Search

With the ability to maximize the exposure of nearly all active sites to reactions, two-dimensional transition metal dichalcogenide (TMD) has become a fascinating new class of materials for electrocatalysis. Recently, electrochemical microcells have been developed, and their unique spatial-confined capability enables understanding of catalytic behaviors at a single material level, significantly promoting this field. This Review provides an overview of the recent progress in microcell-based TMD electrocatalyst studies. We first introduced the structural characteristics of TMD materials and discussed their site engineering strategies for electrocatalysis. Later, we comprehensively described two distinct types of microcells: the window-confined on-chip electrochemical microcell (OCEM) and the droplet-confined scanning electrochemical cell microscopy (SECCM). Their setups, working principles, and instrumentation were elucidated in detail, respectively. Furthermore, we summarized recent advances of OCEM and SECCM obtained in TMD catalysts, such as active site identification and imaging, site monitoring, modulation of charge injection and transport, and electrostatic field gating. Finally, we discussed the current challenges and provided personal perspectives on electrochemical microcell research. [ABSTRACT FROM AUTHOR]

Highlights: A self-powered α-In2Se3/3R MoS2 heterojunction is successfully developed and shows strong photo response to the visible and near infrared light. The heterojunction photodetector delivers an ultrahigh photoresponsivity of 2.9 × 103 A W−1 and a substantial specific detectivity of 6.2 × 1010 Jones under a compressive strain of − 0.26%. This work demonstrates that the transport of photo generated carriers is clearly modulated by mechanical stimuli through the piezo-phototronic effect at the heterojunction interface.Semiconducting piezoelectric α-In2Se3 and 3R MoS2 have attracted tremendous attention due to their unique electronic properties. Artificial van der Waals (vdWs) heterostructures constructed with α-In2Se3 and 3R MoS2 flakes have shown promising applications in optoelectronics and photocatalysis. Here, we present the first flexible α-In2Se3/3R MoS2 vdWs p-n heterojunction devices for photodetection from the visible to near infrared region. These heterojunction devices exhibit an ultrahigh photoresponsivity of 2.9 × 103 A W−1 and a substantial specific detectivity of 6.2 × 1010 Jones under a compressive strain of − 0.26%. The photocurrent can be increased by 64% under a tensile strain of + 0.35%, due to the heterojunction energy band modulation by piezoelectric polarization charges at the heterojunction interface. This work demonstrates a feasible approach to enhancement of α-In2Se3/3R MoS2 photoelectric response through an appropriate mechanical stimulus. [ABSTRACT FROM AUTHOR]

Due to the robust oxidation conditions in strong acid oxygen evolution reaction (OER), developing an OER electrocatalyst with high efficiency remains challenging in polymer electrolyte membrane (PEM) water electrolyzer. Recent theoretical research suggested that reducing the coordination number of Ir−O is feasible to reduce the energy barrier of the rate‐determination step, potentially accelerating the OER. Inspired by this, we experimentally verified the Ir−O coordination number's role at model catalysts, then synthesized low‐coordinated IrOx nanoparticles toward a durable PEM water electrolyzer. We first conducted model studies on commercial rutile‐IrO2 using plasma‐based defect engineering. The combined in situ X‐ray absorption spectroscopy (XAS) analysis and computational studies clarify why the decreased coordination numbers increase catalytic activity. Next, under the model studies' guidelines, we explored a low‐coordinated Ir‐based catalyst with a lower overpotential of 231 mV@10 mA cm−2 accompanied by long durability (100 h) in an acidic OER. Finally, the assembled PEM water electrolyzer delivers a low voltage (1.72 V@1 A cm−2) as well as excellent stability exceeding 1200 h (@1 A cm−2) without obvious decay. This work provides a unique insight into the role of coordination numbers, paving the way for designing Ir‐based catalysts for PEM water electrolyzers. [ABSTRACT FROM AUTHOR]

