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The renewable-electricity-powered CO2 electroreduction reaction provides a promising means to store intermittent renewable energy in the form of valuable chemicals and dispatchable fuels. Renewable methane produced using CO2 electroreduction attracts interest due to the established global distribution network; however, present-day efficiencies and activities remain below those required for practical application. Here we exploit the fact that the suppression of *CO dimerization and hydrogen evolution promotes methane selectivity: we reason that the introduction of Au in Cu favors *CO protonation vs. C−C coupling under low *CO coverage and weakens the *H adsorption energy of the surface, leading to a reduction in hydrogen evolution. We construct experimentally a suite of Au-Cu catalysts and control *CO availability by regulating CO2 concentration and reaction rate. This strategy leads to a 1.6× improvement in the methane:H2 selectivity ratio compared to the best prior reports operating above 100 mA cm−2. We as a result achieve a CO2-to-methane Faradaic efficiency (FE) of (56 ± 2)% at a production rate of (112 ± 4) mA cm−2., The electroreduction of CO2 offers a promising approach to produce carbon-neutral methane using renewable electricity. This study shows that the introduction of Au in Cu enables selective methane production from CO2 by regulating *CO availability.

Photoelectrochemical (PEC) water splitting for solar energy conversion into chemical fuels has attracted intense research attention. The semiconductor hematite (α-Fe2O3), with its earth abundance, chemical stability, and efficient light harvesting, stands out as a promising photoanode material. Unfortunately, its electron affinity is too deep for overall water splitting, requiring additional bias. Interface engineering has been used to reduce the onset potential of hematite photoelectrode. Here we focus instead on energy band engineering hematite by shrinking the crystal lattice, and the water-splitting onset potential can be decreased from 1.14 to 0.61 V vs. the reversible hydrogen electrode. It is the lowest record reported for a pristine hematite photoanode without surface modification. X-ray absorption spectroscopy and magnetic properties suggest the redistribution of 3d electrons in the as-synthesized grey hematite electrode. Density function theory studies herein show that the smaller-lattice-constant hematite benefits from raised energy bands, which accounts for the reduced onset potential.

Considerable effort has been made to develop efficient water-splitting photocatalysts, which are generally composed of light-absorbing semiconductors and so-called cocatalysts that play a key role in accelerating the reaction kinetics of water splitting. Platinum (Pt)-based catalysts have been widely regarded as excellent cocatalysts for photocatalytic water splitting, but the relationship between their valence state and reaction activity for photocatalytic water splitting had never been summarized. This review presents positively charged Pt nanoparticles, clusters and even single atoms that can boost the reaction activity dramatically, and summarises several strategies and techniques to tailor the positive valence states of Pt-based cocatalysts such as by using oxygen atoms. By tailoring the valence states of Pt-based cocatalysts, the capacities of these cocatalysts for water splitting can be significantly enhanced. Moreover, the operando analyses that can determine the real structures of this type of cocatalyst under working conditions are also discussed. These developments suggest that positively charged Pt-based cocatalysts could determine the direction and efficiency of photocatalytic water splitting, which may provide an ideal orientation to design state-of-the-art catalysts for achieving efficient photocatalytic water splitting.

The electrochemical conversion of CO2 to methane provides a means to store intermittent renewable electricity in the form of a carbon-neutral hydrocarbon fuel that benefits from an established global distribution network. The stability and selectivity of reported approaches reside below technoeconomic-related requirements. Membrane electrode assembly-based reactors offer a known path to stability; however, highly alkaline conditions on the cathode favour C-C coupling and multi-carbon products. In computational studies herein, we find that copper in a low coordination number favours methane even under highly alkaline conditions. Experimentally, we develop a carbon nanoparticle moderator strategy that confines a copper-complex catalyst when employed in a membrane electrode assembly. In-situ XAS measurements confirm that increased carbon nanoparticle loadings can reduce the metallic copper coordination number. At a copper coordination number of 4.2 we demonstrate a CO2-to-methane selectivity of 62%, a methane partial current density of 136 mA cm−2, and > 110 hours of stable operation. Electrochemical conversion of carbon dioxide to methane can store intermittent renewable electricity in a staple of global energy. Here, the authors develop a moderator strategy to maintain the catalyst in a low coordination state, thereby enabling stable and selective electrochemical methanation.

