High-Index Faceted Nanocrystals as Highly Efficient Bifunctional Electrocatalysts for High-Performance Lithium-Sulfur Batteries

Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-index faceted iron oxide(Fe_(2)O_(3))nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts,effectively improving the electrochemical performance of Li-S batteries.The theoretical and experimental results all indicate that high-index Fe_(2)O_(3)crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li_(2)S.The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g^(-1)at 0.1 C and excellent cycling performance with a low capacity fading of 0.025%per cycle during 1600 cycles at 2 C.Even with a high sulfur loading of 9.41 mg cm^(-2),a remarkable areal capacity of 7.61 mAh cm^(-2)was maintained after 85 cycles.This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering,deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry,affording a novel perspective for the design of advanced sulfur electrodes.

High-index faceted noble metal nanostructures drive renewable energy electrocatalysis

Noble metallic nanocrystals are used in a wide variety of applications,such as catalysis,batteries,and bio-and chemical sensors.Most of the previous studies focus on the preparation of thermodynamically stable nanocrystals enclosed by low-index facets and discuss their corresponding catalytic properties.Recently,researchers have found that the nanocrystals with high-index facets(HIFs)are of more interest for electrocatalysis.Herein,we review recent key progress in the synthesis of noble metallic nanoparticles enclosed with HIFs and their facetdependent electrocatalytic behaviors.First,we introduce the concept of HIFs,and establish the correlation between their surface structure and catalytic activity.Then,we discuss various synthetic approaches for controlling the shapes and composition of the nanocrystals enclosed by HIFs.Afterwards,we showcase the enhanced electrocatalytic performance realized by HIF-based nanostructures.Finally,we provide guidance on how to improve the electrocatalysis by engineering HIFs on noble metallic nanocrystals.

Co_(2)P nanorods with exposure of high-index facets for efficient photochemical reduction of CO_(2)by promoting the directional transfer of electrons

Herein,Co_(2)P nanorods(NRs)with exposure to high-index facets(HIFs)were prepared by a special assembly-calcination method using thioacetamide(TAA)as a structure-directing reagent.The analysis of adsorption energies of S atoms on different facets as well as the surface energies of Co_(2)P indicate that the HIFs become more stable after adsorbing S atoms.With rich unsaturated sites on HIFs,the photochemical reduction rate of CO_(2)over Co_(2)P NRs is 14.5 mmol h^(-1)g^(-1)for the production of CO within 3 h.The analysis of electron transfer,bond lengths,bond angles and adsorption energies indicate that the CO_(2)molecules are more easily adsorbed and activated on the HIFs.The free energy calculations and d band theory demonstrate that the HIFs are conducive to reducing the formation energy barriers as well as improving the stability of the intermediate^(*)COOH,then enhancing the catalytic performance of CO_(2)reduction.

Tunning the bandgap of MnO_(2)homojunction by building active high-index facet to achieve rapid electron transfer for enhanced photocatalytic sterilization

Photocatalysis has been a research hotspot in recent years,and the design and modification of photocat-alysts have been the key points.Common methods for designing photocatalysts,including constructing heterojunctions and homojunctions,have been developed on the basis of heterojunctions.In this study,two homojunctions of manganese dioxide(MnO_(2)),including a high-index crystal plane homojunction and a general homojunction,are prepared using a stepwise hydrothermal method.Using a capping agent,the high-index crystal surface of the MnO_(2)is exposed.It is found that the electron transport efficiency be-tween the two components of the homojunction with high-index planes is higher and the adsorption capacity of the oxygen is stronger,which leads to higher photocatalytic efficiency.In addition,the newly designed high-index homojunction is used for the treatment of bacterial infections,and it kills Staphy-lococcus aureus(S.aureus)and Escherichia coli(E.coli)at rates of 99.95%±0.04%and 99.31%±0.25%,respectively.It also has excellent therapeutic effects on mouse wounds,which implies superb practical application value.This work provides a new strategy for the improved design of homojunctions and the application of photocatalytic materials.

Deterministic Synthesis of Pd Nanocrystals Enclosed by High-Index Facets and Their Enhanced Activity toward Formic Acid Oxidation

Noble-metal nanocrystals enclosed by high-index facets are of growing interest due to their enhanced catalytic performance in a variety of reactions.Herein,we report the deterministic synthesis of Pd nanocrystals encased by high-index facets by controlling the rate of deposition(V_(deposition))relative to that of surface diffusion(V_(diffusion)).For octahedral seeds with truncated corners,a reduction rate(and thus deposition rate)faster than that of surface diffusion(i.e.,V_(deposition)/V_(diffusion)>1)led to the formation of concave trisoctahedra(TOH)with high-index facets.When the reduction was slowed down,in contrast,surface diffusion dominated the growth pathway.In the case of V_(deposition)/V_(diffusion)≈1,truncated octahedra with enlarged sizes were produced.When the reduction rate was between these two extremes,we obtained concave tetrahexahedra(THH)without or with truncation.Similar growth patterns were also observed for the cuboctahedral seeds.When the Pd octahedra,concave TOH,and concave THH were tested for electrocatalyzing the formic acid oxidation(FAO)reaction,those with high-index facets were advantageous over the conventional Pd octahedra enclosed by{111}facets.This work not only contributes to the understanding of surface diffusion and its role in nanocrystal growth but also offers a general protocol for the synthesis of nanocrystals enclosed by high-index facets.

