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Adapting the coordination environment to influence the electronic configuration of active sites represents an efficient approach for improving the photocatalytic performance of the CO2 reduction reaction (CO2RR) but how to execute it precisely remains challenging. Herein, heteroatom‐substitution in Ni‐porphyrin to break the coordination symmetry of Ni center is proposed to be an effective solution. Based on this, two symmetry‐breaking Ni‐porphyrins, namely Ni(Cl)ON3Por and Ni(Cl)SN3Por, are designed and successfully prepared. By theoretical calculation, it is found that symmetry‐breaking efficiently regulates the 3d orbital energy levels of Ni center. Furthermore, experimental and theoretical findings jointly revealed that coordination symmetry‐breaking of Ni‐porphyrins facilitates the generation of highly reactive NiI species during the catalytic process, effectively stabilizing and reducing the energy barrier of formation of the key *COOH intermediate. As a result, Ni(Cl)ON3Por and Ni(Cl)SN3Por gave CO production rates of 24.7 and 38.8 mmol g−1 h−1 as well as selectivity toward CO of 94.0% and 96.4%, respectively, outperforming that of symmetric NiN4Por (CO production rate of 6.6 mmol g−1 h−1 and selectivity of 82.8%). These findings offer microscopic insights into how to modulate the catalytic activity by precisely tuning the coordination environment of active sites and rational design of competent catalyst for CO2RR photocatalysis. [ABSTRACT FROM AUTHOR]

Bio‐inspired machine visions have caused wide attentions due to the higher time/power efficiencies over the conventional architectures. Although bio‐mimic photo‐sensors and neuromorphic computing have been individually demonstrated, a complete monolithic vision system has rarely been studied. Here, a neuromorphic machine vision system (NMVS) integrating front‐end retinomorphic sensors and a back‐end convolutional neural network (CNN) based on a single ferroelectric‐semiconductor‐transistor (FST) device structure is reported. As a photo‐sensor, the FST shows a broadband (275–808 nm) retina‐like light adaption function with a large dynamic range of 20.3 stops, and as a unit of the CNN, the FST's weight can be linearly programmed. In total, the NMVS has a high recognition accuracy of 93.0% on a broadband‐dim‐image classification task, which is 20% higher than that of an incomplete system without the retinomorphic sensors. Because of the monolithic unit, the NVMS shows high feasibility for integrated bio‐inspired machine vision systems. [ABSTRACT FROM AUTHOR]

Compared to monometallic counterparts, bimetallic two‐dimensional conjugated metal‐organic framework (2D c‐MOF) nanosheets possess preferable metal tunability and synergistic effect for performance optimization, yet rarely developed in photocatalytic hydrogen evolution to date. In this study, a feasible post‐synthetic strategy of second metal installation (SMI) is proposed and applied to construct a crystalline bimetallic 2D c‐MOF nanosheet, HTHATN‐Ni‐Pt‐NS. HTHATN‐Ni‐Pt‐NS exhibits high electrical conductivity and efficient hydrogen evolution with the rate of 47.2 mmol g−1 h−1, which is 13.5‐fold higher than that of pristine HTHATN‐Ni‐NS without PtII decoration under visible light irradiation. Experimental and theoretical analysis reveal that introduction of low amount of PtII provides catalytically active metal sites and optimizes the ΔGH* value of NiII centers, thus resulting in the enhanced performance of proton reduction. This study represents the first example of symbiotic bimetallic centers in MOF nanosheets highlighting SMI strategy as an efficient approach to construct photocatalysts. [ABSTRACT FROM AUTHOR]

Adaptation is the most common and basic feature of living systems, which gives species or individuals a survival advantage. In particular, visual adaptation can enable organisms with a clearer understanding of the real world, thereby avoiding potential harm, which is vital for the life activities of organisms. However, current adaptive devices based on logic circuits are still facing the great challenges for large‐scale integration and limited bionic functions. Therefore, the hardware impleofmentation of biological visual adaptability through the emerging photoelectric devices may provide a great opportunity for the bionic systems facing complex environments. Here, a novel adaptive device based on a mixed‐dimensional van der Waals heterostructure is fabricated by using a gate‐modulated 0D‐CsPbBr3‐quantum‐dots/2D‐MoS2 heterostructure. The device has superior electric adaptabilities and excellent optical absorption abilities owing to its special energy‐band structure. The key characteristics of biological adaptation, such as accuracy, sensitivity, inactivation, and desensitization behaviors, are successfully emulated in the device based on the unique trapping‐detrapping mechanism. Most importantly, with a photoelectric synergy approach, the fascinating visual adaptation function based on an environment‐adjustable threshold is finally demonstrated. These results indicate that the proposed device may be very promising for the future applications of artificial visual systems and intelligent bionic robots. [ABSTRACT FROM AUTHOR]