Due to the robust oxidation conditions in strong acid oxygen evolution reaction (OER), developing an OER electrocatalyst with high efficiency remains challenging in polymer electrolyte membrane (PEM) water electrolyzer. Recent theoretical research suggested that reducing the coordination number of Ir−O is feasible to reduce the energy barrier of the rate‐determination step, potentially accelerating the OER. Inspired by this, we experimentally verified the Ir−O coordination number's role at model catalysts, then synthesized low‐coordinated IrOx nanoparticles toward a durable PEM water electrolyzer. We first conducted model studies on commercial rutile‐IrO2 using plasma‐based defect engineering. The combined in situ X‐ray absorption spectroscopy (XAS) analysis and computational studies clarify why the decreased coordination numbers increase catalytic activity. Next, under the model studies' guidelines, we explored a low‐coordinated Ir‐based catalyst with a lower overpotential of 231 mV@10 mA cm−2 accompanied by long durability (100 h) in an acidic OER. Finally, the assembled PEM water electrolyzer delivers a low voltage (1.72 V@1 A cm−2) as well as excellent stability exceeding 1200 h (@1 A cm−2) without obvious decay. This work provides a unique insight into the role of coordination numbers, paving the way for designing Ir‐based catalysts for PEM water electrolyzers. [ABSTRACT FROM AUTHOR]

The high cost of noble metals is one of the key factors hindering the large‐scale application of proton exchange membrane (PEM) water electrolyzer for hydrogen production. Recently, single‐atom catalysts (SACs) with a potential of maximum atom utilization efficiency enable lowering the metal amount as much as possible; unfortunately, their durability remains a challenge under PEM water electrolyzer working conditions. Herein, a highly‐stable alloyed Pt SAC is demonstrated through a plasma‐assisted alloying strategy and applies to a PEM water electrolyzer. In this catalyst, single Pt atoms are firmly anchored onto a Ru support via a robust metal–metal bonding strength, as evidenced by these complementary characterizations. This SAC is used in a PEM water electrolyzer system to achieve a cell voltage as low as 1.8 V at 1000 mA cm−2. Impressively, it can operate over 1000 h without obvious decay, and the catalyst is present in the form of individual Pt atoms. To the knowledge, this will be the first SAC attempt at a cell level toward long‐term PEM. This work paves the way for designing durable SACs employed in the actual working condition in the PEM water electrolyzer. [ABSTRACT FROM AUTHOR]

Recharging batteries operate at sub‐zero temperature is usually limited by the slow ion diffusion and uneven charge distribution at low temperature. Here, we report a strategy to regulate electric field and thermal field simultaneously, creating a fast and uniform deposition surroundings for potassium ion in potassium metal batteries (PMBs). This regulation is achieved by using a highly ordered 1D nanoarray electrode which provides a dense and flat surface for uniforming the electric field and high thermal conductivity for reducing the temperature fluctuation. Consequently, this electrode could achieve high‐areal capacity of 10 mAh cm−2. Besides, the dependence of potassium nucleation on temperature is unveiled. Furthermore, a full‐cell could steady operate with over 80 % of its room‐temperature capacity at −20 °C. Those respectable performances demonstrate that this strategy is valid, potentially providing guidelines for the rational design of advanced electrodes toward PMBs. [ABSTRACT FROM AUTHOR]

Recharging batteries operate at sub‐zero temperature is usually limited by the slow ion diffusion and uneven charge distribution at low temperature. Here, we report a strategy to regulate electric field and thermal field simultaneously, creating a fast and uniform deposition surroundings for potassium ion in potassium metal batteries (PMBs). This regulation is achieved by using a highly ordered 1D nanoarray electrode which provides a dense and flat surface for uniforming the electric field and high thermal conductivity for reducing the temperature fluctuation. Consequently, this electrode could achieve high‐areal capacity of 10 mAh cm−2. Besides, the dependence of potassium nucleation on temperature is unveiled. Furthermore, a full‐cell could steady operate with over 80 % of its room‐temperature capacity at −20 °C. Those respectable performances demonstrate that this strategy is valid, potentially providing guidelines for the rational design of advanced electrodes toward PMBs. [ABSTRACT FROM AUTHOR]

