Constructing a low-cost, high activity and stable electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) via overall water splitting is of great significance, but remains a big challenge. In this work, vertically aligned core-shell Co(OH) F@FeOOH nanorod arrays (NRs) on Ni foam were constructed via hydrothermal and chemical deposition methods. Due to the synergistic effects and electron interaction at the interface between Co(OH)F and FeOOH, the synthesized core-shell Co(OH)F@FeOOH heterostructure exhibits remarkable OER and HER catalytic activity in 1 M KOH solution, presenting low overpotentials of approximately 205 mV and 137 mV at a current density of 10 mA cm-2, and low Tafel slopes of approximately 48 mV dec-1 and 86 mV dec-1, for OER and HER, respectively. Moreover, the synthesized Co(OH)F@FeOOH serves as a bifunctional electrocatalyst for overall water splitting and it only needs 1.55 V to drive the electrolysis cell yielding 10 mA cm-2 which is much lower than that of 1.68 V for IrO2||Pt/C and showing excellent stability for 37 h. The prepared Co(OH)F@FeOOH catalyst has been successfully used in solar cell-driven water electrolysis, demonstrating its great potential for costeffective electrochemical hydrogen production. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The local structure and spin Hamiltonian parameters (SHPs) g factors (gx , gy , gz ) and the hyperfine structure constants (Ax , Ay , Az ) for Cu2+ doped in the LiTaO3 crystal are theoretically investigated by the perturbation formulas for a 3d9 ion under rhombically elongated octahedral based on the cluster approach. The impurity Cu2+ was assumed to occupy the host trigonally-distorted octahedral Li+ site and experience the Jahn-Teller (JT) distortion from the host trigonal octahedral [TaO6 ]10- to the impurity rhombically elongated octahedral [CuO6 ]10- . Based on the calculations, the impurity-ligand bond lengths parallel and perpendicular to the C2 -axis are found to be R|| (≈ 2.305 Å) and R⊥ (≈ 2.112 Å) for the studied [CuO6 ]10- cluster, with the planar bond angle θ (≈ 78.2°). Meanwhile, the ground-state wave function for Cu2+ center in LiTaO3 was also obtained. The calculated SHPs based on the above local lattice distortions agree well with the experimental data, and the results are discussed.

Interface engineering is an effective approach towards developing low-cost highly efficient electrocatalysts for green hydrogen production in alkaline water or seawater environments. Herein, we have successfully fabricated an interface engineered Mott-Schottky heterostructure catalyst i.e., Fe3O4@Ni3S2, in which, Ni3S2 nanosheets are evenly dispersed on the surface of Fe3O4 flower-like nanosheets, which are supported by a Ni foam substrate. Due to the synergistic effect between Ni3S2 and Fe3O4, the Fe3O4@Ni3S2 heterostructure catalyst demonstrates remarkable catalytic activity under alkaline conditions which is attributed to the- highly exposed active sites, adjustment of the d-band center, and the built-in electric field at the interface. The catalyst Fe3O4@Ni3S2 has low overpotentials of 207 and 217 mV for the OER (oxygen evolution reaction) and 99 and 118 mV for the HER (hydrogen evolution reaction) in alkaline and seawater electrolytes, respectively, allowing it to yield a current density of 10 mA cm- 2 . Furthermore, the Fe3O4@Ni3S2||Fe3O4@Ni3S2 electrolyzer can achieve a current density of 10 mA cm- 2 for alkaline fresh water and seawater (1 M KOH + seawater) electrolysis at low voltages of 1.57 V and 1.58 V, respectively. This study presents a novel approach for fabricating high-performance multi-interface 3D catalysts for overall water/seawater splitting.

