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[Display omitted] • Pulsed laser radiation forms a graphene/SWCNT hybrid film with a developed surface. • Functionalization of graphene/SWCNT film with BaO nanoparticles reduces the work function. • Emission current of carbon film increased by 42 times due to functionalization with BaO. • Hybrid carbon film with BaO nanoparticles can be used as efficient field cathode. This paper presents the manufacturing technology of hybrid nanostructures based on a buffer layer of reduced graphene oxide (rGO) flakes with vertical single-walled carbon nanotubes (SWCNTs) and their bundles functionalized with BaO nanoparticles. Using density functional theory (DFT) calculations, supercells of rGO/SWCNT/BaO films were constructed and the patterns of the electron work function were revealed. It has been demonstrated that the electron work function is influenced by both the mass fraction of BaO nanoparticles and the inter-tube distance. Branched carbon nanostructure was formed using a pulsed laser irradiation. Fragmentation of BaO nanoparticles on the carbon surface was achieved. It was shown that after laser treatment, Ba(NO 3) 2 particles up to 200 nm in size were fragmented into smaller BaO nanoparticles with sizes of a few nanometers, covering the nanotubes. The field emission current–voltage characteristics (CVCs) were measured and showed a 42-fold increase in emission current compared to the nanostructure without BaO functionalization and laser treatment. BaO-functionalized hybrid carbon nanostructures are predicted to be efficient field cathodes, with a current density of at least 2 A/cm2, for use in X-ray tubes, field emission displays, and vacuum microwave devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel seed-mediated growth method was proposed for the synthsis of Ru@Ir core–shell NPs catalysts. • Typical sample model to study core–shell effect for the overall water splitting was provided. • Ir can induce the charge redistribution and optimize the binding strength. Water splitting, one of the primary strategies for advancing the utilization of hydrogen production, necessitates the input of external energies to initiate the reaction due to its thermodynamically uphill nature. Nevertheless, Ru-based compounds, which were widely used as benchmark anodic catalysts, facing significant drawbacks such as their susceptibility to dissolution, significantly restrict the overall water splitting efficiency. In this work, we introduce an approach for functionalization through combining Ru nanospheres with Ir to form a Ru@Ir core–shell structure (denoted as Ru@Ir core–shell NSs), which can activate the superior oxygen evolution reaction (OER) catalytic activity, and simultaneously inherit the hydrogen evolution reaction (HER) performance in all-pH condition. The work function difference between Ru and Ir promotes the necessary energetic impetus for electron migration from Ru to Ir, resulting in the charge redistribution. Density functional theory (DFT) calculations confirmed that the Ir shell, acting as an electron acceptor, could effectively trigger electron rearrangement, augmenting the ligand affinity of hydrogen and oxygen intermediates to attain the most favorable energy states, thereby accelerating the kinetics of hydrogen and oxygen evolution. Our suggested core–shell structure approach for manipulating interface charge distribution might find utility in creating other electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electron-Stimulated desorption of ultra-thin LiCl films on graphene. • Evolution of desorption kinetics through two desorption regimes. • Differences between Photon- and Electron-Stimulated desorption kinetics. Ultra-thin alkali halide films are an important substrate for studying single quantum objects at the atomic scale, as they serve as decoupling scaffolds. However, their stability upon exposure to electrons and photons, the most common probes used to study nanomaterials, is not fully understood. Here we present a study of the evolution of the structure of ultra-thin LiCl films, grown on graphene, upon low-energy electron irradiation by means of microspot-low-energy electron diffraction and microscopy. We find that the intensity of the LiCl diffraction spots irradiated at various electron energies follows a bi-exponential decay function, which can be rationalized by two different desorption regimes. In addition, we detect a change in the work function caused by the electron irradiation, confirming desorption of the LiCl film from the graphene layer. We understand the underlying mechanisms for the electron-induced desorption of the salt film in terms of the evolution of the elementary quasiparticles involved in the process: holes, excitons and F and H center pairs. Moreover, a direct comparison of the electron-induced and the soft X-ray photon-induced processes reveal that, in addition to LiCl desorption, the intercalation of lithium into graphene reported for X-ray induced desorption does not take place in electron-stimulated desorption. [ABSTRACT FROM AUTHOR]

Using first-principles theory, we theoretically investigate the most stable doping site of Ni atom on pristine InN monolayer and adsorption behavior of Ni-doped InN (Ni-InN) monolayer upon four noxious gases (NO, CO 2 , H 2 S and NH 3). Electron localization function (ELF), electron deformation density (EDD) as well as density of state (DOS) are considered to further understand the adsorption behavior of Ni-InN monolayer towards gas molecules. For possible application of our proposed material, work function and band structure of the isolated and gas adsorbed Ni-InN monolayer are analyzed as well. It is found that the Ni dopant prefers to be adsorbed on the pristine InN monolayer at the T N site with the lowest biding force (E b) of −3.02 eV. Four gases could be stably adsorbed on the Ni-InN monolayer surface wherein the chemisorption is identified due to the large adsorption energy (E ad) and charge transfer (Q T). ELF, EDD and DOS analyses corroborate the strong chemical interaction between Ni dopant and activated atoms in gas molecules. The band structure analysis provides the sensing mechanism of Ni-InN based resistance-type chemical sensor for detection of such four gaseous species. Our calculations can supply some guidance to explore promising novel gas sensors using group III-V nitrides in the gas-sensing field and environmental monitoring fields. Unlabelled Image • The Ni-doping behavior on InN monolayer is elucidated to enrich the principle of TM-InN. • Adsorption and sensing behaviors of Ni- InN monolayer upon common pollutant gases were analyzed. • Our calculation can accelerate development of chemical sensors in environment monitoring and industrial manufacturing. [ABSTRACT FROM AUTHOR]

In this work, we investigate on tunability of the local work function, morphological, structural, electrical, and optical properties of ZTO (zinc tin oxide) thin films. Using Kelvin probe force microscopy, we demonstrate that local work function of ZTO films can be tuned from 5.04 to 4.94 eV by varying the film thickness from 60 to 240 nm. X-ray diffraction studies reveal the amorphous nature of ZTO films, whereas AFM measurements confirm their granular nature. It is observed that the average grain size increases (from 24 to 58 nm) with increasing film thickness. In addition, a systematic red shift in the band gap as well as a decrease in the resistivity takes place with increasing thickness. Moreover, current-voltage characteristics show a systematic reduction in the turn-on potential and an enhancement in the leakage current with increasing ZTO film thickness. Above observations are explained in the framework of ZTO thickness-dependent variation in the grain size. This study will be of importance to make a transparent conductive oxide-based electrode in photovoltaic applications and ZTO-based optoelectronic devices. • Roles of film thickness on structural and optoelectronic properties of sputter-grown ZTO thin films are studied. • Red shift in the band-gap and a linear decrease in resistivity are observed with increasing film thickness. • It is observed that work function of films can be tuned from 5.04 to 4.94 eV with increasing film thickness and grain size. • The obtanied results can be attributed to thickness-dependent variation in grain size of ZTO films. • The present study will be useful to fabricate PV cells and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

For the heterostructure-based photocatalytic system, the most critical hindrance is to simultaneously achieve high photoelectric conversion efficiency and strong redox ability of photoinduced e−-h+ pairs. Herein, a direct double Z -scheme O-g-C 3 N 4 /Zn 2 SnO 4 N/ZnO ternary heterojunction was designed according to the band bending theory, which was prepared via a simple UV light irradiation method. The transformation from II-I-type to Z -Z-type heterostructure was attributed to the construction of dual build-in electric fields due to the interface charge transfer caused by the different work functions and the formation of the new bonds at the interface, which had been demonstrated by charge difference density. The prepared g-C 3 N 4 /Zn 2 SnO 4 N/ZnO composite exhibited enhanced photocatalytic performance for the photo-degradation of organic dyes and NO removal compared with the O-g-C 3 N 4 and Zn 2 SnO 4 N/ZnO. The improved photocatalytic activity was ascribed to the synergistic effects of double Z -scheme heterojunction, build-in electric fields and impurity levels, resulting in the wide light response range, rapid interfacial transfer, prolonged lifetime and strong redox ability of the photoinduced charge carriers. This work provided a new idea to design and synthesize the photocatalysts with high visible light activity and understand the enhanced photocatalytic mechanism. Unlabelled Image • Double Z-scheme O-g-C 3 N 4 /Zn 2 SnO 4 N/ZnO is synthesized by UV light irradiation. • Two build-in electric fields are constructed due to the interface charge transfer. • Dual impurity levels act as springboards for electron jump. • The lifetime of photoinduced e−-h+ pairs with strong redox ability is prolonged. • The enhanced photocatalytic activity is obtained for environmental purification. [ABSTRACT FROM AUTHOR]

