Exploring the role of iron in Fe_(5)Ni_(4)S_(8)toward oxygen evolution through modulation of electronic orbital occupancy

Ni-Fe-based catalysts are considered to be among the most active catalysts for the oxygen evolution reaction(OER)under alkaline conditions,with Fe playing a crucial role.However,Fe leaching occurs during the reaction due to thermodynamic instability,which has resulted in conflicting reports within the literature regarding its role.To clarify this point,we propose a strategy consisting of modulating the electronic orbital occupancy to suppress the extensive loss of Fe atoms during the OER process.Theoretical calculations,in-situ X-ray photoelectron spectroscopy,molecular dynamics simulations,and a series of characterization showed that the stable presence of Fe not only accelerates the electron transfer process but also optimizes the reaction barriers of the oxygen evolution intermediates,promoting the phase transition of Fe_(5)Ni_(4)S_(8)to highly active catalytic species.The modulated Fe_(5)Ni_(4)S_(8)-based pre-catalysts exhibit improved OER activity and long-term durability.This study provides a novel perspective for understanding the role of Fe in the OER process.

Palladium single atoms from melting nanoparticles on WO_(3-x) for boosted hydrogen evolution reaction

Surface-supported isolated atoms in single-atom catalysts(SACs)grant maximum utilization of metals in heterogeneous catalysis.Herein,we report a feasible pyrolysis strategy to synthesize Pd single atoms by thermally melting Pd nanoparticles on an oxygen-vacancy-rich tungsten-oxide matrix at reduction atmosphere.Near ambient pressure X-ray photoelectron spectroscopy was used to monitor the formation of zero-valence Pd single atoms and the increased metallic feature of WO_(3-x)substrate.Accordingly,the as-obtained zero-valence Pd single-atom catalyst exhibits a markedly boosted HER activity with a low overpotential(η_(10)=70 mV)at the current density of 10 mA/cm2and a small Tafel slope(b=68 mV/dec),nearly 150 mV and a 3,0-fold enhancement than those of Pd nanoparticles(η_(10)=220 mV,b=133 mV/dec)under the same conditions.In addition,quasi in situ XPS results suggest the hydrogen spillover effect is more likely to occur on Pd single atoms during the electrochemical process.Our work may pave an interesting route for the rational design of highly-efficient single-atom catalysts,and the elucidation of corresponding enhanced reaction mechanisms by the utilization of advanced characterization techniques.

Biological Tissue-Inspired Ultrasoft,Ultrathin,and Mechanically Enhanced Microfiber Composite Hydrogel for Flexible Bioelectronics

Hydrogels offer tissue-like softness,stretchability,fracture toughness,ionic conductivity,and compatibility with biological tissues,which make them promising candidates for fabricating flexible bioelectronics.A soft hydrogel film offers an ideal interface to directly bridge thin-film electronics with the soft tissues.However,it remains difficult to fabricate a soft hydrogel film with an ultrathin configuration and excellent mechanical strength.Here we report a biological tissue-inspired ultrasoft microfiber composite ultrathin(<5μm)hydrogel film,which is currently the thinnest hydrogel film as far as we know.The embedded microfibers endow the composite hydrogel with prominent mechanical strength(tensile stress~6 MPa)and anti-tearing property.Moreover,our microfiber composite hydrogel offers the capability of tunable mechanical properties in a broad range,allowing for matching the modulus of most biological tissues and organs.The incorporation of glycerol and salt ions imparts the microfiber composite hydrogel with high ionic conductivity and prominent anti-dehydration behavior.Such microfiber composite hydrogels are promising for constructing attaching-type flexible bioelectronics to monitor biosignals.

