Defect-rich Structure Research Articles

Upgraded lithium storage performance of defect-rich Si@C anode assisted by Fe2O3-induced pseudocapacitance

Following a flowsheet comprised of a hydrothermal reaction and a dehydration/carbonization, Si-xFe/O@C anodes featured with Fe-doping and carbon encapsulation were assembled. Comparing with pure Si, Si disseminated with in situ generated nano-scaled ferric oxide (Fe2O3) particulates displays remarkably improved cyclic performance. Fe2O3 may induce amorphization and optimize electrical conductivity, by enhancing the formation of Fe and Li2O amidst charging-discharging cycles. The as-derived Fe phase benefits the transport and storage of lithium-ion and electrons. Meanwhile, numerous tiny interfaces can be constructed between Fe granules and adjacent LixSi or Li2O, and generate pseudocapacitance. After the carbonization of resorcinol-formaldehyde resin encapsulated on Si granules, core-shell structured Si-xFe/O@C particulates can be assembled. Owing to the synergism of defect-rich structure, carbon layer well-wrapped thereon and interfacial pseudocapacitance, these nanocomposite anode materials exhibit long cyclic and upgraded rate performance. After 200 cycles, Si-0.42Fe/O@C anode retains a capacity of 929 mAh·g−1 at 1 A·g−1 and 735 mAh·g−1 at 2 A·g−1. In the rate performance test operated at 5 A·g−1, a high current density, 844 mAh·g−1 could be released. Si-0.42Fe/O@C can be charged with a specific capacity exceeding 250 mAh·g−1 over the potential range of 0.75-3 V at various current densities, demonstrating the contribution of nano-Fe pseudocapacitance effect to the energy storage of Si anodes.

Effects of chelating agent on the nanostructure of nickel hexacyanoferrate and its performance in seawater battery application

With the increasing demand for cost-effective and safe energy storage systems, seawater batteries (SWBs) are establishing themselves in the field of rechargeable batteries. In particular, cathode materials based on the intercalation mechanism have received considerable attention owing to their low overpotential and high energy efficiency. In this study, nickel hexacyanoferrate (NiHCF) is used as an intercalation cathode material for SWB. NiHCF, a type of Prussian blue analog, has the advantages of a large interstitial volume to insert Na-ions and stability into seawater; however, it is often fabricated in a defect-rich structure. Therefore, the chelating effect of NiHCF is studied, and its structural and electrochemical properties are investigated. After introducing a chelating agent, defect-less NiHCF can be fabricated, and the well-constructed structure affects the electrochemical properties of the NiHCF. The structural behavior of NiHCF based on the insertion/extraction of Na-ions in the SWB full-cell is studied, and the chelated NiHCF cathode shows reversible cycling ability up to 2000 cycles with a capacity retention of 92.8%. This study offers a comprehensive understanding of the electrochemical properties of NiHCF and the operating mechanisms of intercalation cathode materials in SWB systems.

Vacancy-PBA derived nanoparticle containing defect-rich crystal structure and P, S dual-doping as an outstanding oxygen evolution electrocatalyst

Herein, a uniquely-designed electrocatalyst containing a defect-rich crystal structure and P, S dual dopant (designated v-NiFe-PS) is synthesized for the oxygen evolution reaction (OER). The [Fe(CN)6] vacancy-PBA (v-PBA) precursor is simply synthesized via mixing and post-oxidation. The defect-rich crystal structure is provided by the v-PBA precursor, and the P, S dual doping provides a tailored electronic distribution around the metal active sites, thereby reducing the energy barrier for the OER. This is confirmed by comparison of the v-NiFe-PS with single-doped v-NiFe-P and v-NiFe-S, and with NiFe-PS derived from non-vacancy PBA. As a result, the v-NiFe-PS exhibits the lowest overpotential (263 mV) and Tafel slope (41 mA dec–1) compared to the comparison groups and the benchmark (RuO2). Furthermore, the v-NiFe-PS exhibits a robust stability during 100 charge/discharge cycles, and a low voltage gap of 0.93 V at 1.0 mA cm–2.