The gas sensing performance of monolayer Hf 2 CO 2 was evaluated by means of first-principles calculation. Present results indicate that Hf 2 CO 2 sheet possesses high selectivity and remarkable sensitivity toward NH 3 molecule, by virtue of the moderate adsorption energy, sharply enhanced electronic conductivity beyond a specific bias voltage and appreciable work function change, as well as good stability, short recovery time. Moreover, the interaction of NH 3 with Hf 2 CO 2 can be enhanced by pre-adsorbed H 2 O molecule via forming hydrogen bonds between the adsorbates, while pre-covered O 2 molecule can barely affect the adsorption of NH 3 molecule. Particularly, NH 3 capture/release on monolayer Hf 2 CO 2 is predicted to be realized by applying external strains and/or electric fields. These appealing features signify monolayer Hf 2 CO 2 as promising nanomaterials for gaseous NH 3 detection and storage. Unlabelled Image • Monolayer Hf 2 CO 2 exhibits a high selectivity toward NH 3 molecules. • Monolayer Hf 2 CO 2 is greatly sensitive to NH 3 molecule. • Other molecules (SO 2 , H 2 O, CO 2) can enhance the adsorption of NH 3 by hydrogen-bond. • Applied external strains and electric-fields can realize NH 3 storage/release. [ABSTRACT FROM AUTHOR]

Charge separation and transport of the photo-generated electrons and holes form the basis to determine the kinetics of photocatalytic reactions. In the present work, the photo-generated electron is readily pulled from the photoactive catalyst by an electron sink (graphene) and transported to a site where the oxygen reduction reactions take place at a higher rate owing to better adsorption of other co-catalyst (γ-alumina). In this dual electron-cocatalyst modified TiO 2 -Al 2 O 3 -rGO photocatalyst, rGO works as the electron mediator, and Al 2 O 3 surface acts as the electron reduction site. The synergistic effect of rGO, and Al 2 O 3 as bi-cocatalysts showed higher photocatalytic performance than bare TiO 2 , TiO 2 -Al 2 O 3 and TiO 2 -rGO. This emphasizes the importance of both cocatalysts in electron separation and transfers where a single cocatalyst finds it difficult to carry out the crucial functions simultaneously. The modified TiO 2 -Al 2 O 3 -rGO photocatalyst under solar light reported 76% degradation of phenol in 5 h for 100 mg/L initial concentration. Results suggest that the presence of defects promote theoxygen reduction reactions (ORR) activity on the catalyst (TiO 2 -Al 2 O 3 -rGO) surface. The work also provides some insights to design high-efficiency solar propelled photo-catalysts based on work function theory. Unlabelled Image • Enhanced charge mobility in TiO 2 -rGO- Al 2 O 3 composite, a modified photocatalyst • Formation of Ti-O-Al structures on rGO with Al3+ penetration into TiO 2 lattice • Decreased recombination rate with formation of Oxygen defects in TiO 2 -rGO-Al 2 O 3 • Generation of higher OH radicals owing to synergistic effect of cocatalysts • Reduction of workfunction of TiO 2 by Al and rGO doping due to Fermi level shifts [ABSTRACT FROM AUTHOR]

This work presents a unique role played by swift heavy ion irradiation (SHI) on Co 3 O 4 - reduced graphene oxide (RGO) nanocomposites in modifying its optical, magnetic and surface electronic properties. On exposure to SHI, there occur delinking of the attached functional groups from RGO thus driving towards its purification. Raman spectra of irradiated samples confirm this result, where, an exponential decrease in the intensity ratio of D and G peaks of RGO with fluence occurs. At the same time, SHI generates extended defects in the form of latent tracks in decorated Co 3 O 4 nanoparticles, thus modifying the magnetic and surface electronic properties. Results obtained from magnetization studies using SQUID magnetometer and surface electronic response from scanning Kelvin probe reveals that a linear relationship could be established between magnetization and work function of the nanocomposite. An estimation for variation of defect-induced damage fraction with fluence is made from measured work function values. Here we present, study on Co 3 O 4 /RGO nanocomposites is new which reveals the independent response of each component of the nanocomposites towards swift heavy ion irradiation (SHI). On one hand SHI delinks the functional groups attached to reduced graphene thus purifying it. On the other hand, it generates defects leading to track creation in decorated magnetic nanoparticles thus modifying its magnetic properties. This study can play an important role for its applications as sensors or photo-catalysts etc. Unlabelled Image • Here, the nanocomposites are new which reveals the independent response of each component of the nanocomposites towards swift heavy ion irradiation (SHI). • SHI delinks the functional groups attached to reduced graphene thus purifying it. • The magnetic nanocomposites towards SHI irradiation is not studied before. [ABSTRACT FROM AUTHOR]

Possessing the ability to tune the work function and band gap of transparent conducting oxides (TCOs) is widely sought after, as it allows for improved band alignment in electronic and optoelectronic applications, enhancing overall device performance. Out of the many TCOs, Al-doped zinc oxide (AZO) has received considerable interest for electrode application due to its low electrical resistivity, high optical transparency in the visible regime, and room-temperature fabrication capability. In this study, we report on the effects of post fabrication air-annealing on the work function and band alignment of AZO deposited at room temperature by DC-magnetron sputtering. AZO films were air-annealed at temperatures varying from 25 °C (as-deposited) to 600 °C. The Fermi energy levels, work function values, surface chemistry, and optical band gaps of the AZO films were investigated via X-ray photoelectron spectroscopy (XPS) and UV–Vis spectroscopy. An increase of the work function from ~5.53 eV to ~6.05 eV is observed to take place over an increase of annealing temperatures from 25 °C (as-deposited) to 600 °C, determined to be the result of a decrease in carrier concentration through the promoted extinction of oxygen vacancies. Via XPS analysis, the increased extinction of oxygen vacancies was confirmed due to a notable shift from an oxygen-deficient state to an oxygen-sufficient state in the high resolution O 1s peaks, for which the activation energy was found to be 33.3 meV. Over the course of increasing annealing temperatures, the optical band gap saw a shift from ~3.55 eV to ~3.37 eV, following the Burstein-Moss phenomenon due to a decrease in carrier concentration, further verifying an increase in oxygen vacancy extinction. The reported results confirm that work function tuning of AZO films can be achieved through simple post-fabrication air-annealing. • Facile tuning of the work function of Al-doped ZnO films for band alignment • Identification of the native defect-based doping mechanism through XPS analysis • Identification of donor level location within the bandgap [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) represent a pivotal change in photovoltaics and are emerging as one of the most promising solar cell technologies for highly efficient and cost-effective solar energy production. In PSCs, the hole transport layer (HTL) plays a significant role in achieving high efficiency by improving charge collection and reducing recombination losses at the interface of the HTL/perovskite. Herein, we present a detailed investigation of the photovoltaic performance of PSCs by employing Fe-doped NiOx nanoparticles (NPs) as HTL. A simple solution method is adopted to synthesize Fe-doped NiOx NPs and their corresponding films are deposited by spin coating using Fe-NiOx inks at room temperature without any post treatment. As the obtained Fe-doped NiOx films exhibited an improvement in conductivity and work function, they resulted in an improvement in hole extraction and charge collection, while suppressing the charge recombination. Consequently, Fe-NiOx-based devices provided a significant enhancement in power conversion efficiency (PCE) of 17.57% compared to pristine NiOx of 15.41%. Flexible PSCs also showed an improvement in PCE from 13.37% for pristine NiOx to 14.42% for Fe-NiOx NPs. This work demonstrates that Fe-doped NiOx can be a promising HTL for fabricating highly efficient and flexible PSC production in the future. Unlabelled Image • Fe-doped NiOx nanoparticles have been studied in perovskite solar cells as a hole transport layer. • Fe-NiOx based devices have significantly improved power conversion efficiency up to 17.57%. • In the flexible PSCs, PCE of 14.42% for Fe-NiOx is obtained. [ABSTRACT FROM AUTHOR]