Recent discovered two-dimensional (2D) antiferromagnetic (AFM) van der Waals quantum materials have attracted increasing interest due to the emergent exotic physical phenomena. The spintronic properties utilizing the intrinsic AFM state in 2D antiferromagnets, however, have been rarely found. Here we show that the spin photogalvanic effect (SPGE), which has been predicted in three-dimensional (3D) antiferromagnets, can intrinsically emerge in 2D antiferromagnets for promising spintronic applications. Based on the symmetry analysis of possible AFM orders in the honeycomb lattice, we conclude suitable 2D AFM candidate materials for realizing the SPGE. We choose two experimentally synthesized 2D collinear AFM materials, monolayer MnPS3, and bilayer CrCl3, as representative materials to perform first-principles calculations, and find that they support sizable SPGE. The SPGE in collinear 2D AFM materials can be utilized to generate pure spin current in a contactless and ultra-fast way.

High electrochemical over-potential and low product selectivity are regarded as the main limitations of electroreduction of CO2 . Here, we proposed a new strategy to synthesize metal porphyrin-hybridized porous and ultra-thin carbon nanosheets (MPPCN) by the confinement function of the layered template. The layered confinement reaction protects the coordination structure of metal and nitrogen atoms during subsequent high-temperature treatment while ensuring the formation of ultra-thin structures. This method effectively prevents the aggregation of metal atoms, so that the metal atoms exhibit a dispersed state of a single atomic level. MPPCN exhibit unexpected catalytic activity for electroreduction of CO2 , and the catalytic reaction can be carried out at an over-potential of 0.39 V. The faradaic efficiency of CO can reach 95.9 % at the potential of -0.7 V versus the reversible hydrogen electrode.

The synergistic effect of sulfonate Gemini surfactant (SGS12) with different kinds of conventional surfactants on surface properties and solubility enhancement was investigated. Results indicated that the absolute values of βm were in the following order: SGS12/BQAS > SGS12/DTAB > SGS12/rhamnolipid > SGS12/SDS > SGS12/Triton X-100. The cationic/anionic surfactant mixtures formed micelles at a low concentration, which resulted from the strong attraction among different charged hydrophilic headgroups. Moreover, the molar solubilization ratio and lnKm values indicated that the solubility of SGS12/BQAS, SGS12/Triton X-100, and SGS12/DTAB mixtures toward pyrene was higher than that of either component. The micelle's hydrodynamic sizes of cationic/anionic surfactant mixtures were larger than that of either component, so the hydrophobic space to dissolve additional pyrene was large. Furthermore, dynamic surface tension determination suggested that cationic/anionic surfactant mixtures had a relatively short induction period, and the n values for SGS12/BQAS and SGS12/DTAB mixtures were slightly larger than those for either component. At the total surfactant concentration of 1 μmol·L−1, the plots of γt versus t1/2 for all surfactant mixtures were linear, indicating that the initial adsorption was controlled by diffusion. The values of Dt→0 for SGS12/BQAS, SGS12/DTAB, and SGS12/rhamnolipid mixtures were higher than those of either pure component. Therefore, the mixture of these surfactants accelerated the adsorption process and lowered the adsorption energy barrier, and the mixing of cationic and anionic surfactants was beneficial for dynamic surface activity. In conclusion, the cationic/anionic surfactant mixtures demonstrated good potential for the remediation of polycyclic aromatic hydrocarbon-contaminated soils from equilibrium and dynamic viewpoints.

A natural biosorbent prepared from wheat bran (WB) and multiple quaternary ammonium salts (MQAS) was used to remove dye (AR-18) from aqueous solution. The adsorption kinetics and thermodynamic mechanism of the adsorption of AR-18 on MQAS-WB were also examined. Results reveal that adsorption isotherm data can be well described by Langmuir model. The calculated thermodynamic parameters indicate that the adsorption is exothermic and spontaneous. The adsorption kinetics follows the pseudo-second-order model. MQAS-WB shows potential for large-scale wastewater treatment. Dynamic adsorption studies reveal that the dye removal efficiency of the packing column of MQAS-WB is higher than that of raw WB.

This paper focuses on image segmentation, image correction and spatial-spectral dimensional denoising of images in hyperspectral image preprocessing to improve the classification accuracy of hyperspectral images. Firstly, the images were filtered and segmented by using spectral angle and principal component analysis, and the segmented results are intersected and then used to mask the hyperspectral images. Hyperspectral images with a excellent segmentation result was obtained. Secondly, the standard reflectance plates with reflectance of 2 and 98% were used as a priori spectral information for image correction of samples with known true spectral information. The mean square error between the corrected and calibrated spectra is less than 0.0001. Comparing with the black-and-white correction method, the classification model constructed based on this method has higher classification accuracy. Finally, the convolution kernel of the one-dimensional Savitzky-Golay (SG) filter was extended into a two-dimensional convolution kernel to perform joint spatial-spectral dimensional filtering (TSG) on the hyperspectral images. The SG filter (m = 7,n = 3) and TSG filter (m = 3,n = 4) were applied to the hyperspectral image of Pavia University and the quality of the hyperspectral image was evaluated. It was found that the TSG filter retained most of the original features while the noise information of the filtered hyperspectral image was less. The hyperspectral images of sample 1–1 and sample 1–2 were processed by the image segmentation and image correction methods proposed in this paper. Then the classification models based on SG filtering and TSG filtering hyperspectral images were constructed, respectively. The results showed that the TSG filter-based model had higher classification accuracy and the classification accuracy is more than 98%.