Amorphous Mo-doped NiS0.5 Se0.5 Nanosheets@Crystalline NiS0.5 Se0.5 Nanorods for High Current-density Electrocatalytic Water Splitting in Neutral Media.

It is vitally important to develop highly active, robust and low-cost transition metal-based electrocatalysts for overall water splitting in neutral solution especially at large current density. In this work, amorphous Mo-doped NiS0.5 Se0.5 nanosheets@crystalline NiS0.5 Se0.5 nanorods (Am-Mo-NiS0.5 Se0.5 ) was synthesized using a facil one-step strategy. In phosphate buffer saline solution, the Am-Mo-NiS0.5 Se0.5 shows tiny overpotentials of 48 and 209 mV for hydrogen evolution reaction (HER), 238 and 514 mV for oxygen evolution reaction (OER) at 10 and 1000 mA cm-2 , respectively. Moreover, Am-Mo-NiS0.5 Se0.5 delivers excellent stability for at least 300 h without obvious degradation. Theoretical calculations revealed that the Ni sites in the defect-rich amorphous structure of Am-Mo-NiS0.5 Se0.5 owns higher electron state density and strengthened the binding energy of H2 O, which will optimize H adsorption/desorption energy barriers and reduce the adsorption energy of OER determining step.

ZIF template-based Fe-doped defect-rich hierarchical structure Co3S4/MoS2 as a bifunctional electrocatalyst for overall water splitting.

To replace the current expensive precious metal catalysts for water electrolysis, it is important to develop inexpensive and powerful bifunctional catalysts for hydrogen production. It is an effective way to improve catalytic performance using excellent templates and elemental doping. Here, a hierarchical structure Fe-Co3S4/MoS2 was synthesized using an Fe-ZIF precursor prepared by ion exchange, followed by hydrothermal sulfuration and annealing. It required overpotentials of only 93 mV and 243 mV to achieve a current density of 10 mA cm-2 in the HER and OER, respectively. It also showed excellent catalytic performance for overall water splitting, requiring only 1.42 and 1.71 V to achieve current densities of 10 and 100 mA cm-2 in 1 M KOH. The catalyst also demonstrated excellent ultra-long-term stability. The superb catalytic performance and stability can be attributed to the Fe doping, exposing more active sites while retaining the highly stable framework of the ZIF. The component modulation of Co3S4 and MoS2 by Fe doping induced high intrinsic activity and excellent transfer coefficients. This work presents a novel approach to prepare noble metal-free catalysts with highly stable rich interfaces and defects for overall water splitting.

Boosting the propylene selectivity over embryonic borosilicate zeolite catalyst for oxidative dehydrogenation of propane

Boron-containing zeolites have been proven potential in catalyzing the oxidative dehydrogenation (ODH) process and the boron sites in open coordination are considered as the active center. By considering the diversity and adjustability in the crystal structure of zeolite, there is a great opportunity to further tune the activity and selectivity. Herein, the embryonic borosilicate zeolite with abundant defective sites and developed large porosity is prepared for catalyzing ODH of propane reaction. An ∼ 20 % improvement in propylene selectivity is achieved at propane conversion of 21.5 % at 540 °C, with propylene productivity nearly an order of magnitude higher compared with crystalline MFI-type borosilicate zeolite. Solid-state NMR reveals the formation of boron sites in open coordination derived from the defect-rich structure of embryonic borosilicate zeolite, guaranteeing ample exposure of the active center. Combined with kinetic measurements, the reaction in the gas phase initiated by the active boron sites is mainly responsible for the high catalytic performance in ODH of propane reaction. The designed experiment indicates the strengthened gas-phase reaction facilitates the activation of propane, consequently resulting in the increase of reaction order of propane from 1.06 to 2.30. This work reveals the significant role of gas-phase reactions during the ODH of propane reaction and provides a new insight for boosting the propylene selectivity of zeolite-based catalysts.

Defect-Induced Dense Amorphous/Crystalline Heterophase Enables High-Rate and Ultrastable Sodium Storage.

