Stable CO2reduction under natural air on Ni-Sn hydroxide photocatalyst with dynamic renewable oxygen vacancies.

Advanced photocatalysts are highly desired to activate the photocatalytic CO2reduction reaction (CO2RR) with low concentration. Herein, the NiSn(OH)6with rich surface lattice hydroxyls was synthesized to boost the activity directly under the natural air. Results showed that terminal Ni-OH could serve as donors to feed protons and generate oxygen vacancies (VO), thus beneficial to convert the activated CO2(HCO3-) mainly into CO (5.60µmol g-1) in the atmosphere. It was flexible and widely applicable for a stable CO2RR from high pure to air level free of additionally adding H2O reactant, and higher than the traditional gas-liquid-solid (1.58µmol g-1) and gas-solid (4.07µmol g-1) reaction system both using high pure CO2and plenty of H2O. The strong hydrophilia by the rich surface hydroxyls allowed robust H2O molecule adsorption and dissociation at VOsites to achieve the Ni-OH regeneration, leading to a stable CO yield (11.61µmol g-1) with the enriched renewable VOregardless of the poor CO2and H2O in air. This work opens up new possibilities for the practical application of natural photosynthesis.

Composite interfaces of g-C3N4 fragments loaded on a Cu substrate for CO2 reduction.

Designing an electrocatalyst with high efficiency and product selectivity is always crucial for an electrocatalytic CO2 reduction reaction (CO2RR). Inspired by the great progress of two-dimensional (2D) nanomaterials growing on Cu surfaces and their promising CO2RR catalytic efficiencies at their interfaces, the unique performance of Cu-based 2D materials as high-efficiency and low-cost CO2RR electrocatalysts has attracted extensive attention. Herein, based on density functional theory (DFT) calculations, we proposed a composite structure of graphitic carbon nitride (g-C3N4) fragments loaded on a Cu surface to explore the CO2RR catalytic property of the interface between g-C3N4 and the Cu surface. Three composite interfaces of C3N4/Cu(111), C3N4/Cu(110) and C3N4/Cu(100) have been studied by considering the reaction sites of vertex nitrogen atoms, edge nitrogen atoms and the nearby Cu atoms. It was found that the C3N4/Cu interfaces where nitrogen atoms contact the Cu substrate present competitive CO2RR activity. Among them, C3N4/Cu(111)-N3 exhibited a better activity for CH3OH production, with a low overpotential of 0.38 V. For HCOOH and CH4 production, C3N4/Cu(111)-Cu and C3N4/Cu(100)-N1 have overpotentials of 0.26 V and 0.44 V. The electronic analysis indicates the electron transfer from the Cu substrate to the g-C3N4 fragment and mainly accumulates on the nitrogen atoms of the interface. Such charge accumulation can activate the adsorbed CO bond of CO2 and lead to lower energetic barriers of CO2RR. DFT calculations indicate that the boundary nitrogen sites reduced the energy barrier of *CHO, which is crucial for CO2RR, compared with that of the pristine Cu surface. Our study explores a new Cu-based electrocatalyst and indicates that the C3N4/Cu interface can enhance the activities and selectivity of CO2RR and open a new strategy to design high-efficiency electrocatalysts for CO2RR.

Multifunctional Au/Hydroxide Interface toward Enhanced C-C Coupling for Solar-Driven CO2 Reduction into C2H6.

The high-grade C2+ products from CO2 photoreduction are limited by the kinetic bottleneck. Herein, a multifunctional Au/hydroxide interface was put forward to improve the C-C coupling. As a prototype, the synthesized Au/ZnSn(OH)6 tuned the CO generation and afforded about 50% electrons toward C2H6 selectivity. The prominent enhancement resulted from the following effects: (1) strong metal-support electronic interactions built an electric field at the interface of ZnSn(OH)6 nearby the Au nanoparticles, leading to fast transfer of electrons for the C-H and C-C bonding reactions. (2) The surface solid-state Sn-OH and Zn-OH lattice hydroxyls served as donors to feed rich H+ and oxygen vacancies (OVs) via hole-induced oxidation for the boosted C2H6 formation. (3) The synergetic OVs and Au sites allowed efficient e-/H+ to boost *CO hydrogenation toward *CH3 and *CH3*CH3 formation into the C2H6 product.

Enhance Hydrogen Evolution Reaction Performance via Double-Stacked Edges of Black Phosphorene.