Topological electronics has extended its richness to non-electronic systems where phonons and magnons can play the role of electrons. In particular, topological phases of magnons can be enabled by the Dzyaloshinskii-Moriya interaction (DMI) which acts as an effective spin-orbit coupling. We show that besides DMI, an alternating arrangement of Heisenberg exchange interactions critically determines the magnon band topology, realizing a magnonic analog of the Su-Schrieffer-Heeger model. On a honeycomb ferromagnet with perpendicular anisotropy, we calculate the topological phase diagram, the chiral edge states, and the associated magnon Hall effect by allowing the relative strength of exchange interactions on different links to be tunable. Including weak phonon-magnon hybridization does not change the result. Candidate materials are discussed.

Electroreduction uses renewable energy to upgrade carbon dioxide to value-added chemicals and fuels. Renewable methane synthesized using such a route stands to be readily deployed using existing infrastructure for the distribution and utilization of natural gas. Here we design a suite of ligand-stabilized metal oxide clusters and find that these modulate carbon dioxide reduction pathways on a copper catalyst, enabling thereby a record activity for methane electroproduction. Density functional theory calculations show adsorbed hydrogen donation from clusters to copper active sites for the *CO hydrogenation pathway towards *CHO. We promote this effect via control over cluster size and composition and demonstrate the effect on metal oxides including cobalt(II), molybdenum(VI), tungsten(VI), nickel(II) and palladium(II) oxides. We report a carbon dioxide-to-methane faradaic efficiency of 60% at a partial current density to methane of 135 milliampere per square centimetre. We showcase operation over 18 h that retains a faradaic efficiency exceeding 55%. Electroreduction uses renewable energy to upgrade carbon dioxide to value-added chemicals and fuels. Here, the authors design a suite of ligand-stabilized metal oxide clusters to modulate the reduction pathways on a copper catalyst, enabling record activity for CO2-to-methane conversion.

In magnetic topological insulators, quantized electronic transport is interwined with spontaneous magnetic ordering, as magnetization controls band gaps, hence band topology, through the exchange interaction. We show that considering the exchange gaps at the mean-field level is inadequate to predict phase transitions between electronic states of distinct topology. Thermal spin fluctuations disturbing the magnetization can act as frozen disorders that strongly scatter electrons, reducing the onset temperature of quantized transport appreciably even in the absence of structural impurities. This effect, which has hitherto been overlooked, provides an alternative explanation of recent experiments on intrinsic magnetic topological insulators.

We explore the moir\'e magnon bands in twisted bilayer magnets with next-nearest neighboring Dzyaloshinskii-Moriya interactions, assuming that the out-of-plane collinear magnetic order is preserved under weak interlayer coupling. By calculating the magnonic band structures and the topological Chern numbers for four representative cases, we find that (i) the valley moir\'e bands are extremely flat over a wide range of continuous twist angles; (ii) the topological Chern numbers of the lowest few flat bands vary significantly with the twist angle; and (iii) the lowest few topological flat bands in bilayer antiferromagnets entail nontrivial thermal spin transport in the transverse direction; These properties make twisted bilayer magnets an ideal platform to study the magnonic counterparts of moir\'e electrons, where the statistical distinction between magnons and electrons leads to fundamentally new physical behavior.

Developing efficient, low-cost, and biocompatible electrocatalysts toward hydrogen evolution reaction (HER) in neutral environments is vital to the development of a hybrid water splitting–biosynthetic system to achieve high-efficiency solar-to-fuels conversion. We report here a strategy to improve the sluggish HER kinetics on 3d transition-metal hydroxides by incorporating tungsten through a one-step electrodeposition method. The prepared amorphous CoW(OH)x delivers high HER activity in neutral solution, which only requires overpotentials of −73.6 and −114.9 mV to achieve the current densities of −10 and −20 mA cm–2 in 1.0 M phosphate buffer solution (PBS), respectively. The activity can be ascribed to the synergistic effects between Co and W, where Co sites facilitate H2O dissociation to generate Had intermediates and W sites could effectively convert Had to H2. Meanwhile, the amorphous architecture features homogeneously dispersed Co and W atoms that avoid crystalline phase separation, further strengthe...

