The role of the boron (B) doping induced defect state in the PEC process is still unclear though B doped TiO2 nanotube arrays (TNAs) via anodic oxidation has commonly used to improve the photocatalytic decomposition of water by TNAs. Therefore, this work aims to establish the underlying reasons for the high PEC reactivity and stability maintained by the B doping induced defective states. Special attention is paid to the differences in carrier behavior and surface reactivity in the PEC process between the B doped induced and NaBH4 treatment induced defective states. DFT calculations show that B doping can effectively reduce the generation energy of Ti3+/Vo (oxygen vacancies) pairs and enhance the adsorption energy of defects on the surface of TiO2 (1 0 1) for H2O and ·OH. Moreover, due to the presence of B atoms, the surface defects of TiO2 can maintain high adsorption of H2O and ·OH, without being deactivated by the healing of oxygen vacancies, which ensures the stability and activity of the catalyst. Meanwhile, the lattice stress induced by B doping forms the internal electric field, which ensures the efficient separation of carriers in the bulk phase and avoids the negative effect of bulk phase defects on carrier separation.

Carbon monoxide (CO) is one of the well-studied reactants in many chemical catalytic reactions, and it is important to deeply understand the adsorption behavior as well as chemical reactivity of CO on a solid surface with regards to adsorption/desorption kinetics. Therefore, it is of great interest to study the process of CO adsorption and further catalytic reaction on one of the transition metal dichalcogenides, namely Vanadium diselenide (VSe2) because of its excellent catalytic activities. Herein, based on in-situ scanning tunneling microscopy (STM) study and density functional theory (DFT) calculations, we systematically investigated the absorption effect under different CO pressures. At relatively low pressure of CO (about 1x10-8 mbar), a few CO molecules adsorb on VSe2 and lead to the desorption of the top-Se atoms resulting in point defects. With the rise of pressure, the amount of absorbed CO increases, and the underlying V atoms also desorb due to the interaction of CO, finally leading to the structural transition of the whole VSe2. One thing to note is that, during the experiment CO atmosphere was injected as a continuous flow and some STM images were taken at the same time expressing the dynamic behavior of CO adsorption on VSe2, which has scarcely been in other static systems like UHV-STM.

The gentle electrocatalytic conversion of carbon dioxide into high value-added chemicals electrocatalysis can alleviate the greenhouse effect and energy crisis. Dual-atom catalysts exhibit high atom utilization, and can change their adsorption configuration through double sites to reduce the reaction energy barrier and optimize the reaction path. In this study, the density functional theory calculations were performed to better understand the good performance of NiSn dual-atom catalysts in the reduction of carbon dioxide to HCOOH. The NiSn dual-atom in DM1 model exhibited good stability, activity, and selectivity, which may be the origin of the excellent performance of the NiSn dual-atom catalysts in HCOOH production. The present work provides new ideas for the design of catalysts for the CO2 reduction reaction.

Few studies have reported the catalytic activity of oxidized pyrite. In the paper, oxidized pyrite was first explored as a Fenton reagent to generate active species to degrade carbamazepine (CBZ) in a wide pH range (3.0–11.0). The results showed that oxidized pyrite exhibited excellent catalytic performance on the activation of H2O2 to degrade CBZ with high stability. The influences of oxidized pyrite loading, H2O2 concentration, CBZ concentration, initial pH and co-existing ions on the degradation efficiency of CBZ were studied in detail. The main active species for the degradation of CBZ were HO, O2-, e- and 1O2, which were generated from the comprehensive effects of homogeneous Fenton, heterogeneous Fenton and photo-Fenton reaction. Furthermore, a possible pathway for CBZ degradation was proposed based on the intermediates detected from UPLC-MS/MS. Finally, the potential for practical utilization of oxidized pyrite was confirmed by degrading CBZ in tap water and secondary effluent water. The obtained results provide a new idea for the environment purification using natural pyrite.