Boosting C–C coupling to multicarbon products via high-pressure CO electroreduction

Electrochemical CO reduction reaction(CORR) provides a promising approach for producing valuable multicarbon products(C_(2+)), while the low solubility of CO in aqueous solution and high energy barrier of C–C coupling as well as the competing hydrogen evolution reaction(HER) largely limit the efficiency for C_(2+)production in CORR. Here we report an overturn on the Faradaic efficiency of CORR from being HER-dominant to C_(2+)formation-dominant over a wide potential window, accompanied by a significant activity enhancement over a Moss-like Cu catalyst via pressuring CO. With the CO pressure rising from 1 to 40 atm, the C_(2+)Faradaic efficiency and partial current density remarkably increase from 22.8%and 18.9 mA cm^(-2)to 89.7% and 116.7 mA cm^(-2), respectively. Experimental and theoretical investigations reveal that high pressure-induced high CO coverage on metallic Cu surface weakens the Cu–C bond via reducing electron transfer from Cu to adsorbed CO and restrains hydrogen adsorption, which significantly facilitates the C–C coupling while suppressing HER on the predominant Cu(111) surface, thereby boosting the CO electroreduction to C_(2+)activity.

Regulating ethane and ethylene synthesis by proton corridor microenvironment for CO_(2) electrolysis

Electrocatalytic reduction of carbon dioxide is one of the most effective strategies to achieve carbon neutrality and energy sustainability.Although high-value multi-carbon products have been widely studied,limited electrocatalysts have been reported for the selective conversion of ethane.More importantly,the factors tuning the selectivity between ethane and ethylene have not been clarified.Here,Zn@Cu nanowire arrays(Zn@Cu-NWAs) catalyst is proposed to stimulate the maintenance of efficient CO_(2)-to-C_(2)H_(6) conversion at high current densities.Meanwhile,in order to investigate the factors affecting the interconversion between ethane and ethylene,the counterpart catalyst that facilitates C–C coupling to ethylene was also synthesized.Time-of-flight secondary-ion mass spectroscopy(TOF-SIMS),in-situ Raman spectroscopy,and simulation results show that Zn@Cu-NWAs can provide a localized proton corridor environment for the formation of ethane,accelerating the further proton-coupled CO_(2) reduction reaction(CO_(2)RR)kinetics.Hence,this catalyst delivered an ethane Faraday efficiency of over 65% at-1.14 V vs.RHE with a total current density of 142.3 mA/cm^(2).This work provides a new perspective on regulating the local microenvironment to modify the selectivity of multi-carbon products.

Propane dehydrogenation catalyzed by in-situ partially reduced zinc cations confined in zeolites

Propane dehydrogenation(PDH), employing Pt-or Cr-based catalysts, represents an emerging industrial route for propylene production. Due to the scarcity of platinum and the toxicity of chromium, alternative PDH catalysts are being pursued. Herein, we report the construction of Zn-containing zeolite catalysts,namely Zn@S-1, for PDH reaction. Well-isolated zinc cations are successfully trapped and stabilized by the Si-OH groups in S-1 zeolites via in-situ hydrothermal synthesis. The as-prepared Zn@S-1 catalysts exhibit good dehydrogenation activity, high propylene selectivity, and regeneration capability in PDH reaction under employed conditions. The in-situ partial reduction of zinc species is observed and the partially reduced zinc cations are definitely identified as the active sites for PDH reaction.

Effect of inhomogeneous broadening on threshold current of GaN-based green laser diodes

The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.

Stable Lithium-Carbon Composite Enabled by Dual-Salt Additives

Lithium metal is regarded as the ultimate negative electrode material for secondary batteries due to its high energy density.However,it suffers from poor cycling stability because of its high reactivity with liquid electrolytes.Therefore,continuous efforts have been put into improving the cycling Coulombic efficiency(CE)to extend the lifespan of the lithium metal negative electrode.Herein,we report that using dual-salt additives of LiPF_(6) and LiNO_(3) in an ether solvent-based electrolyte can significantly improve the cycling stability and rate capability of a Li-carbon(Li-CNT)composite.As a result,an average cycling CE as high as 99.30% was obtained for the Li-CNT at a current density of 2.5 mA cm^(-2) and an negative electrode to positive electrode capacity(N/P)ratio of 2.The cycling stability and rate capability enhancement of the Li-CNT negative electrode could be attributed to the formation of a better solid electrolyte interphase layer that contains both inorganic components and organic polyether.The former component mainly originates from the decomposition of the LiNO_(3) additive,while the latter comes from the LiPF_(6)-induced ring-opening polymerization of the ether solvent.This novel surface chemistry significantly improves the CE of Li negative electrode,revealing its importance for the practical application of lithium metal batteries.

