Vanadium-Doped Heterogeneous Bimetallic Phosphides Derived from Layered Double Hydroxides for Saline Water Splitting.

The development of energy- and time-saving synthetic methods to prepare bifunctional and high stability catalysts are vital for overall water splitting. Here, V-doped nickel-iron hydroxide precursor by etching NiFe foam (NFF) at room temperature with dual chloride solution ("NaCl-VCl3"), is obtained then phosphating to obtain V-Ni2P-FeP/NFF as efficient bifunctional (oxygen/hydrogen exchange reaction, OER/HER) electrocatalysts, denoted as NFF(V, Na)-P. The NFF(V, Na)-P requires only 185 and 117 mV overpotentials to reach 10 mA cm-2 for OER and HER. When used as a catalyst for water splitting in a full cell, it can be stably sustained for more than 1000 h in alkaline brine electrolysis at both current densities of 100 and 500 mA cm-2. In situ Raman analyses and density functional theory (DFT) show that the V-doping-induced surface remodeling generates hydroxyl oxides as the true catalytic active centers, which not only enhances the reaction kinetics, but also reduces the free energy change in the rate-determining step. This work provides a cost-effective substrate self-derivation method to convert commercial NFF into a powerful catalyst for electrolytic brine, offering a unique route to the development of efficient electrocatalysts for saline water splitting.

Interface Enables Faster Surface Reconstruction in a Heterostructured CuSey/NiSex Electrocatalyst for Realizing Urea Oxidation.

Creating affordable electrocatalysts and understanding the real-time catalytic process of the urea oxidation reaction (UOR) are crucial for advancing urea-based technologies. Herein, a Cu-Ni based selenide electrocatalyst (CuSey/NiSex/NF) was created using a hydrothermal technique and selenization treatment, featuring a heterogeneous interface rich in Cu2-xSe, Cu3Se2, Ni3Se4, and NiSe2. This catalyst demonstrated outstanding urea electrooxidation performance, achieving 10 mA cm-2 with just 1.31 V and sustaining stability for 96 h. Through in-situ Raman spectroscopy and ex-situ characterizations, it is discovered that NiOOH is formed through surface reconstruction in the UOR process, with high-valence Ni serving as the key site for effective urea oxidation. Moreover, the electrochemical analysis revealed that CuSey had dual effects. An analysis of XPS and electrochemical tests revealed that electron transfer from CuSey to NiSex within the CuSey/NiSex/NF heterostructure enhanced the UOR kinetics of the catalyst. Additionally, according to the in-situ Raman spectroscopy findings, the existence of CuSey facilitates a easier and faster surface reconstruction of NiSex, leading to the creation of additional active sites for urea oxidation. More significantly, this work provides an excellent "precatalyst" for highly efficient UOR, along with an in-depth understanding of the mechanism behind the structural changes in electrocatalysts and the discovery of their true active sites.

Deep Reconstruction of the NiFeSP Nanosheet Catalyst for Large Current-Density Water Oxidation.

Evidence shows that the crucial factor in achieving efficient water electrolysis for hydrogen production is the design and synthesis of electrocatalysts that exhibit both high performance and cost-effectiveness for the oxygen evolution reaction (OER). Herein, the NiFeSP nanosheets were facilely prepared on a Ni foam (NF) substrate through a cost-effective electrodeposition method. The electrode structure composed of nanosheets offers a high density of active sites and superior electrical conductivity, thereby enhancing the efficiency of the OER. In addition, the NiFeSP/NF-600 nanosheets exhibit superhydrophilic and superaerophobic characteristics, which effectively enhance the mass-transfer process by facilitating the penetration of electrolytes and enabling rapid release of gas bubbles. Consequently, NiFeSP/NF-600 demonstrates superior electrocatalytic efficacy for OER, exhibiting an overpotential of 292 mV at a high current density of 500 mA cm-2 as well as an exceptional long-term durability of 100 h. More importantly, the rapid reconstruction of FeOOH and NiOOH species from NiFeSP/NF-600 may be the true active species for OER, which is revealed utilizing in situ Raman spectroscopy in conjunction with ex situ characterization. This study not only offers an ideal "pre-catalyst" for an extremely effective OER but also offers a thorough understanding of the mechanism underlying the structural evolution of electrocatalysts and the identification of their actual active sites.

