The dynamic features and microbial mechanism of nitrogen transformation for hydrothermal aqueous phase as fertilizer in dryland soil.

Hydrothermal aqueous phase (HAP) contains abundant organics and nutrients, which have potential to partially replace chemical fertilizers for enhancing plant growth and soil quality. However, the underlying reasons for low available nitrogen (N) and high N loss in dryland soil remain unclear. A cultivation experiment was conducted using HAP or urea to supply 160 mg N kg-1 in dryland soil. The dynamic changes of soil organic matters (SOMs), pH, N forms, and N cycling genes were investigated. Results showed that SOMs from HAP stimulated urease activity and ureC, which enhanced ammonification in turn. The high-molecular-weight SOMs relatively increased during 5-30 d and then biodegraded during 30-90 d, which SUV254 changed from 0.51 to 1.47 to 0.29 L-1 m-1. This affected ureC that changed from 5.58 to 5.34 to 5.75 lg copies g-1. Relative to urea, addition HAP enhanced ON mineralization by 8.40 times during 30-90 d due to higher ureC. It decreased NO3-N by 65.35%-77.32% but increased AOB and AOA by 0.25 and 0.90 lg copies g-1 at 5 d and 90 d, respectively. It little affected nirK and increased nosZ by 0.41 lg copies g-1 at 90 d. It increased N loss by 4.59 times. The soil pH for HAP was higher than that for urea after 11 d. The comprehensive effects of high SOMs and pH, including ammonification enhancement and nitrification activity inhibition, were the primary causes of high N loss. The core idea for developing high-efficiency HAP fertilizer is to moderately inhibit ammonification and promote nitrification.

Rational design of dense microporous carbon derived from coal tar pitch towards high mass loading supercapacitors.

The compact carbon materials with huge specific surface area (SSA) and proper pore structure are highly desirable towards high-performance supercapacitors at the cell level. However, to well balance of porosity and density is still an on-going task. Herein, a universal and facile strategy of pre-oxidation-carbonization-activation is employed to prepare the dense microporous carbons from coal tar pitch. The optimized sample POCA800 not only possesses a well-developed porous structure with the SSA of 2142 m2 g-1 and total pore volume (Vt) of 1.540 cm3 g-1, but also exhibits a high packing density of 0.58 g cm-3 and proper graphitization. Owing to these advantages, POCA800 electrode at areal mass loading of 10 mg cm-2 shows a high specific capacitance of 300.8 F g-1 (174.5 F cm-3) at 0.5 A g-1 and good rate performance. The POCA800 based symmetrical supercapacitor with a total mass loading of 20 mg cm-2 displays a large energy density of 8.07 Wh kg-1 at 125 W kg-1 and remarkable cycling durability. It is revealed that the prepared density microporous carbons are promising for practical applications.

Structural Transformation by Crystal Engineering Endows Aqueous Zinc-Ion Batteries with Ultra-long Cyclability.

Manganese oxide is a promising cathode material for aqueous zinc batteries. However, its weak structural stability, low electrical conductivity, and sluggish reaction kinetics lead to rapid capacity fading. Herein, a crystal engineering strategy is proposed to construct a novel MnO2 cathode material. Both experimental results and theoretical calculations demonstrate that Al-doping plays a crucial role in phase transition and doping-superlattice structure construction, which stabilizes the structure of MnO2 cathode materials, improves conductivity, and accelerates ion diffusion dynamics. As a result, 1.98% Al-doping MnO2 (AlMO) cathode shows an incredible 15 000 cycle stability with a low capacity decay rate of 0.0014% per cycle at 4 A g-1 . Additionally, it provides superior specific capacity of 311.2 mAh g-1 at 0.1 A g-1 and excellent rate performance (145.2 mAh g-1 at 5.0 A g-1 ). To illustrate the potential of 1.98%AlMO to be applied in actual practice, flexible energy storage devices are fabricated and measured. These discoveries provide a new insight for structural transformation via crystal engineering, as well as a new avenue for the rational design of electrode material in other battery systems.

