Halogen chlorine triggered oxygen vacancy-rich Ni(OH)_(2) with enhanced reaction kinetics for pseudocapacitive energy storage

Two-dimensional (2D)Ni(OH)_(2) nanosheets can theoretically expose their active sites of 100%.Whereas,their intrinsic easy accumulation and low conductivity lead to weak and unsustainable reaction kinetics.Herein,we propose a novel halogen chlorine-triggered electrochemical etching strategy to controllably manage the reaction kinetics of 2D Ni(OH)_(2) nanosheets(EE/Cl-Ni(OH)_(2)).It is found that halogen chlorine doping can adjust the interlamellar spacing flexibly and promote the lattice oxygen activation to achieve controlled construction of superficial oxygen defects at the adjustable voltage.The optimal EE/Cl-Ni(OH)_(2) electrode exhibits a high rate capability and excellent specific capacity of 206.9 mA h g^(-1) at 1 A g^(-1) in a three-electrode system,which is more than twice as high as the pristine Ni(OH)_(2).Furthermore,EE/Cl-Ni(OH)_(2) cathode and FeOOH@rGO anode are employed for developing an aqueous Ni-Fe battery with an excellent energy density of 83 W h kg^(-1),a high power density of 17051 W kg^(-1),and robust durability over 20,000 cycles.This strategy exploits a fresh channel for the ingenious fabrication of highefficiency and stable nickel-based deficiency materials for energy storage.

Minimum-Modified Debye-Hückel Theory for Size-Asymmetric Electrolyte Solutions with Moderate Concentrations

A minimum-modified Debye-Hückel(DH)theory for electrolytes with size asymmetry is developed.Com-pared with the conventional DH theory,the minimum-modified DH theory only introduces an extra surface charge density to capture the electrostatic effect of the size asymmetry of the electrolytes and hence facilitates a boundary element method for electrostatic potential calculation.This theory can distinguish the electrostat-ic energies and excess chemical potentials of ions with the same sizes but opposite charges,and is applied to a binary primitive electrolyte solution with moderate electrostatic coupling.Compared with the hyper-netted chain theory,the validity of this modified DH theory demonstrates significant improvement over the conventional DH theory.

In-situ cation-inserted MnO_(2) with selective accelerated intercalation of individual H^(+) or Zn^(2+) ions in aqueous zinc ion batteries

The recognized energy storage mechanism of neutral aqueous zinc-manganese batteries is the co-insertion/extrusion of H^(+) and Zn^(2+) ions.However,modulating the kinetics of a single H^(+) or Zn^(2+) ion is scarce,which can provide meaningful insights into the energy storage mechanism of Zn ion batteries.Herein,a distinctive doubly electric field in-situ induced cationic anchoring of two-dimensional layered MnO_(2) is successfully constructed to modulate the insertion/extrusion of a single H^(+) or Zn^(2+) ion.As a result,regulating the intercalation of different metal ions can precisely achieve the accelerated induction for the individual H^(+) or Zn^(2+) ions intercalation/deintercalation.Moreover,the introduction of metal ions stabilizes the lattice distortion and alleviates the irreparable structural collapse,leading to an increase in the H^(+)/Zn^(2+) storage sites,efficiently diminishing the stagnation of the ordered structure and creating the more open channels,which is conducive to facilitating the diffusion of ions.This work delivers some innovative insights into pre-embedding strategies,and also serves as a precious reference for the cathode development of advanced aqueous batteries.

Mn-corrolazine-based 2D-nanocatalytic material with single Mn atoms for catalytic oxidation of alkane to alcohol

Heterogenization of organic-macrocyclic metal catalysts is one of the simplest and most efficient methods for effective separation of products and cyclic application of a catalyst.By using an environmentally friendly Mn-corrolazine catalyst as the building unit,which can directly oxidize organic substrates under oxygen atmosphere and mild conditions,we theoretically constructed a novel two-dimensional(2D)Mn-corrolazine nanocatalytic material with high catalytic activity.In this material,each Mn atom maintains its electronic configuration in the monomer and can directly activate O2 as the single-atom catalyst(SAC)center to form a radical-like[Mn]-O-O under mild visible-light irradiation conditions.The newly generated[Mn]–O–O can efficiently and selectively oxidize C–H bonds to form alcohol species through H-abstraction and the rebound reaction.Moreover,the catalytic reaction is easily regulated by an external electric field along its intrinsic Mn–O–O reaction axis.The current study provides a theoretical foundation for further experimental studies and practical applications of the Mn-corrolazine-based SAC.

