Engineering Cu/NiCu LDH Heterostructure Nanosheet Arrays for Highly-Efficient Water Oxidation.

The development of stable and efficient electrocatalysts for oxygen evolution reaction is of great significance for electro-catalytic water splitting. Bimetallic layered double hydroxides (LDHs) are promising OER catalysts, in which NiCu LDH has excellent stability compared with the most robust NiFe LDH, but the OER activity is not satisfactory. Here, we designed a NiCu LDH heterostructure electrocatalyst (Cu/NiCu LDH) modified by Cu nanoparticles which has excellent activity and stability. The Cu/NiCu LDH electrocatalyst only needs a low over-potential of 206 mV and a low Tafel slope of 86.9 mV dec-1 at a current density of 10 mA cm-2 and maintains for 70 h at a high current density of 100 mA cm-2 in 1M KOH. X-ray photoelectron spectroscopy (XPS) showed that there was a strong electronic interaction between Cu nanoparticles and NiCu LDH. Density functional theory (DFT) calculations show that the electronic coupling between Cu nanoparticles and NiCu LDH can effectively improve the intrinsic OER activity by optimizing the conductivity and the adsorption energy of oxygen-containing intermediates.

Atomically Dispersed Silver Atoms Embedded in NiCo Layer Double Hydroxide Boost Oxygen Evolution Reaction.

Bimetallic layered double hydroxides (LDHs) are promising catalysts for anodic oxygen evolution reaction (OER) in alkaline media. Despite good stability, NiCo LDH displays an unsatisfactory OER activity relative to the most robust NiFe LDH and CoFe LDH. Herein, a novel NiCo LDH electrocatalyst modified with single-atom silver grown on carbon cloth (AgSA -NiCo LDH/CC) that exhibits exceptional OER activity and stability in 1.0 m KOH is reported. The AgSA -NiCo LDH/CC catalyst only requires a low overpotential of 192 mV to reach a current density of 10 mA cm-2 , obviously boosting the OER activity of NiCo LDH/CC (410 mV@10 mA cm-2 ). Inspiringly, AgSA -NiCo LDH/CC can maintain its high activity for up to 500 h at a large current density of 100 mA cm-2 , exceeding most single-atom OER catalysts. In situ Raman spectroscopy studies uncover that the in situ formed NiCoOOH during OER is the real active species. Hard X-ray absorption spectrum (XAS) and density functional theory (DFT) calculations validate that single-atom Ag occupying Ni site increases the chemical valence of Ni elements, and then weakens the adsorption of oxygen-contained intermediates on Ni sites, fundamentally accounting for the enhanced OER performance.

In-situ surface reconstruction of single-crystal (NiFe)3Se4 nano-pyramid arrays for efficient oxygen evolution.

Transition metal-based selenides (TMSe) are considered as efficient pre-electrocatalysts towards oxygen evolution reaction (OER). However, the key factor in determining the surface reconstruction of TMSe under OER condition is not yet clear. Herein, we uncover that the crystallinity of TMSe will obviously impact the conversion degree from TMSe to transition metal oxyhydroxides (TMOOH) during OER. A novel single-crystal (NiFe)3Se4 nano-pyramid array grown on NiFe foam is fabricated by a facile one-step polyol process, which exhibits an excellent OER activity and stability, only requiring 170 mV to reach a current density of 10 mA cm-2 and can sustain for more than 300 h. In situ Raman spectrum studies reveals that the single-crystal (NiFe)3Se4 is partially oxidized on its surface during OER, generating a dense heterostructure of (NiFe)OOH/(NiFe)3Se4. Benefiting from the in situ formed heterointerface, the adsorption of OER intermediates on Ni active sites calculated by density functional theory (DFT) analysis is optimized, leading to the reduced energy barrier, which accounts for the enhanced intrinsic activity. This work not only reports a novel single-crystal (NiFe)3Se4 nano-pyramid array electrocatalyst with high-efficient OER performance, but also gains a deep insight into the role of the crystallinity of TMSe on the surface reconstruction during OER.

Engineering cation vacancies in high-entropy layered double hydroxides for boosting the oxygen evolution reaction.

High-entropy layered double hydroxides (HE-LDHs) are emerging as promising electrocatalysts towards the OER due to their high-entropy effect and the cocktail effect. However, the catalytic activity and stability of HE-LDHs is, as yet, unsatisfactory. Herein, we designed FeCoNiCuZn LDHs with rich cation vacancies, which need only low overpotentials of 227, 275 and 293 mV to reach 10, 100 and 200 mA cm-2, respectively, and show almost no decay up to 200 h at 200 mA cm-2. DFT calculations validate that the cation vacancies can boost the intrinsic activity of HE-LDHs through optimizing the adsorption energy of OER intermediates.