The search of efficient and stable photocatalysts for the evolution of hydrogen from water using solar energy is of great importance for material science today. Limited by the relatively inferior stability of oxynitrides, the availability of these visible-light-response materials in photocatalysis is still far below what is expected. Here we report a novel oxynitride Ce0.3Zr0.7O1.88N0.12 as an efficient and stable H2-evolving photocatalyst under visible light irradiation, which can further enable overall water splitting by coupling with an O2-evolving photocatalyst via Z-scheme. Experimental and theoretical results together reveal that the origin of the excellent activity and stability of Ce0.3Zr0.7O1.88N0.12 photocatalyst can be attributed to the improved separation rate of photoexcited charge carriers by surface and sub-surface oxygen vacancies. The present study provides a strategy to engineer efficient and stable photocatalysts, and the oxynitride mentioned above could act as a promising candidate of H2-evolving photocatalyst for designing a prominent Z-scheme photocatalytic system.

Cadmiun sulfide (CdS) is considered as a promising semiconductor photocatalyst for its outstanding light absorbance and photoinduced charge separation, but it suffers from severe photocorrosion, mainly due to the sluggish kinetics of holes transfer. In this work, we introduce the strong local Coulomb attraction, which is demonstrated via the in situ K-edge X-ray absorption near edge (XANES) analysis, to accelerate the migration of holes for long-term photocatalytic activity. As a proof-of-concept sample, the hole-attraction Fe2O3/CdS nanorods evidence an outstanding stability of at least 6 days without obvious deactivation, and feature with an excellent H2 evolution rate of 20.7 mmol g−1 h−1. Moreover, this Coulomb attraction strategy can be leveraged to enhance the photocatalytic performance of Zn0.5Cd0.5S, indicating the wide application of the strategy.

Exploiting high-efficient oxide-based electrocatalysts to accelerate water dissociation kinetics in hydrogen evolution reaction (HER) is crucial for alkaline water electrolysis system. Herein, we demonstrate a dual-defective Co3O4 nanoarrays (F-Co3O4-x) electrocatalyst with well-modulated electronic structure of Co-centers for greatly enhanced overall water-splitting (OWS). DFT calculations and kinetic analysis disclose that F-doping and O-vacancy can synergistically break the energy barrier limit of water dissociation step for facilitating the production of hydrogen free radical (H*) in alkaline HER. The F-Co3O4-x experimentally exhibits supersmall overpotentials of 77 and 192 mV at 10 and 100 mA cm−2, respectively, outperforming the most reported CoOx-based electrocatalysts. Furthermore, F-induced surface self-reconstruction is observed during oxygen evolution reaction (OER), in which abundant key intermediates (*OOH) generate with the F- leaching. The obtained F-Co3O4-x as a dual-functional electrocatalyst therefore gives an ultralow cell voltage of 1.56 V at 10 mA cm−2 with a long-term durability of 120 h in OWS configuration. This work exhibits a rational design of multiple-defect engineered electrocatalysts for high-performance overall water-splitting.

Hydroxyl modified UiO-66 ((OH)2-UiO-66-X%, X represents the mass content ratio of introduced 2,5-dihydroxyterephthalic acid) was prepared via a solvothermal reaction between zirconium tetrachloride, benzene-1,4-dicarboxylic acid (H2BDC), as well as 2,5-dihydroxyterephthalic acid (H2BDC-(OH)2). It was found that hydroxyl groups can act as the intramolecular hole scavenger to boost the photo-induced charge carrier separation to enhance Cr(VI) reduction. The photocatalytic Cr(VI) reduction activities of (OH)2-UiO-66-X% were investigated upon the irradiation of low-power ultraviolet LED light. The findings demonstrated that (OH)2-UiO-66-20% with good cyclicity and stability exhibited superior photocatalytic performances to both UiO-66 and (OH)2-UiO-66. The introduction of hydroxyl groups can also extend the light absorption region to longer wavelength in visible range, which provides possibility for displaying photocatalytic activities under sunlight. The effect of small molecule organic acid (SOAs), pH value, and co-existing inorganic ions on photocatalytic performances of (OH)2-UiO-66-20% were investigated. Tartaric acid (TA) as typical SOAs was introduced to the reaction system to further boost the photocatalytic Cr(VI) reduction via acting as hole scavenger, constructing charge-transfer-complex for quick electron transportation, and producing COO·- radicals. This work opened a new opportunity for modified MOFs for boosted elimination activities for environmental pollutants.

Metallic Ni3 P/Ni can be used as a co-catalyst to replace noble metal Pt for efficient photocatalytic hydrogen evolution, due to its excellent trapping-electron ability. The applications of metallic Ni3 P/Ni co-catalyst on CdS, Zn0.5 Cd0.5 S, TiO2 (Degussa P25) and g-C3 N4 are further confirmed, indicating its versatile applicability nature like Pt.

