Engineering d-band states of(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material for photocatalytic syngas production

The d-band states of catalytic materials participate in adsorbing reactive intermediate species and determine the catalytic behaviors in CO_(2)reduction reactions.However,surface d-band states relating to the photocatalytic CO_(2)reduction reactions behaviors are rarely concerned.Herein,a slightly amount of Cd^(2+)is decorated on the surface of(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material(Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4))to tune the surface d-band states for improved CO_(2)+2reduction reactions.The Cd/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)is fabricated via the facile ions-exchange method to make that slightly Zn2+is substituted by Cd^(2+).The Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)exhibits much enhanced photocatalytic activity in CO_(2)reduction reactions to produce CO and water splitting to produce H_(2).Physical characterizations show that the energy band structure is not changed obviously.Density functional theory reveals that Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)possesses a closer shift of d-band center to Fermi level than(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4),suggesting easier adsorption of CO_(2)reduction reactive intermediates after Cd^(2+)decoration.Further calculations confirm that a relatively reduced adsorption Gibbs energy of reactive intermediates in CO_(2)reduction reaction is required on Zn atoms in Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material,benefiting the photocatalytic CO_(2)reduction reactions.This work engineers surface d-band states by surface Cd^(2+)decoration,which gives an effective strategy to design highly efficient photocatalysts for syngas production.

Revealing the illumination effect on the discharge products in high-performance Li-O_(2) batteries with heterostructured photocatalysts

Aprotic lithium–oxygen batteries(LOBs)have been recognized as novel energy storage devices for their outstanding specific energy density,while the large discharge/charge overpotential is a tough barrier to be overcome.Here,hetero-structured MoS_(2)/ZnIn_(2)S_(4) nanosheets have been prepared to capture visible light and the generated charge carriers are utilized for promoting both the oxygen reduction reaction and the oxygen evolution reaction.With the light illumination in the discharge process,the abundant photo-inspired electrons serve as the reaction sites to promote the reduction of O_(2) into LiO_(2) which is finally deposited as Li_(2)O_(2).On the contrary,the generated holes in the valence band can contribute to the low oxidization potential of Li_(2)O_(2) during the charge process.It delivers a low charge potential of 3.29 V,with an excellent resulting energy efficiency of 96.7%,much superior to that of 69.2%in the dark condition.It is noted that the involvement of photoelectrons has influenced the growth of Li_(2)O_(2) films on the MoS_(2)/ZnIn_(2)S_(4) nanosheets through the surface-adsorption pathway.The insights from the theoretical calculation confirm that the photoelectrons favor the absorption of LiO_(2) and the formation of the Li_(2)O_(2) film through the surface route.Therefore,this paper provides a deeper understanding of the mechanism of photoinspired charge carriers in LOBs and will enable further exploration of photo-involved energy storage systems.

Engineering of carbon and other protective coating layers for stabilizing silicon anode materials

Silicon(Si)has been attracting extensive attention for rechargeable lithium(Li)‐ion batteries due to its high theoretical capacity and low potential vs Li/Li+.However,it remains challenging and problematic to stabilize the Si materials during electrochemical cycling because of the huge volume expansion,which results in losing electric contact and pulverization of Si particles.Consequently,the Si anode materials generally suffer from poor cycling,poor rate performance,and low coulomb efficiency,preventing them from practical applications.Up‐to‐date,there are numerous reports on the engineering of Si anode materials at microscale and nanoscale with significantly improved electrochemical performances.In this review,we will concentrate on various precisely designed protective layers for silicon‐based materials,including carbon layers,inorganic layers,and conductive polymer protective layer.First,we briefly introduced the alloying and failure mechanism of Si as anode materials upon electrochemical reactions.Following that,representative cases have been introduced and summarized to illustrate the purpose and advancement of protective coating layers,for instance,to alleviate pulverization and improve conductivity caused by volume expansion of Si particles during charge/discharge process,and maintain the surface stability of Si particles to form a stable solid‐electrolyte interphase layer.At last,possible strategies on the protective coating layer for stabilizing silicon anode materials that can be applied in the future have been indicated.