Remote plasma-enhanced atomic layer deposition of gallium oxide thin films with NH_3 plasma pretreatment

High quality gallium oxide(Ga_2O_3) thin films are deposited by remote plasma-enhanced atomic layer deposition(RPEALD) with trimethylgallium(TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga_2O_3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 ?/cycle at 250 °C,respectively. The increasing of deposition rate is attributed to more hydroxyls(–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga_2O_3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga_2O_3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.

Realization of high-performance tri-layer graphene saturable absorber mirror fabricated via a one-step transfer process

Graphene,as a saturable absorber(SA),has attracted much attention for its application in ultrashort pulse fiber lasers due to its ultrafast interband carrier relaxation and ultra-broadband wavelength operation.Nevertheless,during the stacking process of monolayer graphene layer,the induced nonuniform contact at the interface of graphene layers deteriorate the device performance.Herein,we report the fabrication of graphene saturable absorber mirrors(SAMs)via a one-step transfer process and the realization of the much enlarged modulation depth and the much reduced nonsaturable loss with tri-layer graphene(TLG)than single-layer graphene(SLG)due to the improved uniform contact at the interface.Moreover,the operation of 1550 nm mode-locked Er-doped fiber laser with the TLG SAM exhibits excellent output characteristics of the maximum output power of 9.9 mW,a slope efficiency of 2.4%and a pulse width of 714 fs.Our findings are expected to pave the way toward high-performance ultrashort pulse fiber lasers based on graphene SAs.

New types of hybrid electrolytes for supercapacitors

Supercapacitors(SCs)are emerging as efficient energy storage devices but still suffering from limited energy density compared with batteries.Electrolytes have been regarded as the key to determine the energy storage performance of SCs.However,none of the conventional electrolytes can fully meet the increasing requirements of SCs in terms of high ion conductivity,excellent stability,wide voltage window and operating temperature range,as well as environmentally friend concerns.To this end,hybrid electrolytes have sprung up in recent years,which are believed to be the candidate to solve these shortcomings.Herein,the state-of-the-art types of hybrid electrolytes for SCs,including the combination of aqueous and organic,aqueous and gel polymer,ionic liquids(ILs)and organic,and ILs and gel polymer hybrid electrolytes,are reviewed.The effects of different hybrid systems on the performance of SCs and the underlying mechanisms are among the focal points of the review,and prospects and possible directions are discussed as well to provide further insight into the future development of this field.

Observation of multiple charge density wave phases in epitaxial monolayer 1T-VSe_(2) film

As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the(■) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe_(2) film. Combining the variable-temperature angle-resolved photoemission spectroscopic(ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts △_(1) and△_(2). The gap part ?1 that closes around ~ 150 K is accompanied with the vanish of the(√7×√3) CDW phase. While another momentum-dependent gap part △_(2) can survive up to ~ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure △_(1) +△_(2), which suggests different forming mechanisms between the(√7×√3) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe_(2) film as a two-dimensional(2D) material.

Exploring the phase transformation in ZnO/Cu(111) model catalysts in CO_(2) hydrogenation

Sustainable methanol production via CO_(2) hydrogenation leads to increased interest in the understanding of active phase of Cu/ZnO/Al_(2)O_(3)(CZA) catalyst. Model catalysts of ZnO/Cu(111) with structures varied from two-dimensional planar to three-dimensional nanoparticles were prepared by atomic layer deposition(ALD) method. By combing scanning tunneling microscopy(STM) and X-ray photoelectron spectroscopy(XPS) at near-ambient pressure of CO_(2) hydrogenation, we reveal that the submonolayer ZnO/Cu(111) transformed into Cu-Zn alloy under 10 mbar CO_(2)/H_(2) at 493 K, and underwent a partial reoxidation during evacuation. The dynamic phase transformation of ZnO/Cu(111) may partly explain the existence of differences and apparently contradictory theories to account for the origin of active phase in CZA catalysts.