PDINH/MIL-88A(Fe) composites (PxMy) were fabricated from MIL-88A(Fe) and perylene-34,910-tetracarboxylic diimide (PDINH) via facile ball-milling strategy. The optimum P25M175 exhibited outstanding degradation performance toward chloroquine phosphate (CQ) by activating peroxydisulfate (PDS) under low power LED visible light. The synergistic effects of photocatalytic activations of PDS via the direct electron transfer PDS activation over P25M175 and indirect electron transfer PDS activation over pristine MIL-88A contributed to the boosted CQ degradation efficiency. The active species capture experimental data and electron spin resonance (ESR) determinations revealed that both active radicals (like SO4−, OH, O2−, h+) and nonradical singlet oxygen (1O2) participated in the CQ decomposition. The CQ degradation pathways and the toxicity evaluation of the intermediates were proposed based on LC–MS determination and DFT calculation. Also, P25M175 demonstrated good reusability and stability. The findings within this work offered deep insights into the mechanisms of organic pollutants degradation via photocatalysis-activated SR-AOP over Fe-MOF photocatalyst.

In the past 45 years, the search for semiconductors as active photocatalysts for overall water splitting has focused on insoluble materials and their hybrids. An important question is whether soluble semiconductors have the capacity for photocatalysis or similar applications. The dissolved semiconductors will lose the energy band structures for light absorption; however, the undissolved part in saturated solution can still generate electrons and holes under illumination. Unfortunately, this possibility has never been realized. Here we clearly demonstrate the use of a water-soluble sodium molybdate salt as an effective photocatalyst. The material can photocatalyze simultaneously the oxidation and reduction of water under band-gap irradiation. We anticipate that, as a large and traditional class of chemical compounds, the soluble semiconductors may have great potential to be applied in numerous important applications such as catalysis, photovoltaics, light emitting diodes and artificial photosynthesis.

The mechanism study of redox mediator to transfer the photogenerated electrons is extremely desirable for artificial Z-scheme photocatalytic systems. Here we find that the α-Fe2O3 exposed by {012} and {104} facets can facilitate the reduction of IO3−, which results in increasing the activity of photocatalytic water oxidation significantly. By employing NaIO3 as an electron acceptor, the O2 evolution activity (309.4 μmol h−1 g−1) of α-Fe2O3 photocatalyst mainly exposed by {012} and {104} facets is 84 times higher than that (3.68 μmol h−1 g−1) of α-Fe2O3 mostly exposed by {101} and {111} planes. We anticipate that the findings in this work may open the door for further development of enhanced Z-scheme photocatalytic systems.

Semiconductor photocatalysts are hardly to be employed for overall water splitting beyond 700 nm, owing to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs, however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Here we report, for the first time, that the black tungsten nitride can be employed as metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red-light irradiation for tungsten nitride. This work represents the first red-light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization.

Exfoliation of bulk graphitic carbon nitride (BCN) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic performance. Compared with BCN, the 2D g-C3N4 nanosheets (CNNS) have larger specific surface areas and more reaction sites. With the etching assistance of anhydrous ethylenediamine, BCN can be successfully peeled off into 2D CNNS with a large lateral size of more than 15 μm which is much larger than that of other works. After appropriate etch by anhydrous ethylenediamine, the specific surface area of g-C3N4 expands from 4.7 to 31.1 m2 g–1 and the photocatalytic hydrogen evolution rate increases 7.4 times, from 4.8 to 35.3 μmol h–1. In contrast to other reported methods, the strategy to fabricate 2D CNNS in this work is convenient and it is the first time to report the fabrication of 2D CNNS with the assistance of alkaline reagent.

Facilitating charge-carrier separation and transfer is fundamentally important to improve the photocatalytic performance of semiconductor materials. Herein, two-dimensional hexagonal WO3 nanoplates were synthesized by a two-step route: rapid evaporation and solid-phase sintering. It exhibits enhanced activity of photocatalytic water oxidation compared with bulk monoclinic WO3. The electron dynamics analysis reveals that a more efficient charge-carrier separation in the former can be obtained, the origin of which can be attributed to increased number of surface defects in hexagonal WO3 nanoplates. This work not only presents a novel and simple method to produce two-dimensional hexagonal WO3 nanoplates, but also demonstrates that surface defects and two- dimensional geometric structure can promote the charge separation, which may be extended to the design of other efficient photocatalysts.