Replacing anodic oxygen evolution reaction (OER) by urea oxidation reaction (UOR) provides a feasible approach to achieve high-efficiency hydrogen (H2) generation. However, the design of a robust catalyst for urea-assisted H2 generation remains a difficult problem. In this study, an innovative strategy to integrate bimetallic spinel sulfides CoNi2S4 nanosheet arrays with graphitized carbonized wood (denoted as CoNi2S4/GCW) for synergistically optimizing the electroconductivity and the hierarchical porous structure of the CoNi2S4/GCW catalyst is proposed. Benefitting from the optimized three-dimensional (3D) porous structure and the CoNi2S4 nanosheet arrays, the CoNi2S4/GCW catalyst exhibit brightly electrocatalytic performance toward both for UOR and hydrogen evolution reaction (HER). The synthesized CoNi2S4/GCW needs an ultralow potential (1.29 V vs. RHE) for UOR and a comparative small overpotential (119 mV) for HER at a current density of 20 mA cm−2, respectively, enabling a two-electrode configuration at a cell voltage of 1.42 V to output 20 mA cm−2 for urea-assisted electrocatalytic H2 generation. The enhanced urea-assisted performance of CoNi2S4/GCW is supposed to arise from a synergistic effect between the CoNi2S4 nanosheets and the 3D hierarchical porous wood framework, which offers sufficient active sites and expedite the mass transfer process between them. This work exhibits the application of bimetallic spinel sulfides CoNi2S4 in urea-assisted H2 generation and provides a promising strategy for utilizing sustainable wood for developing versatile electrocatalyst.

Efficient utilization of near-infrared light (NIR) is critical to optimize the performance of photocatalysts. Herein, an ultrafast process is employed to co-condensation of melamine and NaCl by microwave-assist heating. The fabricated sodium and oxygen co-doped g-C3N4 (NaOCN) shows extended π-conjugated aromatic rings and distortion of the heptazine skeleton, which can enhance the intrinsic π → π* electron transition and active the n → π* electron transition. The robust n → π* excitation of NaOCN leads to a narrowed bandgap of 2.73 eV with the NIR absorption extending to 1400 nm. The apparent quantum yield (AQY) for NaOCN can still keep 7.2 % at 600 nm. This work provides a promising way for the application of NIR-based carbon nitride in photocatalytic H2O2 production.

Two-dimensional (2D) van der Waals materials are potential candidates for high-performance optoelectrical devices owing to the bandgap modulation, high on/off ratio, and ultra-stability. However, the challenge of synthesizing large-area, uniform, and high-quality 2D van der Waals materials should be addressed to manufacture large-scale and uniform optoelectrical devices using these materials. Although several previous studies investigated synthesis methods using chemical vapor deposition and molecular beam epitaxy (MBE), there are certain limitations such as the non-uniformity, lots of grain boundaries, and low carrier mobility. Here, by studying a method for synthesizing PtSe2 on hBN buffer layer using MBE, we fabricated a PtSe2-based broadband photodetector. The high-quality PtSe2 synthesized on hBN was evaluated using Raman spectroscopy and scanning transmission electron spectroscopy. These revealed that the synthesized PtSe2 had a high quality and small grain boundary compared with PtSe2 synthesized on SiO2. Owing to the reduction in the carrier scattering and carrier recombination because of the high-quality and small grain boundaries, the photodetector using PtSe2 synthesized on hBN displayed optoelectrical properties that were significantly better than those of PtSe2 synthesized on SiO2. Therefore, using hBN as a buffer layer for PtSe2 growth, a remarkable performance of complex optoelectrical devices could be achieved.

The search for low-resistance metal contacts on two-dimensional (2D) layered transition metal dichalcogenide (TMDC) materials for high-performance electronic devices remains challenging owing to the lack of interfacial bonding on the surface and a strong Fermi-level pinning effect. In this study, we demonstrate a high-performance 2D large-area homostructured PtSe2/PtSe2 field-effect transistor (FET) by introducing a Schottky-barrier-free and semimetallic PtSe2 film (top layer) as an ohmic contact to semiconducting 2D PtSe2 films (bottom layer) via the wet-transfer method. We successfully improved the current on/off ratio of homostructured 2D/2D PtSe2/PtSe2 FET by more than approximately twofold increase compared to the PtSe2 FET with Pt contacts owing to the barrier-free homojunction PtSe2 layer. Our finding represents a significant achievement in obtaining high-performance electronic devices with barrier-free contacts on homostructured PtSe2 FETs and paves the way toward a promising strategy for wafer-scale 2D TMDC electronic devices.