Abstract The Cs-only and Cs O co-adsorption process of Zn-doped GaAs nanowire surface with negative electron affinity are investigated utilizing the first-principles calculations based on density function theory. The 1Cs, 2Cs, 3Cs and 4Cs adsorption models are built to simulate the process of Cs-only adsorption, while 3Cs/1O, 3Cs/2O and 3Cs/3O models are established to study Cs O co-adsorption process. The adsorption energy, work function, Mulliken charge distribution and dipole moment for each adsorption model are discussed, respectively. During the Cs-only adsorption process, as increasing Cs coverage, the adsorption energy increases accordingly, indicating that the stability of Cs-only adsorption model is gradually weakened. After O adsorption on Cs-covered GaAs nanowire surface, the reduction of adsorption energy means that O incorporation can make the surface adsorption structure more stable. For Cs-only adsorption models, the work function obviously decreases owing to first dipole moment induced by Cs. However, excessive Cs adsorption on the Zn-doped nanowire surface will result in the 'Cs-kill' phenomenon. After O atom incorporation, the work function of Cs-covered nanowire surface further decrease, owing to the dual-dipole caused by Cs, O adatoms and nanowire surface atoms. The lowest work function can be obtained for 2O co-adsorption model, indicating the optimized atomic ratio of Cs/O is 3:2. These calculations provide an attempt to explore the adsorption mechanism of Cs O on nanowire surfaces, and the results are expected to be verified by the experimental results in the future. Graphical abstract Unlabelled Image Highlights • The Cs-only and Cs O co-adsorption process are investigated by first-principles. • Excessive Cs adsorption will result in the 'Cs-kill' phenomenon. • O incorporation can make the Cs-adsorbed GaAs nanowire surface more stable. • The dual-dipole induced by Cs O adsorption can effectively reduce the work function. • The optimized atomic ratio of Cs/O is 3:2. [ABSTRACT FROM AUTHOR]

Abstract In this contribution, using DFT calculations, we take systematic insights into the modified structural and electronic properties of two-dimensional (2D) blue phosphorus (blueP)/graphene-like (g-C 3 N) heterostructure via an external vertical strain. First, four types of representative stacking configurations are considered, i.e. , I, II, III and IV pattern, respectively. The calculated results indicate that the III configuration behaves more energetically, structurally and dynamic stable, under which it is chosen for the following calculations. The lattice constants of the individual blueP and g-C 3 N monolayers, along with their calculated band gaps, are consistent with the previous reported works, supporting the reliability of our theoretical models and computational details. Besides, the relatively large difference in the work function (W F) between the isolated blueP and C 3 N monolayers illustrates a charge transfer from g-C 3 N to blueP layer, in good accordance to the analysis of charge density difference and Mulliken atomic population of 0.16 e. A built-in electric field (E int) has been formed due to the charge transfer at the interface region, which can efficiently hinder the recombination of photongenerated electron-hole pairs, suggesting its significant application prospect in novel optoelectronic devices. A type-II band alignment is presented for the blueP/g-C 3 N heterostructure, demonstrating it great significance for the application in photoelectronic materials. Furthermore, tunable interlayer distances from 2.2 to 5.0 Å are employed to obtain modulated electronic properties for the blueP/g-C 3 N heterostructure. Interestingly, there occurs a semiconductor-to-metal transition when D larger than 4.6 Å, indicating its promising application in the field of electronics and nano-electronics. Moreover, tailored work functions can also be acquired by changing the interlayer distance. These findings together predict significant potential for the blueP/g-C 3 N heterostructure with tunable interlayer distances applied as next-generation nanoelectronic and optoelectronic devices, along with a photocatalyst. Highlights • The difference in work function between blueP and g-C 3 N monolayers illustrates a charge transfer from g-C 3 N to blueP. • A built-in electric field formed at the interface hinder the recombination of photongenerated mobility pairs. • The blueP/g-C 3 N heterostructure owns a type-II band alignment. • A semiconductor-to-metal transition is presented when tailoring D smaller than 2.2 or larger than 4.6 Å. • The work function as a function of interlayer distances implies the blueP/C3N heterostructure as a type of pholocatalyst. [ABSTRACT FROM AUTHOR]

Abstract Nano scale molybdenum disulfide (MoS 2) is a very promising material for the next generation electronics and energy storage devices. The active defect sites located at the periphery of the lattice may influence certain redox reactions, thus classifying it as an excellent non-noble metal catalyst. One effective approach to synthesize large scale MoS 2 films is through simple thermolysis of (NH 4) 2 MoS 4 precursor. Herein, a combined in situ X-ray and Ultra-Violet photoelectron spectroscopies (XPS/UPS) study has been carried out to follow the evolution of atomic composition, the surface chemical species and the electronic properties (Work Function and Ionization Potential) during the thermal decomposition of (NH 4) 2 MoS 4 salt in Ultra High Vacuum conditions. It was found that, up to 400C, thermal conversion of (NH 4) 2 MoS 4 salt to transient intermediates, across amorphous MoSx phase have been performed towards to MoS 2 out of significant percent of suphur active sites. The active sites have been decreased upon heating at higher temperatures. Assignment of the thermally evolved active species at defect sites and the correlation of surface atomic concentration combined with either the Ionization Potential or the Work Function of annealed MoSx nanoflakes makes this study a knowledgeable factor of awareness through electrocatalytic properties of MoS 2 -based nanostructures. Acknowledgement: We acknowledge support of this work by the project "National Infrastructure in Nanotechnology, Advanced Materials and Micro-/ Nanoelectronics" (MIS 5002772) which is implemented under the Action "Reinforcement of the Research and Innovation Infrastructure", funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). Highlights • In situ XPS/UPS study of the thermal decomposition of (NH 4) 2 MoS 4 salt in UHV was performed. • Evolution of the chemical state, composition and electronic properties of thermal conversion of (NH 4) 2 MoS 4 were studied. • Heating at temperatures 400-650C leads to the formation of MoS 2 with a significant decrease of active sites. • Correlation of surface concentration with the Ionization Potential and Work Function of annealed MoS x nanoflakes. [ABSTRACT FROM AUTHOR]