Here, for the first time, we detect reversible structural changes of platinum oxide as an active site in photocatalytic water splitting by operando X-ray absorption fine structure spectroscopy. The platinum–oxygen bond length increases from 2.07 to 2.13 A and the coordination number reduces from 4.0 to 2.5 between the ex situ and operating photocatalysts.

The atomically controlled transition of nanohybrids and their effects on charge-carrier dynamics are highly desirable for fundamental studies in photocatalysis. Herein, for the first time, a method combining atomic monodispersity and single-atom alloy was used to prepare a new form of highly efficient silver-based cocatalysts (Ag25 & Pt1Ag24) on graphitic carbon nitride, representing a novel photocatalytic system for hydrogen evolution.

Metallic nickel nanoparticles well dispersed in graphitized carbon matrix (Ni@C) by pyrolysis of metal-organic frameworks and leaching treatment of hydrochloric acid could greatly enhance the photocatalytic activity of g-C 3 N 4 under visible light irradiation. For 2.0 wt% Ni@C/g-C 3 N 4 , the average hydrogen evolution rate is 2.15 mmol h −1 g −1 , which is around 88 times higher than that of pure g-C 3 N 4 , and even better than that of platinum-loaded g-C 3 N 4 . The remarkably improved photocatalytic activities through loading Ni@C can be attributed to the cooperative work of Ni nanoparticles and graphene layers, which facilitate the separation of photo-generated carriers and suppress the recombination of the electron-hole pairs. In addition, the hollow onion-like structure can restrain the formation of Ni-hydrogen bonds which modulates desorption of hydrogen. Our studies may open up a promising strategy to design economical noble-metal-free co-catalysts for efficient solar energy conversion.

Doping has been widely used to engineer efficient photocatalysts for the water-splitting process in energy conversion and storage systems. Although composition tuning through heteroatom doping is one of the strategies to enhance photoactivity, the origin of the increased activity by doping remains unclear and most illustrations of its role fall in the band engineering area. Herein, it is reported that the rhodium dopants on the surface of Zn2 GeO4 , which affect the band structure negligibly, can act as active sites for water splitting. As a result, the Rhδ+ /Zn2 GeO4 photocatalyst demonstrates excellent stability for up to 460 days and significant enhancement of the photocatalytic activity to that of the undoped photocatalyst. The findings in this work may open the door for a rethink of the detailed principles of dopants in photocatalysis, and highlight a feasible route to fabricating efficient photocatalysts.

This study investigates the degradation of petroleum hydrocarbon in contaminated soil using activated persulfate (PS) with ultrasound (US) and US/Fe. Various controlling factors including different PS dosage, ultrasonic power, pH, soil water ratio and soil particle size were considered. It was found that petroleum hydrocarbon degradation efficiency achieved up to 56.41% and 82.23% in US/PS and US/Fe/PS system, respectively. Based on the experimental results, the reaction rate of US/Fe/PS system was faster than US/PS system and the degradation efficiency enhanced significantly with the increasing ultrasonic power. Changing initial solution pH influenced the petroleum hydrocarbon reaction rate and the best performance would be achieved at pH of 5. The present work identified the main components of petroleum hydrocarbon pollutants in shale gas sites. The mechanism of petroleum hydrocarbon degradation on US/Fe/PS system were analyzed.

Photocatalytic water splitting for H2 evolution is regarded as the most promising way to overcome the energy and environmental crisis. Pt clusters as a cocatalyst can efficiently enhance the performance of H2 generation in most photocatalysts, but the activity is still unsatisfied. By tuning the electronic structures of materials, one can develop catalysts with enhanced activity. Here we synthesize a Pt-Au alloy with subnano size as cocatalyst on TiO2 nanosheets for photocatalytic H2 generation that shows an outstanding activity with a H2 generation rate of 80.1 μmol h-1 for at least 100 h. The activity is twice than the pure Pt cocatalyst, mainly because the optimized hydrogen adsorption energy on Pt cluster is tuned by Au atoms.

Modulating metal oxides The more difficult step in fuel cells and water electrolysis is the oxygen evolution reaction. The search for earth-abundant materials to replace noble metals for this reaction often turns to oxides of three-dimensional metals such as iron. Zhang et al. show that the applied voltages needed to drive this reaction are reduced for iron-cobalt oxides by the addition of tungsten. The addition of tungsten favorably modulates the electronic structure of the oxyhydroxide. A key development is to keep the metals well mixed and avoid the formation of separate phases. Science , this issue p. 333

Porous oxygen-doped graphitic carbon nitride (g-C3N4) with feeble nitrogen vacancies was fabricated through thermal polycondensation of melamine with an appropriate amount of polyvinylpyrrolidone. After optimization, the bandgap of g-C3N4 can be narrowed by 0.2 eV and the specific surface area expanded, which contribute to increasing the utilization of solar energy. Consequently, the optimized g-C3N4 exhibits impressive enhancement in photocatalytic hydrogen evolution performance, by nearly 5 times compared with the pristine one under the irradiation of visible light.