Tuned d-band states over lanthanum doped nickel oxide for efficient oxygen evolution reaction

The d-band state of materials is an important descriptor for activity of oxygen evolution reaction(OER).For NiO materials,there is rarely concern about tuning their d-band states to tailor the OER behaviors.Herein,NiO nanocrystals with doping small amount of La^(3+)were used to regulate d-band states for promoting OER activity.Density of states calculations based on density functional theory revealed that La^(3+)doping produced upper shift of d-band center,which would induce stronger electronic interaction between surface Ni atoms and species of oxygen evolution reaction intermediates.Further density functional theory calculation illustrated that La^(3+)doped NiO possessed reduced Gibbs free energy in adsorbing species of OER intermediate.Predicted by theoretical calculations,trace La^(3+)was introduced into crystal lattice of NiO nanoparticles.The La^(3+)doped NiO nanocrystal showed much promoted OER activity than corresponding pristine NiO product.Further electrochemical analysis revealed that La^(3+)doping into NiO increased the intrinsic activity such as improved active sites and reduced charge transfer resistance.The in-situ Raman spectra suggested that NiO phase in La^(3+)doped NiO could be better maintained than pristine NiO during the OER.This work provides an effective strategy to tune the d-band center of NiO for efficient electrocatalytic OER.

2D Layered Double Hydroxide Nanosheets and Their Derivatives Toward E cient Oxygen Evolution Reaction

Layered double hydroxides(LDHs)have attracted tremendous research interest in widely spreading applications.Most notably,transition-metal-bearing LDHs are expected to serve as highly active electrocatalysts for oxygen evolution reaction(OER)due to their layered structure combined with versatile com-positions.Furthermore,reducing the thickness of platelet LDH crystals to nanometer or even molecular scale via cleavage or delamination provides an important clue to enhance the activity.In this review,recent progresses on rational design of LDH nanosheets are reviewed,including direct synthesis via traditional coprecipitation,homogeneous precipitation,and newly developed topochemical oxidation as well as chemical exfoliation of parent LDH crystals.In addition,diverse strategies are introduced to modulate their electrochemical activity by tuning the composition of host metal cations and intercalated counter-anions,and incorporating dopants,cavi-ties,and single atoms.In particular,hybridizing LDHs with conductive components or in situ growing them on conductive substrates to produce freestanding electrodes can further enhance their intrinsic catalytic activity.A brief discussion on future research directions and prospects is also summarized.

Recent progress in functionalized layered double hydroxides and their application in efficient electrocatalytic water oxidation

Layered double hydroxides (LDHs), a class of anionic clays consisting of brucite-like host layers and interlayer anions, have been widely investigated in the last decade due to their promising applications in many areas such as catalysis, ion separation and adsorption. Owing to the highly tunable compositi on and uniform distribution of metal cations in the brucite-like layers, as well as the facile exchangeability of intercalated anions, LDHs can be modified and functionalized to form various nanostructures/composites through versatile processes such as anion intercalation and exfoliation, decoration of nanoparticles, selfassembly with other two-dimensional (2D) materials, and controlled growth on conductive supports (e.g., nanowire arrays, nano tubes, 3D foams). In this article, we briefly review the recent advances on both the LDH nano structures and functionalized composites toward the applications in energy conversion, especially for water oxidation.

Microcrystallization and lattice contraction of NiFe LDHs for enhancing water electrocatalytic oxidation

The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice contraction and microcrystallization was synthesized via a simple one-step method using sodium gluconate.The lattice contraction is attributed to the interaction of carbon in sodium gluconate and iron in NiFe LDH.The NiFe LDH with optimized microcrystallization and lattice contraction shows a low overpotential of 217 mV at a current density of 10 mA cm^(−2) and excellent durability of 20 h at a high current density of 100 mA cm^(−2).The results revealed that a contractive metal–oxygen bond could boost the intrinsic activity of active sites and the microcrystallization promotes an increase in the number of active sites in terms of unit area.The chemical environment of oxygen elemental characterization and resistance at different chronopotentiometry times confirm that the lattice oxygen element is indeed involved in the process of OER,supporting the lattice-oxygen-mediated mechanism of NiFe LDH.Density functional theory calculations reveal that contractive metal–oxygen bonds induced a reduction of the adsorption energy barrier of intermediate products,thus improving the intrinsic catalytic activity.The special characteristics of microcrystallization and lattice contraction of NiFe LDH provide a strategy to improve both the number and the intrinsic activity of active sites in a versatile manner.