The high brittleness intermetallic compound Fe2Ti is a key obstacle in joining stainless steel and NiTi alloys. In this study, Ni interlayers are introduced to prepare 316-Ni-NiTi multi-material specimens by direct energy deposition to reduce the excessive Fe2Ti in the system while improving the wear resistance of 316 under different loads. The presence of Ni interlayer reduces intermetallic compound Fe2Ti, resulting in the composition of 316-Ni-NiTi phase dominated by NiTi and Ni3Ti. The microstructure shows a typical dendritic morphology, in which eutectic regions existed in the NiTi layer. Both the 316/Ni interface and the Ni/NiTi interface exhibits good metallurgical bonding, the occurrence of the mutual diffusion phenomenon is confirmed by quantitative and qualitative analysis of the chemical composition of the 316-Ni-NiTi specimens. The average microhardness of the NiTi layer is 770 HV, which is 4.9 times higher than the 316, which benefiting from the intermetallic compound with high hardness generated by the introduction of the Ni interlayer. The wear weight loss of the 316-Ni-NiTi coating is less than that of the substrate at different loads, especially at a load of 60N, which is only 29% of the substrate.

Defect engineering is an effective approach to improve the gas conversion properties of photocatalysts. However, revealing the defect microstructures and performance enhancing mechanism remain challenges. In this work, the precise content and atomic-level structure of oxygen vacancy in Bi2MoO6/MXene heterojunction photocatalyst was studied by neutron scattering. Pair distribution function analysis shows that the vacancy percentage of oxygen connected with Mo in Bi2MoO6 is 16.6%, and the metal-O bond length decreases near the vacancy. The performance enhancement mechanism of oxygen vacancy in Bi2MoO6/MXene towards photocatalytic NO oxidation was investigated through experiments and density functional theory (DFT) calculations. The optical properties of the heterojunction photocatalyst can be significantly improved by the oxygen vacancies. The exposed Mo atoms at the vacancies greatly benefit the adsorption and activation of reactants, and also accelerate the generation of reactive oxygen species. The NO removal efficiency of the oxygen vacancy-containing Bi2MoO6/MXene heterojunction can reach up to 94.3% under visible light. This work provides a new approach for studying the microstructure and activity enhancement mechanism of oxygen vacancy in photocatalysts.

The regulation of crystal structure and orientation during direct current (DC) electrodeposition is one of the key factors for achieving performance control of the electrodeposited copper films. In this paper, we found that during continuous DC electrodeposition in acidic electrolytes containing additives, the electrolyte aging promotes spontaneous transformation of the crystal structure of copper. A special crystal structure, i.e., vertical twins with high aspect ratio exhibiting a high (220) orientation, was revealed, which is mainly attributed to the minimization of energy in the deposited film. We further pointed out that the generation priority of vertical twins was between the equiaxed structure (UD-type) and the (111) textured columnar structure (FT-type). The inhibitions resulted from the complex interactions and degradation of additives are the driving forces for crystal transformation. Moreover, the surface roughness changes with the transformation process of the crystal structure, which provide a potential method to regulate the surface roughness of copper film.

Zirconia ceramics can be extensively used as biological implant materials because of its excellent mechanical properties and biocompatibility. In order to further enhance the biocompatibility of zirconia ceramics and its application in oral medicine, a nanosecond laser-silicone oil-heat treatment (LSH) composite process was designed to fabricate superhydrophobic zirconia ceramic surfaces with adjustable adhesion to water droplet. The surface topography, chemical composition and wettability of zirconia ceramic surfaces were characterized. The experimental results indicated that the wettability and adhesion of water droplets on zirconia ceramic surfaces were significantly affected by the surface morphology and density of surface micro/nanostructures. The relative content of chemical elements and polar/non-polar functional groups on the surfaces could be changed as the process parameters changed, which would also affect the transition of surface wettability. Meanwhile, the adhesion of water droplets on the zirconia ceramic surfaces could be precisely regulated by changing the laser texturing parameters. Droplet lossless transport and self-cleaning effect were demonstrated, which could provide a key avenue for the application of superhydrophobic zirconia ceramics in biological implants.

