The reverse water-gas shift (RWGS) reaction is considered an effective way to mitigate global warming by converting CO2 into syngas on a large scale. However, when using Ni-based catalysts, the RWGS reaction is always accompanied by severe methanation, and achieving high CO selectivity while maintaining high activity remains a significant challenge. This study successfully achieved the regulation of CO2 hydrogenation selectivity on Ni/Al2O3 by introducing light into the thermal catalytic system. The results showed that the CO selectivity of Ni(8)/Al2O3 (Ni loading of 8 wt%) increased from 60.5% to 99.9% under 1.5 W cm-2 light irradiation (450 °C). Simultaneously, under light conditions, the CO2 conversion of Ni(8)/Al2O3 was 71.1%, which was 2.0 times higher than that under dark conditions. Comparing the CO2 consumption rate at different wavelengths, it was confirmed that the enhanced catalytic activity of Ni(8)/Al2O3 under illumination was mainly due to ultraviolet light. Combined transient experiments and in situ/operando spectroscopic characterization demonstrate that, compared to dark conditions, the introduction of light weakened the adsorption strength of the *CO intermediate on the catalyst surface, making it easier to desorb and form CO, thus significantly improving product selectivity. This study provides an innovative approach for regulating the selectivity of CO2 hydrogenation products through light-induced modulation.

Abstract Ferroelectric tunnel junctions (FTJs), which feature an ultrathin ferroelectric barrier sandwiched between two electrodes, have emerged as a promising candidate for next-generation non-volatile memories. This review focuses on two emerging material systems: CMOS-compatible hafnium-based ferroelectrics and two-dimensional (2D) van der Waals ferroelectrics (e.g., α-In₂Se₃, CuInP₂S₆, and h-BN). It summarizes the latest research progress and concludes by outlining the challenges and future research directions.

Photothermal catalytic CO2 hydrogenation offers an effective route for efficient CO2 conversion under mild conditions; however, its reaction mechanism remains insufficiently understood. In this work, a series of alumina-supported copper catalysts (Cu/Al2O3) were prepared via incipient wetness impregnation. Under 1.5 W cm(-2) full-spectrum irradiation at a catalyst surface temperature of 459.6 degrees C, the optimal catalyst with 5 wt.% Cu loading (Cu(5)/Al2O3) achieved a CO production rate of 312.0 mmol g(-1) h(-1), approximately 4.5 times higher than that under dark conditions (69.5 mmol g(-1) h(-1)). The apparent activation energy decreased from 63.0 to 23.9 kJ mol(-1) under illumination. Wavelength-dependent studies reveal that ultraviolet light plays a dominant promoting role, infrared light provides a minor contribution, while visible light shows a slight inhibitory effect. Photoelectrochemical analyses indicate that Cu incorporation enhances charge separation, thereby improving catalytic performance. Combined transient reaction studies, pseudo in situ XPS/EPR, CO2-TPD, H-2-TPSR, and operando DRIFTS identify dynamic Cu2+/Cu delta+ (0 <= delta < 2) species as the primary active sites. The reaction follows a redox pathway centered on these copper species. This work clarifies wavelength-dependent photothermal effects and provides mechanistic insights for designing efficient photothermal catalysts.

Light irradiation regulates *CO adsorption on Ni nanoparticles and promotes CO 2 hydrogenation, thereby achieving the synergy of high activity and high selectivity in the RWGS reaction.

Van der Waals (vdW) semiconductors are promising candidates for next-generation electronic devices. Although plasticity has been observed in these materials, strain hardening and large uniform tensile elongation remain elusive. Here we report that GaSe single crystals exhibit exceptional tensile ductility when loaded along directions inclined to the [0001] zone axis, achieving uniform tensile elongation exceeding 40% together with pronounced strain hardening. Using atomic-resolution, stress-quantified experiments, we uncover a delocalized interlayer shear mechanism in which alternating slip between adjacent vdW layers homogenizes tensile strain and suppresses localization. This cooperative slip process drives an ε-to-γ phase transformation and introduces constrained slip pathways, giving rise to a previously unrecognized vdW strain hardening mechanism. Comparable tensile ductility and strain hardening behaviour are further observed in other chalcogenides, such as InSe and SnSe2, suggesting the generality of this mechanism. These findings revise the mechanical paradigm of vdW semiconductors and establish a basis for their use in flexible and stretchable electronics.