Currently, the construction of amorphous/crystalline (A/C) heterophase has become an advanced strategy to modulate electronic and/or ionic behaviors and promote structural stability due to their concerted advantages. However, their different kinetics limit the synergistic effect. Further, their interaction functions and underlying mechanisms remain unclear. Here, a unique engineered defect-rich V2 O3 heterophase structure (donated as A/C-V2 O3- x @C-HMCS) composed of mesoporous oxygen-deficient amorphous - hollow core (A-V2 O3- x /HMC) and lattice-distorted crystalline shell (C-V2 O3 /S) encapsulated by carbon is rationally designed via a facile approach. Comprehensive density functional theory (DFT) calculations disclose that the lattice distortion enlarges the porous channels for Na+ diffusion in the crystalline phase, thereby optimizing its kinetics to be compatible with the oxygen-vacancy-rich amorphous phase. This significantly reduces the high contrast of the kinetic properties between the crystalline and amorphous phases in A/C-V2 O3- x @C-HMCS and induces the formation of highly dense A/C interfaces with a strong synergistic effect. As a result, the dense heterointerface effectively optimizes the Na+ adsorption energy and lowers the diffusion barrier, thus accelerating the overall kinetics of A/C-V2 O3- x @C-HMCS. In contrast, the perfect heterophase (defects-free) A/C-V2 O3 @C-HCS demonstrates sparse A/C interfacial sites with limited synergistic effect and sluggish kinetics. As expected, the A/C-V2 O3- x @C-HMCS achieves a high rate and ultrastable performance (192 mAh g-1 over 6000 cycles at 10 A g-1 ) when employed for the first time as a cathode for sodium-ion batteries (SIBs). This work provides general guidance for realizing dense heterophase cathode design for high-performance SIBs and beyond.

Carbon nanotube-vertical edge rich graphene hybrid sponge as multifunctional reinforcements for high performance epoxy composites

Thermal management materials with excellent electromagnetic interference (EMI) shielding performance have attracted research interest in the field of modern electronic devices. Herein, vertical edge rich graphene (VG) was in-situ grafted on the carbon nanotube (CNT) sponge to create connective 3D hybridized carbon skeleton with covalent bonding, then CNT-VG/epoxy composites were constructed to meet the needs of multifunctional application. Impressively, mainly owing to the connectivity of 3D CNT sponge, the conduction ability of interfaces and the defect-rich structure of VG, the obtained CNT-VG/epoxy composites possessed an enhanced EMI shielding effectiveness of 46.9 dB with a thickness of 1 mm and an improved thermal conductivity of 2.23 W m−1 K−1 which contributes to superior thermal management capability. In addition, the excellent structural design also increases the flexural strength by 349.39% compared to pure epoxy resin, achieving a flexural strength of 275.32 MPa and a work of fracture of 9956.98 kJ m−3. The novel multifunctional CNT-VG/epoxy composites with enhanced mechanical property show a bright application prospect in next-generation electronic devices.

Novel aptasensing strategy for efficiently quantitative analyzing Staphylococcus aureus based on defective copper-based metal–organic framework

We have proposed a novel electrochemical aptasensing strategy for efficiently detecting staphylococcus aureus (S. aureus) based on copper-based metal–organic framework encapsulated with plenty of Cu2O nanocrystals (represented by ML-Cu2O@Cu-MOF) synthesized using the mixed ligands of diphenylethyne-3,3′,5,5′-tetracarboxylic acid, 1,3,5-benzenetricarboxylic acid, and terephthalic acid. The ML-Cu2O@Cu-MOF nanospheres comprised multiple Cu valence states (Cu0/Cu+/Cu2+) and Cu2O nanocrystals, possessed defect-rich crystal structure, high anchoring ability toward aptamer and boosted electrical conductivity. The gained ML-Cu2O@Cu-MOF-based biosensor exhibited lower limit of detection toward S. aureus, as low as 2.0 and 1.6 CFU mL−1 within the S. aureus concentration from 10 to 1 × 108 CFU mL−1 obtained by electrochemical impedance spectroscopy and differential pulse voltammetry techniques, respectively. Additionally, the developed aptasensor also demonstrated high superior stability, excellent reproducibility, acceptable regeneration ability, and wide practicality. The present work can give rise to an alternative aptasensing strategy for analyzing foodborne bacteria or other food containments and ensuring food safety assessment.