[Display omitted] High-mobility van der Waals ambipolar semiconductors are promising in logic and reconfigurable circuits, integrated optoelectronic circuits, due to the excellent gate-controlled capability and effectively tunability of major charge carriers by electrostatic field. Controllable growth of high-quality ambipolar semiconductors with high mobility and stability is highly glamorous and indispensable for further research. Here, we demonstrate a straightforward space-confined chemical vapor deposition (CVD) method to synthesize high-quality quasi-one-dimensional (1D) tellurium (Te) nanoribbons (NRs). By introducing H 2 into the gas flow, endothermic compound H 2 Te was generated from the reaction of liquid Te with H 2 , and consequently decomposed into elemental Te at low temperature. Further, the Te NRs have been utilized for in-situ fabrication of field-effect transistors (FETs) without transferring process. Ambipolar features are achieved using nickel (Ni) as an ohmic contact. More importantly, the mobilities of the Te NR transistor for hole/electron are as high as 1755/28.6 cm2V−1s−1 and 4024/278 cm2V−1s−1 at room temperature and under a temperature below 20 K, respectively. Our findings confirm the novel strategy for synthesizing 1D elemental semiconductors and their applications with ambipolar behaviors. [ABSTRACT FROM AUTHOR]

Efficient assimilation of alternative carbon sources in glucose-limited host niches is critical for colonization of Candida albicans, a commensal yeast that frequently causes opportunistic infection in human. C. albicans evolved mechanistically to regulate alternative carbon assimilation for the promotion of fungal growth and commensalism in mammalian hosts. However, this highly adaptive mechanism that C. albicans employs to cope with alternative carbon assimilation has yet to be clearly understood. Here we identified a novel role of C. albicans mitochondrial complex I (CI) in regulating assimilation of alternative carbon sources such as mannitol. Our data demonstrate that CI dysfunction by deleting the subunit Nuo2 decreases the level of NAD+, downregulates the NAD+-dependent mannitol dehydrogenase activity, and consequently inhibits hyphal growth and biofilm formation in conditions when the carbon source is mannitol, but not fermentative sugars like glucose. Mannitol-dependent morphogenesis is controlled by a ROS-induced signaling pathway involving Hog1 activation and Brg1 repression. In vivo studies show that nuo2Δ/Δ mutant cells are severely compromised in gastrointestinal colonization and the defect can be rescued by a glucose-rich diet. Thus, our findings unravel a mechanism by which C. albicans regulates carbon flexibility and commensalism. Alternative carbon assimilation might represent a fitness advantage for commensal fungi in successful colonization of host niches. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) with a maximum atom utilization efficiency have received growing attention in heterogeneous catalysis. The supporting substrate that provides atomic‐dispersed anchoring sites and the local electronic environment in these catalysts is crucial to their activity and stability. Here, inspired by N‐doped graphene substrate, the role of N is explored in transition metal nitrides for anchoring single metal atoms toward single‐atom catalysis. A pore‐rich metallic vanadium nitride (VN) nanosheet is fabricated as one supporting‐substrate example, whose surface features abundant unsaturated N sites with lower binding energy than that of widely used N‐doped graphene. Impressively, it is found that this support can anchor nearly all platinum‐group single atoms (e.g., platinum, palladium, iridium, and ruthenium), and even be extendable to multiple SACs, i.e., binary (Pt/Pd) and ternary (Pt/Pd/Ir). As a proof‐of‐concept application for hydrogen production, Pt‐based SAC (Pt1‐VN) performs excellently, exhibiting a mass activity up to 22.55 A mg−1Pt at 0.05 V and a high turnover frequency value close to 0.350 H2 s−1, superior to commercial platinum/carbon catalyst. The catalyst's durability can be further improved by using binary (Pt1Pd1‐VN) SAC. This work provides inexpensive and durable nitride‐based support, giving a possible pathway for universally constructing platinum‐group SACs. [ABSTRACT FROM AUTHOR]

Abstract: A new microwave plasma process is developed to refine and purify metallurgical grade silicon (MG-Si) effectively. Inductively coupled plasma-atomic emission spectrometry analysis (ICP-AES) indicates that the concentrations of impurities in silicon decrease significantly in the process, particularly for phosphorus, whose average removal rate is close to 100% after microwave plasma treatment of only 5min. The underlying mechanisms of the ultra-high removal rate of impurity atoms are discussed in detail in this paper. The photoresponse switching behavior of n+-Si wafers that are made of as-purified silicon provides further evidence for the unique advantage arising from the use of microwave plasma in the purification of MG-Si. [Copyright &y& Elsevier]