Synthesis and Characterization of a Displacement-Type Ferroelectric-Ferroelectric Phase Transition Compound [(NH3)(CH2)3(NH3)]2[InBr6]Br·H2O.

Ferroelectric materials have aroused the researchers' great interest due to their wide applications. Here, a displacement-type ferroelectric-ferroelectric phase transition material [(NH3)(CH2)3(NH3)]2[InBr6]Br·H2O (1) with Tc = 143 K was successfully prepared. The ferroelectric phase transition is verified by the characterization techniques such as differential scanning calorimetry, single-crystal structure elucidation, dielectric and ferroelectric measurements. The single-crystal structure elucidation reveals that the displacement and distortion of [(NH3)(CH2)3(NH3)]2+ cations lead to the phase transition from Cmc21 to Pca21. The spontaneous polarizations at 293 and 133 K are 0.15 and 0.12 µC·cm-2, respectively. We expect that this work will help in further exploration of some new ferroelectric materials.

Phosphate Ion-Functionalized CoS with Hexagonal Bipyramid Structures from a Metal-Organic Framework: Bifunctionality towards Supercapacitors and Oxygen Evolution Reaction.

To solve energy-related environmental problems and the energy crisis, efficient electrochemical materials have been developed as alternative energy storage and conversion systems. Abundant transition metals and their sulfides are attractive electrochemical materials. Herein, we report an efficient phosphorization strategy, which improves the overall electrochemical performance of metal sulfides. In detail, CoS hexagonal bipyramids were synthesized through simple calcination combined with in situ sulfurization of a cobalt-based metal-organic framework template, and then phosphate ion-functionalized CoS (P-CoS) was prepared through a phosphorization reaction. P-CoS exhibited outstanding electrochemical activity as both supercapacitor electrode and oxygen evolution reaction (OER) catalyst. Supercapacitors based on CoS and P-CoS as the electrodes had high specific capacitances of 304 and 442 F g-1 , respectively, and remained stable for over 10 000 cycles at 5 A g-1 . For OER, P-CoS showed a current density of 10 mA cm-2 at an overpotential of 340 mV, with a small Tafel slope. In conclusion, functionalizing CoS with phosphate ions is a promising method for enhancing chemical reactivity and accelerating ion and electron transfer.

Template Construction of Porous CoP/COP2 Microflowers Threaded with Carbon Nanotubes toward High-Efficiency Oxygen Evolution and Hydrogen Evolution Electrocatalysts.

Low-cost, high-efficiency, and non-noble metal electrocatalysts are greatly urgent for sustainable energy conversion technologies with CO2-free emission, but these are challenging to construct. Herein, we demonstrate a novel cobaltic-formate frameworks (Co-FFs)-induced strategy to obtain porous flowerlike CoP/CoP2 composite threaded with carbon nanotubes (CoP/CoP2/CNTs). In this approach, a wet chemical precipitation process and then a gas-solid phosphorization method are involved to synthesize the flowerlike Co-FFs/CNTs precursor and the porous CoP/CoP2/CNTs composite, respectively. As bifunctional electrocatalyst, the composite attains a current density of 10 mA cm-2 at a low driving overpotentials of 270 mV for OER and 126 mV for HER in basic and acidic media, respectively. Furthermore, it discloses an exceptional electrocatalytic durability. This excellent electrochemical performance can be attributed to its porous structure and synergistic contribution among different components. The present work provides a facile procedure for fabricating multifunctional materials coated with CNTs.

MOF-Derived Hierarchical CoSe2 with Sheetlike Nanoarchitectures as an Efficient Bifunctional Electrocatalyst.