Zn5(OH)6(CO3)2-assisted controlled fabrication of microcrystalline cellulose-derived hierarchical porous carbon for high-performance lithium storage

The proper N doping engineering and microstructure design are of essential importance to develop advanced carbon anodes for Li-ion batteries. Herein, a facile strategy was developed to fabricate hierarchical porous carbon with controllable pore structures, N doping content and configurations, which was easily realized via introducing zinc salt as recyclable activator and regulator in the precursors. The zinc salt could not only function as pore-forming agent to facilitate the formation of hierarchical porous defect-rich structure, but also act as N-confined reactor to preserve the N-containing intermediates and promote N doping in the carbon matrix during thermal conversion. Specifically, 21.7% N content (increased by 115%) which was mainly composed of pyridinic/pyrrolic N (88.6%) was achieved with the addition of Zn5(OH)6(CO3)2. Meanwhile, desirable mesopore-dominant hierarchical porous carbon with appropriate specific surface area was obtained. Benefiting from the unique microstructure and N functionalities, the NC-Zn5(OH)6(CO3)2 anode delivered a high reversible capacity of 564 mAh g−1 at 200 mA g−1 over 100 cycles, which was almost two times higher than those for NC, and remarkable long-term cycling stability with high coulombic efficiency around 100% after 1300 cycles at 1000 mA g−1. This work provides an intriguing and feasible avenue for the reasonable structure design of carbon material with superior electrochemical performance for sustainable energy storage.

Boosting fast and stable symmetric sodium-ion storage by synergistic engineering and amorphous structure

Tuning the microstructure and crystallinity of electrode materials is a great challenge and crucial for the development of high-performance sodium-ion batteries (SIBs). Herein, we develop a series of rationally designed carbon-coated V2O5 core-shell nanostructures (S-V2O5-HS, S-V2O5-HCS, P-V2O5/C-SCS, A-V2O5/C-SCS, and A-V2O5/C-WCS) in which the phase (single/polycrystalline, amorphous), microstructure (hollow, solid, porous) for the V2O5 core, and the thickness of the carbon shell are controlled via a one-pot solvothermal method followed by a single calcination process, and the performance differences between them are systematically studied. In this composite of amorphous carbon-coated V2O5 well-defined porous core-shell heterostructure (A-V2O5/C-WCS), synergistically the amorphous V2O5 core accelerates ions diffusion, carbon shell boosts the electronic conductivity, and the defect-rich porous structure lowers the binding energy compared to its counterparts as confirmed by DFT calculations and electrochemical results. Out of the ordinary, the A-V2O5/C-WCS used as a symmetric electrode for SIBs exhibits an excellent rate capability of 148 mAh g−1 at 5.0 A g−1 and outstanding ultralong cyclic stability (95% capacity retentions over 3000 cycles at 2.0 A g−1), when applied as a cathode (1.5–4.0 V) and anode (0.01–3.0 V) for SIBs. The A-V2O5/C-WCS displays a fully pseudocapacitive manner over the whole voltage thus the electrochemical performance of cathode and anode are well-matched. Impressively, the symmetric full-cell possesses a superior energy density of 219 Wh kg−1 at a high specific density of 6.0 KW kg−1 and superior cycling stability (95% capacity retained over 1200 cycles at 1.0 A g−1), demonstrating the great potential for practical application.

Structural Engineering of Cobalt-Free Perovskite Enables Efficient and Durable Oxygen Reduction in Solid Oxide Fuel Cells.