Graphical abstract Thickness dependent study of MBE grown β-MoO 3 nanoribbons in the light of quantum size effect and their application to field emission. Highlights • The growth and characteristics of defect free, mixed phase free metastable molybdenum trioxide (β-MoO 3) nanostructures on varied substrates and of different thicknesses and their effect on optical band gap, local work function and field emission has been reported. • As the total average thickness of the MoO 3 is increased from 5 to 30 nm, the aspect ratio is increased from 3.9 to 14.1 with resulting larger nanostructures (length varying from 58 nm to 195 nm) at higher thickness values of MoO 3. • We report band gap decreasing with increasing thickness (3.38 ± 0.01 eV for 5 nm thickness to 3.17 ± 0.01 eV for 30 nm thickness) of β-MoO 3 nanostructures. We determine electron effective mass and de Broglie wavelength in MoO 3 using experimental observations. • The Kelvin probe force microscopy (KPFM) measurements showed the average work function of different thickness of β-MoO 3 NRs and found increasing of work function from ≈5.397 ± 0.025 eV (for 5 nm thickness) to ≈5.757 ± 0.030 eV (for 30 nm thickness). • To best of our knowledge, the self-assembled grown β-MoO3 NRs sample (30 nm thickness) exhibits lowest turn-on field (2.5 V/µm for10 µA/cm2) and highest field enhancement factor. Abstract Monoclinic molybdenum trioxide (β-MoO 3) nanostructures (shaped like nanoribbons: NRs) were grown on Si(1 0 0), Si(5 5 1 2) and fluorine-doped tin oxide (FTO) by molecular beam epitaxy (MBE) technique under ultra-high vacuum (UHV) conditions. The dependence of substrate conditions and the effective thickness of MoO 3 films on the morphology of nanostructures and their structural aspects were reported. The electron microscopy measurements show that the length and the aspect ratio of nanostructures increased by, 260% without any significant change in the width for a change in effective thickness from 5 nm to 30 nm. NRs are grown along 〈0 1 1〉 for all the effective thickness of MoO 3 films. Similarly, when we increased the film thickness from 5 nm to 30 nm, the optical band gap decreased from 3.38 ± 0.01 eV to 3.17 ± 0.01 eV and the local work function increased from 5.397 ± 0.025 eV to 5.757 ± 0.030 eV. Field emission turn-on field decreased from 3.58 V/μm for 10 μA/cm2 to 2.5 V/μm and field enhancement factor increased from 1.1 × 104 to 5.9 × 104 for effective thickness variation of 5–30 nm β-MoO 3 structures. The β-MoO 3 nanostructures found to be much better than the α-MoO 3 nanostructures due to low work function, low turn on field and high field enhancement factor, and are expected to be useful applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The possibility of using 2D CoOOH as a sensor for H 2 O 2 and NH 3 is investigated. • H 2 O 2 is adsorbed more strongly over 2D CoOOH than NH 3. • The Electronic band gap of 2D CoOOH increases after interaction with H 2 O 2 and NH 3. • NH 3 increases the work function of 2D CoOOH by 2% and H 2 O 2 decreases by 10%. • Higher selectivity of 2D CoOOH observed for H 2 O 2 and NH 3 than CO, CO 2 , NO and NO 2. Abstract To the chain of development of 2D materials, recently synthesized ultrathin cobalt oxy-hydroxide (CoOOH) nano sheets gain potential interest due to its structural, electronic and other properties. We have studied the interaction mechanism of two toxic gases hydrogen peroxide (H 2 O 2) and ammonia (NH 3) adsorbed over 2D CoOOH to understand the role of 2D CoOOH as a toxic gas sensor. We employ first principles based dispersion corrected density functional calculations to study the sensing behavior of 2D CoOOH towards H 2 O 2 and NH 3 by calculating adsorption energy, electronic band structure, density of states (DOS) and work function. The electronic band structure, DOS and work function of 2D CoOOH are modulated after adsorption of H 2 O 2 and NH 3 molecules. Adsorption of gas molecules confirms the sensing behavior of 2D CoOOH towards these molecules and depicts its use in a sensing device. The full phonon dispersion curves and phonon density of states reveal the dynamical stability of 2D CoOOH. The calculated adsorption energy of H 2 O 2 and NH 3 molecules is −0.532 and −0.460 eV respectively which indicates the strong physisorption of these gases over 2D CoOOH. The ultrafast recovery time of 1239 and 1203 ns respectively were found for H 2 O 2 and NH 3 on 2D CoOOH. The work function which is 6.29 eV found for 2D CoOOH, decreases to 5.63 eV for H 2 O 2 as it follows the reduction process on 2D CoOOH, and increases to 6.44 eV for NH 3 molecules as it acts as oxidation gas on CoOOH. Our study reveals that the 2D CoOOH can be a better sensor for the H 2 O 2 and NH 3 gases than some traditional two-dimensional materials. [ABSTRACT FROM AUTHOR]

Highlights • Metallic octahedral prismatic 1T- and trigonal prismatic bulk crystal 2H-phase MoS 2. • The work functions are ∼3.5 eV and ∼3.3 eV for 1T- and 2H-phase MoS 2 respectively. • Photoluminescence intensity gradually decrease with synthesized temperature. Abstract Molybdenum di-sulfide thin films of thickness <1500 Å, were prepared by the dip-coating technique at different baking temperatures within the range 400 °C–450 °C using methanolic solution of ammonium molybdate and ammonium thiocyanate and hence studied their different properties using X-ray diffraction (XRD), UV-vis spectroscopy, Photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and Current-Voltage (I-V) relationship measurements. XRD result shows that the MoS 2 films are mixed metallic octahedral prismatic 1T- and trigonal prismatic bulk crystal 2H-phases. The I-V relationships show higher electrical conductivity for the films prepared at 400 °C and 450 °C than the films prepared at 425 °C. XPS measurement also shows the formation of mixed phases of MoS 2 thin films as revealed by XRD. We have estimated the valence band maximum (VBM) and work functions from higher and lower energy range of UPS (He-I) spectra of MoS 2 thin films prepared at 425 °C and 450 °C. The VBM are ∼4.4 eV & ∼4.2 eV and their work functions are ∼3.5 eV & ∼3.3 eV respectively that are correlated with conductivity and formation of mixed phases of MoS 2 thin films. [ABSTRACT FROM AUTHOR]

Graphical abstract The use of well-controlled defects provides an alternative approach to better performance of hybrid organic-inorganic devices. Highlights • Both defect and adsorbates at surface modify the work function of the oxide substrate. • MEA molecules adsorb at oxygen vacancy on TiO 2 (1 1 0) surface in a dissociated form. • On perfect TiO 2 (1 1 0) surfaces, MEA molecules adsorb at Ti rows. • The largest reduction in work function can be achieved by dissociative adsorption of MEA at oxygen vacancy. Abstract Controlling defects is one of the basic strategies for tailoring electronic structure of materials, which has not been explored that much yet for organic-inorganic hybrid systems. In this study, we investigated the control of work function of oxide electrode by defect-associated adsorption of molecules at the single-molecule level by means of scanning tunneling microscopy and first principle calculations. The equilibrium adsorption configuration of monoethanolamine (MEA, HO(CH 2) 2 NH 2), an effective coating for lowering the work function of an oxide electrode, varies as a function of surface coverage at TiO 2 (1 1 0) surfaces. Our results showed that defects at the oxide surface and intermolecular interactions dominate the stable configuration of adsorbates as well as work function of the system. The dissociative adsorption at O v was found to be more efficient at lowering the work function of TiO 2 (1 1 0) surface, suggesting that defect control can be used to improve the performance of organic-inorganic hybrid systems. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The irregular microstructures of the non-EP specimen are gradually removed by EP treatment. • New imperfections formed during EP treatment affect the surface properties and corrosion. • The surface roughness and nanohardness of the tubes gradually decreased with increased EP time. • The EWF and WCA of the tubes gradually increased with increased EP time. • The corrosion rate was reduced through EP treatment by approximately 60% compared to that of non-EP specimen. Abstract The purpose of this study is to investigate the effect of electropolishing (EP) time on the general corrosion of Alloy 690TT steam generator tubes in a simulated PWR primary water of at 330 °C. The surface roughness and nanohardness of the tubes gradually decreased, and the electron work function and water contact angle gradually increased with increasing the EP time. However, the effect of EP time on the surface properties mainly changed after 8 min. The corrosion rate was reduced through EP treatment by approximately 60% compared to that of the commercial as-received tube. [ABSTRACT FROM AUTHOR]