Interfacial dynamics of GaP/Si(100) heterostructure grown by molecular beam epitaxy

The atomic structure and surface chemistry of GaP/Si(100)heterostructure with different pre-layers grown by molecu-lar beam epitaxy are studied.It is found that GaP epilayer with Ga-riched pre-layers on Si(100)substrate has regular surface mor-phology and stoichiometric abrupt heterointerfaces from atomic force microscopes(AFMs)and spherical aberration-corrected transmission electron microscopes(ACTEMs).The interfacial dynamics of GaP/Si(100)heterostructure is investigated by X-ray photoelectron spectroscopy(XPS)equipped with an Ar gas cluster ion beam,indicating that Ga pre-layers can lower the inter-face formation energy and the bond that is formed is more stable.These results suggest that Ga-riched pre-layers are more con-ducive to the GaP nucleation as well as the epitaxial growth of GaP material on Si(100)substrate.

Honeycomb Lattice in Metal-Rich Chalcogenide Fe_(2)Te

Two-dimensional honeycomb crystals have inspired intense research interest for their novel properties and great potential in electronics and optoelectronics. Here, through molecular beam epitaxy on SrTiO_3(001), we report successful epitaxial growth of metal-rich chalcogenide Fe_(2)Te, a honeycomb-structured film that has no direct bulk analogue, under Te-limited growth conditions. The structural morphology and electronic properties of Fe_(2)Te are explored with scanning tunneling microscopy and angle resolved photoemission spectroscopy, which reveal electronic bands cross the Fermi level and nearly flat bands. Moreover, we find a weak interfacial interaction between Fe_(2)Te and the underlying substrates, paving a newly developed alternative avenue for honeycomb-based electronic devices.

Molecular beam epitaxy growth of monolayer hexagonal MnTe_(2)on Si(111)substrate

Monolayer MnTe_(2)stabilized as 1 T structure has been theoretically predicted to be a two-dimensional(2 D)ferromagnetic metal and can be tuned via strain engineering.There is no naturally van der Waals(vdW)layered MnTe_(2)bulk,leaving mechanical exfoliation impossible to prepare monolayer MnTe_(2).Herein,by means of molecular beam epitaxy(MBE),we successfully prepared monolayer hexagonal MnTe_(2)on Si(111)under Te rich condition.Sharp reflection high-energy electron diffraction(RHEED)and low-energy electron diffraction(LEED)patterns suggest the monolayer is atomically flat without surface reconstruction.The valence state of Mn^(4+)and the atom ratio of([Te]:[Mn])further confirm the MnTe_(2)compound.Scanning tunneling spectroscopy(STS)shows the hexagonal MnTe_(2)monolayer is a semiconductor with a large bandgap of~2.78 eV.The valence-band maximum(VBM)locates at theΓpoint,as illustrated by angle-resolved photoemission spectroscopy(ARPES),below which three hole-type bands with parabolic dispersion can be identified.The successful synthesis of monolayer MnTe_(2)film provides a new platform to investigate the 2D magnetism.

K_(3)C_(60)表面量子自旋诱导的YSR多重态和量子相变

Magnetic impurities in superconductors are of increasing interest due to emergent Yu-Shiba-Rusinov(YSR)states and Majorana zero modes for fault-tolerant quantum computation.However,a direct relationship between the YSR multiple states and magnetic anisotropy splitting of quantum impurity spins remains poorly characterized.By using scanning tunneling microscopy,we systematically resolve individual transition-metal(Fe,Cr,and Ni)impurities induced YSR multiplets as well as their Zeeman effects in the K_(3)C_(60)superconductor.The YSR multiplets show identical d orbital-like wave functions that are symmetry-mismatched to the threefold K_(3)C_(60)(111)host surface,breaking point-group symmetries of the spatial distribution of YSR bound states in real space.Remarkably,we identify an unprecedented fermion-parity-preserving quantum phase transition between ground states with opposite signs of the uniaxial magnetic anisotropy that can be manipulated by an external magnetic field.These findings can be readily understood in terms of anisotropy splitting of quantum impurity spins,and thus elucidate the intricate interplay between the magnetic anisotropy and YSR multiplets.

