Alloying engineering for thermoelectric performance enhancement in p-type skutterudites with synergistic carrier concentration optimization and thermal conductivity reduction

The enhancements in thermoelectric(TE)performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more impurity phases induced by inherent structural instability of a Fe-based skutterudite.As shown in this study,alloying engineering of Ni doping at Fe sites in a p-type CeFe_(3.8)Co_(0.2)Sb_(12)skutterudite can not only reduce the impurity phases with high thermal conductivity but also regulate the carrier concentration,and thus significantly increase the Seebeck coefficient.The thermal conductivity was largely suppressed due to the enhanced point defect phonon scattering and decreased hole concentration.As a result,a TE figure of merit ZT of the CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)sample reached 0.8,which is approximately 50%higher than that of a Ni-free sample.Appropriate Ni doping can maintain a high ZT at a high temperature by controlling the reduction in a band gap.Therefore,a high average ZT close to 0.8 at 650–800 K for CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)was obtained,which was comparable to or even higher than those of the reported Ce-filled Fe-based skutterudites due to the synergistic optimization of electrical and thermal performances.This study provides a strategy to synergistically optimize electrical–thermal performances of the p-type skutterudites by alloying engineering.

Approaching Superior Potassium Storage of Carbonaceous Anode Through a Combined Strategy of Carbon Hybridization and Sulfur Doping

Carbonaceous materials are promising anode candidates for potassium-ion batteries(PIBs)given its high conductivity,stable property,and abundant resource,while its practical implementation is still hampered by its limited capacity and inferior rate behavior.Herein,we report a superior carbonaceous anode through a combined strategy of carbon hybridization and heteroatom doping.In this composite,hollow carbon spindles(HCS)were anchored on the surface of graphene(G)followed with sulfur doping treatment,aiming to integrate the high conductivity of graphene,the good structure stability of HCS,and the S doping-induced ample active sites.As a PIB anode,the S-G@HCS composite can display high capacity(301 mAh g^(-1)at 0.1 A g^(-1)after 500 cycles)and long-term cyclability up to 1800 cycles at 2 A g^(-1).Impressively,it can deliver an outstanding rate capacity of 215 mAh g^(-1)at 10 A g^(-1),which is superior to most carbon anodes as-reported so far for PIBs.Experimental and theoretical analysis manifests that the construction of graphene/amorphous carbon interface as well as S doping enables the regulation of electronic structure and ion adsorption/transportation properties of carbonaceous material,thus accounting for the high capacity and superior rate capability of S-G@HCS composite.

Neutral color and self-healable electrochromic system based on CuI/Cu and I_(3)^(-)/I^(-)conversions

The electrochromic(EC)mechanisms of inorganic materials are usually based on reversible cation insertion/extraction or metal deposition/dissolution,which are plagued by ion trapping and dendrite growth,respectively.In this paper,a novel conversion-type electrochromic mechanism is proposed,by making good use of the CuI/Cu redox couple.This CuI-based electrochromic system shows a neutral color switching from transparent and dim grey.By simply increasing the bleaching voltage,I_(3)^(-)/I^(-)redox couple can be further activated.The generated I_(3)^(-)will readily react with Cu,effectively improving the conversion reversibility and thereby rejuvenating the degraded electrochromic performance.Thanks to the well-designed electrode and the self-healing ability,this conversion electrochromic system achieves rapid response times(tcoloring:23 s,tbleaching:6 s),decant optical modulation amplitude(26.4%),high coloration efficiency(86.15 cm^(2)·C^(-1)),admirable cyclic durability(without performance degradation after 480 cycles)and excellent optical memory ability(transmittance variation<1%after 10 h open-circuit storage).The establishment of this conversion-type electrochromism may inspire the exploration of novel electrochromic materials and devices.

Bucket Effect to Improve Third-Order Nonlinear Optical Response on Metal-Heteroaromatic Compounds

Carbolong compounds as a metal-heteroaromatic compound with both organometallic properties andπ-conjugated systems exhibit great potential in organic catalysis and optoelectronic devices.In this work,for the first time,the“Bucket Effect”is revealed to promote the third-order nonlinear optical(NLO)performance in metal-heteroaromatic compounds.We have successfully constructed and investigated a series of novel metallapentalenes with higher third-order NLO performance benefited from the“Bucket Effect”.Meanwhile,aromaticity and electron−hole analysis further confirm the internal homogeneity of organometallic rings,reduced bandgap,and enhanced low-energy peak response resulted in the enhanced third-order NLO effects.The success of this work is discovering an emerging material library of high third-order NLO effects,and illustrating the feasibility of engineering the high response metal-heteroaromatic optical devices at the electronic structure level.