Abstract: As an emerging 2D layered material, Bi2O2Se has shown great potential for applications in thermoelectric and electronics, due to its high carrier mobility, near‐ideal subthreshold swing, and high air‐stability. Although Bi2O2Se has a suitable band gap for infrared (IR) applications, its photoresponse properties have not been investigated. Here, high‐quality ultrathin Bi2O2Se sheets are synthesized via a low‐pressure chemical vapor deposition method. The thickness of 90% Bi2O2Se sheets is below 10 nm and lateral sizes mainly distribute in the range of 7–11 µm. In addition, it is found that triangular sheets largely lack “O” content, even only 0.2 for Bi2O0.2Se. The near‐IR photodetection performance of Bi2O2Se nanosheets is systematically studied by variable temperature measurements. The response time, responsivity, and detectivity can approach up to 2.8 ms, 6.5 A W−1, and 8.3 × 1011 Jones, respectively. Additionally, the critical performance parameters, including responsivity, rising time, and decay time, remain at almost the same level when the temperature is changed from 80 to 300 K. These phenomena are likely due to the fact that as‐grown ultrathin Bi2O2Se sheets have no surface trap states and shallow defect energy levels. The findings indicate ultrathin Bi2O2Se sheets have great potentials for future applications in ultrafast, flexible near‐IR optoelectronic devices. [ABSTRACT FROM AUTHOR]

2D materials, represented by transition metal dichalcogenides (TMDs), have attracted tremendous research interests in photoelectronic and electronic devices. However, for their relatively small bandgap (<2 eV), the application of traditional TMDs into solar-blind ultraviolet (UV) photodetection is restricted. Here, for the first time, NiPS3 nanosheets are grown via chemical vapor deposition method. The nanosheets thinning to 3.2 nm with the lateral size of dozens of micrometers are acquired. Based on the various nanosheets, a linearity is found between the Raman intensity of specific Ag modes and the thickness, providing a convenient method to determine their layer numbers. Furthermore, a UV photodetector is fabricated using few-layered 2D NiPS3 nanosheets. It shows an ultrafast rise time shorter than 5 ms with an ultralow dark current less than 10 fA. Notably, this UV photodetector demonstrates a high detectivity of 1.22 × 1012 Jones, outperforming some traditional wide-bandgap UV detectors. The wavelength-dependent photoresponsivity measurement allows the direct observation of an admirable cut-off wavelength at 360 nm, which indicates a superior spectral selectivity. The promising photodetector performance, accompanied with the controllable fabrication and transfer process of nanosheet, lays the foundation of applying 2D semiconductors for ultrafast UV light detection. [ABSTRACT FROM AUTHOR]

Holding novel physical properties, high flexibility and strong integration ability with Si-based electronic devices, two-dimensional (2D) non-layered materials have received considerable attentions in recent years. To achieve the 2D anisotropic growth, various strategies have been developed. And a variety of applications have been demonstrated. This review provides an overview on the recent progress of this material family. The scope will cover the preparation strategies, including dry methods and wet chemical approaches, as well as the applications in catalysis, energy conversion and storage, optoelectronic devices and topological crystalline insulators. Conclusion and future perspectives are also given. [ABSTRACT FROM AUTHOR]

For increasing scalability and reducing cost, transition metal dichalcogenides-based electrocatalysts presently have been proposed as substitutes for noble metals to generate hydrogen, but these alternatives usually suffer from inferior performance. Here, a Ravenala leaf-like W xC@WS2 heterostructure is grown via carbonizing WS2 nanotubes, whose outer walls being partially unzipped along with the W x C 'leaf-valves' attached to the inner tubes during the carbonization process. This heterostructure exhibits a catalytic activity for hydrogen evolution reaction with low overpotential of 146 mV at 10 mA cm−2 and Tafel slope of 61 mV per decade, outperforming the performance of WS2 nanotubes and W xC counterparts under the same condition. Density functional theory calculations are performed to unravel the underlying mechanism, revealing that the charge distribution between W xC and WS2 plays a key role for promoting H atom adsorption and desorption kinetics simultaneously. This work not only provides a potential low-cost alternative for hydrogen generation but should be taken as a guide to optimize the catalyst structure and composition. [ABSTRACT FROM AUTHOR]