Carrier doping is the basis of the modern semiconductor industry. Great efforts are put into the control of carrier doping for 2D semiconductors, especially the layered transition metal dichalcogenides. Here, the direct laser patterning of WSe2 devices via light‐induced hole doping is systematically studied. By changing the laser power, scan speed, and the number of irradiation times, different levels of hole doping can be achieved in the pristine electron‐transport‐dominated WSe2, without obvious sample thinning. Scanning transmission electron microscopy characterization reveals that the oxidation of the laser‐radiated WSe2 is the origin of the carrier doping. Photocurrent mapping shows that after the same amount of laser irradiation, with increasing thickness, the laser patterned PN junction changes from the pure lateral to the vertical‐lateral hybrid structure, accompanied by the decrease in the open circuit voltage. The vertical‐lateral hybrid PN junction can be tuned to a pure lateral one by further irradiation, showing possibilities to construct complex junction profiles. Moreover, a NOR gate circuit is demonstrated by direct patterning of p‐doped channels using laser irradiation without introducing passive layers and metal electrodes with different work functions. This method simplifies device fabrication procedures and shows a promising future in large scale logic circuit applications. [ABSTRACT FROM AUTHOR]

Abstract: Low‐grade heat to electricity conversion has shown a large potential for sustainable energy supply. Recently, the low‐grade heat harvesting in the thermally regenerative electrochemical cycle (TREC) is a promising candidate with high energy conversion efficiency. In this system, the electrochemical temperature coefficient (α) plays a dominant role in efficient heat harvesting. However, the internal factors that affect α are still not clear and significant improvements are needed. Here, α of various Prussian Blue analogues (PBAs) is investigated and their lattice change during cation intercalation is monitored using the ex situ X‐ray diffraction (XRD) method. For the first time, it is found that α is highly related to the lattice parameter change. Large lattice shrinkage exhibits a large negative α, while lattice expansion is corresponding to a positive α. These are mainly attributed to the different phonon vibration entropy changes upon cation intercalation in various PBAs. Especially, purple cobalt hexacynoferrate delivers the largest α of −0.89 mV K−1 and enables highly efficient heat conversion efficiency up to 2.65% (21% of relative efficiency). The results of this study provide a fundamental understanding of temperature coefficient in electrochemical reactions and pave the way for designing high‐performance material for low‐grade heat harvesting. [ABSTRACT FROM AUTHOR]

The emergence of semiconducting transition metal dichalcogenide (TMD) atomic layers has opened up unprecedented opportunities in atomically thin electronics. Yet the scalable growth of TMD layers with large grain sizes and uniformity has remained very challenging. Here is reported a simple, scalable chemical vapor deposition approach for the growth of MoSe2 layers is reported, in which the nucleation density can be reduced from 105 to 25 nuclei cm−2, leading to millimeter-scale MoSe2 single crystals as well as continuous macrocrystalline films with millimeter size grains. The selective growth of monolayers and multilayered MoSe2 films with well-defined stacking orientation can also be controlled via tuning the growth temperature. In addition, periodic defects, such as nanoscale triangular holes, can be engineered into these layers by controlling the growth conditions. The low density of grain boundaries in the films results in high average mobilities, around ≈42 cm2 V−1 s−1, for back-gated MoSe2 transistors. This generic synthesis approach is also demonstrated for other TMD layers such as millimeter-scale WSe2 single crystals. [ABSTRACT FROM AUTHOR]

Here, we present a kind of SnO 2 nanowires/TiO 2 nanoneedles/CdS quantum dots multi-heterojunction structure. In this rational heterojunction structure, three dimensional SnO 2 nanowires were directly grown on conductive fluorine doped tin oxide (FTO) glass by chemical vapor deposition method and served as the faster electron transport network for highly efficient photoelectrochemical system. Moreover, after artful design of branched TiO 2 nanoneedles on this network and then sensitized by CdS quantum dots, a multi-heterojunction structure of SnO 2 /TiO 2 /CdS was formed. This novel three dimensional multi-heterojunction structure exhibited remarkable performances on photoelectrochemical hydrogen production. The photocurrent density is as high as 8.75 mA cm −2 at a potential of 0 V vs . saturated calomel electrode (SCE) by using the optimized conditions. More impressively, the photocurrent density is more than 4 times larger than that of single SnO 2 –TiO 2 heterojunction (1.72 mA cm −2 ) at 0 V vs. SCE. [ABSTRACT FROM AUTHOR]