CeO2/MnOx@C hollow cathode derived from self-assembly of Ce-Mn-MOFs for high-performance aqueous zinc-ion batteries.

The construction of composite materials is an effective strategy to solve the problems of poor conductivity, manganese dissolution, and volume expansion of manganese-based materials. Herein, a CeO2/MnOx@C hollow composite cathode derived from the self-assembly of Ce-Mn-metal-organic frameworks (Ce-Mn-MOFs) was synthesized. The abundant oxygen vacancies and good electronic/ionic conductivity of CeO2 improve the electrical conductivity of composite, enhancing the rate performance. The unique hollow structure could inhibit manganese dissolution and alleviate volume expansion. The results indicate that the 1 % CeO2/MnOx@C composite cathode possesses a high reversible capacity and excellent cycling stability. Specifically, the 1 % CeO2/MnOx@C composite cathode shows a remarkable reversible specific capacity of 130 mAh/g at a current density of 500 mA g-1, 6.5 times more than the pure MnOx (20 mAh/g). The capacity retention is up to 99.5 % relative to the initial capacity after 800 cycles. This study provides a new strategy for designing rare-earth composite electrodes to improve electrochemical performance.

MoS2/Ni3S2 Schottky heterojunction regulating local charge distribution for efficient urea oxidation and hydrogen evolution.

Electrocatalytic urea oxidation reaction (UOR) is a prospective method to substitute the slow oxygen evolution reaction (OER) and solve the problem of urea-rich water pollution due to the low thermodynamic voltage, but its complex six-electron oxidation process greatly impedes the overall efficiency of electrolysis. Here, density functional theory (DFT) calculations imply that the metallic Ni3S2 and semiconductive MoS2 could form Mott-Schottky catalyst because of the suitable band structure. Therefore, we synthesized MoS2/Ni3S2 electrocatalyst by a simple hydrothermal method, and studied its UOR and hydrogen evolution reaction (HER) performance. The formed MoS2/Ni3S2 Schottky heterojunction is only required 109  and 166 mV to obtain ±10 mA cm-2 for UOR and HER, respectively, showing great bifunctional catalytic activity. Moreover, the full urea electrolysis driven by MoS2/Ni3S2 delivers 10 and 100 mA cm-2 at a relatively low potential of 1.44 and 1.59 V. Comprehensive experiments and DFT calculations demonstrate that the MoS2/Ni3S2 Schottky heterojunction causes self-driven charge transfer at the interface and forms built-in electric field, which is not only benefit to reduce H* adsorption energy, but also helps to adjust the absorption and directional distribution of urea molecules, thereby promoting the activity of decomposition of water and urea. This research furnishes a tactic to devise more efficient catalysts for H2 generation and the treatment of urea-rich water pollution.

Pore structure regulation of hierarchical porous carbon derived from coal tar pitch via pre-oxidation strategy for high-performance supercapacitor.

Carbon materials with rational pore structure have attracted tremendous attention in high-performance supercapacitor applications. However, designing and constructing such carbon materials with excellent performances via a simple and low-cost route is still a challenge. Herein, the nitrogen self-doped oxygen-rich hierarchical porous carbons (OTSx-PC) derived from coal tar pitch are constructed via a facile strategy of air pre-oxidation-activation. The air pre-oxidation treatment can effectively regulate the small-sized mesopore structure (2-4 nm) of samples. The optimal OTS350-PC sample exhibits a high specific capacitance of 298 F g-1 at 0.5 A g-1, and delivers a high energy density of 14.9 Wh kg-1 at a power density of 0.15 kW kg-1 with remarkable cycling stability in KOH aqueous electrolyte. This excellent electrochemical performance is attributed to its ultrahigh specific surface area (SSA, 2941 m2 g-1), huge total pore volume (Vt, 1.9 cm3 g-1), rational pore structure and reasonable heteroatom configuration, which ensure sufficient charge storage, rapid electrolyte ions diffusion, as well as the contributed pseudocapacitance. This research not only offers a facile route for high-value utilization of coal tar pitch but also provides the cost-effective and excellent porous carbons for supercapacitor with high performance.