Highlights • The anti-corrosion property of nano-TiO 2 /Ni composite foil becomes worse after UV light illumination, while that of the micro-TiO 2 /Ni composite foil showed little changes. • UV illumination stimulated the nano-TiO 2 semiconductor, leading to elevated conductivity in favor of passing corrosion current. • The UV illumination increased the fraction of Ni 2 O 3 component in formed oxide film on the nano-TiO 2 /Ni foil, which is porous, loose, brittle and less protective compared to the naturally formed NiO film on Ni. Abstract Effects of ultraviolet (UV) light illumination on the corrosion behavior, surface state, and activities of electrodeposited micro-TiO 2 /Ni and nano-TiO 2 /Ni composite foils in 3.5% NaCl solution were investigated by means of polarization measurement, electrochemical impedance spectra (EIS), electron work function mapping (EWF) and XPS spectra analysis using an electrochemical system, the atom force microscopy (AFM) and X-ray photoelectric spectroscopy (XPS), respectively. The UV light illumination resulted in a considerable decrease in corrosion resistance of the nano-TiO 2 /Ni composite foil but showed much less effect on the micro-TiO 2 /Ni composite foil. Surface state analysis demonstrated that the UV illumination stimulated the nano-TiO 2 semiconductor with elevated conductivity in favor of passing corrosion current. The UV illumination increased the fraction of Ni 2 O 3 component in formed oxide film on the nano-TiO 2 /Ni foil , which is porous, loose, brittle and less protective, compared to the naturally formed NiO film on Ni. The changes in surface state were responsible for variations in the corrosion behavior of micro-TiO 2 /Ni and nano-TiO 2 /Ni composite foils caused by the UV light illumination. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • An unconventional use of Schrödinger equation is proposed. • A precise equation for work function is presented. • The values obtained directly from presented equation are compared with results obtained by other authors. Abstract A precise equation for the work function showing the dependence of the work function on basic metal parameters such as density, atomic mass and valence is presented in the article. Presented equation is a result of a combination of the unconventional use of Schrödinger equation and thorough analysis of experimental data related with the work function. Introduced model is applied to discuss the change of the work function due to the number of valence electrons with respect to transition metals. The values obtained directly from the equation are compared with the results obtained by other authors specializing in these issues. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel D-A type Z-scheme heterojunction photocatalyst was fabricated. • Interfacial electric field of CCN/Pt 6 NCs was formed via donor–acceptor interaction. • Interfacial electric field provides the driving force for Z-scheme charge transfer. • The CCN/Pt 6 NCs photocatalyst presents enhanced photocatalytic activity and favorable photostability. Enhancing the solar energy conversion of metal-free graphitic carbon nitride (g-C 3 N 4) based photocatalyst remains a great challenge. Herein, a novel Z-scheme heterojunction photocatalyst is constructed by in-situ anchoring Pt 6 NCs on carbon self-doping g-C 3 N 4 (CCN/Pt 6 NCs) for boosting photocatalytic H 2 evolution activity. Remarkably, the optimized CCN/Pt 6 NCs photocatalyst exhibits high H 2 evolution rate of 6.32 mmol·h−1·g−1 and 36.25 mmol·h−1·g−1, which is ≈150.5 and ≈412 times than that of pristine CN under visible light (λ > 420 nm) and full solar spectrum irradiation, respectively, outperforming majority of the reported g-C 3 N 4 -based photocatalysts. Systematic characterizations have revealed that CCN with delocalized electrons and larger the work function is deemed to be a preferable electron-acceptor. Meanwhile, Pt 6 NCs with appropriate HOMO-LUMO level is regarded as an electron-donor. Theoretical and experimental works reveal that the favorable photocatalytic performance of CCN/Pt 6 NCs heterojunction is mainly attributed to the giant internal electric field induced donor–acceptor interaction, which achieves Z-scheme charge transfer mechanism. This work opens up new insights for rational fabrication of metal-free g-C 3 N 4 based photocatalysts to boost the solar energy conversion. [ABSTRACT FROM AUTHOR]

Quantum mechanical calculations of the structure and properties of a range of Ba x Sc y O z adsorbate layers on W (0 0 1), (1 1 0), and (1 1 2) surfaces reveal the importance of O chemical potential in controlling the surface structure, surface energy, equilibrium crystal shape, and work function of W particles in Sc-containing (scandate) cathodes. Using the experimentally observed shape of W particles present in a high-emission scandate cathodes as a constraint, screening of ∼ 2000 possible combinations of surface configurations reveals that the observed W grains are terminated with Ba 0.50 O/W (0 0 1) , Ba 0.25 O/W (1 1 0) and Ba 0.50 O/W (1 1 2) surfaces, and were equilibrated in an O-poor environment with μ O between ∼ −8.5 and −8.0 eV/at. Examination of the surface structures studied reveals that competing Ba-O and O-W interactions control the net surface dipole and that this dipole directly correlates with computed work functions, implying that the surface dipole alone is sufficient to explain low work functions observed for scandate cathodes. Analysis of the present results suggests that the role of Sc in scandate cathodes is to tune μ O and that difficulties in manufacturing scandate cathodes likely arises from variability in the availability of O at the cathode surface during activation and operation. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2 ) has attracted great attention, with scientific and technological advances over the past few decades due to its reversible metal-insulator transition at 340 K. However, the high phase transition temperature ( T c ) of VO 2 limits its practical applications. Our first-principles calculations show that VO 2 (1 1 0) surfaces with adsorbed noble metals (Ag, Au, Pt) exhibit a lower work function compared with the clean surface and further induces a lower T c due to charge transfer from the noble metals to the VO 2 (1 1 0) surface. However, the work functions of the VO 2 (1 1 0) surfaces after the incorporation of noble metals are higher than that of the clean surface. In addition, the results of formation energies of various configurations show that the VO 2 (1 1 0) surface with the adsorption and incorporation of Ag is energetically more favorable than those with Au and Pt. Therefore, it may be concluded that the adsorption and incorporation of noble metals can not only tailor the work function of VO 2 , in turn realizing the rational tuning of T c of VO 2 , but also stabilize the structures of VO 2 thin films. These results provide guidance for further exploration of VO 2 -based optical switching devices and smart windows. [ABSTRACT FROM AUTHOR]

Low energy electron emission microscopy (LEEM) was used to measure local transition energy that was directly correlated to electron work function (EWF) of multiphase manganese-aluminum bronze alloys. We developed color mapping to distinguish the EWF of multiple phases and clarified that the EWF were in the following order: EWF of α > EWF of β > EWF of κ (EWF α  > EWF β  > EWF κ ). De-alloying corrosion took place due to the micro-galvanic cell at grain boundaries before it propagated into the β phase that had lower EWF than the α phase. The α phase was a stable phase because it contained high Cu while the β phase contained high Al and Mn. In addition, XRD analysis showed that the texture coefficient of the β phase revealed that almost all of the grains had (2 2 0) orientation, the lowest EWF compared to (1 1 1) and (2 0 0). Furthermore, transmission electron microscopy illustrated that there were fine Cu 3 Mn 2 Al precipitates in the Cu 2 MnAl matrix of the β phase. These precipitates formed micro-galvanic cells which played an important role in accelerating de-alloying corrosion. [ABSTRACT FROM AUTHOR]

Hybrid emitters consisting of ZnO nanowires decorated with Zn nanoflakes were prepared for electron emission applications. The ZnO nuclei, having a pyramidal shape, were deposited on the ZnO:Al buffer layer, which offered surface protrusions for vertical nanowire growth. The Zn hexagonal nanoflakes, having thicknesses of 15–20 nm, were decorated to increase the conductivity and number of emission sites of the ZnO nanowires. The field enhancement factor increased from 8623 to 18108 and the work function was reduced from 5.3 to 3.35 eV after decorating the nanowires with Zn nanoflakes. A low turn-on field of 0.65 MV/m and high current density of 1.46 mA/cm 2 were obtained. The current density variation measured at 350 V was less than 23% over a measurement time of 180 min. [ABSTRACT FROM AUTHOR]

The (001) surface of cubic silicon carbide (3C SiC) after cleaning, Ar sputtering and three different wet chemical etching procedures was thoroughly investigated via (angle resolved) XPS, HREELS, and LEED. While Ar sputtering was found to be unsuitable for surface preparation, all three employed wet chemical etching procedures (piranha/NH 4 F, piranha/HF, and RCA) provide a clean surface. HF as oxide removal agent tends to result in fluorine traces on the sample surface, despite thorough rinsing. All procedures yield a 1 × 1 Si–OH/C–H terminated surface. However, the XPS spectra reveal some differences in the resulting surface states. NH 4 F for oxide removal produces a flat band situation, whereas the other two procedures result in a slight downward (HF) or upward (RCA) band bending. Because the band bending is small, it can be concluded that the number of unsaturated surface defects is low. [ABSTRACT FROM AUTHOR]