Coherent twin boundary (CTB) can markedly enhance the strength of metallic materials because thermally stable CTBs act as strong barriers for blocking dislocation motion. CTB sliding should rarely happen because twinning dislocations (TDs) nucleate with a lower activation energy than a full dislocation while the gliding of TDs migrates the CTB. Here, the atomic-scale sliding process of CTB was in situ captured in a twin-structured Pt, involving two TDs that glide toward each other on two non-coplanar (111) planes separated by the CTB. They meet and then exchange their sliding planes assisted by short-range atomic diffusion to continue gliding, resulting in pure sliding across the CTB without migration of the CTB. Repeat of this pure sliding process requires the assistance of atoms diffusion to annihilate the created vacancies. This sliding mechanism enriches CTB-related plastic deformation mechanisms.

Interface engineering in ferroelectric tunnel junctions is a fertile playground to realize large tunneling electroresistance (TER) ratios. Here, the TER effect of Pt/La0.8Ca0.2MnO3 (LCMO)/BaTiO3 (BTO)/Nb: SrTiO3 (NSTO) ferroelectric tunnel junctions (FTJs) is investigated. It is found that the TER is enhanced by 2 orders of magnitude for the FTJ with a 0.5 nm (similar to one unit cell) LCMO layer, as compared to its counterpart without LCMO. The observed effect is attributed to the NSTO/BTO and LCMO/BTO interfaces, both of which are responsive to ferroelectric polarization. These interfaces exhibit metallic or insulating behavior synchronously depending on the direction of the polarization in the BTO layer, resulting from the ferroelectric electric field effect and metal-insulator phase transition, respectively. This switching action with polarization reversal significantly increases the contrast in electrical resistance between the high resistance state (OFF state) and the low resistance state (ON state), therefore triggering a large TER. The increase in LCMO thickness (from 0.5 to 1 and 2 nm) leads to the decrease in TER, owing to the decreased barrier height/width at the NSTO/BTO interface, as revealed by the electron transport mechanism of Fowler-Nordheim (FN) tunneling.

Electrically induced resistive switching (RS) effects have been proposed as the basis for future non-volatile memories. In this work, 9 nm-thick BiFeO3 (BFO) epitaxial thin films were deposited on (001)-oriented SrTiO3 substrates by pulsed laser deposition and their resistive switching (RS) behaviors were investigated. A large resistive switching with ON/OFF ratio of similar to 10(6) is observed, surpassing the performance of most resistive random access memories ever reported. The conducting filament is proposed to dominate the RS behavior in the positive voltage region, while the modulation of ferroelectric polarization is suggested to play a significant role in the negative voltage region. Our study significantly deepens the understanding of the physical origin of RS and could provide a reference for designing high-performance memories and memristors based on ultrathin ferroelectric films. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).

非共格孪晶界(ITB)能显著影响金属力学性能, 受到了研究者极大关注. 理论模型预测ITB是由系列偏位错组成, ITB两侧的晶面没有沿[111]方向的相对位移. 本文利用分子静力学模拟研究了Ag, Cu, Ni和Al中ITB的结构, 发现ITB的结构具有显著的尺寸效应. 对于较薄的ITB, 界面两侧的晶面处于同一水平面, 没有沿[111]方向的相对位移, 与理论模型结果一致. 而对于较厚的ITB, 界面两侧的晶面有明显的[111]方向的相对位移, 且相对位移随着ITB厚度的增加而增加. 此外, 研究揭示出ITB两侧晶面沿[111]方向的位移与金属的层错能直接相关. 该研究表明ITB的结构并不唯一, 不同的厚度、 层错能对应不同的ITB结构. 本研究为理解孪晶厚度和层错能对金属力学性能的影响提供了新见解.

Cancers, Down's syndrome, Alzheimer's and other diseases of gene mutation always occur with anomalous changes of DNA nucleic acid base. Therefore, the development of highly sensitive and reproducible nucleic acid sensors that based upon surface enhanced Raman scattering (SERS) is of immense interest for clinical medical analysis and diagnosis. Herein, a rationally designed core-shell assembly of Au nanoparticle wrapped with Au doped Bi5O7Br nanotube with eliminated fluorescent background and notable chemical enhancement effect was exploited and served as a SERS sensor for detection of adenine. Especially, we found the fluorescent background was remarkably suppressed in Raman spectra by introducing Au element into Bi5O7Br. The sensor exhibited a maximum SERS enhancement factor of up to 5.45 x 107 and a detection limit as low as 10-11 M after con-structing Au nanoparticle/Au atom doped Bi5O7Br heterojunction. More importantly, good reproducibility and long term stability under work condition were achieved. To gain in-depth understanding into chemical mech-anism (CM) of the Raman signal enhancement, density functional calculations (DFTs) were combined with atom-specific model derived via aberration corrected transmission electron microscope (AC-TEM) to demonstrate the enhanced charge transfer (CT) and substrate-adsorbate adsorption. The doping and coupling strategy holds the potential to fabricate high signal-to-noise ratio SERS sensors for other molecule detection.