Super-Hydrophilic Microporous Ni(OH)x/Ni3 S2 Heterostructure Electrocatalyst for Large-Current-Density Hydrogen Evolution.

Exploiting active and stable non-precious metal electrocatalysts for alkaline hydrogen evolution reaction (HER) at large current density plays a key role in realizing large-scale industrial hydrogen generation. Herein, a self-supported microporous Ni(OH)x/Ni3 S2 heterostructure electrocatalyst on nickel foam (Ni(OH)x/Ni3 S2 /NF) that possesses super-hydrophilic property through an electrochemical process is rationally designed and fabricated. Benefiting from the super-hydrophilic property, microporous feature, and self-supported structure, the electrocatalyst exhibits an exceptional HER performance at large current density in 1.0 M KOH, only requiring low overpotential of 126, 193, and 238 mV to reach a current density of 100, 500, and 1000 mA cm-2 , respectively, and displaying a long-term durability up to 1000 h, which is among the state-of-the-art non-precious metal electrocatalysts. Combining hard X-rays absorption spectroscopy and first-principles calculation, it also reveals that the strong electronic coupling at the interface of the heterostructure facilitates the dissociation of H2 O molecular, accelerating the HER kinetics in alkaline electrolyte. This work sheds a light on developing advanced non-precious metal electrocatalysts for industrial hydrogen production by means of constructing a super-hydrophilic microporous heterostructure.

Boron Coordination Effect in Ni-Nx Doped Graphene Catalysts on the ORR Performance Based on DFT Calculations.

The coordination atoms of metal active site in transition metal N-doped carbon single atom electrocatalysts play a vital role in dominating the catalytic performance of oxygen reduction reaction (ORR) at the cathode of fuel cells or metal-air cells. In view of weak adsorption ability of Ni active site in NiN4 -C catalysts to oxygen intermediate states, herein we introduce boron atoms with smaller electronegativity than N and C atoms to modulate the local coordination environment and electronic structures of Ni site. First-principles density functional calculations reveal that both B substitution for N atoms (NiN2 B2 -C) and B coordinating with N and C (NiN4 B8 -C) can effectively optimize the Gibbs free energy of oxygen intermediate states and hence improve the catalytic activity of the materials. In addition, we propose that the trend change in catalytic activity is mainly governed by the filling of antibonding orbitals between Ni-3d and O-2p states near the Fermi level.

Engineering sulfur vacancies into Fe9S10 nanosheet arrays for efficient alkaline hydrogen evolution.

The development of Earth-abundant transition metal sulfide electrocatalysts with excellent activity and stability toward the alkaline hydrogen evolution reaction (HER) is critical but challenging. Iron-based sulfides are favored due to their economic benefits and good stability, but their intrinsic catalytic activity still needs to be improved urgently. Herein, we successfully prepared Fe9S10 nanosheet arrays on iron foam (Fe9S10/IF) through a simple one-step method and utilized plasma treatment to introduce S vacancies (Fe9S10-Vs/IF) to regulate their intrinsic catalytic activity. The final materials demonstrate excellent HER performance, and only need 149 mV to drive a current density of 10 mA cm-2 and a small Tafel slope of 50 mV dec-1. The experimental results show that the existence of S vacancies can enhance their intrinsic electrocatalytic activity. This work provides a reference value for the future regulation of iron-based sulfides and is devoted to the development of non-precious metal catalysts toward the HER.

Designing Zn-doped nickel sulfide catalysts with an optimized electronic structure for enhanced hydrogen evolution reaction.

Designing non-noble-metal electrocatalysts with excellent performance and economic benefits toward the hydrogen evolution reaction (HER) is extremely crucial for future energy development. In particular, the rational cationic-doped strategy can effectively tailor the electronic structure of the catalysts and improve the free energy of the adsorbed intermediate, thus enhancing HER performance. Herein we reported Zn-doped Ni3S2 nanosheet arrays supported on Ni foam (Zn-Ni3S2/NF) that were synthesized by a two-step hydrothermal process for improving HER catalysis under alkaline conditions. Remarkably, the obtained Zn-Ni3S2/NF displays excellent HER catalytic performance with an overpotential of 78 mV to reach a current density of 10 mA cm-2 and dramatic long-term stability for 18 h in 1 M KOH. In addition, the results based on the density functional theory calculations reveal that Zn dopants can modulate the electronic structure of Ni3S2 and optimize the hydrogen adsorption free energy (ΔGH*). Thus cationic-doping engineering provides an efficient method to enhance the intrinsic activities of transition-metal sulfides, which may contribute to the development of nonprecious electrocatalysts for HER.