Local electron density manipulation can optimize the adsorption and desorption nature of catalysts leading to enhanced catalytic activity for water oxidation. Construction a Mott-Schottky barrier allows the electron transition in catalysts because of their different Fermi levels. Herein, a Pt@NiFc-MOF Mott-Schottky heterojunction is constructed, in which electrons are transferred from NiFc-MOF to Pt as triggered by the formed built-in electric field at the interface. The as-prepared Pt@NiFc-MOF reveals exceptional performance toward the hydrazine oxidation reaction (HzOR), hydrogen evolution reaction (HER), and overall hydrazine splitting (OHzS) at ampere-level current densities. The advanced nature of the configured Mott-Schottky heterojunction can also be further evidenced from a concept direct liquid N2H4/H2O2 fuel cell (Pt@NiFc-MOF//Pt Net), yielding a maximum power density of 415.2 mW cm-2 at 80 degrees C and can work stably for 190 h at 500 mA cm-2 (at 25 degrees C). One more function of Pt@NiFc-MOF is clarified as well, that is it can purify hydrazine-rich wastewater from 718 to 6 ppb (less than the U.S. Environmental Protection Agency of 10 ppb) in 120 min at 500 mA cm-2. This work represents a breakthrough in interface engineering of metal-organic frameworks (MOFs) toward industry-level hydrogen generation and its beyond. A Pt@NiFc-MOF Mott-schottky heterojunction is constructed, allowing favorable electron transfer because of the generated build-in electric field at interface, which yields exceptional HzOR and HER performance at ampere-level current densities. The advanced nature of the prepared mott-schottky junction can also be clarified from the configured direct liquid N2H4/H2O2 fuel cell and its function for purifying hydrazine-rich wastewater. image

Green hydrogen production through electrocatalytic water/seawater splitting has recently received significant attention. However, the practical utilization for this technique is still limited due to the poor performance and stability of electrocatalysts. Herein, a heterogeneous core-shell hybrid, containing Ni3S2 nanorod arrays and CoFe layered double hydroxide (LDH) nanosheets, has been fabricated via a developed two-step hydrothermal and electrodeposition method. The build-in electronic field in the as-formed Mott-Schottky barrier endows the efficient electron transfer from CoFe LDH to Ni3S2, subsequently enhancing the reaction kinetics. The as-prepared Ni3S2@CoFe catalyst exhibits exceptional performance for oxygen evolution reaction (OER, eta 10 = 222 and 237 mV) and hydrogen evolution reaction (HER, eta 10 = 83 and 109 mV) in 1 M KOH as well as alkaline seawater environments, respectively. Notably, it only requires a cell voltage of 1.51 and 1.55 V to achieve a current density of 10 mA cm-2 for overall seawater and water splitting, respectively, outperforming the commercial benchmark Pt/C||RuO2 (1.56 V). This work paves a solid way for construction of Mott-Schottky catalysts for green hydrogen production and its beyond.

Pathways for the hydrogen evolution reaction under acidic and alkaline (or neutral) conditions.

The collision integrals for N, N+, N++, N2, O, O+, O++ and O2 were calculated by using the Sonine polynomial expansion based on Chapman theory. The calculations of collision integral have some dependent relationship on the electron temperature. Since resonant charge exchange exists between singly ionized ions and their parent neutral atoms, this requires a special consideration of inelastic collisions in calculating some neutral–ion interactions. Furthermore, the electron temperature, electron density and particle composition of the artificially triggered lightning were diagnosed. And the diffusion coefficient and electrical conductivity of the artificially triggered lightning were also determined.

Developing low-cost, high-efficiency and stable electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is crucial but highly challenging. Density functional theory (DFT) calculations reveal that doping ruthenium (Ru) into catalysts can effectively optimize their electronic structure, hence leading to an optimal Gibbs free energy on the catalyst surface. Herein, an ultra-low Ru (about 2.34 wt%)-doped Ni3Se2 nanowire catalyst (i.e., Ru/Ni3Se2) supported on nickel foam has been fabricated by a hydrothermal reaction followed by a chemical etching process. The unique three-dimensional (3D) interconnected nanowires not only endow Ru and Ni3Se2 with uniform distribution and coupling, but also provide higher electrical conductivity, more active sites, an optimized electronic structure and favorable reaction kinetics. Therefore, the as-obtained Ru/Ni3Se2 catalyst exhibits excellent electrocatalytic performance, with low overpotentials of 24 and 211 mV to supply a current density value of 10 mA cm-2 towards the HER and OER in an alkaline environment, respectively. Notably, the as-fabricated Ru/Ni3Se2 catalyst only requires a low voltage of 1.476 V to derive a current density of 10 mA cm-2 in the constructed two-electrode alkaline electrolyzer and exhibits exceptionally high stability. This work will provide a novel strategy for the design and fabrication of low-cost and high-performance bifunctional electrocatalysts for hydrogen production by water electrolysis.

