐based polyanions have been intensively investigated for sodium‐ion batteries owing to their superior structural stability and thermal safety. However, their low working potential hindered further applications. Now, a cation and anion dual doping strategy is used to boost the redox potential of Ti‐based cathodes of Na3Ti0.5V0.5(PO3)3N as a new cathode material for sodium ion batteries. Both the Ti3+/Ti4+ and V3+/V4+ redox couples are reversibly accessed, leading to two distinctive voltage platforms at ca. 3.3 V and ca. 3.8 V, respectively. The remarkably improved cycling stability (86.3 %, 3000 cycles) can be ascribed to the near‐zero volume strain in this unusual cubic symmetry, which has been demonstrated by in situ synchrotron‐based X‐ray diffraction. First‐principles calculations reveal its well‐interconnected 3D Na diffusion pathways with low energy barriers, and the two‐sodium‐extracted intermediate NaTi0.5V0.5(PO3)3N is also a stable phase according to formation energy calculations. [ABSTRACT FROM AUTHOR]

The use of TiO2 nanoparticles in sunscreen products has raised concern over their oxidative potential and adverse health effects brought about by their propensity to produce free radicals when exposed to UV radiation. In this study, an investigation into industry-scalable methods for synthesizing rutile TiO2 nanorods with controllable morphological characteristics was carried out. The effects of hydrothermal reaction temperature and nitric acid concentration on the crystal phase, composition and morphology were explored to assess the most suitable conditions for reproduction. Optimal reaction conditions for obtaining purely rutile TiO2 nanorods occurred when treating the titania precursor at 150 °C for 24 h with 16 M nitric acid. Here, these rutile nanorods are decorated with CeO2 nanoparticles, as a means of producing a material with high UV attenuation and low photocatalytic activity. The nanocomposite materials are prepared using facile hydrothermal and precipitation methods and showed selective UV absorption whilst also demonstrating a reduction in photocatalytic activity compared to bare rutile TiO2 nanorods of up to 88% and 77% when exposed to UV and solar simulated light. The results suggest CeO2/TiO2 could be safely applied as an 'active' inorganic UV absorber in sunscreen products. [ABSTRACT FROM AUTHOR]

Structural evolution of the cathode during cycling plays a vital role in the electrochemical performance of sodium‐ion batteries. A strategy based on engineering the crystal structure coupled with chemical substitution led to the design of the layered P2@P3 integrated spinel oxide cathode Na0.5Ni0.1Co0.15Mn0.65Mg0.1O2, which shows excellent sodium‐ion half/full battery performance. Combined analyses involving scanning transmission electron microscopy with atomic resolution as well as in situ synchrotron‐based X‐ray absorption spectra and in situ synchrotron‐based X‐ray diffraction patterns led to visualization of the inherent layered P2@P3 integrated spinel structure, charge compensation mechanism, structural evolution, and phase transition. This study provides an in‐depth understanding of the structure‐performance relationship in this structure and opens up a novel field based on manipulating structural evolution for the design of high‐performance battery cathodes. [ABSTRACT FROM AUTHOR]

The strategy of inducing interlayer anionic ligands in 2D MoS1.5Se0.5 nanosheets is employed to consolidate the interlayer band gap and optimize the electronic structure for the potassium ion battery. It combines complementary advantages from two kinds of anionic ligands with high conductivity and good affinity with potassium ions. The potassium ion diffusion rate is accelerated as well by an optimized lower energy barrier for ion diffusion pathways, with the formation of highly reversible KMo3Se3 crystal other than K0.4MoS2/K2MoS4, which encounters a much slower electro/ion diffusion rate upon discharging. These advances deliver enhanced potassium storage properties with excellent cycling stability, with retained specific capacity of 531.6 mAh g−1 at a current density of 200 mA g−1 even after 1000 cycles, and high rate capability with specific capacity of 270.1 mAh g−1 at 5 A g−1. The insertion and conversion mechanism are also elucidated by a combination of density functional theory computations and in situ synchrotron measurements. [ABSTRACT FROM AUTHOR]