Based on the density functional theory (DFT) calculations, we explored the structures and HER catalytic properties of reconstructed and double-stacked black phosphorene (BP) edges. Ten bilayer BP edges were constructed by the double stacking of three typical monolayer edges, i.e., zigzag (ZZ) edge, armchair (AC) edge, skewed diagonal (SD) edge, and their reconstructed derivatives with their layer's configurations, edge deformations and thermodynamic stabilities were discussed. Based on these edges, five chemical sites on four bilayer BP edges were selected to be promising candidates for a HER catalyst, which present higher HER activities than that of Pt(111). Besides, among these four edges, two edges have even lower energetic barriers for the Tafel reaction. Compared with the monolayer edges, these selected bilayer BP edges confirm the remarkable enhancement of the HER catalytic properties, which can be attributed to their unique edge structures and the enhanced electronic densities after the hydrogen adsorptions. Finally, the thermostability of these edges at room temperature has also been proved by the DFT-MD simulations. This theoretic study deepens our fundamental understanding of the double-stacked edge structures of the BP and provides a new way for the rational design of highly efficient and noble-metal-free HER catalysts.

High Detectivity of PbS Films Deposited on Quartz Substrates: The Role of Enhanced Photogenerated Carrier Separation.

PbS films grown on quartz substrates by the chemical bath deposition method were annealed in an O2 atmosphere to investigate the role of oxygen in the sensitization process at different annealing temperatures. The average grain size of the PbS films gradually increased as the annealing temperature increased from 400 °C to 700 °C. At an annealing temperature of 650 °C, the photoresponsivity and detectivity reached 1.67 A W-1 and 1.22 × 1010 cm Hz1/2 W-1, respectively. The role of oxides in the sensitization process was analyzed in combination with X-ray diffraction and scanning electron microscopy results, and a three-dimensional network model of the sensitization mechanism of PbS films was proposed. During the annealing process, O functioned as a p-type impurity, forming p+-type PbS layers with high hole concentrations on the surface and between the PbS grains. As annealing proceeds, the p+-type PbS layers at the grain boundaries interconnect to form a three-dimensional network structure of hole transport channels, while the unoxidized p-type PbS layers act as electron transport channels. Under bias, photogenerated electron-hole pairs were efficiently separated by the formed p+-p charge separation junction, thereby reducing electron-hole recombination and facilitating a higher infrared response.

Single atom-doped arsenene as electrocatalyst for reducing nitrogen to ammonia: a DFT study.

Due to the wide application of NH3 in the energy and chemical industry, the rational design of a highly efficient and low-cost electrocatalyst for nitrogen fixation at moderate conditions is highly desirable to meet the increasing demand for sustainable energy production in the modern society. Herein, we have systematically studied the catalytic performance of transition metal (TM) atom (i.e., V, Cr, Fe, Co, Cu, Ru, Pd, Ag, Pt, Au)-doped arsenene nanosheet, a new two-dimensional (2D) nanomaterial in VA group, as a heterogeneous catalyst for nitrogen reduction reaction (NRR). By density functional theory (DFT) calculation and systematic theoretical screening, our study predicts that the systems of V-, Fe-, Co- and Ru-doped arsenene have promising potentials as NRR electrocatalysts with high-loading TM and highly stable adsorption of N2 molecule. Particularly, the V-doped system exhibits two feasible configurations for N2 adsorption and an ultralow overpotential (0.10 V) via the enzymatic pathway, which is very competitive among similar reported electrocatalysts. This theoretical study not only extends the electrocatalyst family for nitrogen fixation, but also further deepens our physical insights into catalytic improvement, which can be expected to guide the rational design of novel NRR catalysts.

Na-Ions Diffusion Impacts Supercapacitor Performance for Amaryllis-like NiCo2O4 Nanostructures.

NiCo2O4 nanomaterials with exceptional electrochemical performances are synthesized via a simple and low-cost method. The synthesized nanostructures exhibit a high specific surface area of 121.52 m2 g-1 and excellent specific capacitance of 2498.49 F g-1 at a current density of 2 A g-1, an energy density of 79 Wh kg-1, and power density of 3570 W kg-1. The remarkable cycling stability of 92.61% retention after 5000 cycles demonstrates that NiCo2O4 nanomaterials have a potential for practical application in energy storage devices. The Na+ ion diffusion (by VASP) affirms a low activation energy barrier for Na ion intercalations onto the electrode material, illuminating excellent electrochemical performances.

Immobilisation of sulphur on cathodes of lithium-sulphur batteries via B-doped atomic-layer carbon materials.