Doping Ru endows optimized electronic structure of NiCo 2 O 4 , which in turn modifies its d-band center towards optimum H* adsorption energy. The as-prepared spinel yields splendid HER, OER and UOR performances.

A vital step towards sustainable hydrogen production is to develop high-efficiency electrocatalysts for pHuniversal hydrogen evolution reaction (HER). Modulation of the electronic structure of electrocatalysts by constructing Mott-Schottky heterojunction could be regarded as an effective strategy to promote the electrochemical performances. Herein, we report hybrid Mott-Schottky electrocatalyst composed of metallic Co4N and n-type semiconducting Co2P, fabricated via the hydrothermal method followed by the subsequent phosphating and nitriding treatment. Due to the Mott-Schottky effect, the self-driven charge carriers transfer occurs at the heterointerfaces of Co2P/Co4N, leading to a built-in electric field, accelerated charge transfer rate, and improved chemisorption free energies of the reaction intermediates, ultimately boosting the dissociation of water molecules. Therefore, the as-prepared Co2P/Co4N electrocatalyst exhibits outstanding pH-universal HER performance with extremely low overpotentials of 53, 19, and 32 mV at a current density of 10 mA cm-2 in 0.5 M H2SO4, 1 M phosphate buffer solution (PBS), and 1 M KOH electrolytes, respectively. Further, the electrocatalyst reveals low Tafel slopes of 38, 26, and 50 mV dec- 1, which outperform those of the previously reported Co-based catalysts. Density functional theory (DFT) calculations clarify that the Schottky contact can regulate the adsorption energy of water, and the electronic structure at interface of the heterojunction weakens the hydrogen adsorption free energy (Delta GH*) of Co2P/Co4N to nearly zero, which is the reason for the addressed splendid HER performance.

Exploring highly efficient, stable and durable electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is a challenging task for energy-saving H2 generation during water electrolysis. Herein, a rose-like crystalline/amorphous heterostructure of NiFe2O4/NiO/NF grown on Ni-foam (NF) was synthesized via a simple two-step (i.e. , hydrothermal-annealing) pathway. The as-synthesized NiFe2O4/NiO/ NF catalyst presents outstanding electrocatalytic performance towards OER with small overpotentials of 122 and 145 mV to deliver 20 and 100 mA cm-2 current densities in 1.0 M KOH electrolyte, respectively. Further, the electrocatalyst revealed robust stability for over 168 h. For UOR, ultra-low potentials of 1.181 and 1.315 V (vs. the RHE) are required at current densities of 10 and 100 mA cm-2, relatively lower than those required for the OER process. Furthermore, employing the NiFe2O4/NiO/NF catalyst as an anode and Pt/C/NF as a cathode in 1 M KOH electrolyte, only 1.356 and 1.498 V is required to drive current densities of 10 mA cm-2 and 300 mA cm-2 during the overall water splitting reaction. Significantly, the urea electrolyzer presents ultra-low cell voltages of 1.218 and 1.490 V at 10 and 300 mA cm-2 current densities, respectively. The performance of the electrocatalyst is better than many of the reported transition-metal based elec-trocatalysts and even superior to most of the noble metal-based electrocatalysts. This work presents a solid step for the cost-effective and energy-saving hydrogen generation. (c) 2022 Elsevier B.V. All rights reserved.

The local structures and electron paramagnetic resonance (EPR) parameters (the g factors g(i) and the hyperfine structure constants A(i) , with i = x, y, z) of the V4+ and Cu2+ centers in WO3 were theoretically investigated based on the perturbation formulas of the EPR parameters for 3d(1) and 3d(9) ions under rhombically compressed and elongated octahedra, respectively. In these formulas, the adopted crystal-field parameters (CFPs) are obtained from the superposition model which enables connection of the CFPs and hence the EPR parameters to the rhombic distortion. Based on the calculations, the impurity-ligand distances of the studied [VO6](8-) (or [CuO6](10-)) cluster are found to suffer the axial compression (or elongation) delta z of about 0.098 angstrom (or 0.132 angstrom) along the z-axis, and the additional planar bond length variation delta r (approximate to 0.052 or 0.047 angstrom) along x- and y-axis, respectively, due to the Jahn-Teller (JT) effect.