[Display omitted] • Correlation of catalytic activity to band center and work function. • Al 5 @N 4 -DVG as par to Ru single atom catalyst with ΔG max of 0.78 eV. • Exclusive NRR selectivity on Al 5 @N 4 -DVG electrocatalyst. Density Functional Theory (DFT) investigation on the most earth-abundant Al-based catalysts, has been conducted detailing its electronic properties and catalytic efficacy for nitrogen reduction at ambient condition. The Al-based catalysts have been modulated to perform as par a highly performing, but rare, Ru-single atom catalytic center by varying number of Al atoms, shape, and size. The coalesce of band-center, work function and electronic properties in metal atom catalysts along with N-N bond activation has been demonstrated to be responsible for an efficient nitrogen reduction reaction (NRR) with ΔG max of 0.78 eV in Al 5 supported on N-doped double vacancy graphene (Al 5 @N 4 -DVG) catalyst. Electron localization function analysis has shown a weak physisorption of N 2 in the Al-based catalysts. Projected Density of States (PDOS) illustrates the enhancement of aluminium electron density in Al 5 @N 4 -DVG led to enhanced orbital densities overlap of Al p and N p electrons. The Bader charge analysis and electronic analysis of the intermediates show efficient electron gain on the N atoms, leading to formation of NH 3 from the N x H y intermediates in Al 5 @N 4 -DVG catalyst. [ABSTRACT FROM AUTHOR]

The adsorption of alkali-metal atoms on GaN nanowires photocathode was investigated by using first principles with density functional theory. The calculation of electronic and optical properties indicates that alkali metal adsorbed GaN nanowires are direct band gap semiconductor, and the band gap of GaN nanowires could be decreased by alkali metal adsorption. A new surface state near the Fermi level results from the Ga, N and alkali metal hybridization, which leads to form a metal electrical conductivity for GaN nanowires. More importantly, alkali metal adsorption can decrease the work function of GaN nanowires. Furthermore, the absorption spectrum of GaN nanowires is red shifted and moves to lower energy side because of alkali metal adsorption. Accordingly, this study will provide the theoretical basis for producing the alkali metal adsorbed GaN photoelectric devices. [ABSTRACT FROM AUTHOR]

Interactions between graphene and anatase TiO 2 (110) surface with and without oxygen vacancy ( V O ) are investigated by first-principle calculations. The close but non-destroyed contact at interface facilitates photo-excited electron transfer between graphene and TiO 2 . With a work function (WF) smaller than perfect TiO 2 substrate, graphene is typically electron depleted. However, the introduction of surface V O decreases the WF of TiO 2 remarkably and smaller than graphene, which induces electron transfer with reversed direction and accumulate at graphene sheet. Especially, the evident red shift of the optical absorption edge and obviously enhanced absorption intensity in the visible region for both combined configurations illustrate the enhancement mechanism of photocatalytic performance. [ABSTRACT FROM AUTHOR]

The surface modification of graphite by oxygen plasma was investigated experimentally (X-ray diffraction, nanoparticle tracking analysis, laser desorption ionization mass spectrometry, thermogravimetry, water contact angle) and by molecular modelling (Density Functional Theory). Generation of surface functional groups (mainly OH surf ) leads to substantial changes in electrodonor properties and wettability gauged by work function and water contact angle, respectively. The invoked modifications were analyzed in terms of Helmholtz model taking into account the theoretically determined surface dipole moment of graphite—OH surf system ( μ = 2.71 D) and experimentally measured work function increase (from 0.75 to 1.02 eV) to determine the OH surface coverage (from 0.70 to 1.03 × 10 14 groups cm −2 ). Since the plasma treatment was confined to the surface, the high thermal stability of the graphite material was preserved as revealed by the thermogravimetric analysis. The obtained results provide a suitable quantitative background for tuning the key operating parameters of carbon electrodes: electronic properties, interaction with water and thermal stability. [ABSTRACT FROM AUTHOR]

Large area, Si-nanofacets are synthesized by obliquely incident low energy Ar + -ion-beam bombardment at room temperature (RT). The field emission properties of such nanofacets are studied based on current–voltage measurements and the Fowler–Nordheim equation. Low turn-on field with relatively high current density is obtained due to the shape and an overall rough morphology. We demonstrate a tunable field emission property from the silicon nanofacets by varying the ion exposure time. Atomic force microscopy (AFM) in conjunction with Kelvin probe force microscopy (KPFM) measurements provide the information on the aspect ratio and confirms the presence of native oxide layer near the apexes of the facets, respectively. The inhomogeneous oxidation leads to an increase in the local work function at the apexes of the facets, restricting the electron emission from the same. Due to its room temperature fabrication, the present method is of great significance to the low-cost vacuum field emission devices fabrication. [ABSTRACT FROM AUTHOR]

The density functional theory calculation has been conducted to investigate the structural and electronic properties, including the adsorption energies, bond structures, work functions, charge transfer behaviors, and density of states for pristine, Ni-, and Fe-embedded capped (5, 5) single-walled carbon nanotubes (SWNTs) with different coverage of atomic hydrogen, oxygen, and nitrogen adsorptions. Ni or Fe embedment enhances the adatom-SWNT interactions significantly for three kinds of gas atoms with the increases of the adsorption energies. The SWNT work function drops with H adsorption, while Ni or Fe embedment assists further the reduction. When increasing the coverage, the adsorption energy decreases and the work function climbs for O adsorption, but the nitrogen adsorption energy increases. The Bader charge transfer analysis implies that the cap possesses higher oxygen reduction activities than the tube, and the density of states analysis shows that Ni or Fe embedment deepens the C-adatom hybridizations. [ABSTRACT FROM AUTHOR]

In present study, electrostatic force microscopy (EFM) is used to estimate the intrinsic work function of few layer graphene (FLG) transferred on SiO 2 (300 nm)/Si (500 μm) substrate. This FLG has been prepared by using the mechanical exfoliation technique. In exfoliated FLG, adhesive residues are always left from scotch tape on its surface. These residues as well as SiO 2 substrate could modify the work function due to the formation of dipoles on the surface. Taking the effect of adhesive into account, FLG is pre-charged and then scanned with a tip biased with dc voltage. Intrinsic work function of FLG is determined and found to be 4.52 ± 0.1 eV. [ABSTRACT FROM AUTHOR]

In this paper, thermal-assisted field emission properties of barium oxide (BaO) nanowire synthesized by a chemical bath deposition method were investigated. The morphology and composition of BaO nanowire were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SED), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX) respectively. The turn-on field, threshold field and the emission current density could be affected relatively due to the thermal-assisted effect when the electric field was applied, in the meanwhile, the turn-on field for BaO nanowire was measured to be decreased from 1.12 V/μm to 0.66 V/μm when the temperature was raised from 293 K to 593 K, whereas for the threshold field was found to decrease from 3.64 V/μm to 2.12 V/μm. The improved performance was demonstrated due to the reduced work function of the BaO nanowire as the agitation temperature increasing, leading to the higher probability of electrons tunneling through the energy barrier and enhancement of the field emission properties of BaO emitters. [ABSTRACT FROM AUTHOR]