Van der Waals heterostructures (vdWHs), obtained by artificially stacking 2D layered material (2DLM) plains upon each other, are brand new structures that have exhibited novel electronic and optoelectronic properties and attracted a great deal of attention. So far, the results are only based on devices with symmetrical configurations: devices predominated by vdWH parts, or cross-like configurations combined with both vdWHs and extra individual 2DLM layers. Quite different gate tunable phenomena have been observed for these two configurations even though 2DLMs with similar band alignments were used, which may be due to the different device configurations utilized. For a deeper understanding, rational investigation on configuration-dependent properties of vdWHs is needed. Here, using MoTe2/MoS2 as an example, vdWH device is artificially designed with two asymmetrical configurations. Through comparing the respective results, it is found that the properties that stem only from the vdWH, i.e., the rectification behavior and open voltage in photovoltaic effect, are independent of the device structures. However, other properties, i.e., drain currents, short circuit currents, and photoreponse performances, strongly depend on the configuration used. These results give a guideline on studying the intrinsic properties of vdWHs and optimizing the device structures for better performances. [ABSTRACT FROM AUTHOR]

As an effective alternative to noble platinum electrocatalyst, earth abundant and inexpensive layered transition metal dichalcogenides (TMDs) are investigated for the hydrogen evolution reaction (HER). Compared with binary TMDs, the tunably composed ternary TMDs have hitherto received relatively little attention. Here, few-layered ternary WS2(1− x)Se2 x nanoribbons (NRs) with metallic 1T phases, much more catalytically active in HER, are prepared for the first time. The favorable Δ GHo introduced by the tensile region on the surface, along with the presence of local lattice distortions of the WS2(1− x)Se2 x nanoribbons with metallic 1T phases, greatly promotes the HER process. These ternary NRs achieve the lowest overpotential of ≈0.17 V at 10 mA cm−2 and a Tafel slope of ≈68 mV dec−1 at a low catalyst loading (≈0.30 ± 0.02 mg cm−2). Notably, the long-term durability suggests the potential of practical applications in acid electrolytes. The results here suggest that the ternary WS2(1− x)Se2 x NRs with 1T phases are prominent alternatives to platinum-based HER electrocatalysts. [ABSTRACT FROM AUTHOR]

2D materials have been interested in recent years due to their unique properties and enormous potential in various fields. In particular, 2D ferroionics with both ferroelectricity and ionic conductivity shed light on new possibilities for van der Waals nanoelectronics. Here, supported by theoretical calculations and electrical characterizations, the reconfigurable van der Waals ferroionic barristor that can be used in multifunctional electronics including resistive devices and steep‐slope transistors is reported. Large modulation on the device properties is achieved by electrically driven migration and redistribution of mobile ions. The memory device shows an unprecedented long‐term stability with a switching ratio of ≈1010. Utilizing this ferroionic nature, 2D transistors able to beat the Boltzmann tyranny, with different gate configurations, are designed. The subthreshold swing (SS) exhibits sub‐60 mV per decade values over five decades of the drain current with a minimum of 12.1 mV per decade. This work paves the way for investigating the symbiotic relationship of ferroelectricity and ionic activities in van der Waals ferroionics and highlights their applications in advanced nanoelectronics. [ABSTRACT FROM AUTHOR]

With the interplay between magnetism and topological bands, magnetic kagome semimetals provide promising platforms for exploring exotic correlated electronic states and quantum phenomena such as anomalous Hall effect, quantum spin liquid, and unconventional magnetoresistance, as well as driving advances in electronic and spintronic applications. Here, a field‐induced butterfly‐like anomalous anisotropic magnetoresistance (AMR) effect in an intriguing kagome semimetal Co3In2S2 is reported. The kagome‐lattice Co3In2S2 single crystals are synthesized via a polycrystal‐source chemical vapor transport approach, possessing a high carrier mobility reaching 104 cm2V−1s−1. The Co3In2S2 single crystal exhibits a canted antiferromagnetic state below 5 K, but intriguingly, it is easily transformed into a ferromagnetic state under a small external magnetic field. Furthermore, the planar Hall effect (PHE) is detected, stemming from the complex contribution of field‐induced ferromagnetism and orbital magnetoresistance. Remarkably, as the magnetic field increases, the low‐temperature magnetoresistance behavior of the Co3In2S2 reveals a butterfly‐like AMR effect with a maximum value of 850%, exhibiting a superposition of the two‐, four‐, and six‐fold AMR terms. Band structure calculations suggest that such a field‐induced butterfly‐like AMR effect may originate from the modulations of the electronic structure near the Fermi level by the magnetic moment. The findings offer a valuable platform for understanding the anomalous AMR effect and for the development of advanced spintronic devices. [ABSTRACT FROM AUTHOR]