Metal-N-C materials have attracted considerable attention for electrocatalytic CO2 reduction. Local electronic and geometric structure of active sites in the metal-N-C catalysts significantly determine catalytic reactivity. In this work, atomically dispersed Fe species with different coordination environment are anchored into carbon supports through introducing aminated carbon nanotubes, as effectively revealed by the Cs-corrected transmission electron microscope and X-ray absorption near edge structure spectra. Electrochemical tests show that the catalyst with the aminated carbon nanotubes has a low overpotential (0.39 V) and high selectivity of CO up to 95.47 % at -0.6 V vs. RHE. The density functional theory calculation results indicate that the additional axial Fe-N coordination compared with the planar Fe-N coordination can reduce the free energy required for the desorption of CO from the adsorption site and inhibit the occurrence of hydrogen evolution reaction, thus leading to improve the selectivity of CO.

Identifying the influence of the step defects is crucial for the development of high-performance Pt-based catalysts towards oxygen reduction reaction (ORR). To this end, intense research based on the oxygen adsorption energy (Eads(O)) criterion has been carried out for Pt single crystals, yet hardly can these studies be applied to the alloy system, considering the strain and ligand effects. Here we demonstrated that for a typical alloy (that is Pt1.2Cu octahedron), the activity is in positive correlation with the number of steps which, however, are detrimental to ORR as determined by the Eads(O) results. Using a combination of kinetics and electron density differences calculations, a novel “hydrogen activation” pathway is put forward. It is shown that the step-edge atoms can apply a repulsive force on the adsorbed hydrogen atoms, which reduces the energy barrier of the rate-determining oxygen hydrogenation process by 0.1 eV compared with the corresponding smooth surface and eventually accelerates the ORR kinetics.

The post-processing of the measured velocity in particle image velocimetry (PIV) is a critical step in reducing error and predicting missing information of the flow field. In this work, time-resolved PIV data are incorporated with the incompressible Navier–Stokes (N–S) equations to reduce the measurement error and improve the accuracy. A pressure correction scheme (PCS) based on the projection method is adopted to solve the N–S equations, and an optimization algorithm is introduced to balance the fidelity between the PIV data and the numerical solutions. The PCS for PIV data, called PIV–PCS, cannot only reduce the errors in the velocity divergence and the curl of the pressure gradient but also ensure that the flow field satisfies the dynamic constraints imposed by the momentum equation. An important weight coefficient s that balances the level of the velocity modification with the residual of the governing equation is defined and numerically assessed. A method for optimizing the value of s is provided. The new approach is evaluated by two time-resolved PIV experiments: one on the 2D wake flow of a circular cylinder at low Reynolds number and one on tomographic PIV for the 3D wake flow of a hemisphere at high Reynolds number. All the numerical assessments and experimental applications are compared with the divergence-free smoothing (DFS) method. The results indicate that the presented PIV–PCS method is superior to the DFS method in terms of reducing the measurement error and recovering the real physical flow structures.

The sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics in air cathode severely refrain the development of the reversible Zn-air battery. Herein, we report the design and synthesis of co-doped Fe-Co4N@N-C nanosheet array derived from MOF precursor on carbon cloth as the dual-functional electrocatalyst to boost the reaction kinetics. The Fe, N co-doping significantly promotes the generation of abundant Pyridinic-N-M active sites for ORR due to the strong coordination effect between metal center and pyridinic nitrogen. The enriched Co3+ sites concurrently motivate the formation of targeted *OOH intermediates during OER with decreased charge transfer resistance. Such electrocatalyst therefore delivers high catalytic activity for both ORR and OER. When applied as air cathode for liquid Zn-air battery, the device exhibits a high specific energy density of 934 Wh kg−1 with excellent cycling stability, which is superior to the referenced Pt and Ru-based Zn-air batteries. Flexible solid-state Zn-air battery can also achieve a high volumetric power density of 72 mW cm-3 and good cycling durability under different bending states. This work gives a facile and cost-efficient strategy to construct bifunctional flexible electrode with enriched active sites for Zn-air batteries.

Electrochemical carbon dioxide reduction is a key reaction for carbon dioxide conversion to valuable fuels and chemicals. Due to the intrinsic stability of the carbon dioxide molecule, a catalyst is required to minimize the energy input and improve the reaction rates. Although the developed catalysts still suffer from low catalytic activity, selectivity, and stability, these could be enhanced by the involvement of sharp tip structure. Here, we report a nanowire-like zinc electrocatalyst with sharp tips for carbon dioxide reduction. The catalyst achieves a geometry current density of -40 mA cm-2 at a potential of -0.95 V versus reversible hydrogen electrode over 35 hours with a stable carbon monoxide Faradaic efficiency of 98±2 %. The carbon monoxide partial current density surpasses by 60 % of that of the best reported zinc catalyst.