The self-assembly behaviors of a benzothiadiazole-based liquid crystalline molecule (BT-C14) were investigated by scanning tunneling microscopy (STM). STM observations show the coexistence of three kinds of self-assembled patterns without apparent concentration dependence at the heptanoic acid/graphite interface, in which the molecules adopt two conformations due to different orientations of two flanked thiophene groups relative to cyano groups. BT-C14 molecules with one conformation form a linear structure by intermolecular CH∙∙∙NC hydrogen bonds and interchain van der Waals (vdWs) interactions. Meanwhile, the zigzag-like and separated-dimer patterns are observed, in which the molecules adopt another conformation. The CH∙∙∙NC hydrogen bonds and the S∙∙∙N chalcogen bonding in dimers, the dipolar interactions, along with the interchain vdWs interactions are the dominated forces to drive their structural formation. Density functional theory (DFT) approaches are utilized to determine the molecular conformations and the noncovalent interactions. Molecular dynamics (MD) calculations unravel that these three nanostructures have analogous interaction energies and molecular stacking densities, indicating that the coexistence is thermodynamically and kinetically favorable. This study not only instructs the design of liquid crystalline molecules but also provides a strategy for analyzing multi-configuration and multi-structure system in the self-assembly process.

Based on the first-principles calculations, we have investigated the mechanical, phonon, electronic and optical properties of two-dimensional (2D) In2Te3 (FE-WZ′ phase) family. The Y(θ) value for all M2X3 materials exceeds 67 N/m, with Al2S3 exhibiting the best mechanical strength, surpassing to that of MoS2 (∼124.3 N/m in the x and y directions). Phonon calculations reveal that the acoustic branch with the lowest frequency is mainly dominated by out-of-plane vibrations of the metal atoms and non-metallic atoms. Ga2Te3 exhibits dynamic instability due to the softening of the optical phonon branch. Incorporating spin–orbit coupling (SOC) in In2Se3 and In2Te3 converts them into direct semiconductors. These materials possess an electrostatic potential difference ranging from 0.73 to 2.11 eV, which effectively reduces the band gap required for water splitting in the infrared region. Moreover, the M2X3 monolayers with intrinsic electric fields are great coveted photocatalysts for overall water splitting. Remarkably, In2Se3 displays a solar-to-hydrogen efficiency of 28.6%, which is significant for commercial applications.

A novel method based on Direct Laser Interference Patterning with 2 beams allowing to pattern surfaces with 2 dimensional periodicity and presenting several symmetry axes has been developped. It consists in the picoseond laser writing of the same 1D pattern for different sample orientations. The resulting final morphology depends on the rotation angle between the patterning steps and the number of scans. This way, various 2D short and long range periodic structures can be obtained. We show that by increasing the number of symmetry axes, the sample orientation dependance of the reflectivity, measured at 2 different wavelengths, is reduced, approaching an isotropic behaviour beyond 3 axes. Moreover, as the number of symmetry axes increases, the reflectivity decreases reaching ∼10−3 %, which is explained by the increase of roughness.

In this work, we present the influence of annealing atmospheres during rapid thermal annealing (40 °C/s) on nanostructured Ti platforms modified by 10 nm layer of AuCu alloy obtained via magnetron sputtering. The AuCu/Ti platform annealed under hydrogen atmosphere exhibits the best photoelectrochemical activity under visible light, i.e. 27 times higher photocurrent than for pure Ti dimpled platform, and the lowest reflectance with minimum at ca. 750 nm. Synchrotron radiation studies allow for inspection in three zones, such as the upper (2–3 nm) and deeper (5–7 nm) surface layers as well as the bulk structure (12–15 nm). Taking into account hydrogenated AuCu/Ti platforms gold presence was confirmed in the upper and deeper surface layers as well as in bulk whereas AuxCuy nanoalloy only in the deeper layer. In the case of copper, Cu2O or Cu were distinguished in the upper and deeper surface layers, where Cu+1/Cutot ratio reaches 70 % in the upper layer and drops to about 40 % at a depth of 5–7 nm. Hydrogenation has a positive effect on photovoltaic performance by efficient acceptor–donor configuration of AuCu doping on/into TiO2 semiconductor showing its potential ability as photoanode in solar cells.