Synergistic mechanism of Ni(OH)2/NiMoS heterostructure electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all pH ranges.

Designing and fabricating efficient electrocatalysts is a practical step toward the commercial application of the efficient hydrogen evolution reaction (HER) over all pH ranges. Herein, novel Ti@Ni(OH)2-NiMoS heterostructure with interface between crystalline Ni(OH)2 and amorphous NiMoS was rationally designed and fabricated on Ti mesh (denoted as Ti@Ni(OH)2-NiMoS). Acid etching and calcination experiments helped in accurate elucidation of the synergistic mechanism as well as the vital role on crystalline Ni(OH)2 and amorphous NiMoS. In acidic solutions, the HER performance of Ti@Ni(OH)2-NiMoS was mainly attributed to the amorphous NiMoS. In neutral, alkaline, and natural seawater solutions, the HER performance was mainly determined by the synergistic interface behaviors between the Ni(OH)2 and NiMoS. The crystalline Ni(OH)2 accelerated water dissociation kinetics, while the amorphous NiMoS provided abundant active sites and allowed for fast electron transfer rates. To deliver current densities of 10 mA·cm-2 in acidic, neutral, alkaline, and natural seawater solutions, the Ti@Ni(OH)2-NiMoS required overpotentials of 138, 198, 180 and 371 mV, respectively. This paper provides general guidelines for designing efficient electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all-pH ranges.

In situ fabrication of Bi2MoO6/Bi2MoO6-x homojunction photocatalyst for simultaneous photocatalytic phenol degradation and Cr(VI) reduction.

In this work, we designed a novel Bi2MoO6/Bi2MoO6-x homojunction photocatalyst and successfully fabricated by a facile solvothermal-calcination approach. Experimental characterizations indicated that the formation of Bi2MoO6/Bi2MoO6-x homojunction was caused by controlling oxygen vacancies formation. Such Bi2MoO6/Bi2MoO6-x homojunction exhibits about 240 times higher photocatalytic activity towards phenol degradation as compared with pure Bi2MoO6 under visible light irradiation. Similarly, for a co-existed phenol and Cr(VI) model system, Bi2MoO6/Bi2MoO6-x-catalyzed the photodegradation of phenol and the reduction of Cr(VI) simultaneously occur, and Bi2MoO6/Bi2MoO6-x homojunction also displays a superior photocatalytic activity, that is 4 and 8 times higher than pure Bi2MoO6, respectively. The remarkably boosted photocatalytic activity could be attributed primarily to the highly efficient separation of photogenerated electrons/holes due to the homojunction and the synergistic effect between phenol oxidation and Cr(VI) reduction. Thus, the present insight provides an effective strategy for designing and preparing highly active photocatalysts with the incorporation of oxygen vacancies modulation and applying for environmental remediation.

Catalytic degradation of caffeic acid by DBD plasma and Mn doped cobalt oxyhydroxide catalyst.

In this study, caffeic acid (CA) was degraded by electrical discharge plasma combined with Mn doped CoOOH catalyst. Doping of Mn significantly improve the catalytic activity of CoOOH. CA degradation efficiency was 75.6% with dielectric barrier discharge treatment for 10 min, and it reached 97% using CoOOH as the catalyst at the same treatment time. CA was 100% degraded with only 8 min using Mn/CoOOH as the catalyst. The introduction of Mn into the lattice of CoOOH induced the formation of oxygen vacancy, causing part of coordinate number of Co decreased from 6 to 5, and thus produces unsaturated Co to be the Lewis acid sites. Lewis acid sites (unsaturated Co) could coordinate with O3 and H2O2 and break their chemical bonds to form O and -OH. Assisting in the conversion of O3 to ·OH was the main role of H2O2 in the catalytic process. The degradation products and pathway of CA were studied by three-dimensional fluorescence, liquid chromatograph-mass spectrometer and density functional theory calculations.