The redox‐active organic compounds including potassium 1,1′‐biphenyl‐4,4′‐dicarboxylate (K‐BPDC) are attracting considerable attention as anodes for potassium‐ion batteries (PIBs). Nevertheless, the practical applications of K‐BPDC organic anodes are severely hindered by short cycle life due to their relatively sluggish redox kinetics and instability. In this work, Ni single atoms (up to 6 wt.%) are implanted into K‐BPDC (NiSA@K‐BPDC) by using an electrochemical‐induced reconstruction (EIR) strategy to enhance the reaction kinetics and stability of PIBs. During the EIR process, Ni‐based metal‐organic framework (Ni‐BPDC) is in situ reconstructed into K‐BPDC by replacing Ni2+ with K+ to make the rest nickel species exist in the form of single atoms in K‐BPDC. By kinetic analysis and theoretical calculations, it is uncovered that the Ni single atoms supported on K‐BPDC efficiently redistribute the local charge of K‐BPDC to accelerate the K+ transport rate, and thermodynamically reduce the redox energy barrier. As a result, the NiSA@K‐BPDC anode exhibits outstanding cycle stability with 88.5% capacity retention during 4000 cycles at 1 A g−1 and an excellent rate capability (114 mAh g−1 at 2 A g−1). This study opens up a new door to the design of organic anodes with single atoms for high‐performance PIBs. [ABSTRACT FROM AUTHOR]

Bandpass photodetectors have tremendous applications in colorimetric analysis, light communication, imaging and machine vision systems. Compared to broadband photodetectors combined with external optical filters, solution‐processed filterless bandpass photodetectors enjoy high integration density and low cost, but suffer from broadened response edges and insufficient spectral rejection ratios (SRRs). Here, prototype filterless bandpass photodetectors with near square‐shape photoresponse are developed based on (CmH2m+1NH3)2PbI4/MAPbI3 (m = 4–8) and (CmH2m+1NH3)2PbBr4/MAPbBr3 (m = 2–8) perovskite heterojunctions. The strong and sharp excitonic absorption of 2D perovskites defines the ultranarrow response onset widths of 10 ± 1 nm. Besides, the strong photoluminescence (PL) self‐absorption of 2D perovskites suppresses the PL leakage from the front absorber to the back photoactive region, which is crucial to the achieved record high SRR of >2000. By integrating Br‐based 2D/3D perovskite photodetectors with onset edge wavelength discrimination of ≈20 nm, a multiple‐channel optical communication system with low spectral crosstalk is demonstrated. [ABSTRACT FROM AUTHOR]

Controlling the conduction behavior of 2D materials is an important prerequisite to achieve their electronic and optoelectronic applications. However, most of the reported approaches are aware of the shortcomings of inflexibility and complexity, which limits the possibility of multifunctional integration. Here, taking advantage of van der Waals heterostructure engineering, a simple method to achieve a dynamically controlled binary channel in a semivertical MoTe2/MoS2 field effect transistor is proposed. It is enabled by the high switchability between tunneling and thermal transports through simply changing the sign of voltage bias. In addition, the proposed system allows for multifunctional integration of transistor with on/off ratio >107 and diode with rectification ratio >106. Moreover, the devices show screen capability to negative photoresponse effect that is widely observed in ambipolar materials, hence improving the photodetection reliability and sensitivity. This study broadens the functionalities of van der Waals heterostructures and opens up more possibilities to realize multifunctional devices. A new application of vdWHs to dynamically control and optimize the electronic and optoelectronic properties of 2D materials is demonstrated. The semivertical MoTe2/MoS2 structure allows for a desirable multifunctional integration of field effect transistors with an on/off ratio >107 and diode with rectification ratio >106. Moreover, the devices exhibit strong capability of suppressing the widely observed trap states–related negative photoresponse effect. [ABSTRACT FROM AUTHOR]

Van der Waals heterostructures (vdWHs), obtained by artificially stacking 2D layered material (2DLM) plains upon each other, are brand new structures that have exhibited novel electronic and optoelectronic properties and attracted a great deal of attention. So far, the results are only based on devices with symmetrical configurations: devices predominated by vdWH parts, or cross-like configurations combined with both vdWHs and extra individual 2DLM layers. Quite different gate tunable phenomena have been observed for these two configurations even though 2DLMs with similar band alignments were used, which may be due to the different device configurations utilized. For a deeper understanding, rational investigation on configuration-dependent properties of vdWHs is needed. Here, using MoTe2/MoS2 as an example, vdWH device is artificially designed with two asymmetrical configurations. Through comparing the respective results, it is found that the properties that stem only from the vdWH, i.e., the rectification behavior and open voltage in photovoltaic effect, are independent of the device structures. However, other properties, i.e., drain currents, short circuit currents, and photoreponse performances, strongly depend on the configuration used. These results give a guideline on studying the intrinsic properties of vdWHs and optimizing the device structures for better performances. [ABSTRACT FROM AUTHOR]