Enhancing hydrogen evolution of MoS_(2) basal planes by combining single-boron catalyst and compressive strain

M0 S2 is a promising candidate for hydrogen evolution reaction(HER),while its active sites are mainly distributed on the edge sites rather than the basal plane sites.Herein,a strategy to overcome the inertness of the M0 S2 basal surface and achieve high HER activity by combining single-boron catalyst and compressive strain was reported through density functional theory(DFT)computations.The ab initio molecular dynamics(AIMD)simulation on B@MoS2 suggests high thermodynamic and kinetic stability.We found that the rather strong adsorption of hydrogen by B@MoS2 can be alleviated by stress engineering.The optimal stress of -7%can achieve a nearly zero value of △Gh(〜-0.084 eV),which is close to that of the ideal Pt-SACs for HER.The novel HER activity is attributed to(i)the Bdoping brings the active site to the basal plane of M0 S2 and reduces the band-gap,thereby increasing the conductivity;(ii)the compressive stress regulates the number of charge transfer between(H)-(B)-(MoS2),weakening the adsorption energy of hydrogen on B@MoS2.Moreover,we constructed a SiN/B@MoS2 heterojunction,which introduces an 8.6%compressive stress for B@MoS2 and yields an ideal AGh-This work provides an effective means to achieve high intrinsic HER activity for M0 S2.

Effect of rare-earth doping on adsorption of carbon atom on ferrum surface and in ferrum subsurface:A first-principles study

The adsorption of carbon atom on Fe surface and in Fe subsurface with and without rare earth(La and Ce)substitution in the surface layer and subsurface layer was studied by first-principles calculations.The carbon atom is predicted to adsorb at hollow and long bridge site on Fe(100)and Fe(110),respectively.However,the carbon atom shifts to occupy preferentially hollow site on both Fe(100)and Fe(110)with rare earth atom doping at surface layer.The lower adsorption energies involved with stronger adsorption abilities were obtained for carbon atoms on Fe surface with rare earth doping at surface layer,which was determined by the electronic structure of the surface atoms.The La atom was pulled out the surface after carbon adsorption due to strong interaction of La-C,which is consistent with the more charge transfer.In the subsurface region,the carbon atom prefers to occupy at octahedral site with rare earth doping at surface layer in Fe slab.These strong adsorption energies of the carbon atoms on Fe surface and in Fe subsurface with rare earth pose relevant insights into the interaction between carbon and rare earth,which helps to understanding the influence mechanism of rare earth in carburizing.

TM_(3)(TM=V,Fe,Mo,W)single-cluster catalyst confined on porous BN for electrocatalytic nitrogen reduction

Confined metal clusters as sub-nanometer reactors for electrocatalytic N_(2) reduction reaction(eNRR)have received increasing attention due to the unique metal-metal interaction and higher activity than singleatom catalysts.Herein,the inspiration of the superior capacitance and unique microenvironment with regular surface cavities of the porous boron nitride(p-BN)nanosheets,we systematically studied the catalytic activity for NRR of transition-metal single-clusters in the triplet form(V_(3),Fe_(3),Mo_(3) and W_(3))confined in the surface cavities of the p-BN sheets by spin-polarized density functional theory(DFT)calculations.After a two-step screening strategy,Mo_(3)@p-BN was found to have high catalytic activity and selectivity with a rather low limiting potential(-0.34 V)for the NRR.The anchored Mo_(3) singlecluster can be stably embedded on the surface cavities of the substrate preventing the diffusion of the active Mo atoms.More importantly,the Mo atoms in the Mo_(3) single-cluster would act as“cache”to accelerate electron transfer between active metal centers and nitrogen-containing intermediates via the intimate Mo-Mo interactions.The cooperation of Mo atoms can also provide a large number of occupied and unoccupied d orbitals to make the"donation-backdonation"mechanism more effective.This work not only provides a quite promising electrocatalyst for NRR,but also brings new insights into the rational design of triple-atom NRR catalysts.