Photocatalytic performance and mechanism insights of a S-scheme g-C3N4/Bi2MoO6 heterostructure in phenol degradation and hydrogen evolution reactions under visible light.

Photocatalysis with potentially low cost and sustainable utilization is a typically environmentally benign method for the degradation of organic pollutants, but the rational design and fabrication of photocatalysts with high catalytic performance is still an enormous challenge. The efficient segregation of photogenerated electron-hole pairs in photocatalysts is a key and essential factor to decide photocatalytic activity. Herein, a novel Step-scheme (S-scheme) heterojunction photocatalyst, a g-C3N4/Bi2MoO6 (g-CN/BMO) composite, was successfully fabricated using g-C3N4 nanosheet-wrapped Bi2MoO6 microspheres. By adjusting the amount of g-C3N4 in BMO, a series of g-CN/BMO composites was prepared while optimizing posttreatment temperature. The resulting g-CN/BMO indicated well the photocatalytic performance for the degradation of phenol and hydrogen evolution reactions, especially, 100 g of g-CN was integrated into 100 g of the pre-calcined BMO at 200 °C to produce 100% g-CN/BMO-200, showing the highest photocatalytic performance compared to single composite BMO, BMO-200, g-CN, and g-CN/BMO-200 with other mass ratios. Combining the results from the density functional theory calculations and the results of X-ray photoelectron spectroscopy, for S-scheme heterojunction-structured g-CN/BMO-200, the internal electric field-, band edge bending- and coulomb interaction-driven efficient segregation of photogenerated electrons and holes at the interface is elucidated to explain the photocatalytic mechanism, and the resulting holes on the VB of BMO and electrons on the CB of g-CN are responsible for the improvement of the photocatalytic performance. This study revealed that for the S-scheme g-CN/BMO composite the internal electric field, band edge bending and coulomb interaction at the interface between g-CN and BMO can not only promote the effective segregation of electrons and holes, but also retain stronger redox ability. Such an investigation provides a facile and simple strategy to fabricate novel S-scheme heterojunction-structured photocatalysts for solar energy conversion.

High-Capacity, Dendrite-Free, and Ultrahigh-Rate Lithium-Metal Anodes Based on Monodisperse N-Doped Hollow Carbon Nanospheres.

To unlock the great potential of lithium metal anodes for high-performance batteries, a number of critical challenges must be addressed. The uncontrolled dendrite growth and volume changes during cycling (especially, at high rates) will lead to short lifespan, low Coulombic efficiency (CE), and security risks of the batteries. Here it is reported that Li metal anodes, employing the monodisperse, lithiophilic, robust, and large-cavity N-doped hollow carbon nanospheres (NHCNSs) as the host, show remarkable performances-high areal capacity (10 mAh cm-2), high CE (up to 99.25% over 500 cycles), complete suppression of dendrite growth, dense packing of Li anode, and an extremely smooth electrode surface during repeated Li plating/stripping. In symmetric cells, a highly stable voltage hysteresis over a long cycling life >1200 h is achieved, and a low and stable voltage hysteresis can be realized even at an ultrahigh current density of 64 mA cm-2. Furthermore, the NHCNSs-based anodes, when paired with a LiFePO4 (LFP) cathode in full cells, give rise to highly improved rate capability (104 mAh g-1 at 10 C) and cycling stability (91.4% capacity retention for 200 cycles), enabling a promising candidate for the next-generation high energy/power density batteries.

The Novel Z-Scheme Ternary-Component Ag/AgI/α-MoO3 Catalyst with Excellent Visible-Light Photocatalytic Oxidative Desulfurization Performance for Model Fuel.