[Display omitted] • The uniformity Cu 2 O film with (100) and (111) facets exposed was synthesized via an electrodeposition process. • (100) facet exposed Cu 2 O has a significantly SERS enhancement, as well as the low LOD for 4–NBT molecules. • The superior SERS activity of Cu 2 O(100) can be ascribed to the relatively low work function and enhanced charge transfer ability. Semiconductors have been extensively studied for SERS applications owing to the advantage of inexpensive, nontoxic and easy fabrication. However, the facile design of uniformity substrates with enhanced charge transfer and SERS activity are highly desirable. Herein, we reported the fabrication of Cu 2 O films with (100) and (111) facets exposed by adjusting the pH value of electrolyte. When using 4–NBT as probe molecule, the Cu 2 O(100) exhibits an improvement of enhancement factor about 2.7 times than Cu 2 O(111), as well as relatively low limit of detection up to 1 × 10−7 M. All calculated relative standard deviation values are lower than 5 %, which demonstrates the uniformity and reproducibility of as–prepared Cu 2 O films. UPS analysis reveals that (100) facet possesses lower electron work function, and can promote the efficient interfacial charge transfer. Furthermore, First–principles calculation confirms that (100) facet possess the better adsorption ability for 4–NBT, which can transfer more electrons from Cu 2 O to the molecule due to its lower work function, and thus resulting in the remarkable improvement of SERS activity. This research will offer more choices for the design of uniformity semiconductor substrates with enhanced SERS sensitivity based on crystal facet engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption and electronic properties of gases on nanoporous CN monolayer were studied. • NO, SO 2 , H 2 S, and NH 3 molecules are weakly chemisorbed on the monolayer. • Adsorption of NO, H 2 S and NH 3 efficiently tunes electronic properties of CN monolayer. • CN monolayer has high sensitivity and selectivity to NO, H 2 S and NH 3 with moderate recovery time. • CN monolayer as a good candidate for NO, H 2 S, NH 3 gas sensors at room temperature. To explore the possibility of the nanoporous CN (p-CN) monolayers as high-performance gas sensors, the adsorption, electronic properties and gas-sensing performance of various gases on the p-CN monolayers have been studied by first-principles methods. Only NO, SO 2 , H 2 S and NH 3 have weak chemisorption on the monolayer, which and the physical adsorption of NO 2 and C 2 H 4 changed efficiently the electronic properties and work function of p-CN monolayer. The p-CN monolayer towards NO, NH 3 , and H 2 S gases has comparatively high sensitivity, while has quite low sensitivity towards other gases. The characteristics on the I-V curves and work function can effectively distinguish various gases. The recovery time for NO, NH 3 , and H 2 S is about 4.1 s, 0.27 s, and 0.018 s at 300 K, respectively, which is fairly moderate for the reuse of the CN-based sensor for NO, NH 3 , and H 2 S detection. However, the over-short (or over-long) recovery time for NO 2 and C 2 H 4 (<10−6 s) (or SO 2 , c. 35 min) gravely hinders the p-CN-based gas sensors for these gases monitoring. Therefore, the p-CN monolayers as reusable gas sensors have high sensitivity and selectivity at room temperature for NO, H 2 S and NH 3 detection. [ABSTRACT FROM AUTHOR]

The coupling of metal-metal interaction and coordination effect in dual-Pd-site catalysts has more opportunities to adjust the electronic structure of Pd atoms, thus optimizing the adsorption strength of O-containing intermediates on the active site and improving the catalytic activity of ORR. [Display omitted] • We constructed single/dual-Pd-site catalysts coordination with C, B and N on graphene, and compared the ORR performance with Pd(1 0 0). • The coordination with B makes Pd with high electron density and the lowest work function, which facilitates electron transfer to O 2. • The dual-Pd-site catalysts have a higher activation degree of O–O bond, which promotes the cleavage of the O–O bond. Coordination engineering is a promising strategy to improve the electrocatalytic ORR activity of single/dual-metal-site catalysts. In this work, the electrocatalytic processes of graphene-supported C, B and N coordination single/dual-Pd-site catalysts were investigated by systematic density functional theory (DFT) calculations, and compared with Pd(1 0 0). The results show that different coordination environments (C, B and N) can strongly affect the adsorption and reaction characteristics of O 2 and O-containing intermediates. The B coordination (PdB 4 /C and Pd 2 B 6 /C) catalysts are located in the left region of the volcano, removal of *OH is the potential determining step (PDS), while the C and N coordination (Pd 2 C 6 /C, PdN 4 /C and Pd 2 N 6 /C) catalysts are located in the right region, where the formation of *OOH is the PDS. In addition, Pd 2 B 6 /C catalyst greatly promote the cleavage of O–O bond, enabling the ORR to occur through both dissociative and associative mechanisms. Among all catalysts, Pd 2 B 6 /C stands out with a low overpotential of 0.48 V and shows good ORR performance. Therefore, it has great potential to replace Pt-based catalysts. Finally, the origin of ORR activity was revealed by analyzing the electronic structure and work function, which provided guidance for the design of effective ORR electrocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of corrosion mechanism assisted by first-principle calculation. • Correlation between interface properties and electrochemical stability. • Reinforcement on interface stability by TiC/TaC and TaC/C contacting. • A low corrosion current density of 0.28 μA cm−2 for the TaC/TiC/TaC/C coating. In this study, first-principle calculation is used to investigate the TiC (1 1 1)/TaC (1 1 1) interface in terms of surface energy, work function, adhesion energy, and electronic structure. Compared with TaC (1 1 1), the TiC (1 1 1) surface shows a higher surface energy and a lower electronic work function. The surface passivation of TiC can be achieved by covering the TaC layer. Besides, the interface bonding configuration of TiC (1 1 1)/TaC (1 1 1) that relates to corrosion resistance is studied in detail. In experimental verification, a set of TiC-based coatings are investigated by potentiodynamic polarization, potentiostatic polarization, and impedance. Compared with pure TiC and TiC/C coatings, the TaC/TiC/TaC/C structure exhibits the lowest corrosion current density of 0.28 μA cm−2 and the lowest corrosion tendency. SEM observation also reveals its minimal morphological damage after potentiostatic polarization. The modified multilayer coating presented in this work is successfully used as the protecting structure of stainless-steel bipolar plate, which may be of great significance to the light weight metallic bipolar plate in proton exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

VO 2 is an attractive material for application to thermochromic optoelectronic devices such as smart windows, and Ag/VO 2 double-layered structure can effectively decrease the phase transition temperature ( T c ) of VO 2 thin film, which is very important for practical application of VO 2 . Previous works has shown that the decrease in phase transition temperature ( T c ) seems to be relevant with the work function of VO 2 in Ag/VO 2 double-layered thin film, although the underlying mechanism of tuning its T c by Ag incorporation and adsorption on the VO 2 (1 0 0) surface has been rarely investigated. Our first-principles calculations reveal that the adsorption of Ag atoms on the VO 2 (1 0 0) surface rather than incorporation of Ag exhibits a lower work function, which is ascribed to an integrated effect of charge transfer from Ag to VO 2 (1 0 0) surface and enhanced surface dipole moment. The results suggest that the decrease in work function of VO 2 with Ag adsorption favors the reduction in T c . The current findings are helpful to understand the fundamental mechanism for yielding high-efficiency VO 2 -based optoelectronic devices. [ABSTRACT FROM AUTHOR]

The effect of grain refinement on corrosion resistance of alloy 690 was investigated. The electron work function value of coarse grained alloy 690 was higher than that of nano/ultrafine grained one. The grain refinement reduced the electron work function of alloy 690. The passive films formed on coarse grained and nano/ultrafine grained alloy 690 in borate buffer solution were studied by potentiodynamic curves and electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The results showed that the grain refinement improved corrosion resistance of alloy 690. This was attributed to the fact that grain refinement promoted the enrichment of Cr 2 O 3 and inhibited Cr(OH) 3 in the passive film. More Cr 2 O 3 in passive film could significantly improve the corrosion resistance of the nano/ultrafine grained alloy 690. [ABSTRACT FROM AUTHOR]

Hafnium carbide (HfC) is regarded as one of the most promising cathode materials for field emission. But the experimental results did not provide a detail picture of the surface properties. In this work, we perform an ab initio study of the surface energies and work functions for the (1 0 0), (1 1 0), (1 1 1), (2 1 0), (3 1 0) and (3 1 1) surfaces of hafnium carbide. For the polar surface of (1 1 1) and (3 1 1) plane, a new method is taken to calculate the surface energy of the different surface terminations. The results indicate that the Hf termination surface is most stable, which are consistent with the experimental results. Additionally, we focused in particular on oxygen atom induced work function changes on HfC(1 1 1) plane as a function of coverage. An unexpected decrease of the work function is found at low coverage, and a reasonable resolution for this anomaly is given based on the method of Roman et al. [ABSTRACT FROM AUTHOR]

The effect of reactive gases—oxygen and hydrogen—on the tunable work function of Al-doped ZnO (AZO) films was studied. An increase in the work function with an increase in the oxygen flow rate was mainly interpreted as reflecting a decrease in the carrier concentration, which was attributed to the filling of oxygen vacancies. However, a decrease in the carrier concentration would result in the resistivity increasing sharply. This article presents a new concept for improving the performance of organic light-emitting diodes (OLEDs) through easy and effective hole injection from a multilayer AZO anode to the organic layer. A bilayer AZO film prepared using a tunable work function technique was used to modify the surface of AZO anodes and to ensure that the anodes had low resistivity. The AZO anode stacked with high-work-function AZO films, similar to hole transport buffer layers, had a low turn-on voltage of 2.89 V, and its luminance efficiency and power efficiency were 5.01% and 6.1% greater than those of tin-doped indium oxide anodes used in OLEDs. [ABSTRACT FROM AUTHOR]