For the miniaturization of dynamic random-access memory (DRAM), it is necessary to obtain low equivalent oxide thickness (EOT) and low leakage capacitor materials with complementary metal-oxide semiconductor (CMOS) process compatibility. Herein, we explore the influence of the dose of H2O reactants on the phase structure and electrical characteristics of Hf0.3Zr0.7O2 (HZO) thin films during the atomic layer deposition (ALD). By controlling the H2O dose as well as other conditions including inserting alumina, adjusting annealing temperature and electric field cycling, a high dielectric constant of ∼45 (EOT ∼ 0.54 nm) and low leakage current density (1012 cycles (even extrapolated to 1015 cycles under voltage pulse of 0.5 V @10 MHz) at both room temperature and 85 °C. These results are helpful for achieving a high dielectric constant and low leakage for future generation DRAM capacitor materials.

Zirconium and hafnium are critical metals mainly extracted from the zircon mineral. However, due to the unclear surface properties of zircon, most designed flotation collectors (Surfactants to selectively enhance the hydrophobicity of targeted materials) cannot recover zircon effectively. Herein, zircon surface hydration microstructures and their effects on the adsorption of typical flotation collectors (i.e., phosphates, hydroxamic acids, carboxylic acids) have been revealed by systematic first-principles calculations. The speciation diagram and the surface hydration microstructures of zircon have shown that surface Zr sites with small coordination numbers have stronger water affinity. Water molecules have affected the final stable adsorption configurations of the collector. The further obtained adsorption energy of collectors shows that water molecules have weakened the activity of zircon surfaces and reduced the interaction intensity between collectors and surfaces. These results indicate that collectors with stronger negative charges and a lower highest occupied molecular orbital(HOMO) energy can tightly bind with the zircon surface. The electron localization function, density of states, and crystal orbital overlap population have consistently shown that collectors have formed ionic bonds with surface Zr sites. These conclusions should be meaningful for further design of flotation collectors to realize selective zircon flotation.

Capping agents such as halide and citrate (CA) are crucial in the colloidal synthesis of noble metal nanoparticles (NPs) with desirable shape for specific catalytic reaction. Halide ions have been shown to stabilize the cubic NP while CA ions favor the octahedral NP regardless of the noble metals, but the mechanism remains unclear. We combine DFT calculations and Wulff construction to understand how the morphology of Pd particle changes with Cl and CA chemical potential (μ). Three main factors are identified to affect the morphology of Pd particle: μ of adsorbate, its number per unit area (NAS/S), and rigidity or flexibility. Increasing μ of adsorbate or its NAS/S causes decreased surface free energy and increased exposed surface area. Moreover, rigid adsorbates (PdClx) occupy a larger surface area for surfaces with high atomic density such as Pd(1 1 1), leading to cubic Pd particle at high μCl. Conversely, flexible adsorbates (CA) that can adjust their structure based on the surface occupy smaller surface area on Pd(1 1 1), favoring octahedral Pd particle. This work reveals the origin for capping agent tuned morphology of Pd NP, and the insights can be used to guide metal NP synthesis with desired morphology for catalytic reactions of technological interest.

The sluggish kinetic process of oxygen conversion reaction directly limits the energy density of Zn-air batteries (ZABs), construction of multi-layered catalytic active sites to promote dioxygen fragmentation is an urgent need for high-performance ZABs. Herein, a bead-like 1D/3D hierarchical conductive network catalyst (Fe/Co-NC) is fabricated, where polypyrrole nanotubes served as skeleton, its surface was coated with polymerized Hemin which have the first active site and double propionic groups as the adsorption sites for the formation of second site precursor of ZIF-67. We defined the Fe/Co-Nx derived by pyrolysis dispersed in 1D/3D structure as multi-layered active sites. Fe/Co-NC catalyst exhibits excellent catalytic performance (E1/2=0.86 V) and stability (the E1/2 loses 0.21 mV after 5000 cycles). After assembling to ZABs, the results show an inspiring peak power density of 238.6 mW cm-2, which is 1.8 times that of Pt/C catalyst. Density functional theory (DFT) indicates that multi-layered active sites can promoting dioxygen fragmentation rate−determining steps at higher limiting potential of 0.70 V. Partial density of states further demonstrates that multi-layered active sites with a downshift of the d-band center (-0.95 eV) weakens the adsorption of oxygen intermediates. Combined with conductivity calculations, density of states can reach higher levels, facilitating 4-electron transfer process.