The novel ternary-component Ag/AgI/α-MoO3 (AAM) photocatalyst was successfully fabricated by a facile hydrothermal method combined with a charge-induced physical adsorption and photo-reduced deposition technique. X-ray diffraction, scanning/transmission electron microscope, X-ray photoelectron, UV-vis diffuse reflectance, photoluminescence and electrochemical impedance spectroscopy were employed to characterize the composition, morphology, light-harvesting properties and charge transfer character of the as-synthesized catalysts. The ternary-component AAM heterojunctions exhibited an excellent visible-light photocatalytic oxidative desulfurization activity, in which the AAM-35 (35 represents weight percent of AgI in AAM sample) possessed the highest photocatalytic activity of the conversion of 97.5% in 2 h. On the basis of band structure analysis, radical trapping experiments and electron spin resonance (ESR) spectra results, two different catalytic mechanisms were suggested to elucidate how the photogenerated electron-hole pairs can be effectively separated for the enhancement of photocatalytic performance for dual composites AM-35 and ternary composites AAM-35 during the photocatalytic oxidative desulfurization (PODS) of thiophene. This investigation demonstrates that Z-scheme Ag/AgI/α-MoO3 will be a promising candidate material for refractory sulfur aromatic pollutant's removal in fossil fuel.

Efficient Degradation of Phenol and 4-Nitrophenol by Surface Oxygen Vacancies and Plasmonic Silver Co-Modified Bi2 MoO6 Photocatalysts.

In this work, the surface plasmon resonance effect of metallic Ag, surface oxygen vacancies (SOVs), and Bi2 MoO6 (BMO) material were rationally combined to construct new oxygen-vacancy-rich Ag/Bi2 MoO6 (A/BMO-SOVs) photocatalysts. Their synergistic effect on the photocatalytic degradation of phenol and 4-nitrophenol under visible-light irradiation (λ≥420 nm) was also investigated. TEM, EPR, and Raman spectra demonstrate the co-existence of metallic Ag nanoparticles, surface oxygen vacancies, and Bi2 MoO6 due to a controlled calcination process. The experimental results disclose that the 2 %A/BMO-SOVs-375 sample exhibited the highest photocatalytic activity for the degradation of both phenol and 4-nitrophenol under visible-light irradiation, achieving nearly 100 and 80 % removal efficiency, respectively, and demonstrated the apparent reaction rate constants (kapp ) 183 and 26.5 times, respectively, higher than that of pure Bi2 MoO6 . The remarkable photodegradation performance of A/BMO-SOVs for organic substances is attributed to the synergistic effect between the surface oxygen vacancies, metallic Ag nanoparticles, and Bi2 MoO6 , which not only improves the visible-light response ability, but also facilitates charge separation. Thus, this work provides an effective strategy for the design and fabrication of highly efficient photocatalysts through integrating surface oxygen vacancies and the surface plasmon resonance effect of nanoparticles, which has the potential for both water treatment and air purification.

Structure, stability, electronic, magnetic, and catalytic properties of monometallic Pd, Au, and bimetallic Pd-Au core-shell nanoparticles.