We study the transport properties of a superconductor-quantum spin Hall insulator-superconductor Josephson junction both in the absence and in the presence of a DC bias voltage. As the system is predicted to host Majorana fermions at its interfaces, the Andreev bond states are supposed to exhibit a distinct $4\pi$ periodicity in the superconducting phase difference, namely the fractional Josephson effect. Using the non-equilibrium Greens function method, we calculate the current and the related current noise based on a tight-binding Hamiltonian. Our direct results show that the fractional Josephson effect can not be seen in equilibrium junctions. While in non-equilibrium junctions, this effect can be confirmed by the multiple Andreev reflections induced peaks of the non-equilibrium noise, which appear at discrete frequencies $\omega=neV$ with $n$ being an integer number.

The conductance measurement of a half quantized plateau in a quantum anomalous Hall insulator-superconductor structure is reported by a recent experiment [Q. L. He \textit{et al.}, Science 357, 294-299 (2017)], which suggests the existence of the chiral Majorana fermion modes. However, such half quantized conductance plateau may also originates from a disorder-induced metallic phase. To identify the exact mechanism, we study the transport properties of such a system in the presence of strong disorders. Our results show that the local current density distributions of these two mechanisms are different. In particular, the current noises measurement can be used to distinguish them without any further fabrication of current experimental setup.

A simple cadmium sulfide nanomaterial is found to be an efficient and stable electrocatalyst for CO2 reduction in aqueous medium for more than 40 h with a steady CO faradaic efficiency of approximately 95 %. Moreover, it can realize a current density of -10 mA cm-2 at an overpotential of -0.55 V on a porous substrate with similar selectivity. Theoretical and experimental results confirm that the high selectivity for CO2 reduction is due to its (0 0 0 2) face with sulfur vacancies that prefers CO2 molecule reduction in aqueous medium.

Boosting the sluggish kinetics of the hydrogen evolution reaction in alkaline environments is key for the large-scale application of water-alkali and chlor-alkali electrolysis. In this study, nitrogen atoms are used to precisely modulate electrochemical active sites on the surface of nickel oxide with low-coordinated oxygen atoms, to achieve enhanced kinetics in alkaline hydrogen evolution. Theoretical and experimental results demonstrate that surface charge redistribution after modulation facilitates both the initial water dissociation step and the subsequent recombination of Had from low-coordinated oxygen sites and desorption of OHad- from nickel sites, thus accelerating the overall hydrogen evolution process. The N-modulated nickel oxide enriched in low-coordinated oxygen atoms exhibits significantly enhanced activity with a small overpotential of -100 mV at the current density of -10 mA cm-2 and a robust stability over 90 h for hydrogen evolution in 1.0 m KOH.

We study the transport properties of a superconductor-quantum spin Hall insulator-superconductor (S-QSHI-S) hybrid system in the presence of a microwave radiation. Instead of adiabatic analysis or using the resistively shunted junction model, we start from the microscopic Hamiltonian and calculate the DC current directly with the help of the non-equilibrium Green's Functions method. The numerical results show that (i) the I-V curves of background current due to multiple Andreev reflections (MAR) exhibit a different structure with that in the conventional junctions, (ii) all Shapiro steps are visible and appear one by one at high frequency, while at low frequency, the steps evolve exactly as the Bessel functions and the odd steps are completely suppressed, implying a fractional Josephson effect., Comment: 5 pages, 3 figures

Extensive research interest has been attracted by the fact that recent experiments in cold atoms simulate the chiral edge states of (1 + 1)-dimensional quantum Hall systems with laser-assisted transitions between different atomic nuclear spin states in a one-dimensional optical lattice. Within such an optical lattice, we study the phase diagrams of filling hard-core fermions and hard-core bosons with internal spin states in the presence of dipole-dipolar interactions. Our results show that the interaction drives the fermionic (bosonic) systems from the normal (superfluid) phase into the fractional topological phase with possible crystalline orderings. The topological nature of the latter phase is identified by the numerical evaluation of the many-body Chern number. Remarkably, we find that a considerable spectrum gap stabilizes the fractional topological phase with a moderate interaction strength, while, for the normal/superfluid phase, the Thouless charge pumping fluctuates strongly for small spin systems but approaches its universal value 1/3 for fermionic and 1/2 for bosonic systems with large spins.