The electron paramagnetic resonance (EPR) parameters-g factors gi (i = || and ⊥) and hyperfine structure constants Ai (M) and Ai (N), with M and N belonging to isotopes 63 Cu2+ and 65 Cu2+ -and local structure of Cu2+ ion occupying W6+ site in CaWO4 crystal are theoretically studied based on the perturbation formulas of these parameters for a 3d9 ion under tetragonally elongated tetrahedra. In these formulas, the ligand orbital (LO) and spin-orbit coupling (SOC) contributions are included due to the shorter impurity-ligand distance R (≈1.83 Å) and hence the strong covalency of the studied [CuO4 ]6- cluster, and the related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way; meanwhile, the required crystal field (CF) parameters for the tetragonally distorted tetrahedron (TDT) are estimated from the superposition model and the local structure of the impurity Cu2+ center. According to the calculation, the bond angle θ between the four equivalent Cu2+ -O2- bonds and the C4 axis in the CaWO4 :Cu2+ is found to be about 2.1° smaller than that (θ0 ≈ 54.74°) for an ideal tetrahedron due to the Jahn-Teller (JT) effect and the size mismatch. The fitted results agree well with the observed values, and the validity of the present assignment for the local structure of the Cu2+ center is also discussed.

Hydrogen is an efficient energy carrier alternative to the non-renewable traditional fossil fuels energy. Water electrolysis is a promising technique used for clean hydrogen generation. Usually, the oxygen-evolution reaction (OER) and urea-oxidation reaction (UOR) processes play a vital role in hydrogen production and pollution control. Herein, we report the fabrication of a three-dimensional (3D) crystalline/amorphous heterostructure NiTe/Ni-S electrocatalyst grown on nickel-foam (NF) via facile two steps (i.e., hydrothermal and electrodeposition) strategy. The synthesized NiTe/Ni-S catalyst exhibits an excellent performance toward the OER with a small overpotential of 216 mV to achieve 10 mA cm(-2) current density in 1.0 M KOH. Further, it only requires a small voltage of 1.315 V (vs. the reversible-hydrogen-electrode (RHE)) to drive 10 mA cm(-2) current density for UOR in 1 M KOH with 0.33 M urea, and reveals excellent long-term catalytic stability. Moreover, the overall water splitting experiments were conducted in 1 M KOH electrolyte with the NiTe/Ni-S catalyst as an anode and Pt/C as a cathode. It is obvious that only 1.500 and 1.527 V is required to achieve a current densities of 10 mA cm(-2) and 20 mA cm(-2), respectively. (C) 2022 Elsevier B.V. All rights reserved.

Arteriovenous fistula (AVF) is frequently believed to be the best vascular access for chronic renal failure (CRF) patients. Vascular endothelial cell dysfunction has been implicated in AVF maturation. Quercetin (Quer) is a natural polyphenolic compound widely used in traditional Chinese medicine. We aimed to uncover the impacts of Quer on vascular endothelial cells in a CRF rat model and human umbilical vein endothelial cells (HUVECs) stimulated by lipopolysaccharide (LPS) and serum from rat with CRF. Blood urea nitrogen and serum creatinine levels were tested in CRF rat model after administration of Quer. H&E staining was used to estimate endothelial damage. Nitric oxide (NO), endothelial NO synthase (eNOS), EPH receptor B4 (EphB4), EphrinB2, and p-caveolin-1 (p-Cav-1) levels in the serum were examined by enzyme-linked immunosorbent assay. Western blot was employed to analyze the expressions of eNOS, phosphorylated (p)-eNOS, EphB4, and Cav-1 in arterial tissues and HUVECs. Cell counting kit-8 was applied for assessing cell proliferation. TUNEL (terminal-deoxynucleotidyl transferase-mediated nick end labeling) assay was employed to estimate cell apoptosis. Results showed that Quer ameliorated renal function impairment and endothelial injury in vivo. Meanwhile, Quer boosted the proliferation and suppressed the apoptosis of HUVECs stimulated by LPS and serum from rat with CRF. Additionally, Quer elevated NO and eNOS levels, upregulated p-eNOS expression but downregulated EphB4, EphrinB2, and p-Cav-1 expressions. Moreover, EphB4 inhibitor had the similar effect as Quer treatment in HUVECs stimulated by LPS and serum from rat with CRF. Collectively, Quer might effectively regulate vascular function to prevent AVF failure in CRF via modulation of Eph/Cav-1 signaling.