Engineering Bimetallic NiFe-Based Hydroxides/Selenides Heterostructure Nanosheet Arrays for Highly-Efficient Oxygen Evolution Reaction.

Developing cost-effective and high-efficiency electrocatalysts toward alkaline oxygen evolution reaction (OER) is crucial for water splitting. Amorphous bimetallic NiFe-based (oxy)hydroxides have excellent OER activity under alkaline media, but their poorly electrical conductivity impedes the further improvement of their catalytic performance. Herein, a bimetallic NiFe-based heterostructure electrocatalyst that is composed of amorphous NiFe(OH)x and crystalline pyrite (Ni, Fe)Se2 nanosheet arrays is designed and constructed. The catalyst exhibits an outstanding OER performance, only requiring low overpotentials of 180, 220, and 230 mV at the current density of 10, 100, and 300 mA cm-2 and a low Tafel slope of 42 mV dec-1 in 1 m KOH, which is among the state-of-the-art OER catalysts. Based on the experimental and theoretical results, the electronic coupling at the interface that leads to the increased electrical conductivity and the optimized adsorption free energies of the oxygen-contained intermediates plays a crucial role in enhancing the OER activities. This work focusing on improving the OER performance via engineering amorphous-crystalline bimetallic heterostructure may provide some inspiration for reasonably designing advanced electrocatalysts.

Al-doped nickel sulfide nanosheet arrays as highly efficient bifunctional electrocatalysts for overall water splitting.

The development of low-cost, high-activity, durable non-precious metal bifunctional electrocatalysts is of great importance in the production of hydrogen by water electrolysis. In this work, we have prepared new Al-doped Ni3S2 nanosheet arrays grown on Ni foam (Al-Ni3S2/NF) as an excellent bifunctional electrocatalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The Al-Ni3S2/NF electrode obtained only requires extremely low overpotentials of 86 and 223 mV for the HER and OER to achieve a current density of 10 mA cm-2 in 1 M KOH, respectively. Moreover, the electrolytic cell assembled using this electrode as both cathode and anode provides a current density of 10 mA cm-2 at an extremely low battery voltage of 1.58 V relative to that with Ni3S2/NF (1.71 V). Additionally, both experimental results and theoretical calculations reveal that the increased electrochemical active surface area and optimized intermediate adsorption free energies are responsible for the enhanced electrocatalytic performance. This work provides a promising bifunctional electrocatalyst for water electrolysis in alkaline media with broad application prospects.

Interface engineering of Ag-Ni3S2 heterostructures toward efficient alkaline hydrogen evolution.

Exploring Earth-abundant transition-metal-based electrocatalysts with high performance toward the alkaline hydrogen evolution reaction (HER) is crucial for sustainable hydrogen production. Ni3S2 has been recently identified as a promising HER catalyst, but it has unfavorable water dissociation and hydrogen adsorption characteristics. Here, we report Ag-decorated Ni3S2 nanosheet arrays grown on Ni Foam (NF) (Ag-Ni3S2/NF) as efficient heterostructure electrocatalysts for the HER in alkaline media. The catalyst only requires a low overpotential of 89 mV at 10 mA cm-2, as well as sustaining long-term durability for 15 h. The experimental analysis, in combination with density functional theory calculation, demonstrates that the electronic coupling at the interface between Ni3S2 and Ag results in enhanced electronic conductivity and optimized hydrogen adsorption and water adsorption/dissociation free energies. This work not only develops a highly efficient catalyst toward the HER, but also sheds light on the structure-activity relationship of the heterostructure catalyst on an atomic scale.

Biological Control of Tomato Gray Mold Caused by Botrytis Cinerea with the Entomopathogenic Fungus Metarhizium Anisopliae.