Advanced silicon nanostructures derived from natural silicate minerals for energy storage and conversion

To effectively alleviate the ever-increasing energy crisis and environmental issues,clean and sustainable energy-related materials as well as the corresponding storage/conversion devices are in urgent demand.Silicon(Si) with the second most elemental abundance on the crust in the form of silicate or silica(SiO_(2)) minerals,is an advanced emerging material showing high performance in energy-related fields(e.g.batteries,photocatalytic hydrogen evolution).For the improved performance in industry-scale applications,Si materials with delicate nanostructures and ideal compositions in a massive production are highly cherished.On account of the reserve,low cost and diverse micro-nanostructures,silicate minerals are proposed as promising raw materials.In the article,crystal structures and the reduction approaches for silicate minerals,as well as recent progress on the as-reduced Si products for clean energy storage/conversion,are presented systematically.Moreover,some cutting-edge fields involving Si materials are discussed,which may offer deep insights into the rational design of advanced Si nanostructures for extended energy-related fields.

Controllable fabrication and structure evolution of hierarchical 1T-MoS_(2) nanospheres for efficient hydrogen evolution

The layered materials have demonstrated great prospects as cost-effective substitutes for precious electrocatalysts in hydrogen evolution reaction.Research efforts have been devoted to synthesizing highly conductive MoS_(2) with the substantial cardinal plane and edge active sites.Here,we successfully synthesized a hierarchical 1T/2H–MoS_(2) with sodium ion insertion via a facile hydrothermal method.The contents of the 1T-phase can be flexibly controlled by different hydrothermal temperatures(160 ~ 200°C).And the modified uniformly dispersed 1T/2H–MoS_(2) nanospheres with different d spacings were designed to enhance the electrocatalytic efficiency by adding SiO_(2) and through the ion exchange process of Na OH and HF solution.The as-synthesized Na+intercalated 1T-MoS_(2) nanosphere with an expanded interlayer of 0.95 nm obtained at 160°C exhibits a prominent electrocatalytic performance of hydrogen evolution reaction with a comparable overpotential of 255 m V and a remarkably small Tafel slope of 44 m V/decade.Therefore,this study provides a facile and controllable strategy to yield interlayerexpanded 1T-MoS_(2) nanospheres,making it a potentially competitive hydrogen evolution catalyst for the hydrogen cell.

β-cyclodextrin as Lithium-ion Diffusion Channel with Enhanced Kinetics for Stable Silicon Anode

Silicon(Si)is regarded as a promising anode material for next-generation lithium-ion batteries due to its ultrahigh theoretical capacity.However,the drastic volume change and the continuous solid electrolyte interphase(SEI)formation during the lithiation/delithiation process seriously hinder its practical application as commercial anodes.Herein,macrocyclic betacyclodextrin(β-CD)has been designed as the diffusion channel for lithium ions at the molecular scale.The diameter of molecular channel is approximately comparable with the solvated lithium ions,which enables the transport of lithium ions and prevents the penetration of solvent molecules.Moreover,the addition ofβ-CD changes the formation behavior of SEI layer and stabilizes the Si nanoparticles.The enhanced electrochemical performances in terms of fast kinetics and improved stability have been achieved.The Si anode with the particularly selected lithium-ion diffusion channel and stabilized SEI layer exhibits a high reversible capability of 2562 m Ah g-1 after 50 cycles at the current density of 500 m A g-1,1944 m Ah g-1 after 200 cycles at the current density of 1 A g-1,and high rate performance.The novel strategy of molecular channel for lithium-ion diffusion offers new insights into the design of alloy-typed anode electrodes with high capacity for lithium-ion batteries.

Anchoring Active Sites by Pt_(2)FeNi Alloy Nanoparticles on NiFe Layered Double Hydroxides for Efficient Electrocatalytic Oxygen Evolution Reaction

Strategy of anchoring alloy nanoparticles made up of the efficient catalytic element(e.g.,Ni,Fe)on dodecyl sulfate(DS^(-))-intercalated NiFe layered double hydroxides(DS^(-)-NiFe LDH)obtained by a convenient one-step hydrothermal coprecipitation method for essentially enhancing oxygen evolution reaction(OER)performance was proposed.The results of structural characterization indicate Pt_(2)FeNi alloy nanoparticles evenly distribute on the surface of DS^(-)-NiFe LDH.The sizes of the Pt_(2)FeNi nanoparticles,closely related to their OER performance,could be wellcontrolled by adjusting the amount of H;PtCl;addition.The composite structure of as-prepared product was stable during processes of synthesis,exfoliation,self-assembly,and subsequent electrocatalytic OER.Rigorous electrochemical test proving the contributing catalytic active sites was located at the interface between Pt_(2)FeNi and DS^(-)-NiFe LDH,and the Ni and Fe were the major active elements while O atoms are adsorption sites.The formation of Pt_(2)FeNi nanoparticles could greatly prompt the reduction of Tafel slope.The best-performing Pt_(2)FeNi/DS^(-)-NiFe LDH with a Pt content of 0.98 wt%achieved low overpotential of 204 mV at 10 mA cm^(-2)and 262 mV at 50 mA cm^(-2).This work provides a convenient and effective strategy to create additional active sites for enhancing OER performance of NiFe LDH and make contribution to its wide application.