The electrical resistivity, structure, and composition and work function of ZnO thin films deposited by sputtering and post-treated with He plasma were studied. First, the treating effects of ZnO films by He, Ar and H 2 plasmas were compared. The electrical resistivity depended on the treated type of plasmas, the treated powers and times, and the thickness of film. The Ar plasma has the highest ion moment energy to disrupt the Zn-O bonding during treatment. The injection of H in ZnO can also act as the shallow donors to decrease the resistivity besides by desorption of weakly bonded oxygen species. The H 2 and He plasmas have the etching effects on the surface of ZnO films at higher power and time. For the ZnO films before and after optimized He plasma treating, the electrical resistivity decreased from 10 4 to 7.0 × 10 −3 Ω cm, the carrier concentration increased from 7.0 × 10 15 to 1.8 × 10 2 ° cm −3 , and the interstitial Zn and O vacancy deficiencies increased from 29.1 to 58.7% and 52.1 to 71.4%, and the work functions reduced from 8.5 to 7.6 eV, but with no significant change of crystal structure. [ABSTRACT FROM AUTHOR]

Electron work function (EWF), adhesion and friction coefficient of three passive alloys were investigated. During dry sliding tests, surfaces having higher work functions showed larger coefficients of friction. While under oil-lubricated sliding condition, the trend was reversed. It appears that when the surface passive film was damaged, the surface broken atomic bonds became active, leading to larger friction. However, under the oil-lubricated sliding condition, the passive film was retained, resulting in a different trend. Surface adhesive forces of freshly polished surfaces and etched ones were measured using an atomic force microscope. Results of the adhesion measurement are consistent with the behaviors of the alloys observed during the friction tests. [ABSTRACT FROM AUTHOR]

Adsorption and formation of ordered structures of Ho atoms on Mo(1 1 2) surface are studied by LEED, work function measurement and first-principle calculations. It is found that the most favorable energetically periodic structure is (3 × 2) structure at coverage of θ = 2/3, in which separation of Ho atoms is very close to metallic diameter of holmium. LEED measurements and the ground state analysis have revealed that structures (4 × 1) with θ = 3/4 and (5 × 1) with θ = 4/5 are also favorable. There are no ordered structures at low coverages although the long-range indirect interaction between adatoms is present. [ABSTRACT FROM AUTHOR]

The effect of low energy Ar ion bombardment on the structure and field emission properties of CuO nanowires was studied. The morphology and structure were characterized by scanning electron microscopy and high resolution transmission electron microscopy. Non-crystallization of the nanowire was found after bombardment, which was due to the diffusion of the defects induced by knock-on ions. The work function of nanowires decreased after bombardment which was attributed to the preferential sputtering of oxygen. Field emission measurements showed that after bombardment with different energy the turn-on field decreased first and then increased with increasing ion energy. The lowest turn-on field was obtained with the optimal ion energy of 215 eV. The typical turn-on fields of the as-grown samples and samples after Ar ion bombardment with energy of 215 eV were about 6.5 V/μm and 5.25 V/μm, respectively. The lowered field emission turn-on field was attributed to the increase of field enhancement factor and decrease of work function. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu/SrTiO 3 composite is fabricated by a facile spin-coating method. • The charge transfer of Cu/SrTiO 3 is investigated via an in-situ KPFM approach. • The reversible charge transfer under external bias is proposed by experiment and theoretical calculation. Supported metal–metal oxide heterojunctions are ubiquitous in designing highly efficient catalysts for energy conversion and storage devices. The interaction between metal and supports has attracted significant interest in developing novel catalysts. Especially, surface charge distribution and charge transfer between metallic particles and oxide supports are vital for understanding the catalytic reaction. Here, we investigate the effect of the external electric field and circumstances on the charge transfer within the Cu/SrTiO 3 heterojunction. Based on the in-situ Kelvin probe force microscopy (in-situ KPFM) and density functional theory (DFT) calculations, we observe and analyze that the specific behavior of charge transfer could be switched by reversing the external electric field, indicating the role of Cu microparticles could be altered electrically between donor and acceptor. Moreover, the circumstances surrounding the Cu/SrTiO 3 heterojunction influenced the transfer of charge as well. We also present a comprehensive model of the observed behavior based on work functions and electronic structure of Cu/SrTiO 3 heterojunction. Our work provides insight into the charge transfer in metal–semiconductor heterojunction and is helpful to design highly active heterostructured catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A RHEA coating possesses a single-phase BCC structure with an average grain size ∼12 nm. • At a given F− ion, the corrosion resistance of the RHEA coating is higher than that of CP-Ti substrate. • EN analysis indicates that the RHEA coating always stays passive state in PEMFC operating environments. • The RHEA coating show a stronger ability to repel aggressive F− ions with respect to bare CP-Ti. • The RHEA has a high EWF values and a lowtendency to exchange electrons with anions. A TiZrHfMoW refractory high entropy alloy (RHEA) nanocrystalline coating was engineered onto a commercially pure Ti (CP-Ti) substrate to enhance its corrosion resistance for potential application as bipolar plates for use in proton exchange membrane fuel cells (PEMFCs). The as-prepared RHEA coating possesses a single-phase BCC structure with an average grain size of ∼12 nm. The electrochemical corrosion behavior of the RHEA coating in simulated PEMFC environment, with varying HF concentrations, was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), in conjunction with detection and analysis of electrochemical noise (EN). The potentiodynamic polarization and EIS measurements of the RHEA coating indicated that, at a given HF concentration, the RHEA coating exhibits a higher E corr , a lower i corr and a larger resistance value compared to uncoated CP-Ti. The analysis of the EN signals indicated that the RHEA coating has low correlation dimensions (below 1.4) and small instantaneous amplitudes in the Hilbert spectra, confirming that the RHEA coating was capable of maintaining a stable passive state, regardless of the HF concentrations. Furthermore, the electron work function of TiZrHfMoW RHEA was derived by first-principles calculations to unravel the physics origin of the corrosion resistance of the RHEA coating. [ABSTRACT FROM AUTHOR]

[Display omitted] • The C 7 N 6 monolayer physically adsorbs all test gases, hindering its application for gas sensing and capturing. • The Li decoration on the C 7 N 6 monolayer is energetically and kinetically favorable. • The Li-C 7 N 6 monolayer is highly sensitive to toxic gases (NO 2 , SO 2 , NO and NH 3) • The Li-C 7 N 6 monolayer would be a promising potential gas sensing and capturing materials for NO and NH 3 gases. • The Li-C 7 N 6 monolayer is an effective scavenger of NO 2 and SO 2 in specific scenarios in dry environments. We have investigated the geometrics, energetics, charge transfer, electron localization function (ELF), electron difference density (EDD), work function, electronic and gas sensing and capturing properties of the pure and metal-decorated C 7 N 6 monolayers toward gases like NO 2 , SO 2 , NO, NH 3 , H 2 O, H 2 S, CO, CH 4 , CO 2 and N 2 by means of first-principles calculations. It is discovered the pristine C 7 N 6 monolayer is not suitable for gas sensing and capturing materials. The Li decoration on the C 7 N 6 monolayer is energetically and kinetically favorable, and remarkably enhances the adsorption strength of toxic gases (NO 2 , SO 2 , NO, and NH 3), which in turn significantly influences the electronic properties (particularly conductivity) of the Li-decorated monolayer with apparent charge transfer and changes in work functions. Based on the analysis of recovery time, adsorption strength, changes in electronic properties and work function, the capture capacities and the influence of humidity on the sensing and capturing properties of NO 2 , SO 2 , NO, and NH 3 on the monolayer, the Li-decorated C 7 N 6 monolayer would be a promising potential of highly sensitive gas sensing and capturing materials for NO and NH 3 gases, and an effective scavenger of NO 2 and SO 2 in specific scenarios in dry environment that call for experimental evaluation. [ABSTRACT FROM AUTHOR]