Non-Adiabatic Molecular Dynamics Simulations of Non-Charge-Transfer and Charge-Transfer Scattering in H^++CO2 at ELab=30 eV

The H^++CO2 reaction at high energies is relevant in atmospheric chemistry,astrophysics,and proton cancer therapy research.Therefore,we present herein a complete investigation of H^++CO2 at ELab=30 eV with the simplest-level electron nuclear dynamics(SLEND)method.SLEND describes nuclei via classical mechanics and electrons with a singledeterminantal Thouless wavefunction.The 3402 SLEND conducted simulations from 42 independent CO2 target orientations provide a full description of all the reactive processes and their mechanisms in this system:non-charge-transfer scattering(NCTS),charge-transfer scattering(CTS),and single C=O bond dissociation;all this valuable information about reactivity is not accessible experimentally.Numerous details of the projectile scattering patterns are provided,including the appearance and coalescence of primary and secondary rainbow angles as a function of the target orientation.SLEND NCTS and CTS differential cross sections(DCSs)are evaluated in conjunction with advanced semi-classical techniques.SLEND NCTS DCS agrees well with its experimental counterpart at all the measured scattering angles,whereas SLEND CTS DCS agrees well at high scattering angles but less satisfactorily at lower ones.Remarkably,both NCTS and CTS SLEND DCSs predict the primary rainbow angle signatures in agreement with the experiment.

Li adsorption on monolayer and bilayer MoS_2 as an ideal substrate for hydrogen storage

Based on the first-principles plane wave calculations, we show that Li adsorbed on monolayer and bilayer MoS2 forming a uniform and stable coverage can serve as a high-capacity hydrogen storage medium, and Li-coated MoS2 can be recycled by operations at room temperature due to Li having strength binding, big separation and is stable against clustering. The full Li coverage MoS2 system（2 ＊ 2 hexagonal MoS2 supercell） can reach up to eight H2 molecules on every side, corresponding to the gravimetric density of hydrogen storage up to 4.8 wt% and 2.5 wt% in monolayer and bilayer MoS2, respectively. The adsorption energies of hydrogen molecules are in the range of 0.10 e V/H2–0.25 e V/H2,which are acceptable for reversible H2 adsorption/desorption near ambient temperature. In addition, compared with light metals decorated low dimension carbon-based materials, the sandwiched structure of MoS2 exhibits the greatly enhanced binding stability of Li atoms as well as slightly decreased Li-Li interaction and thus avoids the problem of metal clustering.It is interesting to note that the Li atom apart from the electrostatic interaction, acts as a bridge of hybridization between the S atoms of MoS2 and adsorbed H2 molecules. The encouraging results show that such light metals decorated with MoS2 have great potential in developing high performance hydrogen storage materials.

A universal design for triggering the precise micro-structure reconstruction through in-situ electro-regulating to boost the pseudocapacitance of MnO_(2)

Developing a precise controllable strategy for modulating the micro-morphology,atom coordination environment,and electronic structure of electrode materials is crucial for the performance in the field of energy storage,yet still a tremendous challenge.Herein,a facile and universal in-situ electrochemical self-optimization design,electro-regulating,is designed to controllably produce electrode materials with abundant defects.Through detailed characterization studies,the microstructure of MnO_(2) is reconstructed after electro-regulating,which exhibits a structure of small fragments with numerous holes due to the partial self-dissolution of acidic oxides under an alkaline operating environment.Furthermore,the electro-regulating strategy not only presents the formation steps of numerous holes but is also accompanies by a number of O vacancies generation process due to the activation of an external electric field.This study provides a new inspiration for reasonably designing advanced functional electrode materials for various electrochemical applications and beyond.