Gray mold disease caused by Botrytis cinerea is a devastating disease that leads to serious financial loss. In this study, the entomopathogenic fungus Metarhizium anisopliae that acts against the gray mold pathogen B. cinerea was evaluated. M. anisopliae produced a significant inhibition zone in front of the B. cinerea colony in the dual culture test. In addition, volatile organic compounds generated by M. anisopliae were shown to have an inhibitory effect on B. cinerea mycelia growth and reduced 41% of gray mold severity of postharvest tomatoes. The 10% concentration of the culture filtrate of M. anisopliae inhibited 88.62% of colony radial growth as well as 63.85% of sclerotia germination and all conidia germination of B. cinerea. Furthermore, the culture filtrate of M. anisopliae retained its inhibitory effect against the radial growth of B. cinerea even after heating for 15 min at 100 °C. Feasible mechanisms of M. anisopliae involved in the control of B. cinerea were explored, and it was demonstrated that the plasma membrane of B. cinerea conidia was damaged by the product of metabolism of M. anisopliae. In addition, after treating with culture filtrate of M. anisopliae, the B. cinerea phenotype was shown to be abnormal, and cell organelles of B. cinerea mycelia were damaged significantly. A significant control efficacy of M. anisopliae against tomato gray mold was detected on both the detached leaf assay (84.24%) as well as the whole plant (72.38%). In addition, a 78% reduction in tomato fruit mold was detected at a 10% treated concentration of M. anisopliae. These findings suggest that M. anisopliae possesses potential as a biocontrol agent against tomato gray mold in the greenhouse and during the postharvest stage.

Flower-Like MoSe2/MoO2 Composite with High Capacity and Long-Term Stability for Lithium-Ion Battery.

A simple method is developed for the preparation of MoSe2/MoO2 composite with a flower-like structure for high-performance lithium-ion batteries (LIBs). MoSe2 could lead to fast and facile movement of Li+ due to its larger interlayer spacing. Meanwhile, MoO2 could protect the lamellar structure of MoSe2 from being destroyed in the charging/discharging processes to maintain the required active surface to electrolytes. In addition, the flower-like structure of the composite could effectively alleviate the volume expansion during charging/discharging. As LIBs are anode material, MoSe2/MoO2 composite demonstrates an excellent specific discharge capacity of 1042 mAh g-1 after 100 cycles at 0.1 A g-1, which is attributed to the synergistic effects of MoSe2 and MoO2 in the composite.

P-Doped Iron-Nickel Sulfide Nanosheet Arrays for Highly Efficient Overall Water Splitting.

Iron-nickel sulfide ((Ni,Fe)3S2) is one of the most promising bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media because of their metallic conductivity and low cost. However, the reported HER activity of (Ni,Fe)3S2 is still unsatisfactory. Herein, three-dimensional self-supported phosphorus-doped (Ni,Fe)3S2 nanosheet arrays on Ni foam (P-(Ni,Fe)3S2/NF) are synthesized by a simple one-step simultaneous phosphorization and sulfuration route, which exhibits dramatically enhanced HER activity as well as drives remarkable OER activity. The incorporation of P significantly optimized the hydrogen/water absorption free energy (ΔGH*/ΔGH2O*), enhanced electrical conductivity, and increased electrochemical surface area. Accordingly, the optimal P-(Ni,Fe)3S2/NF exhibits relatively low overpotentials of 98 and 196 mV at 10 mA cm-2 for HER and OER in 1 M KOH, respectively. Furthermore, an alkaline electrolyzer comprising the P-(Ni,Fe)3S2/NF electrodes needs a very low cell voltage of 1.54 V at 10 mA cm-2 and exhibits long-term stability and outperforms most other state-of-the-art electrocatalysts. The reported electrocatalyst activation approach by anion doping can be adapted for other transition-metal chalcogenides for water electrolysis, offering great promise for future applications.

Genome-Wide Identification and Characterization of the Cyclophilin Gene Family in the Nematophagous Fungus Purpureocillium lilacinum.

Purpureocillium lilacinum has been widely used as a commercial biocontrol agent for the control of plant parasitic nematodes. Whole genome analysis promotes the identification of functional genes and the exploration of their molecular mechanisms. The Cyclophilin (CYP) gene family belongs to the immunophillin superfamily, and has a conserved cyclophilin-like domain (CLD). CYPs are widely identified in prokaryotes and eukaryotes, and can be divided into single- and multi-domain proteins. In the present study, 10 CYP genes possessing the CLD, named PlCYP1-P10, were identified from the genome of P. lilacinum strain 36-1. Those 10 PlCYPs were predicted to have different cellular localizations in P. lilacinum. Phylogenetic and gene structure analysis revealed the evolutionary differentiation of CYPs between Ascomycotina and Saccharomycotina fungi, but conservation within the Ascomycotina fungi. Motif and gene structure distributions further support the result of phylogenetic analysis. Each PlCYP gene had a specific expression pattern in different development stages of P. lilacinum and its parasitism stage on eggs of Meloidogyne incognita. In addition, the 10 PlCYP genes exhibited different expression abundances in response to abiotic stresses, among which PlCYP4 was highly expressed at a high temperature (35 °C), while PlCYP6 was up-regulated under 5 mM of H2O2 stress. Furthermore, the heterologous expression of PlCYP4 and PlCYP6 in Escherichia coli enhanced the cellular tolerance against a high temperature and H2O2. In summary, our study indicates the potential functions of PlCYPs in virulence and the stress response, and also provides a frame for further analysis of the CYP gene family in Ascomycotina fungi.