The exploitation of efficient and stable non-noble-metal bifunctional electrocatalysts is key to the development of hydrogen production technology. Although some progress has been made in the synthesis of transition-metal selenide nanostructures, the preparation of metal-organic framework (MOF)-derived transition-metal selenide electrode materials with more active sites and nanosheet structures remains a significant challenge. Herein, on the basis of the MOFs, the hierarchical CoSe2-160 microcube with sheetlike nanoarchitectures was successfully prepared. In addition, the morphology of cobalt selenides was controlled by adjusting the hydrothermal reaction temperature. Electrochemical experiments show that the CoSe2-160 microcube has a splendid electrocatalytic performance with 10 mA cm-2 at an overpotential of 156 mV and a small Tafel slope of 40 mV dec-1 (in 0.5 M H2SO4) for hydrogen evolution reaction as well as 328 mV and a small Tafel slope of 73 mV dec-1 (in 1 M KOH) for oxygen evolution reaction, respectively. This arises from the nanosheet structures, large surface areas, and abundant active sites. This strategy provides a neoteric synthesis route for the MOF-derived transition-metal selenides with a striking electrocatalytic performance.

Structure-Designed Synthesis of CoP Microcubes from Metal-Organic Frameworks with Enhanced Supercapacitor Properties.

Metal-organic framework-based supercapacitors have been widely recognized as the best energy storage devices for future portable electronic equipment. Herein, CoP- T ( T = 300, 350, and 400 °C) microcubes with a solid and hollow microstructure were successfully synthesized by low-temperature phosphorization of [CH3NH3][Co(HCOO)3] precursor at desired temperatures. The morphology, structure, and composition of the prepared CoP-350 °C samples were analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Hollow CoP-350 °C microcube has a larger specific surface area (25.9 m2 g-1) than that of solid ones (16.1 m2 g-1). When the two samples were used as electrode raw materials for supercapacitors, the hollow CoP-350 °C electrode exhibits better electrochemical performance (560 F g-1) than that of the solid one (427.6 F g-1) at a current density of 1 A g-1. The enhanced supercapacitor properties may be attributed to the large surface area and the unique hollow structure. Further, an asymmetric supercapacitor was prepared by employing the hollow CoP-350 °C microcubes as anode and N-doped graphene as cathode. It has a high rate capability (capacitance retention of 69% from 0.5 to 8 A g-1), a high energy density (21.4 W h kg-1 at a power density of 373 W kg-1), and outstanding cycling stability (remained 81.2% after 6000 cycles).

Phase transitions, prominent dielectric anomalies, and negative thermal expansion in three high thermally stable ammonium magnesium-formate frameworks.

We present three Mg-formate frameworks, incorporating three different ammoniums: [NH4][Mg(HCOO)3] (1), [CH3CH2NH3][Mg(HCOO)3] (2) and [NH3(CH2)4NH3][Mg2(HCOO)6] (3). They display structural phase transitions accompanied by prominent dielectric anomalies and anisotropic and negative thermal expansion. The temperature-dependent structures, covering the whole temperature region in which the phase transitions occur, reveal detailed structural changes, and structure-property relationships are established. Compound 1 is a chiral Mg-formate framework with the NH4(+) cations located in the channels. Above 255 K, the NH4(+) cation vibrates quickly between two positions of shallow energy minima. Below 255 K, the cations undergo two steps of freezing of their vibrations, caused by the different inner profiles of the channels, producing non-compensated antipolarization. These lead to significant negative thermal expansion and a relaxor-like dielectric response. In perovskite 2, the orthorhombic phase below 374 K possesses ordered CH3CH2NH3(+) cations in the cubic cavities of the Mg-formate framework. Above 374 K, the structure becomes trigonal, with trigonally disordered cations, and above 426 K, another phase transition occurs and the cation changes to a two-fold disordered state. The two transitions are accompanied by prominent dielectric anomalies and negative and positive thermal expansion, contributing to the large regulation of the framework coupled the order-disorder transition of CH3CH2NH3(+). For niccolite 3, the gradually enhanced flipping movement of the middle ethylene of [NH3(CH2)4NH3](2+) in the elongated framework cavity finally leads to the phase transition with a critical temperature of 412 K, and the trigonally disordered cations and relevant framework change, providing the basis for the very strong dielectric dispersion, high dielectric constant (comparable to inorganic oxides), and large negative thermal expansion. The spontaneous polarizations for the low-temperature polar phases are 1.15, 3.43 and 1.51 µC cm(-2) for 1, 2 and 3, respectively, as estimated by the shifts of the cations related to the anionic frameworks. Thermal and variable-temperature powder X-ray diffraction studies confirm the phase transitions, and the materials are all found to be thermally stable up to 470 K.