Permanent structural changes in pure metals that are caused by plastic activity are normally irreparable after unloading. Because of the lack of experimental evidence, it is unclear whether the plastic activity can be repaired as the size of the pure metals decreases to several nanometers; it is also unclear how the metals accommodate the plastic deformation. In this study, the in situ atomic-scale loading and unloading of ∼2 nm Ag nanocrystals was investigated, and three modes of plastic deformation were observed: (i) the phase transition from the face-centered cubic (fcc) phase to the hexagonal close-packed (hcp) phase, (ii) stacking faults, and (iii) deformation twin nucleation. We show that all three modes resulted in structural changes that were reparable, and their generation and restoration during loading and unloading were observed in situ. We discovered that the deformation modes of nanosized metals can be predicted from the ratio of the energy barriers of the fcc-hcp phase transition (ΔγH) and the deformation twin nucleation (ΔγT), which differ from those of the theoretical modes of relatively large-sized metals. The proposed ΔγH/ΔγT criterion provides insights into the deformation mechanism of nanometals.

In situ atomic-scale bending tests of twin-structured Ni nanowires were realised using a homemade deformation device. The results showed that the plastic deformation mechanism in twin-structured Ni nanowires depended on the deformation stage. At the early stages of bending deformation, the plasticity of twin-structured Ni nanowires was controlled by dislocations interacting with the twin boundaries or parallel to them. With increasing bending strain, both dislocation and face-centred cubic–body-centred tetragonal phase transition occurred. At very high bending strain, grain boundaries resulting from the lattice distortion/collapse were formed. This study details the deformation mechanisms of the twin-structured Ni nanowires under bending deformation, which advances the basic understanding of the plasticity mechanisms in metals.

Resonant tunneling is a quantum‐mechanical effect in which electron transport is controlled by the discrete energy levels within a quantum‐well (QW) structure. A ferroelectric resonant tunneling diode (RTD) exploits the switchable electric polarization state of the QW barrier to tune the device resistance. Here, the discovery of robust room‐temperature ferroelectric‐modulated resonant tunneling and negative differential resistance (NDR) behaviors in all‐perovskite‐oxide BaTiO3/SrRuO3/BaTiO3 QW structures is reported. The resonant current amplitude and voltage are tunable by the switchable polarization of the BaTiO3 ferroelectric with the NDR ratio modulated by ≈3 orders of magnitude and an OFF/ON resistance ratio exceeding a factor of 2 × 104. The observed NDR effect is explained an energy bandgap between Ru‐t2g and Ru‐eg orbitals driven by electron–electron correlations, as follows from density functional theory calculations. This study paves the way for ferroelectric‐based quantum‐tunneling devices in future oxide electronics.

Nanocrystalline metals often display a high strength up to the gigapascal level, yet they suffer from poor plasticity. Previous studies have shown that the development of hetero-sized grains can efficiently overcome the strength-ductility trade-off of nanocrystalline metals. However, whether this strategy can lead to the fabrication of nanocrystalline nanowires exhibiting both high strength and superplasticity is unclear, similar to the atomistic deformation mechanism. In this paper, we show that ultra-small nanocrystalline Au nanowires comprising grains in both the Hall–Petch and inverse Hall–Petch grain-size regions can exhibit extremely high uniform elongation（236%） and high strength（2.34 gigapascals） at room temperature. In situ atomic-scale observations revealed that the plastic deformation underwent two stages.In the first stage, the super-elongation ability originated from the intergrain plasticity of small grains via mechanisms such as grain boundary migration and grain rotation. This intergrain plasticity caused the grains in the heterogeneous-structured nanowires to grow very large. In the second stage, the superelongation ability originated from intragrain plasticity accompanied by the diffusion of surface atoms. Our results show that the hetero-grain-sized nanocrystalline nanowires, comprising grains with sizes both in the strongest Hall–Petch effect region and the inverse Hall–Petch effect region, were simultaneously ultrastrong and ductile. They displayed neither a strength-ductility trade-off nor plastic instability.

Grain boundaries (GBs) play an important role in the mechanical behavior of polycrystalline materials. Despite decades of investigation, the atomic-scale dynamic processes of GB deformation remain elusive, particularly for the GBs in polycrystals, which are commonly of the asymmetric and general type. We conducted an in situ atomic-resolution study to reveal how sliding-dominant deformation is accomplished at general tilt GBs in platinum bicrystals. We observed either direct atomic-scale sliding along the GB or sliding with atom transfer across the boundary plane. The latter sliding process was mediated by movements of disconnections that enabled the transport of GB atoms, leading to a previously unrecognized mode of coupled GB sliding and atomic plane transfer. These results enable an atomic-scale understanding of how general GBs slide in polycrystalline materials.