Three-Dimensional S/CeO2/RGO Composites as Cathode Materials for Lithium⁻Sulfur Batteries.

In this paper, the synthesis of the three-dimensional (3D) composite of spherical reduced graphene oxide (RGO) with uniformly distributed CeO2 particles is reported. This synthesis is done via a facile and large-scalable spray-drying process, and the CeO2/RGO materials are hydrothermally compounded with sulfur. The morphology, composition, structure, and electrochemical properties of the 3D S/CeO2/RGO composite are studied using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), Raman spectra and X-ray photoelectron spectroscopy (XPS), etc. The electrochemical performance of the composites as electrodes for lithium⁻sulfur batteries is evaluated. The S/CeO2/RGO composites deliver a high initial capacity of 1054 mAh g-1, and retain a reversible capacity of 792 mAh g-1 after 200 cycles at 0.1 C. Profiting from the combined effect of CeO2 and RGO, the CeO2/RGO materials effectively inhibit the dissolution of polysulfides, and the coating of spherical RGO improves the structural stability as well as conductivity.

Ultrafast fabrication of nickel sulfide film on Ni foam for efficient overall water splitting.

Development of low-cost, high performance and stable non-noble electrocatalysts with both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities for overall water splitting is essential for future energy supply. Herein, for the first time, a facile and ultrafast synthetic method has been reported to fabricate nickel sulfide (Ni3S2) films on Ni foam (Ni3S2/NF) as efficient bifunctional electrodes for overall water splitting through direct dropping of mercaptoethanol solution followed by annealing at 300 °C for only 50 s. Thanks to the integrated three-dimensional (3D) configuration, the obtained Ni3S2/Ni foam exhibits excellent activity and stability for HER and OER with low overpotentials of 131 and 312 mV, respectively, to attain a current density of 10 mA cm-2 in alkaline media. Ni(OH)x species formed on the Ni3S2 surface serves as the actual catalytic site during OER reaction. Given the well-defined bifunctionality, an overall water-splitting device using two identical Ni3S2/NF electrodes delivers a current density of 10 mA cm-2 at a low cell voltage of 1.68 V in an alkaline water electrolyzer. This approach is promising as a simple method for depositing a wide range of useful transition metal sulfide electrocatalysts on corresponding metal substrate bifunctional electrodes for overall water splitting, shedding some light on the development of functional materials in energy chemistry.

High-Switching-Ratio Photodetectors Based on Perovskite CH3NH3PbI3 Nanowires.

Hybrid organic-inorganic perovskite materials have attracted extensive attention due to their impressive performance in photovoltaic devices. One-dimensional perovskite CH3NH3PbI3 nanomaterials, possessing unique structural features such as large surface-to-volume ratio, anisotropic geometry and quantum confinement, may have excellent optoelectronic properties, which could be utilized to fabricate high-performance photodetectors. However, in comparison to CH3NH3PbI3 thin films, reports on the fabrication of CH3NH3PbI3 nanowires for optoelectrical application are rather limited. Herein, a two-step spin-coating process has been utilized to fabricate pure-phase and single-crystalline CH3NH3PbI3 nanowires on a substrate without mesoporous TiO2 or Al2O3. The size and density of CH3NH3PbI3 nanowires can be easily controlled by changing the PbI2 precursor concentration. The as-prepared CH3NH3PbI3 nanowires are utilized to fabricate photodetectors, which exhibit a fairly high switching ratio of ~600, a responsivity of 55 mA/W, and a normalized detectivity of 0.5 × 1011 jones under 532 nm light illumination (40 mW/cm²) at a very low bias voltage of 0.1 V. The as-prepared perovskite CH3NH3PbI3 nanowires with excellent optoelectronic properties are regarded to be a potential candidate for high-performance photodetector application.