The cytotoxic and genotoxic effects of titanium dioxide (TiO2) nanoparticles when exposed to ultraviolet (UV) radiation, particularly wavelengths between 320–400 nm, has raised concern over their safe use in health and cosmetic related products such as sunscreens. Cerium dioxide (CeO2) nanoparticles have been demonstrated to display biocompatible properties and antioxidant activity due to redox cycling of the Ce3+/Ce4+ oxidation states. In this work, CeO2/TiO2 nanocomposites were prepared through a standard precipitation method at atomic concentrations (at%) of Ce relative to Ti of 2.5, 5 and 10 at%, with the aim of reducing the photocatalytic activity of the core TiO2 nanoparticles and improve biocompatibility. The UV absorptive properties of the nanocomposite samples revealed excellent absorbance across the UV region as compared to pristine TiO2 and CeO2. Furthermore, a drastic reduction in the photocatalysed decomposition of crystal violet, when in the presence of the nanocomposite samples, under both UV and solar simulated light was observed compared to the highly photoactive pristine TiO2. An optimal CeO2 nanodot loading, displaying both high UV attenuation and low photocatalytic performance was determined at 5 at% and further in vitro biological testing revealed minimal impact on the cell viability of the human keratinocyte cell line (HaCaT) over a 24 h period with and without prior exposure to UV irradiation. In contrast, pristine TiO2 nanoparticles induced toxicity to HaCaT cells with prior UV exposure before incubation, particularly at a dosage of 100 mg L−1. Our findings demonstrate the effectiveness of CeO2 nanodots in improving biocompatibility and its potential as a coating material for active inorganic UV filters. [ABSTRACT FROM AUTHOR]

Nanoindentation measurements of polygonal ferrite (PF), bainitic ferrite (BF) lath, ferrite in granular bainite (GB) and retained austenite (RA) in a low-alloyed multi-phase transformation-induced plasticity steel were carried out in conjunction with electron backscattering diffraction and scanning transmission electron microscopy (STEM). PF returned the lowest hardness followed by ferrite in GB, BF lath and RA. Dislocation glide and austenite-to-martensite transformation can be correlated with the first and second pop-in observed in the load–displacement curve, respectively. The martensite transformation induced by nanoindentation was demonstrated via correlative STEM. Film RA generally shows a higher stability than blocky RA, associated with a larger average onset load for martensite transformation in the former. It is noted that some ferrite in GB had similar hardness to BF lath and some blocky RA grains in GB showed a similar stability to that of film RA between BF lath, which can be attributed to a higher carbon content in GB due to chemical inhomogeneity. [ABSTRACT FROM AUTHOR]

Herein, we introduce a 4.0 V class high‐voltage cathode material with a newly recognized sodium superionic conductor (NASICON)‐type structure with cubic symmetry (space group P213), Na3V(PO3)3N. We synthesize an N‐doped graphene oxide‐wrapped Na3V(PO3)3N composite with a uniform carbon coating layer, which shows excellent rate performance and outstanding cycling stability. Its air/water stability and all‐climate performance were carefully investigated. A near‐zero volume change (ca. 0.40 %) was observed for the first time based on in situ synchrotron X‐ray diffraction, and the in situ X‐ray absorption spectra revealed the V3.2+/V4.2+ redox reaction with high reversibility. Its 3D sodium diffusion pathways were demonstrated with distinctive low energy barriers. Our results indicate that this high‐voltage NASICON‐type Na3V(PO3)3N composite is a competitive cathode material for sodium‐ion batteries and will receive more attention and studies in the future. [ABSTRACT FROM AUTHOR]

Exploring economically efficient electrocatalysts with robust bifunctional oxygen conversion catalytic activity and designing appropriate structures are essential to realize ideal zinc–air batteries with high energy density and long lifespan. Two-dimensional metallic state Co3FeN nanosheets with a holey-structured architecture are designed and shown to exhibit enhanced catalytic properties owing to the complete exposure of the atoms in the large lateral surfaces and in the edges of pore areas, together with the lowest OH* adsorption energy on exposed surfaces due to bimetallic synergistic effects. Meanwhile, this porous architecture can not only accelerate electron transportation by its metallic state highly oriented crystallized structure, but also facilitate the diffusion of intermediates and gases. These edge-enriched 2D holey Co3FeN nanosheets exhibit enhanced catalytic activity towards reversible oxygen conversion. When employed in zinc–air batteries, they exhibit a maximum power density of 108 mW cm−2 and cycle life up to 900 cycles with a low round-trip voltage of 0.84 V. The Co3FeN nanosheets maintain a strong stable structure in an oxygen-rich electrochemical environment with a high-orientation crystalline texture during the whole cycling time. This work may provide a promising candidate to promote the further development of zinc–air batteries. [ABSTRACT FROM AUTHOR]