An overview of two dimensional materials

Research on two dimensional(2D)materials,one of the most extensively studied classes of materials,has grown rapidly over the past several years and attracted great attention of thousands of scientists from across materials science,physics,chemistry,engineering,medicine and industry.This research activity has triggered the emergence of a new generation of atomically thin metals,semimetals,semiconductors,nitrides,oxides/hydroxides,transition metal dichalcogenides(TMDs),topological insulators and even polymers,demonstrating the potential for novel properties and technological innovations.The topics of the special issue include TMDs and transition metal oxides(TMOs),graphene and graphene-derived materials,black phosphorus(BP),2D metals,and related heterostructures/hybrids/composites and their potential applications in energy,environment,electronics,and biology fields.

Hollow spherical rare-earth-doped yttrium oxysulfate： A novel structure for upconversion

A facile biomolecule-assisted hydrothermal route followed by calcination has been employed for the preparation of monoclinic yttrium oxysulfate hollow spheres doped with other rare-earth ions （Yb3＋ and Eu3＋ or Er3＋）. The formation of hollow spheres may involve Ostwald ripening. The resulting hybrid materials were used for upconversion applications. The host crystal structure allows the easy co-doping of two different rare-earth metal ions without significantly changing the host lattice. The luminescent properties were affected by the ratio and concentration of dopant rare-earth metal ions due to energy transfer and the symmetry of the crystal field. The type of luminescent center and the crystallinity of samples were also shown to have a significant influence on the optical properties of the as-prepared products.

3D multicore-shell CoSn nanoboxes encapsulated in porous carbon as anode for lithium-ion batteries

Due to its high theoretical capacity and appropriate potential platform,tin-based alloy materials are expected to be a competitive candidate for the next-generation high performance anodes of lithium-ion batteries.Nevertheless,the immense volume change during the lithium-ion insert process leads to severe disadvantages of structural damage and capacity fade,which limits its practical application.In this work,a three-dimensional(3 D)multicore-shell hollow nanobox encapsulated by carbon layer is obtained via a three-step method of hydrothermal reaction,annealing and alkali etching.During the electrochemical reactions,the CoSn@void@C nanoboxes provide internal space to compensate the volumetric change upon the lithiation of Sn,while the inactive component of Co acts as chemical buffers to withstand the anisotropic expansion of nanoparticles.Owing to the above-mentioned advantages,the elaborated anode delivers an excellent capacity of 788.2 m Ah/g at 100 m A/g after 100 cycles and considerable capacity retention of 519.2 mAh/g even at a high current density of 1 A/g after 300 cycles.The superior stability and high performance indicate its capability as promising anodes for lithium-ion batteries.

Photo-enhanced rechargeable high-energy-density metal batteries for solar energy conversion and storage

Solar energy is considered the most promising renewable energy source.Solar cells can harvest and convert solar energy into electrical energy,which needs to be stored as chemical energy,thereby realizing a balanced supply and demand for energy.As energy storage devices for this purpose,newly developed photo-enhanced rechargeable metal batteries,through the internal integration of photovoltaic technology and high-energy-density metal batteries in a single device,can simplify device configuration,lower costs,and reduce external energy loss.This review focuses on recent progress regarding the working principles,device architectures,and performances of various closed-type and open-type photo-enhanced rechargeable devices based on metal batteries,including Li/Zn-ion,Li-S,and Li/Zn-I_(2),and Li/Zn-O_(2)/air,Li-CO_(2),and Na-O_(2) batteries.In addition to provide a fundamental understanding of photo-enhanced rechargeable devices,key challenges and possible strategies are also discussed.Finally,some perspectives are provided for further enhancing the overall performance of the proposed devices.