Transition rates, collision excitation cross sections, and collision excitation rate coefficients of neutral N I atom and N II ions were calculated by Flexible Atomic Code that is based on the multiconfiguration Dirac-Fock method. The line intensity of some strong spectral lines were calculated. Then the dependent relationship among the ratio of line intensity I′I, the electron density ne and the electron temperature T were obtained. The calculation shows that the electron density has some dependence on the temperature and the ratio of line intensity. Furthermore, through applying the theoretical calculations to the channel plasma spectra of artificially triggered lightning, the electron densities were diagnosed at different channel locations and times. The accuracy of the electron density was estimated using the degree of accordance, which can pick out the diagnostic data that can best reflect the real state of plasma from a large number of statistical data.

Abstract Given a plane graph $G=(V,E)$ , a Petrie tour of G is a tour P of G that alternately turns left and right at each step. A Petrie tour partition of G is a collection ${\mathscr P}=\{P_1,\ldots,P_q\}$ of Petrie tours so that each edge of G is in exactly one tour $P_i \in {\mathscr P}$ . A Petrie tour P is called a Petrie cycle if all its vertices are distinct. A Petrie cycle partition of G is a collection ${\mathscr C}=\{C_1,\ldots,C_p\}$ of Petrie cycles so that each vertex of G is in exactly one cycle $C_i \in {\mathscr C}$ . In this paper, we study the properties of 3-regular plane graphs that have Petrie cycle partitions and 4-regular plane multi-graphs that have Petrie tour partitions. Given a 4-regular plane multi-graph $G=(V,E)$ , a 3-regularization of G is a 3-regular plane graph $G_3$ obtained from G by splitting every vertex $v\in V$ into two degree-3 vertices. G is called Petrie partitionable if it has a 3-regularization that has a Petrie cycle partition. The general version of this problem is motivated by a data compression method, tristrip, used in computer graphics. In this paper, we present a simple characterization of Petrie partitionable graphs and show that the problem of determining if G is Petrie partitionable is NP-complete.

Design of high-performance pH-universal electrocatalysts is critical to practical large-scale hydrogen generation as a carbon-neutral fuel, yet challenging. Herein, we report an unique motif with crystalline nickel tellurium nanorods enclosed by amorphous rhodium hydroxide (a-Rh(OH)(3)/NiTe), formed through a hydrothermal synthesis and a subsequent chemical etching process, to address this challenge. The as-prepared a-Rh(OH)(3)/NiTe cathode enables a current density of 100 mA cm(-2) with low overpotentials of 51, 109, and 64 mV for HER in alkaline, neutral and acidic media, respectively. As revealed by density functional theory (DFT) calculations, the electronic interactions between a-Rh(OH)(3) and NiTe enhance the performance of Rh active sites. More importantly, the motif possesses superhydrophilicity and aerophobicity features, which not only facilitates the access to electrolytes but also ensures the fast release of hydrogen bubbles, endowing the electrocatalyst with advanced pH-universal HER activity. This work provides insights for the design of highly efficient electrocatalysts for hydrogen evolution at both molecular and mesoscopic levels.

Design and synthesis of highly active, inexpensive and durable catalyst for simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly desired for green hydrogen generation. In this work, high conductivity NiTe nanorods are coupled with amorphous CoFe layered double hydroxide (LDH) to achieve a hierarchical NiTe@CoFe LDH heterostructure via a hydrothermal reaction and a subsequent electrodeposition process. The as-prepared three-dimensional (3D) self-supported NiTe@CoFe LDH nanorods endow highly efficient electron transfer and mass diffusion, and this architecture with abundant electrode/electrolyte interfaces can provide more active sites. Consequently, with the synergistic effect of NiTe and CoFe LDH, the as-prepared NiTe@CoFe LDH electrocatalyst achieved a current density of 10 mA cm(-2) with low overpotentials of 218 mV and 103 mV for OER and HER, respectively, and showing a robust stability for 50 h. Furthermore, an alkaline electrolyzer with NiTe@CoFe LDH serving as both the anode and cathode requires a cell voltage of 1.56 V to yield 10 mA cm(-2) current density, and can sustain for more than 50 h, with a slightly current density increase of 5%, showing potential for practical industrial application to generate hydrogen. This work highlights the construction low cost highly efficient 3D rods electrode for promising applications in green hydrogen generation. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.