Developing low-cost, efficient, and durable cobalt-free perovskite oxides for oxygen reduction reaction at intermediate-to-low temperatures is crucial to enhance the viability of solid oxide fuel cells (SOFCs), a promising ingredient for establishing a more sustainable future. Herein, a highly active and robust cobalt-free perovskite Ba0.75 Sr0.25 Fe0.95 P0.05 O3-δ (BSFP) oxygen electrode via a facile co-doping strategy for intermediate-to-low temperature SOFCs (ILT-SOFCs) is reported by a combined experimental and theoretical approach. Attributed to stable and oxygen defect-rich structure, and remarkable intrinsic oxygen transport kinetics, the BSFP cathode shows exceptional catalytic performance, including record-level power output among iron-based perovskite cathodes (1464mW cm-2 at 600 °C), low area-specific resistance (≈0.1 Ω cm2 at 600 °C), robust stability both in symmetrical and single cell configurations, and outstanding CO2 tolerance/reversibility. The first-principle calculations validate the role of co-doping of strontium and phosphorus for the high activity and durability. Central to this work is the combined experiment-calculation approach to point to an effective strategy in the development of highly active and stable perovskite-type cathodes for ILT-SOFCs and related applications.

Additive manufacturing of nanocellulose/polyborosilazane derived CNFs-SiBCN ceramic metamaterials for ultra-broadband electromagnetic absorption

• Defect-rich CNFs were developed as electromagnetic absorbents. • Metamaterials were developed by the combination of 3D printing and PDC route. • Cole-Cole circle plots indicates the materials possess strong polarization capability. • Ultra-broad EAB of 32.4 GHz was achieved by multi-scale design. Electromagnetic absorption materials that possess efficient absorption performance and broad absorption bandwidth are needed to combat the electromagnetic interference (EMI). SiBCN ceramic-based metamaterials modified with defect-rich carbon nanofibers (CNFs) were developed by combining the additive manufacturing technique and polymer derived ceramic route. Meta-structures were patterned by additive manufacturing of preceramic polymer and followed by thermolysis of the green bodies. Defect-rich CNFs were in-situ generated by thermolysis of nanocellulose introduced into the preceramic green bodies. When the content of cellulose is 6.0 wt% and the annealing temperature is 1200 °C, the real and imaginary part of permittivity can reach as high as 17.0 and 7.0, respectively. Cole-Cole circle plots indicates that the CNFs-SiBCN ceramics possess strong polarization capability due to the defect-rich structure of CNFs. At the thickness of 1.8 mm, the minimal reflection loss (RL min ) can reach −20.0 dB while the effective absorption bandwidth reached 2.85 GHz. Through multi-scale (nano and macro) designing, a simulated ultra-broad effective absorption bandwidth of 32.4 GHz from 7.6 GHz to 40 GHz was achieved, where the RL min reached −46.0 dB at the frequency of 26.8 GHz. This work finds innovative route for the development of ceramic-based broadband electromagnetic absorption materials and new application for the polymer derived ceramics.

Green synthesis of graphite-based photo-Fenton nanocatalyst from waste tar via a self-reduction and solvent-free strategy

Thermochemical conversion of biomass yields large quantities of tar as a by-product, which is a potential precursor for the synthesis of renewable carbon-based functional materials. In this study, high-performance photo-Fenton catalyst of graphite‑carbon-supported iron nanoparticles was synthesized using a self-reduction and solvent-free approach. The results showed that the tar-derived catalyst had unique properties including a defect-rich graphitic structure, high surface area, and an abundant porous structure resulting from the inherent properties of biomass tar. The iron nanoparticles were highly dispersed within the prepared catalysts and were stably anchored on the carbonaceous surface by the FeC bond. The prepared nanocatalyst showed the highest decomposition constant (91.87 × 10−3 min−1) for 20 mM H2O2, and 40 mg/L RhB can be completely degraded within 2 h under catalyst dosage of 1 g/L and H2O2 addition of 20 mM. The degradation mechanism under the photo-Fenton catalyst/H2O2/light system included the heterogeneous Fenton reaction of iron nanoparticles and photo-Fenton reaction of iron oxide, and the efficient RhB degradation was mainly ascribed to the heterogeneous Fenton reaction. In addition, recycling and leaching tests demonstrated that the photo-Fenton catalyst had excellent reusability and stability, where only 7.3% catalytic reactivity was reduced after five cycles. This work provided a green, sustainable, and facile approach for synthesizing photo-Fenton catalysts by value-added utilization of tar wastes.