A multifunctional flexible sensor based on PI-MXene/SrTiO_(3) hybrid aerogel for tactile perception

The inadequacy of tactile perception systems in humanoid robotic manipulators limits the breadth of available robotic applications.Here,we designed a multifunctional flexible tactile sensor for robotic fingers that provides capabilities similar to those of human skin sensing modalities.This sensor utilizes a novel PI-MXene/SrTiO_(3) hybrid aerogel developed as a sensing unit with the additional abilities of electromagnetic transmission and thermal insulation to adapt to certain complex environments.Moreover,polyimide(PI)provides a high-strength skeleton,MXene realizes a pressure-sensing function,and MXene/SrTiO_(3) achieves both thermoelectric and infrared radiation response behaviors.Furthermore,via the pressure response mechanism and unsteady-state heat transfer,these aerogel-derived flexible sensors realize multimodal sensing and recognition capabilities with minimal cross-coupling.They can differentiate among 13 types of hardness and four types of material from objects with accuracies of 94%and 85%,respectively,using a decision tree algorithm.In addition,based on the infrared radiation-sensing function,a sensory array was assembled,and different shapes of objects were successfully recognized.These findings demonstrate that this PI-MXene/SrTiO_(3) aerogel provides a new concept for expanding the multifunctionality of flexible sensors such that the manipulator can more closely reach the tactile level of the human hand.This advancement reduces the difficulty of integrating humanoid robots and provides a new breadth of application scenarios for their possibility.

油墨粘度对卷对卷印刷有机光活性层的油墨转移速率和薄膜缺陷的影响机理

卷对卷(R2R)凹版印刷具有高的边缘分辨率、可图案化、高加工速度等优势,是制备大面积柔性有机太阳能电池(FOSCs)的一种可行技术.有机光活性层的薄膜质量是决定有机太阳能电池器件性能的关键.对于凹版印刷过程而言,墨水的转移是影响印刷薄膜厚度和质量的关键.本文深入研究了有机光活性层的墨水粘度对墨水转移率和薄膜缺陷的影响.我们开发了紫外可见光谱法,量化凹版印刷过程中墨水的转移率.通过对墨水的流变行为分析、流体动力学模拟和实验验证,深入研究了油墨粘度与油墨转移率、膜厚和膜均匀性之间的关系.结果表明,油墨粘度约为25 m Pa·s是R2R凹版印刷有机光活性层薄膜的适合粘度.通过对油墨配方的优化,我们制备了全R2R印刷FOSCs,其中1 cm^(2);电池的效率超过12%.

A machine learning-assisted multifunctional tactile sensor for smart prosthetics

The absence of tactile perception limits the dexterity of a prosthetic hand and its acceptance by amputees.Recreating the sensing properties of the skin using a flexible tactile sensor could have profound implications for prosthetics,whereas existing tactile sensors often have limited functionality with cross-interference.In this study,we propose a machine-learning-assisted multifunctional tactile sensor for smart prosthetics,providing a human-like tactile sensing approach for amputations.This flexible sensor is based on a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)-melamine sponge,which enables the detection of force and temperature with low cross-coupling owing to two separate sensing mechanisms:the open-circuit voltage of the sensor as a force-insensitive intrinsic variable to measure the absolute temperature and the resistance as a temperature-insensitive extrinsic variable to measure force.Furthermore,by analyzing the unsteady heat conduction and characterizing it using real-time thermal imaging,we demonstrated that the process of open-circuit voltage variation resulting from the unsteady heat conduction is closely correlated with the heatconducting capabilities of materials,which can be utilized to discriminate between substances.Assisted by the decision tree algorithm,the device is endowed with thermal conductivity sensing ability,which allows it to identify 10 types of substances with an accuracy of 94.7%.Furthermore,an individual wearing an advanced myoelectric prosthesis equipped with the above sensor can sense pressure,temperature,and recognize different materials.We demonstrated that our multifunctional tactile sensor provides a new strategy to help amputees feel force,temperature and identify the material of objects without the aid of vision.