Electron regulation of CeO2 on CoP multi-shell hetero-junction micro-sphere towards highly efficient water oxidation.

CeO2 has been identified as a significant cocatalyst to enhance the electrocatalytic activity of transition metal phosphides (TMPs). However, the electrocatalytic mechanism by which CeO2 enhances the catalytic activity of TMP remains unclear. In this study, we have successfully developed a unique CeO2-CoP-1-4 multishell microsphere heterostructure catalyst through a simple hydrothermal and calcination process. CeO2-CoP-1-4 exhibits great potential for electrocatalytic oxygen evolution reaction (OER), requiring only an overpotential of 254 mV to achieve a current density of 10 mA cm-2. Moreover, CeO2-CoP-1-4 demonstrates excellent operating durability lasting for 55 h. The presence of CeO2 as a cocatalyst can regulate the microsphere structure of CoP, the resulting multishell microsphere structure can shorten the mass transfer distance, and improve the utilization rate of the active site. Furthermore, in situ Raman and ex situ characterizations, and DFT theoretical calculation results reveal that CeO2 can effectively regulates the electronic structure of Co species, reduces the reaction free energy of rate-limiting step, thus increase the reaction kinetic. Overall, this study provides experimental and theoretical evidence to better comprehend the mechanism and structure evolution of CeO2 in enhancing the OER performance of CoP, offering a unique design inspiration for the development of efficient hollow heterojunction electrocatalysts.

Solvent-induced structural regulation over Ni2P/CNT hybrids towards boosting the performance of supercapacitors.

Although nickel-based phosphides have attracted increasing attention due to their good theoretical specific capacity, the poor rate capability weakness their advantage in electrochemical energy storage. It is, however, challenging to improve these issues by only adjusting composition. Here, we employ a synergistic strategy, both hybridizing with highly conductive materials and regulating morphology, to enhance the electrochemical performance of Ni2P. Based on solvent-induced effects, flower/rod-like [CH3NH3][Ni(HCOO)3] precursors hybridized with CNTs are prepared and then employed as templates to construct flower/rod-like Ni2P/CNT hybrids via a gas-solid phosphorization method. Benefiting from the synergistic advantages of both structure and components, the flower-like Ni2P/CNT hybrid, as an electrode materials for supercapacitor, exhibit outstanding specific capacitance of up to 1480 F g-1 at 1 A g-1, as well as improved rate capability. Additionally, the assembled asymmetric supercapacitor (Ni2P/CNTs//AC, ASC) delivers a high capacitance retention of up to 83.5% after 5000 cycles at 10 A g-1, and an expected energy density of 25.2 W h kg-1 at a power density of 749.8 W kg-1.

Substrate self-derived porous rod-like NiS/Ni9S8/NF heterostructures as efficient bifunctional electrocatalysts for overall water splitting.

A self-derivation strategy using conductive substrates is used to prepare one-piece highly efficient bifunctional electrodes, where the chosen substrate acts as both an active catalyst precursor and a conductive carrier. Here, a bifunctional catalyst, porous NiS/Ni9S8/NF-2 nanorods, was synthesized by low-temperature vulcanization after an oxalic acid etching process. To reach a current density of 10 mA cm-2, NiS/Ni9S8/NF-2 requires only a tiny overpotential of 115 mV for the HER and 176 mV for the OER, and demonstrates sustained activity for 100 hours with almost any degradation. The substrate self-derived NiS/Ni9S8/NF-2 catalyst for overall water splitting requires only a small voltage of 1.52 V to deliver 10 mA cm-2 with excellent stability. Experimental results show that the heterostructured electrocatalysts impart good catalytic properties of NiS/Ni9S8/NF-2 by modulating the electronic structure and promoting the reconstruction process from sulfides to hydroxides. This work demonstrates the success of the substrate self-derivation strategy to achieve high catalytic activity and provide a new autogenous growth technique for electrode fabrication.

Anchoring cobalt molybdenum nickel alloy nanoparticles on molybdenum dioxide nanosheets as efficient and stable self-supported catalyst for overall water splitting at high current density.