Vacancy-Pba Derived Nanoparticle Containing Defect-Rich Crystal Structure and P, S Dual-Doping as an Outstanding Oxygen Evolution Electrocatalyst

Vacancy-Pba Derived Nanoparticle Containing Defect-Rich Crystal Structure and P, S Dual-Doping as an Outstanding Oxygen Evolution Electrocatalyst

Nanocellulose-polysilazane single-source-precursor derived defect-rich carbon nanofibers/SiCN nanocomposites with excellent electromagnetic absorption performance

Ceramic SiCN nanocomposites modified with nanocellulose derived defect-rich carbon nanofibers (CNFs-SiCN) were developed by thermolysis of nanocelulose-polysilazane single-source precursors (SSPs). Multi-loss mechanisms (i.g. polarization loss and conductive loss) were established in the SiCN ceramic nanocomposites by employing the defect-rich structure of CNFs. Cole-Cole circle plots indicate that the CNFs-SiCN ceramics possess strong polarization capability due to the defect-rich structure of the CNFs. Dielectric loss values fitted by the Debye theory showed that the proportion of polarization loss reaches an unprecedented high value, accounting for 52.1% of the total dielectric loss. When the content of nanocellulose is 10 wt% of SSPs, the minimal reflection coefficient (RCmin) and effective absorption bandwidth (EABs) of CNFs-SiCN ceramic can reach −36.3 dB and 3.0 GHz, respectively. This work may contribute new ideas for establishing multi-loss mechanisms in ceramic-based materials, finding a new application for nanocellulose, and shaping the design of novel absorbents.

Defect-rich CoMoS nanosheets on PANI nanowires as excellent hybrid electrocatalyst for water splitting

Developing economic, efficient, and stable bifunctional electrocatalysts for producing oxygen and hydrogen simultaneously remains challenging. Here, we design and fabricate vertically aligned cobalt molybdenum sulfide (CoMoS) nanosheets on a conductive polyaniline (PANI) nanowire on nickel foam (NF) by a one-step solvothermal synthesis. The hybrid CoMoS-PANI array demonstrates low overpotentials of 250 and 98 mV, to achieve a current density of 10 mA cm–2 in an alkaline solution, for the oxygen and hydrogen evolution reactions, respectively. As an electrolyzer for overall water splitting, CoMoS-PANI/NF, as both the anode and the cathode, exhibits a current density of 10 mA cm–2 at a low cell voltage, 1.58 V. Furthermore, good stability for 50 h at a current density of 20 mA cm–2 during overall splitting suggests that CoMoS-PANI can be promoted as a highly efficient and stable bifunctional catalyst. The upgraded electrocatalytic activity of CoMoS-PANI can be ascribed to its defect-rich structure, the exhibition of the PANI nanowire to effective electron transfer, and the ample of active catalytic sites provided by the synergistic effect of the hybrid structures. This work is a promising step towards the design and exploration of hybrid materials as excellent electrocatalysts for renewable energy generation.

Hydrothermal synthesis of Co3O4 nanoparticles decorated three dimensional MoS2 nanoflower for exceptionally stable supercapacitor electrode with improved capacitive performance

In this study, a novel, Co3O4 nanoparticle decorated MoS2 nanoflower (MoS2/Co3O4) has been fabricated via a facile hydrothermal method by taking different concentrations of Co3O4 (0, 1, 2, 4, and 6%). The FE-SEM images represent a three-dimensional flower-like structure for MoS2 and MoS2/Co3O4. The different structural parameters of the nanoflowers were estimated from the XRD analysis. TEM analysis revealed that the inter-planar spacing of the nanostructure varied with the concentration of the Co3O4 nanoparticles. The Raman spectroscopy of MoS2/Co3O4 nanoflower showed a distinct low-shift of the first-order Raman peaks suggesting n-type doping due to the incorporation of Co3O4. The specific capacitance as high as 220.72 mFcm-2 at 0.14 mAcm-2 together with high energy density and superior cycling stability (87% capacitance retention after 10,000 charge/discharge cycles) were obtained for the MoS2/Co3O4 (4%) nanocomposite from the electrochemical analysis. This improved specific capacitance of MoS2/Co3O4 can be attributed to the higher surface area, defect-rich structure, and lower charge transfer resistance of the prepared sample. The MoS2/Co3O4 nanostructure with improved specific capacitance and higher stability synthesized from a simple, low-cost process will pave the way to the production of efficient and economic energy storage devices.