Developing new host materials for cathodes and exploring their binding mechanisms in lithium-sulphur batteries are crucial issues since the present host materials exhibit low sulphur entrapment properties, thus resulting in the rapid decay of overall performance. In this work, we systematically investigated B-doped atomic-layer carbon materials as the cathode hosts of lithium-sulphur batteries via density functional theory calculations. Based on the analysis of optimised molecular structures, binding energies and surface charge densities, we found that B-doping can help materials suppress the dissolution of sulphides during cycles, further improving the performance of lithium-sulphur batteries. Additionally, we concluded that the internal interactions among multiple Li2Sn-adsorbed structures facilitate the capture of Li2Sn. Furthermore, we found that B-doped graphdiyne is a promising host material since it exhibits a stronger attraction to Li2Sn than other selected materials and an outstanding sulphur loading of ∼70 wt%.

Influence of Interaction Components on the NOx Adsorption Properties of Cu-Ba-Ce Composite Catalysts.

For further investigating the role of components in copper-cerium-barium composite oxide catalysts, a series of noble metal-free catalysts with different barium contents were synthesized by citric acid method. The prepared catalysts were characterized by X-ray diffraction, Brunauer-Emmett- Teller method, scanning electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy. Catalysts were evaluated by NO oxidation, NOx adsorption, and NOx temperature-programmed desorption. The results showed that barium content significantly affected the catalysts' properties. With barium addition, interactions among components considerably changed; hence, the microstructure and performance of catalysts were distinctly different. In general, the interactions of barium-copper and barium-cerium were not conducive to catalyst adsorption. Adsorption performance derived from barium carbonate was superior to those of the other two components.

Native point defects on hydrogen-passivated 4H-SiC (0001) surface and the effects on metal adsorptions.

With the continued expansion of silicon carbide's (SiC) applications, atomistic understanding on the native point defects of its surfaces, particularly on those of the hydrogen-passivated (HP) 4H-SiC (0001) surface, becomes imperative. Using first-principles calculations, the structures and formation energies of several typical native point defects (e.g., ISi, IC, VSi, VC, and SiC) on the (0001) HP-surface of 4H-SiC were systematically explored, including the effects of the unit cell size, environmental condition, charge state, and hydrogen incorporation. Furthermore, their adsorptions of Ag (Mo) atom on these defective sites were systematically investigated. The formation energies of these defects in the HP-surface, clean surface, and bulk SiC were concluded together with their thermodynamic concentrations in the HP-surface estimated. The influences of these defects to metal (Ag, Mo) adsorptions of HP-surfaces were concluded. Based on these conclusions, the wettability improvement between the metal liquid and ion (Ag or Mo) implanted SiC substrates in the previous studies can be well understood at the atomistic scale. This study provides a theoretical guideline to SiC surface modification for the production of metal-SiC composites, brazing of SiC with metals, fabrication of electronic devices, or the growth of two dimensional nanofilms.

The fabrication of In2O3/In2S3/Ag nanocubes for efficient photoelectrochemical water splitting.

In this work, for the first time, a three-component In2O3/In2S3/Ag nanocomposite heterostructured photoanode is prepared on a F-doped SnO2 (FTO) glass substrate. The three-component photoanode exhibits significantly enhanced photoelectrochemical properties compared with the single-component (In2O3) and two-component (In2O3/In2S3 or In2O3/Ag) systems. Ag nanoparticles deposited on the surface of In2O3/In2S3 nanocubes can facilitate the separation of photogenerated charge carriers and enhance the absorption of visible light. In I-V curves, the In2O3/In2S3/Ag photoanode generates a remarkable photocurrent density of 8.75 mA cm(-2) (at 0 V vs. SCE), which is higher than those of the two-component In2O3/In2S3 (4.47 mA cm(-2)) and In2O3/Ag (3.50 mA cm(-2)). Furthermore, it also gives efficiency as high as 67% around 350 nm in the incident photon to electron conversion efficiency (IPCE) spectrum. These results open up a promising avenue for the design and fabrication of novel heterojunctions for photoelectrochemical water splitting.

Unexpected high-temperature stability of ß-Zn4Sb3 opens the door to enhanced thermoelectric performance.

ß-Zn4Sb3 has one of the highest ZT reported for binary compounds, but its practical applications have been hindered by a reported poor stability. Here we report the fabrication of nearly dense single-phase ß-Zn4Sb3 and a study of its thermoelectric transport coefficients across a wide temperature range. Around 425 K we find an abrupt decrease of its thermal conductivity. Past this point, Zn atoms can migrate from crystalline sites to interstitial positions; ß-Zn4Sb3 becomes metastable and gradually decomposes into Zn(hcp) and ZnSb. However, above 565 K it recovers its stability; in fact, the damage caused by decomposition can be repaired completely. This is key to its excellent thermoelectric performance at high temperature: the maximum ZT reaches 1.4. Molecular dynamics simulations are used to shed light on the microscopic behavior of the material.