Developing bifunctional electrocatalysts with efficient and stable catalytic performance at high current density to improve the productivity of water splitting is important for relieving the environmental pollution and energy crisis. Herein, the Ni4Mo and Co3Mo alloy nanoparticles were anchored on MoO2 nanosheets (H-NMO/CMO/CF-450) by annealing the NiMoO4/CoMoO4/CF (CF: self-made cobalt foam) under Ar/H2 atmosphere. Benefitting from the nanosheets structure, synergistic effect of the alloys, existence of oxygen vacancy and the cobalt foam with smaller pore sizes as conductive substrate, the self-supported H-NMO/CMO/CF-450 catalyst demonstrates outstanding electrocatalytic performance, which delivers small overpotential of 87 (270) mV at 100 (1000) mA·cm-2 for HER and 281 (336) mV at 100 (500) mA·cm-2 for OER in 1 M KOH. Meanwhile, the H-NMO/CMO/CF-450 catalyst is used as working electrodes for overall water splitting, which just require 1.46 V @ 10 mA·cm-2 and 1.71 V @ 100 mA·cm-2, respectively. More importantly, the H-NMO/CMO/CF-450 catalyst can stabilize for 300 h at 100 mA·cm-2 in both HER and OER. This research provides an idea for the preparation of stable and efficient catalysts at high current density.

N,S co-doped porous carbon with Co9S8 prepared with a Co-FF-derived Co3O4 template: a bi-functional electrocatalyst for rechargeable zinc-air batteries.

To achieve broad commercialization of rechargeable metal-air batteries, the development of non-precious metal-based bi-functional oxygen electrocatalysts is critical. In this study, we prepared N,S co-doped porous carbon materials containing Co9S8 nanoparticles (Co9S8/NSC) through a one-step pyrolysis process. The process involved the pyrolysis of a polydopamine (PDA) coated Co-formic acid framework (Co-FF) derived Co3O4 and thiourea. The improved catalyst Co9S8/NSC-1 exhibited satisfactory long-term durability and superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity, the half-wave potential (E1/2) of the ORR reached 0.83 V, and the OER overpotential at 10 mA cm-2 (η10) was 300 mV. The zinc-air battery (ZAB) based on Co9S8/NSC-1 assembly had a maximum power density of 102.0 mW cm-2 and the cycle life reached 500 cycles. The material preparation method was simple, environmentally friendly and inexpensive, providing a feasible strategy for the development of non-precious metal-based electrocatalysts.

Ultrafine cobalt molybdenum phosphide nanoparticles embedded in crosslinked nitrogen-doped carbon nanofiber as efficient bifunctional catalyst for overall water splitting.

As a kind of high-performance and cost-efficient electrocatalyst in water splitting, the transition bimetal phosphides exhibit a promising prospect. Here, the composite of cobalt molybdenum phosphide nanoparticles embedded in crosslinked nitrogen-doped carbon nanofiber (Co0.4Mo0.6P@CL-NCNF) has been synthesized via an electrospinning process and pyrolysis treatment. As an effective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalyst, the Co0.4Mo0.6P@CL-NCNF only requires the overpotentials of 81 mV and 219 mV at the current densities of 10 mA cm-2 and 20 mA cm-2, respectively. Moreover, the water electrolyzer with the Co0.4Mo0.6P@CL-NCNF as the cathode and anode catalysts requires a cell voltage of 1.59 V to reach a current density of 10 mA cm-2. The Co0.4Mo0.6P@CL-NCNF also achieves the excellent stability up to 24 h for HER, OER and overall water spitting in 1.0 M KOH. The excellent catalytic activity of the Co0.4Mo0.6P@CL-NCNF is benefits from the synergistic effect between components and the crosslinked structure of carbon nanofiber. Thus, the research provides a promising method for preparing carbon-based TMPs materials towards electrocatalysis.

Coexistence of magnetic and electric orderings in the metal-formate frameworks of [NH4][M(HCOO)3].