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III)Complex

Spin crossover(SCO)is commonly accompanied by a synchronous phase transition.A few phase transitioncoupled SCO compounds have been reported,yet the synergy between SCO and phase transition on different time scales has not been explored.Herein,we report an[Fe(H-5-Cl-thsa-Et)(5-Cl-thsa-Et)]·H2O(1·H2O;H2-5-Cl-thsa-Et=5-chloro-salicylaldehyde ethylthiosemicarbazone)Fe(III)complex that displays a two-dimensional supramolecular structure and SCO behavior above room temperature.Its dehydrated form1 exhibits a two-step spin transition with aplateau in the temperature-dependent magnetization(M−T)curve at room temperature and a 51 K thermal hysteresis loop(Tc↑↓=299/248 K)at a rate of 5 K/min.The improved SCOperformance in 1 could be attributed to the stronger intralayer but weaker interlayer interactions,which is supported by single-crystal structural analysis and density functional theory calculations.Remarkably,complex 1 displays an unusual scan rate-dependent SCO behavior at rates of 0.5−30 K/min,in whichM−T curveplateaus appear at lower scan rates(<10 K/min)but vanish at faster scan rates(≥10 K/min).Scan rate-dependent differential scanning calorimetry,powder X-ray diffractometry,timedependent magnetic moment decays,and infrared spectroscopy consistently reveal that the slow structural relaxation is coupled with a slowcrystallographic phase transition,which is the mechanism for the unusual scan rate-dependent SCO.

Ultrastable single-atom gold catalysts with strong covalent metal-support interaction （CMSI）

Supported noble metal nanoparticles （including nanoclusters） are widely used in many industrial catalytic processes. While the finely dispersed nanostructures are highly active, they are usually thermodynamically unstable and tend to aggregate or sinter at elevated temperatures. This scenario is particularly true for supported nanogold catalysts because the gold nanostructures are easily sintered at high temperatures, under reaction conditions, or even during storage at ambient temperature. Here, we demonstrate that isolated Au single atoms dispersed on iron oxide nanocrystallites （Aul/FeOx） are much more sintering- resistant than Au nanostructures, and exhibit extremely high reaction stability for CO oxidation in a wide temperature range. Theoretical studies revealed that the positively charged and surface-anchored Aul atoms with high valent states formed significant covalent metal-support interactions （CMSIs）, thus providing the ultra-stability and remarkable catalytic performance. This work may provide insights and a new avenue for fabricating supported Au catalysts with ultra-high stability.

A systematic theoretical study on FeOx-supported single-atom catalysts： M1/FeOx for CO oxidation

A single-atom catalyst （SAC） that was first proposed by us in 2011 has aroused significant recent interest. Among the various SACs, FeOx-based ones including Pt1/FeOx, Ir1/FeOx, Au1/FeOx, Ni1/FeOx, and Fe1/FeOx have been investigated either experimentally or theoretically for CO oxidation. However, a systematic study of FeO,-based SACs has not been conducted. For a comprehensive understanding of FeOx-supported single-metal-atom catalysts, extensive density functional theory calculations were carried out on the activities and catalytic mechanisms of SACs with the 3d, 4d, and 5d metals of group VIII to IB, i.e., M1/FeOx （M = Fe, Co, Ni, Cu; Ru, Rh, Pd, Ag; Os, Ir, Pt, Au） for CO oxidation. Remarkably, a new noble metal SAC, Pd1/FeOx, with high activity in CO oxidation was found and is predicted to be even better than the previously reported Pt1/FeOx and Ni1/FeOx. In comparison, other M1/FeOx SACs （M = Fe, Co, Cu; Ru, Rh, Ag; Os, Ir, Au） showed only low activities in CO oxidation. Moreover, the adsorption strength of CO on the single-atom active sites was found to be the key in determining the catalytic activity of these SACs for CO oxidation, because it governs the recoverability of oxygen vacancies on their surfaces in the formation of a second CO2 during CO oxidation. Our systematic studies of FeOx-supported SACs will help in understanding the fundamental mechanisms of the interactions between singly dispersed surface metal atoms and FeOx substrate and in designing highly active FeOx-supported SACs.