The electrocatalytic nitrogen reduction reaction (NRR) is emerging as an attractive strategy for sustainable and distributed production of ammonia (NH3) under ambient conditions. Because of the use of unsatisfactory electrocatalysts, however, it is still encountering issues of low yield rates and limited efficiency, resulting from the sluggish reaction kinetics, the competing hydrogen evolution reaction and additional reaction product formation. Herein, an atomically dispersed transition metal dimer species was employed to selectively accelerate the nitrogen reduction reaction kinetics for high reduction efficiency and simultaneously alleviate the additional reaction. In this system, atomic Fe and Mo metal dimer in situ anchored on defect-rich graphene layers can realize selective electroreduction of nitrogen to ammonia by numerous FeMoNxC active sites. It exhibits higher catalytic activity than its counterparts (Fe@NG and Mo@NG) owing to a combination of ligand, geometric and synergistic effects, with a yield rate of 14.95 μg h−1 mg−1 at −0.4 V and a faradaic efficiency of 41.7% at −0.2 V. The superior performance of this atomic transition metal dimer catalyst can outperform some precious metal-based catalysts due to its excellent selectivity and high catalytic activity. The specific structure of the N-coordinated FeMo dimer was further identified to be FeMoN6 by density functional theory (DFT). The catalytic reaction pathway and mechanism were explored by (DFT) calculations and proposed based on the FeMoN6 model. The existence of numerous FeMoN6 active sites can not only weaken the N≡N bond, but also efficiently catalyze nitrogen reduction through the alternating pathway. [ABSTRACT FROM AUTHOR]

Metallic‐state 2D SnS2 nanosheets with expanded lattice spacing and a defect‐rich structure were synthesized by the intercalation of Ni into the van der Waals gap of SnS2. The expanded lattice spacing efficiently enhanced the electrochemical performance of the SnS2 for sodium‐ion batteries owing to the change electron state density and energy band structure. In operando synchrotron XRD and theoretical calculations were used to gain insight into the influence of foreign metal‐ion doping and its location. The optimized architecture obtained by in situ uniform growth of nanosheets on carbon fibers significantly enhanced the electrochemical performance. The inherent advantages of this architecture are shorter paths for ion insertion and extraction, larger contact area for more sodium diffusion pathways, and superior electrolyte penetration. Benefiting from the Ni intercalated SnS2 bilayer, the internal adjustment of the electronic state and the enlarged interlayer spacing significantly enhanced the electron transport kinetics, which can be explained by the metallic‐state properties. The integrated electrode exhibited an initial high reversible capacity of 795 mAh g−1 at 0.1 A g−1, with a stable capacity retention of 666 mAh g−1 after 100 cycles. Good rate capability was also exhibited with specific capacities of 691, 564, 437 mAh g−1 at current densities of 200, 500, and 1000 mA g−1, respectively. [ABSTRACT FROM AUTHOR]

Two-dimensional structured materials have attracted much attention and are commonly employed as active materials for sodium ion batteries owing to their inherent advantages. The reaction mechanisms behind sodium ion storage and diffusion pathways in a composite of MoSe2@graphene were monitored and explored by the in situ synchrotron technique. Based on nanocages in the MoSe2 structure and efficient sodium ion pre-location on the extensive surfaces of graphene, the combination of a sodium ion storage mechanism and an ordered transfer mechanism is proposed in different voltage windows. First, numerous sodium ions are pre-located on the surface by an adsorption reaction. In the second step, all the pre-located sodium ions are immediately inserted into MoSe2 nanosheets, which corresponds to the intercalation reaction mechanism. In the final step, the intercalated sodium ions will undergo a conversion reaction with MoSe2. Meanwhile, numerous nanocages resulting from sufficient deficiency of MoSe2 and layer dislocation will be beneficial to the capacity enhancement and rate capability. The prior adsorption reaction can efficiently improve the rate capability as well. Benefitting from these merits, the composite exhibits a high specific capacity of 640 mA h g−1 and robust rate performance. The cycling lifetime is also increased as well, with a capacity retention of ∼85% over 1000 cycles at a current density of 1.0 A g−1. Therefore, this composite shows promising potential for application in future sodium ion batteries. [ABSTRACT FROM AUTHOR]