Epigenetic-Hydrothermal Fluorite Veins in a Phosphorite Deposit from Balaton Highland (Pannonian Basin, Hungary): Signatures of a Regional Fluid Flow System in an Alpine Triassic Platform

The middle Anisian extensional tectonics of the Neotethyan realm developed a small, isolated carbonate platform in the middle part of the Balaton Highland (western Hungary), resulted in the deposition of uranium-bearing seamount phosphorite on the top of the drowned platform and produced some epigenetic fluorite veins in the Middle Triassic sequence. The stable C-O isotope data of carbonates are shifted from the typical Triassic carbonate ranges, confirming the epigenetic-hydrothermal origin of veining. Primary fluid inclusions in fluorite indicate that these veins were formed from low temperature (85–169 °C) and high salinity NaCl + CaCl2 + H2O type (apparent total salinity: 15.91–22.46 NaCl wt%) hydrothermal fluids, similar to parent fluids of the Alpine-type Pb-Zn deposits. These findings indicate that the Triassic regional fluid circulation systems in the Alpine platform carbonates also affected the area of the Balaton Highland. This is also in agreement with the previously established palinspatic tectonic reconstructions indicating that the Triassic carbonate and basement units in the Balaton Highland area were a part of the Southern Alpine. Similar fluorite veining in phosphorite deposits is also known in the Southern Alpine areas (e.g., Monte San Giorgi, Italy). Raman spectroscopic analyses detected H2 gas in the vapor phase of the fluid inclusions and a defect-rich fluorite structure in violet to black colored growth zones. This unique phenomenon is assumed to be the result of interaction between the uranium-rich phosphorite and the parent fluids of the epigenetic fluorite veins.

Imidazolatic-Framework Bimetal Electrocatalysts with a Mixed-Valence Surface Anchored on an rGO Matrix for Oxygen Reduction, Water Splitting, and Dye Degradation.

This paper presents a simple strategy for manufacturing bifunctional electrocatalysts—graphene nanosheets (GNS) coated with an ultrafine NiCo-MOF as nanocomposites (denoted NiCo-MOF@GNS) having a N-doped defect-rich and abundant cavity structure through one-pool treatment of metal–organic frameworks (MOFs). The precursors included N-doped dodecahedron-like graphene nanosheets (GNS), in which the NiCo-MOF was encompassed within the inner cavities of the GNS (NiCo-MOF@GNS) at the end or middle portion of the tubular furnace with several graphene layers. Volatile imidazolate Nx species were trapped by the NiCo-MOF nanosheets during the pyrolysis process, simultaneously inserting N atoms into the carbon matrix to achieve the defect-rich porous nanosheets and the abundantly porous cavity structure. With high durability, the as-prepared nanomaterials displayed simultaneously improved performance in the oxygen reduction reaction (ORR), the oxygen evolution reaction (OER), and photocatalysis. In particular, our material NiCo-MOF@GNS-700 exhibited excellent electrocatalytic activity, including a half-wave potential of 0.83 V (EORR, 1/2), a low operating voltage of 1.53 V (EOER, 10) at 10 mA cm–2, a potential difference (ΔE) of 1.02 V between EOER, 10 and EORR, 1/2 in 0.1 M KOH, and a low band gap of 2.61 eV. This remarkable behavior was due to the structure of the defect-rich porous carbon nanosheets and the synergistic impact of the NPs in the NiCo-MOF, the N-doped carbon, and NiCo-Nx. Furthermore, the hollow structure enhanced the conductivity and stability. This useful archetypal template allows the construction of effective and stable bifunctional electrocatalysts, with potential for practical viability for energy conversion and storage.