ZnO-Au@ZIF-8 core-shell nanorod arrays for ppb-level NO2 detection.

ZnO-Au@ZIF-8 core-shell heterostructures were prepared by ZIF-8 encapsulation of sacrificial ZnO-Au nanorods. Because of the catalytic activity of the Au nanoparticles and the sieving effects of the ZIF-8, the ZnO-Au@ZIF-8 heterostructures showed an outstanding response of 1.8 to 5 ppb NO2, and exhibited higher selectivity, stability, anti-humidity and fast response and recovery properties. The combination of the gas-selective catalytic activity of noble metals with the MOF filter used in this work can be easily extended to synthesize other types of MOS@MOF sensors, opening a new avenue for the detection of hazardous gases.

Engineering "three-in-one" fluorescent nanozyme of Ce-Au NCs for on-site visual detection of Hg2.

Hg2+ contamination poses a serious threat to the environment and human health. Although gold nanoclusters (Au NCs) have been utilized as fluorescence probes or colorimetric nanozymes for performing Hg2+ assays by using a single method, designing multifunctional nanoclusters as fluorescent nanozyme remains challenging. Herein, Ce-aggregated gold nanoclusters (Ce-Au NCs) were reported with "three in one" functions to generate strong fluorescence, excellent peroxidase-like activity, and the highly specific recognition of Hg2+ via its metallophilic interaction. A portable fluorescence and colorimetric dual-mode sensing device based on Ce-Au NCs was developed for on-site visual analysis of Hg2+. In the presence of Hg2+, fluorescence was effectively quenched and the paper-based chips gradually darkened from green till they became completely absent, while peroxidase-like activity was significantly enhanced. Two independent signals were captured by one identification unit, which provided self-validation to improve reliability and accuracy. Therefore, this work presents a simple synthesis of a multifunctional fluorescent nanozyme, and the developed portable device for on-site visual detection has considerable potential for application in the rapid on-site analysis of heavy metal ions in the environment.

A 2D-0D-2D Sandwich Heterostructure toward High-Performance Room-Temperature Gas Sensing.

The construction of two-dimensional (2D) van der Waals (vdW) heterostructures over black phosphorus (BP) has been attracting significant attention to better utilize its inherent properties. The sandwich of zero-dimensional (0D) noble metals within BP-based vdW heterostructures can provide efficient catalytic channels, modulating their surface redox potentials and therefore inducing versatile functionalities. Herein, we realize a 2D WS2-Au-BP heterostructure, in which Au nanoparticles are connected between BP and WS2 via ionic bonds. The ultralow conduction band minimum position, the reduced adsorption energies of O2, and the increased dissociation barrier energy of O2- into 2O contribute greatly to improving the long-term stability of BP in the air. The formation of heterostructures can reduce the potential barrier energy in target gas molecules, thus enhancing the absorption energy and charge transfer. Taking the paramagnetic NO2 gas molecules as a representative, a stable response magnitude of 2.11 to 100 ppb NO2 is achieved for 80 days, which is far larger than the initial responses of most BP-based materials. A practical gas sensing system is also developed to demonstrate its real-world implementation. This work provides a promising demonstration of 0D noble metal within 2D BP-based vdW heterostructure for simultaneously improving the long-term stability and room-temperature reversible gas sensing.

Polymerization-induced spinodal decomposition of ethylene glycol∕phenolic resin solutions under electric fields.

Temporal evolution of polymerization-induced spinodal decomposition (PISD) under electric fields was investigated numerically in ethylene glycol∕phenolic resin solutions with different initial composition. A model composed of the nonlinear Cahn-Hilliard-Cook equation for spinodal decomposition and a rate equation for curing reaction was utilized to describe the PISD phenomenon. As initial composition varied, deformed droplet-like and aligned bi-continuous structures were observed in the presence of an electric field. Moreover, the anisotropic parameter (D), determined from the 2D-FFT power spectrum, was employed to quantitatively characterize the degree of morphology anisotropy. The value of D increased quickly in the early stage and then decreased in the intermediate stage of spinodal decomposition, which was attributed to the resistance of coarsening process to morphology deformation and the decline of electric stress caused by polymerization reaction. The results can also provide a guidance on how to control the morphology of monolithic porous polymer and carbon materials with anisotropic structures.

Exploring the gas-sensing properties of MOF-derived TiN@CuO as a hydrogen sulfide sensor.