Heterostructures, which can possess advantages of materials with different properties, have attracted enormous attention in various research fields including solar cells, photocatalysts, and optical electronic devices. In this work, a 2D/3D atomic epitaxial heterostructure with ultrathin BiOCl nanosheets and YF3:Yb, Tm octahedral crystals was fabricated via the halogen atom exchange method in the solution phase. The epitaxial heterointerface can facilitate energy transfer between BiOCl and YF3:Yb, Tm and suppress the energy quenching induced by grain boundaries. By carrying out single-particle confocal characterization, the energy upconverted by YF3:Yb, Tm is quantitatively confirmed to be transferred to ultrathin BiOCl nanosheets. As a result, YF3:Yb, Tm@BiOCl displays outstanding NIR-driven water splitting and waste-water cleaning properties. This study paves the way to fabricate 2D/3D epitaxial heterostructures, which helps to broaden the application of typical 2D materials. [ABSTRACT FROM AUTHOR]

Low‐cost layered oxides free of Ni and Co are considered to be the most promising cathode materials for future sodium‐ion batteries. Biphasic Na0.78Cu0.27Zn0.06Mn0.67O2 obtained via superficial atomic‐scale P3 intergrowth with P2 phase induced by Zn doping, consisting of inexpensive transition metals, is a promising cathode for sodium‐ion batteries. The P3 phase as a covering layer in this composite shows not only in excellent electrochemical performance but also its tolerance to moisture. The results indicate that partial Zn substitutes can effectively control biphase formation for improving the structural/electrochemical stability as well as the ionic diffusion coefficient. Based on in situ synchrotron X‐ray diffraction coupled with electron‐energy‐loss spectroscopy, a possible Cu2+/3+ redox reaction mechanism has now been revealed. The P2@P3 Na0.78Cu0.33−xZnxMn0.67O2 composite induced by Zn doping with revealed redox behavior of Cu2+/3+ is a promising cathode for Na ion batteries. Zn doping not only induces the formation of a P3 phase, which shows a distinct crystal and atomic arrangement with nanoscale thickness, but also offered a high and flat voltage profile, leading to improvement in both structural/electrochemical stability and humidity resistance. [ABSTRACT FROM AUTHOR]