Incoherent-twin boundaries (ITBs) can significantly affect the mechanical properties exhibited bymetals. Although numerous studies have been conducted to date, the atomic structures of such ITBs remain unclear, owing to difficulties in imaging their structure. In this study, high-angle annular dark-field imaging was used to reveal the atomic structure of the ITBs present in Pt. We discovered that both the twin thickness and the dislocation-ITB interaction can affect the ITB phase structure. In thin twins, the {111} planes between the ITB remain flat without any obvious displacement along the < 111 > direction, whereas in thicker twins, the {111} planes between the ITB exhibit clear displacement along the < 111 > direction, with this displacement increasing as the twin thickness increases. The ITBs frequently absorb full dislocations, which leads to the formation of dislocation-misaligned ITBs. This twin- thickness effect and dislocation-ITB interaction, which resulted ITB-phase variation, has rarely been reported.

The current-voltage (I-V) characteristics and ON/OFF ratio in hafnium oxide (HfO2)-based ferroelectric tunnel junctions (FTJs) were investigated under different poling sequences. When -5 V poling pulse is applied prior to +5 V pulse (-5 V-poling-first operation), both ON-state and OFF-state show relatively low currents, whereas the ON/OFF ratio is more than doubled, as compared to the reverse poling sequence (+5 V-poling-first operation, i.e., + 5 V pulse applied prior to -5 V). Interestingly, the ON-state I-V curves exhibit the Ohmic behavior, while the OFF-state curves are nonlinear that can be described by direct tunneling across a barrier, regardless of the poling sequence. The poling sequence-dependent tunneling electroresistance in our FTJs is explained by the evolution of domain structure in the ferroelectric films driven by the poling pulse, as supported by both I-V measurements and data fitting. This work provides a guidance to modulate the performance of FTJs, and further help understand the structure-property relationship of HfO2-based ferroelectric memories at the nanoscale.

Understanding the deformation behavior of crack tips in metals is of great significance for improving fracture toughness. However, how crack tips in nanosized metallic alloys behave under loading is unclear, because most previous studies focused on pure metals. In this study, the atomic-scale deformation behavior of the crack tip in AuAg alloy nanocrystals was observed in situ. We revealed that the deformation mechanism near the crack tip depended on the distance from the tip. For the 'near region' close to the crack tip, plastic deformation was governed by partial dislocations, twinning, and their interactions. For the 'far region', further than -15 nm from the crack tip, full dislocations dominated, and their interactions resulted in Lomer-dislocation (LD) lock formation and destruction. We uncovered that the combination of blunting dislocation-twin interactions, twin-twin intersections, and formation and destruction of LD locks, as a previously unrecognized fracture toughness improvement mechanism in metals.

A detailed monitoring of atomic-scale processes accomplishing grain rotation is important for understanding the deformation mechanisms in nanocrystalline metals. However, direct observations have been rare thus far, such that our knowledge about grain rotation has to rely heavily on hypothetical models and simulations. Here, we present in situ atomic-resolution evidence, indicating that the atomic processes accomplishing grain rotation in nanocrystalline Pt depend on the type of grain boundary (GB) separating the rotating grains. The grains around general (mixed) GBs rotate via the Frank–Bilby dislocation activities together with atomic shuffling and disconnection activities, the former being the generation, climb, glide and reaction of GB dislocations, whereas the latter leading to GB migration accompanying the grain rotation. While for the grains with a tilt GB in between: their rotation is accomplished almost entirely via the Frank–Bilby dislocation activities. We also discover that the GB dislocation climb, glide, and reaction often involve the formation and destruction of Lomer-like dislocations.

The formation of metallic glass through melt processing proves to be the most challenging for pure monatomic face-centered cubic (FCC) metals. Though it has long been conjectured that amorphous monatomic metals can be generated through deforming a solid at room temperature, there is rarely direct evidence to prove that is indeed the case. In this study, mechanical loading was applied to nanometer-sized crystals inside an aberration-corrected transmission electron microscopy, and atomic-scale in situ evidence is provided of strain-induced amorphization in Pt and Ni near room temperature. The loading was applied in such a way that the stress state is complicated, and the strain distribution is non-uniform, restricting dislocation activities in accommodating the imposed strain. The local lattice distortion is then rendered so large and the associated strain energy is so high that the crystal collapses into the amorphous state. As such, even elemental FCC metals can be forced to become amorphous.