In an effort to develop a long-lasting gas sensor, this article presents titanium nitride (TiN) as a potential substitute sensitive material in conjunction with (copper(II) benzene-1,3,5-tricarboxylate) Cu-BTC-derived CuO. The work focused on the gas-sensing characteristics of TiN/CuO nanoparticles in detecting H2S gas at various temperatures and concentrations. XRD, XPS, and SEM were utilized to analyze the composites with varied Cu molar ratios. The responses of TiN/CuO-2 nanoparticles to 50 and 100 ppm H2S gas at 50 °C and 250 °C are 34.8 and 60.0, respectively. The related sensor had high selectivity and stability towards H2S, and the response of TiN/CuO-2 is still 2.5-5 ppm H2S. The gas-sensing properties as well as the mechanism are fully explained in this study. TiN/CuO might be a choice for the detection of H2S gas, opening up new avenues for applications in industries, medical facilities, and homes.

CuO-decorated MOF derived ZnO polyhedral nanostructures for exceptional H2S gas detection.

Considering that H2S is a hazardous gas that poses a significant risk to people's lives, research into H2S gas sensors has garnered a lot of interest. This work reports a CuO/ZnO multifaceted nanostructures(NS) created by heat treating Cu2+/ZIF-8 impregnation precursors, and their microstructure and gas sensing characteristics were examined using various characterization techniques (XRD, XPS, SEM, TEM, and BET). The as-prepared hollow CuO/ZnO multifunctional nanostructures had a high gas response value (425@50 ppm H2S gas), quick response and recovery times (57/191s @20 ppm), a low limit of detection (1.6@500 ppb H2S), good humidity resistance and highly selective towards H2S gas. The hollow CuO/ZnO multifaceted nanostructures possessed enhanced gas sensing capabilities which may be related to their porous hollow nanostructures, the manufactured p-CuO/n-ZnO heterojunctions, and the spillover effect between CuO and H2S.

Metal-organic frameworks-derived In2O3/ZnO porous hollow nanocages for highly sensitive H2S gas sensor.

The detection of hydrogen sulfide (H2S) is critical because of its potential harm and widespread presence in the oil and gas sectors. The zeolitic imidazolate framework-8 (ZIF-8) derived ZnO nanostructures manufactured as gas sensors have exceptional sensitivity and selectivity for H2S gas. In/Zn-ZIF-8 template material was synthesized by a simple one-step co-precipitation method followed by thermal annealing in air. The heat treatment resulted in In2O3/ZnO nanostructures with mixed heterostructures. The crystal structure (XRD), morphology (SEM/TEM), chemical state (XPS), surface area (BET), etc were investigated to ascertain the nature of the as-prepared material. SEM imagery revealed that the as-prepared In2O3/ZnO sensitive material had a microstructure of porous hollow nanocages with an average particle size of about 200 nm, which is beneficial to the diffusion and adsorption of gas molecules. The gas sensing performance test results of the In2O3/ZnO hollow nanocages show that their response to H2S gas is significantly improved 67.5 @50 ppm H2S (about 11 times that of pure ZnO nanocages) at an optimal temperature of 200 °C, better selectivity, lower theoretical detection limit and good linearity between gas concentration and response values. The enhanced gas sensing feat to H2S gas is mainly attributed to the formation of n-n heterojunction and the wide surface area of the newly formed In2O3/ZnO porous hollow nanocages.

Facile fabrication of nanoflower-like WO3/WS2 heterojunction for highly sensitive NO2 detection at room temperature.

Realizing efficient detection of ultra-low concentrations of hazardous gases contributes to air pollution monitoring, ecosystem and human health protection. Herein, we firstly fabricated the nanoflower-like WO3/WS2 composites by a facile process to highly sensitively detect NO2 at room temperature. The WO3 content in the WO3/WS2 composites can be adjusted by altering the calcination temperature, and the WO3 nanoparticles disperse uniformly on the WS2 surface, forming the WO3/WS2 heterojunction. The room-temperature responses of WO3/WS2 composites gradually climb with the NO2 concentration increasing from 0.005 to 5 ppm, and the WW-280 and WW-300 composites possess the optimal gas sensitivity when the NO2 concentrations are lower and higher than 100 ppb, respectively. In particular, the two WO3/WS2 composites present the limitation of detection (LOD) of ≤ 5 ppb, and they exhibit the excellent selectivity, good reproducibility and long-term stability towards NO2. A possible gas sensing mechanism was also proposed from the point of views of gas adsorption, redox reactions and electron transfer. The appropriate WO3 content and molar ratio of hexagonal to monoclinic WO3, and the formation of WO3/WS2 p-n heterojunction can contribute to the high sensitivity of WO3/WS2 composite to various concentrations of NO2. This work offers a promising gas sensing material for room-temperature detection to low concentrations of NO2.