Stochastic description of quantum Brownian dynamics

Classical Brownian motion has well been investigated since the pioneering work of Einstein, which inspired mathematicians to lay the theoretical foundation of stochastic processes. A stochastic formulation for quantum dynamics of dissipative systems described by the system-plus-t）ath model has been developed and found many applications in chemical dynamics, spectroscopy, quantmn transport, and other fields. This article provides a tutorial review of the stochastic formulation for quantum dissipative dynamics. The key idea is to decouple the interaction between the system and the bath by virtue of the Hubbard-Stratonovich transformation or Ito calculus so that the system and the bath are not directly entangled during evolution, rather they are correlated due to the complex white noises introduced. The influence of the bath on the system is thereby defined by an induced stochastic field, which leads to the stochastic Liouville equation for the system. The exact reduced density matrix can be calculated as the stochastic average in the presence of bath-induced fields. In general, the plain implementation of the stochastic formulation is only useful for short-time dynamics, but not efficient for long-time dynamics as the statistical errors go very fast. For linear and other specific systems, the stochastic Liouville equation is a good starting point to derive the master equation. For general systems with decomposable bath-induced processes, the hierarchical approach in the form of a set of deterministic equations of motion is derived based on the stochastic formulation and provides an effective means for simulating the dissipative dynamics. A combination of the stochastic simulation and the hierarchical approach is suggested to solve the zero-temperature dynamics of the spin-boson model. This scheme correctly describes the coherent-incoherent transition （Toulouse limit） at moderate dissipation and predicts a rate dynamics in the overdamped regime. Challenging problems such as the dynamical description of quantum phase transition （localization） and the numerical stability of the trace-conserving, nonlinear stochastic Liouville equation are outlined.

Magic hybrid structure as multifunctional electrocatalyst surpassing benchmark Pt/C enables practical hydrazine fuel cell integrated with energy-saving H_(2)production

A hybrid catalyst structure can provide abundant active sites and tailored electronic properties,but the major challenge lies in achieving delicate control over its composition and architecture to improve the catalytic activity toward different electrochemical reactions simultaneously.Herein,we present the rational design of a magic hybrid structure with low Pt loading(5.90 wt%),composed of CoPt_(3)and CoPt nanoparticles supported on N-doped carbon(CoPt_(3)/CoPt⊂PLNC).Importantly,it shows superior multifunctional catalytic activity in alkaline conditions,requiring a low overpotential of 341 and 20 mV to achieve 10 mA cm^(−2)for the hydrazine oxidation reaction(HzOR)/hydrogen evolution reaction(HER),respectively,and it delivers a half-wave potential of 0.847 V for the oxygen reduction reaction(ORR).Theoretical calculations reveal that the metal-carbon hybrid modulates kinetic behavior and induces electron redistribution,achieving the energetic requirements for multiple electrocatalysis.We demonstrate sustainable H_(2)production utilizing solely the CoPt_(3)/CoPt⊂PLNC catalyst,without external electric power input,suggesting its inspiring practical utility.

Social Network Analysis of Coauthor Networks in Inclusive Finance in China

The proposal and innovation of inclusive finance provide a very valuable pathway to realize social equity and eliminate poverty,which has attracted extensive attention,especially from developing countries.Based on the papers on inclusive finance published in the Chinese journal database CNKI from 2014 to 2018,we constructed an undirected weighted coauthor network 2154 authors.By employing social network analysis,we found that the number of authors in the field of inclusive finance increased rapidly.Although the cooperation between them was still very low and the cooperation authors were relatively fixed,the scale of cooperation was rapidly expanding.Although no scholar could always be at the center position in the coauthor network,the knowledge transfer path was significantly reduced.Financial universities and some financial institutions were the most important promoters of inclusive finance.Knowledge discovery in this field was promoted alternately by several center authors and cooperation by many scholars 2014-2018.We believe these discoveries are of great significance to promote knowledge sharing and innovation in the academic community of inclusive finance.