Bimetallic core-shell nanoparticles (CSNPs) often exhibit excellent and tunable properties, depending on their composition, sizes, morphology, atomic arrangement, thickness, and sequence of both core and shell. In this study, the geometrical structure, thermodynamic stability, chemical activity, electronic and magnetic properties, and catalytic activity in the hydrogen evolution reaction (HER) of 13- and 55-atom Pd, Au NPs, and Pd-Au CSNPs were systematically investigated using density functional theory calculations. The results showed that Au atoms prefer to segregate to the surface-shell, while Pd atoms were inclined to aggregate in the core region for bimetallic Pd-Au CSNPs; therefore, Pd@Au CSNPs with an Au surface-shell were thermodynamically more favorable than both the monometallic Pd/Au NPs and the Au@Pd CSNPs with a Pd surface-shell. The Pd surface-shell of the Au@Pd CSNPs displayed a positive charge, while the Au surface-shell of the Au@Pd CSNPs exhibited a negative charge due to the charge transfer in the Pd-Au CSNPs, resulting in that the d-band center of Au@Pd with the Pd surface-shell showed larger shift toward the Fermi level and higher chemical activity. The Pd@Au CSNPs with the Au surface-shell showed similar d-band curves and d-band centers with monometallic Au NPs. All 13-atom Pd, Au NPs, and Pd-Au CSNPs were magnetic, while the 55-atom NPs were non-magnetic with symmetry partial density of states' curves except for Pd55. Changing the location of Pd and Au atoms in the Pd-Au CSNPs influenced their total magnetic moments. In addition, an opposite trend was found: small 13-atom NPs with a Pd surface-shell showed superior HER activity to the ones with an Au surface-shell, while large 55-atom NPs with an Au surface-shell possessed higher HER activity than the ones with a Pd surface-shell.

A 1,2-propylene oxide sensor utilizing cataluminescence on CeO2 nanoparticles.

A simple and sensitive gas sensor was proposed for the determination of 1,2-propylene oxide (PO) based on its cataluminescence (CTL) by oxidation in the air on the surface of CeO2 nanoparticles. The luminescence characteristics and optimal conditions were investigated in detail. Under optimized conditions, the linear range of the CTL intensity versus the concentration of PO was 10-150 ppm, with a correlation coefficient (r) of 0.9974 and a limit of detection (S/N = 3) of 0.9 ppm. The relative standard deviation for 40 ppm PO was 1.2% (n = 7). There was no or only weak response to common foreign substances including acetone, formaldehyde, ethyl acetate, acetic acid, chloroform, propanol, carbon tetrachloride, ether and methanol. There was no significant change in the catalytic activity of the sensor for 100 h. The proposed method was simple and sensitive, with a potential of detecting PO in the environment and industry.

Single-molecule magnet based on a C-type polyoxomolybdate with an S = 11 ground state: [Fe5CoMo22As2O85(H2O)]15-.

A C-type polyoxomolybdate containing a mixed-transition metal cluster Fe(5)Co has been prepared as an ammonium salt, (NH(4))(15)[Fe(5)CoMo(22)As(2)O(85)(H(2)O)]·15H(2)O (1). Interestingly, the magnetism measurements show that the compound exhibits not only an overall ferromagnetic cluster with a large spin ground state of S = 11 but also the behavior of single-molecule magnets.

Double sandwich polyoxometalate and its Fe(III) substituted derivative, [As2Fe5Mo21O82]17­ and [As2Fe6Mo20O80(H2O)2]16­.

A double sandwich polyoxometalate and its Fe(III) substituted derivative, [As(2)Fe(5)Mo(21)O(82)](17-) (1) and [As(2)Fe(6)Mo(20)O(80)(H(2)O)(2)](16-) (2), were synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, fluorescent spectroscopy, UV spectra, thermogravimetry-differential scanning calorimetry analyses, electrospray ionization mass spectrometry, and magnetism measurements. The polyoxoanion is composed of a central fragment FeMo(7)O(28) for 1 (Fe(2)Mo(6)O(26)(H(2)O)(2) for 2) and two external AsMo(7)O(27) fragments linked together by two distinct edge-sharing dimeric clusters Fe(2)O(10) to lead to a C(2v) molecular symmetry. The central FeMo(7)O(28) fragment and external AsMo(7)O(27) fragment have a similar structure, and both of them can be viewed as a monocapped hexavacant α-Keggin subunit with a central FeO(4) group or a central AsO(3) group. Both of the polyoxoanions contain a oxo-bridged Fe(III)(5) magnetic core with the angles of Fe-O-Fe in the range of 96.4(4)-125.7(5)°, and magnetism measurements show an overall ferromagnetic interactions among the five-nuclearity cluster Fe(5) with the spin ground state S = 15/2.