Abstract: The cathode materials in the Na‐ion battery system are always the key issue obstructing wider application because of their relatively low specific capacity and low energy density. A graphene oxide (GO) wrapped composite, Na2Fe2(SO4)3@C@GO, is fabricated via a simple freeze‐drying method. The as‐prepared material can deliver a 3.8 V platform with discharge capacity of 107.9 mAh g−1 at 0.1 C (1 C = 120 mA g−1) as well as offering capacity retention above 90% at a discharge rate of 0.2 C after 300 cycles. The well‐constructed carbon network provides fast electron transfer rates, and thus, higher power density also can be achieved (75.1 mAh g−1 at 10 C). The interface contribution of GO and Na2Fe2(SO4)3 is recognized and studied via density function theory calculation. The Na storage mechanism is also investigated through in situ synchrotron X‐ray diffraction, and pseudocapacitance contributions are also demonstrated. The diffusion coefficient of Na+ ions is around 10−12–10−10.8 cm2 s−1 during cycling. The higher working voltage of this composite is mainly ascribed to the larger electronegativity of the element S. The research indicates that this well‐constructed composite would be a competitive candidate as a cathode material for Na‐ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: In this research, a new route of surface passivation is reported by introducing hydrogen from the atomic layer deposited (ALD) Al2O3 layer into pure sulfide Cu2ZnSnS4 (CZTS) solar cells. Different amounts of hydrogen are incorporated into the Cu2ZnSnS4/CdS interface through controlling the thickness of the ALD‐Al2O3 layer. The device with three cycles of ALD‐Al2O3 yields the highest efficiency of 8.08% (without antireflection coating) with improved open‐circuit voltage of up to 70 mV. With closer examination on the passivation route of ALD‐Al2O3, it is revealed by the surface chemisty study that the Al2O3 can be etched away by ammonium hydroxide in the CdS buffer deposition process. Instead, the hydrogen is detected within a shallow depth from the CZTS surface, and makes a significant difference in the measured distribution of contact potential difference and device performance. This may be interpreted by the effect of hydrogen passivation of the CZTS surface by curing dangling bonds at the surface of CZTS grains. This work may provide a new direction of further improving the performance of kesterite solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Planar perovskite solar cells obtained by low‐temperature solution processing are of great promise, given a high compatibility with flexible substrates and perovskite‐based tandem devices, whilst benefitting from relatively simple manufacturing methods. However, ionic defects at surfaces usually cause detrimental carrier recombination, which links to one of dominant losses in device performance, slow transient responses, and notorious hysteresis. Here, it is shown that several different types of ionic defects can be simultaneously passivated by simple inorganic binary alkaline halide salts with their cations and anions. Compared to previous literature reports, this work demonstrates a promising passivation technology for perovskite solar cells. The efficient defect passivation significantly suppresses the recombination at the SnO2/perovskite interface, contributing to an increase in the open‐circuit voltage, the fast response of steady‐state efficiency, and the elimination of hysteresis. By this strong leveraging of multiple‐element passivation, low‐temperature‐processed, planar‐structured perovskite solar cells of 20.5% efficiencies, having negligible hysteresis, are obtained. Moreover, this defect‐passivation enhances the stability of solar cells with efficiency beyond 20%, retaining 90% of their initial performance after 30 d. This approach aims at developing the concept of defect engineering, which can be expanded to multiple‐element passivation from monoelement counterparts using simple and low‐cost inorganic materials. [ABSTRACT FROM AUTHOR]

Abstract: 2D Dirac materials supported by nonmetallic substrates are of particular interest due to their significance for the realization of the quantum spin Hall effect and their application in field‐effect transistors. Here, monolayer germanene is successfully fabricated on semiconducting germanium film with the support of a Ag(111) substrate. Its linear‐like energy–momentum dispersion and large Fermi velocity are derived from the pronounced quasiparticle interference patterns in a √3 × √3 superstructure. In addition to Dirac fermion characteristics, the theoretical simulations reveal that the energy gap opens at the Brillouin zone center of the √3 × √3 restructured germanene, which is evoked by the symmetry‐breaking perturbation potential. These results demonstrate that the germanium nanosheets with √3 × √3 germanene can be an ideal platform for fundamental research and for the realization of high‐speed and low‐energy‐consumption field‐effect transistors. [ABSTRACT FROM AUTHOR]

Abstract: An integrated, free‐standing, and binder‐free type of flexible anode electrode is fabricated from numerous holey‐structured, 2D nickel‐based phosphide nanosheets connected with carbon nanotubes. This electrode architecture can not only uniformly disperse the nanosheets throughout the whole electrode to avoid aggregation or detachment, but also provide an ideal sodium ion and electrolyte diffusion and penetration network with high electronic conductivity. Meanwhile, bimetallic phosphide formation by introducing secondary metal species will lead to a synergistic effect to modify the electrochemical properties. Due to the excellent compositional and structural characteristics of this electrode, it delivers superior performance. This designed flexible anode with Ni1.5Co0.5Px nanosheets demonstrates a reversible capacity of 496.4 mAh g−1 at 0.5 C and a good rate capacity of 276.1 mAh g−1 at 8 C. Meanwhile, this connected integrated network woven from carbon nanotubes can effectively restrain volumetric expansion and shrinkage, and affect the conversion reaction products formation as well, from large‐sized microspheres to film structure, which is primarily credited with the improvement in electrochemical performance. This work may open up a new path for the synthesis of morphology‐controlled phosphides and promote the further development of flexible devices. [ABSTRACT FROM AUTHOR]