A family of three-dimensional chiral metal-formate frameworks of [NH(4)][M(HCOO)(3)] (M = Mn, Fe, Co, Ni, and Zn) displays paraelectric to ferroelectric phase transitions between 191 and 254 K, triggered by disorder-order transitions of NH(4)(+) cations and their displacement within the framework channels, combined with spin-canted antiferromagnetic ordering within 8-30 K for the magnetic members, providing a new class of metal-organic frameworks showing the coexistence of magnetic and electric orderings.

Two In-based organic-inorganic hybrid compounds with reversible phase transition derived from the order-disorder changes of cations or anions.

Solid-state phase transition materials have received extraordinary interest due to their rich physical properties, such as thermal, dielectric, and ferroelectric properties. Here, two In-based organic-inorganic hybrid compounds, (C6H5CH2CH2NH3)3[InBr5(H2O)] (1) and [(C3H7)4N][InCl4] (2), both display reversible phase transition and dielectric response. Differential scanning calorimetry measurements indicate that the phase transition temperatures (Tc) of 1 and 2 are 167 K and 351 K, respectively. Moreover, structural analyses disclose that the phase transition of 1 can be attributed to the order-disorder changes of phenethylammonium organic cations whereas the phase transition of 2 is caused by the order-disorder changes of [InCl4]- anions. The phase transitions of In-based organic-inorganic hybrid compounds can be driven by the order-disorder changes of cations or anions. Therefore, the system of In-based organic-inorganic hybrid compounds is very suitable for exploring organic-inorganic hybrid phase transition materials.

CoFeP hierarchical nanoarrays supported on nitrogen-doped carbon nanofiber as efficient electrocatalyst for water splitting.

Developing high-efficient bifunctional electrocatalysts is significant for the overall water splitting. Bimetallic phosphides show great potential for the bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts due to the excellent catalytic performance. Herein, the CoFeP two-dimensional nanoarrays successfully grown on nitrogen doped electrospun carbon nanofibers (CoFeP NS@NCNF) through template-directed growth and following phosphorization treatment. Benefiting from the hierarchical nanoarrays structure, synergistic effect of high electrical conductivity carbon nanofiber substrate and bimetallic phosphide, the CoFeP NS@NCNF exhibits efficient bifunctional electrocatalytic activities for OER and HER in 1 M KOH with overpotentials of 268 mV (η20) and 113 mV (η10), respectively. Moreover, the CoFeP NS@NCNF coupled two-electrode system needs a low voltage of 1.59 V at 10 mA cm-2 for overall water splitting. This work provides a promising way for the preparation of transition metal-based electrocatalysts with hierarchical structure derived from Prussian blue analogues (PBAs) for OER and HER.

Novel Copper(II) Complex with a 4-Acylpyrazolone Derivative and Coligand Induce Apoptosis in Liver Cancer Cells.

A novel pyrazolone-based copper complex [CuL(phen)(CH3OH)][CuL(phen)]·CH3CH2OH·CH3OH (P-FAH-Cu-phen) was synthesized and characterized. The asymmetric structural unit of P-FAH-Cu-phen was composed of two independent complex units [CuL(phen)(CH3OH)] and [CuL(phen)]:Cu12+ center with six coordination mode and Cu22+ center with five coordination mode. The growth of BEL-7404 cells and H22 cells was significantly inhibited by P-FAH-Cu-phen with IC50 values of 1.175 µg/mL and 1.097 µg/mL, respectively, which were much lower than IC50 of cisplatin for BEL-7404 cells (23.32 µg/mL) and H22 cells (27.5 µg/mL). P-FAH-Cu-phen induced cell cycle arrest at G2/M and apoptosis in BEL-7404 cells through mitochondria- and endoplasmic reticulum stress-associated pathways. Moreover, P-FAH-Cu-phen significantly suppressed the migration of BEL-7404 cells and the tumor growth in H22 tumor mouse model without severe side effects and improved the survival of tumor mice. The results suggested that P-FAH-Cu-phen might be a potential drug candidate for the treatment of live cancer.

Disorder-order ferroelectric transition in the metal formate framework of [NH4][Zn(HCOO)3].

A three-dimensional chiral metal formate framework compound, [NH(4)][Zn(HCOO)(3)], undergoes a paraelectric-ferroelectric phase transition at 191 K triggered by the disorder-order transition of NH(4)(+) cations within the structure.