An atomically thin optoelectronicmemory array for image sensingis demonstrated with layered CuIn7Se11and extendedto InSe and MoS2atomic layers. Photogenerated charge carriersare trapped and subsequently retrieved from the potential well formedby gating a 2D material with Schottky barriers. The atomically thinlayered optoelectronic memory can accumulate photon-generated chargesduring light exposure, and the charges can be read out later for dataprocessing and permanent storage. An array of atomically thin imagememory pixels was built to illustrate the potential of fabricatinglarge-scale 2D material-based image sensors for image capture andstorage. [ABSTRACT FROM AUTHOR]

Highlights: [•] We demonstrated that the solvent plays a critical role in the nanotubes formation process which can be controlled by the ambient temperature. [•] For a selected solvent, the saturated vapor pressure was the intrinsic factor for the morphologies determining during the electrospinning process. [•] The formation process of nanotubes was observed by TEM and a possible formation mechanism was proposed. [•] The magnetic properties of magnesium ferrite calcined at different temperature stages were systematically studied. [ABSTRACT FROM AUTHOR]

In2O3/α-Fe2O3 (IFO) heterostructure nanotubes, with cubic-In2O3 nanocrystals randomly distributed on the surface of α-Fe2O3 nanotube-based backbones, were successfully prepared through a facile single-capillary electrospinning method. The morphologies of the resulting electrospun products were characterized by scanning electron microscopy and transmission electron microscopy. The crystal structures and components were determined by X-ray diffraction and energy-dispersive X-ray spectra, respectively. The results show that the morphology and structure of the products could be tailored by changing the content of indium nitrate in the precursor solutions and the calcination temperatures. Moreover, the IFO-0.1 (In/Fe = 1 : 9, molar ratio) nanotubes based sensor shows a high sensitivity to ethanol with a fast response/recovery time, and the performance is stable at a low operating temperature, which gives a potential application in ethanol gas sensors. A possible gas sensing mechanism based on the role of In2O3 in such a heterostructure is also discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: Titanium (Ti)-capped ZnO samples with different roughness were prepared to investigate the effect of ZnO morphology on surface plasma energy of ZnO/Ti interface. ZnO nanoparticle samples with diverse particle shapes, sizes and filling factors were obtained by annealing at different temperatures. Ti-capped ZnO films annealed at 700°C exhibit excellent photoluminescence property, which can attribute to the high degree of crystallinity (DC) and appropriate surface roughness. Tuning the microcrystalline structure and the ratio of inter-particle distance to the nanoparticle diameter of ZnO can facilitate the surface plasma resonance energy at ZnO/Ti interface close to the near-band-gap emission energy of ZnO, leading to an enhancement of the near-band-gap emission. [Copyright &y& Elsevier]

Battery-type supercapacitors that exhibit both high power density from capacitor-like behaviour, and high energy density from battery-like behaviour, have attracted significant interest recently. However, compared to conventional capacitor technology, these supercapacitors present new challenges for the design of the electrode materials, since they require not only high conductivity for fast electron transport, but also a suitable crystal structure for efficient ion intercalation. Here, we report a large-capacity wire supercapacitor, which is assembled by forming TiN nanowire arrays on carbonized cotton threads. The resulting structure is capable of both acting as the cathode and the anode, with specific capacities of 12.9 mAh cm−1 and 25.0 mAh cm−1 in Li-ion aqueous electrolyte, respectively. Sweep voltammetry analysis further reveals that the storage characteristics include both battery and capacitor-like behaviour, that is, 50–60% of the energy storage arises from the intercalation/deintercalation of Li/Na ions (battery-like) with the balance coming from the adsorption/desorption of electrolyte ions on the electrode surface (capacitor-like). Finally, two types of wire supercapacitors are assembled (lithium and sodium ion based), which exhibited excellent energy density of 52.5 μW h cm−2 for the lithium ion capacitor and 93.1 μW h cm−2 for the sodium ion capacitor, with 74.9% and 51.5% of the specific capacity retained after 10,000 cycles. This work demonstrates the possible application of these materials and structures in high-performance wearable energy storage systems. [ABSTRACT FROM AUTHOR]