基于FACET滤波加权局部对比度的红外小目标检测

针对低空复杂背景下红外图像中目标与背景对比度低、边缘高亮的问题,提出一种基于FACET滤波加权局部对比度的红外小目标检测算法。首先,通过FACET滤波运算获取目标候选像素;然后,利用目标区域和背景区域灰度差异的比率计算局部对比度,同时基于目标和背景的异质性设计了一种加权函数,用来增强目标显著性和抑制背景;最后,通过自适应阈值分割提取真实的目标。在5组真实红外小目标图像数据集上与不同的算法进行性能比较分析,实验结果表明,提出的算法在不同低空复杂场景中具有较好的检测性能。

Mg-doped CaCO_(3)nanoarchitectures assembled by(441)high-index facets for efficient trace removal of Pb(Ⅱ)

Removal of trace heavy metal ions puts high demands on designing adsorbents with favorable surfaces.Crystal-plane engineering can provide controllable adsorption energy between surficial planes and adsorbents.Herein,we have creatively synthesized Mg-doped CaCO_(3)nanoarchitectures assembled by layered sheets(Mg-CaCO_(3)LSs)with high-index facets of(441)through a facile wet chemical process.Adsorption tests reveal that the layer-bylayer assembled sample exhibits a maximum Pb(II)adsorption capacity of 1961.9 mg·g^(-1),agreeing with the monolayer-adsorption Langmuir model.At an initial Pb(II)ion concentration of 20 mg·L^(-1),the adsorption can achieve a high removal rate near 99.0%within 1 min,and the adsorption kinetics follows a chemisorption pseudo-second-order model.Interestingly,the Mg-CaCO_(3)LSs show much-improved adsorption properties towards low-concentration Pb(II)ions,which could reduce the concentration from 1 mg·L^(-1)to~2.9μg·L^(-1)in 3 h(within 30 min decrease to less than 10μg·L^(-1),meeting drinking water standard from WHO).For comparison,the commercial CaCO_(3)and collected CaCO_(3)scale show much lower adsorption values with Pb(Ⅱ)ion residual concentration of~935.0 and~944.9μg·L^(-1)in 3 h,respectively.Xray diffraction(XRD),energy dispersive spectroscopy(EDS),and inductively coupled plasma(ICP)characterizations on the Mg-CaCO_(3)LSs before and after adsorbing Pb(Ⅱ)confirm that the high removal performance could be ascribed to fast metal ion exchange and excellent physical adsorption contributed by high-index planes.The density functional theory(DFT)calculations also confirm that the much-enhanced adsorption kinetics benefits from the optimal adsorption of the(441)planes.This work will provide a feasible route to design highefficient low-cost adsorbents through crystal-plane engineering.

Shape transformation of gold nanoparticles in aqueous CTAB/CTAC solution to generate high-index facets for electrocatalysis and SERS activity

Gold nanoparticles(Au NPs)have demonstrated great potential in chemical and biological sensing,catalysis,biomedicine,X-ray computed tomography,and other applications,owing to their unique properties.Au NPs with high-index facets have attracted more attention in the past decade owing to their superior electrocatalytic activity in fuel cells and enhanced performance in surface-enhanced Raman spectroscopy(SERS)applications.This review presents an overview of our achievements in the direct synthesis of Au NPs with controlled shapes in water using cationic surfactants.By deliberately adjusting the nature of the surfactant stabilizers,preformed Au NPs with simple shapes can be readily transformed into Au NPs with complicated shapes with controlled high-index facets by simple seeded growth.The high-index facets of the as-prepared Au NPs can be consistently correlated with their superior performance in the electrooxidation of methanol and ethanol and their enhanced SERS activity.

Multifaceted control of focal points along an arbitrary 3D curved trajectory

Metalenses can integrate the functionalities of multiple optical components thanks to the unprecedented capability of optical metasurfaces in light control.With the rapid development of optical metasurfaces,metalenses continue to evolve.Polarization and color play a very important role in understanding optics and serve as valuable tools for gaining insights into our world.Benefiting from the design flexibility of metasurfaces,we propose and experimentally demonstrate a super metalens that can realize multifaceted control of focal points along any 3D curved trajectory.The wavelengths and polarization states of all focal points are engineered in a desirable manner.The super metalens can simultaneously realize customized 3D positioning,polarization states,and wavelengths of focal points,which are experimentally demonstrated with incident wavelengths ranging from 501 to 700 nm.We further showcase the application of the developed super metalenses in 3D optical distance measurement.The compact nature of metasurfaces and unique properties of the proposed super metalenses hold promise to dramatically miniaturize and simplify the optical architecture for applications in optical metrology,imaging,detection,and security.

Optical facet coatings for high-performance LWIR quantum cascade lasers atλ∼8.5μm

We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)AR coating exhibits higher catastrophic optical mirror damage(COMD)level,and the optical facet coatings of both material systems have no beam steering effect.A 3-mm-long,9.5-μm-wide buried-heterostruc⁃ture(BH)LWIR QCL ofλ~8.5μm with Y_(2)O_(3)metallic high-reflection(HR)and AR of~0.2%reflectivity coating demonstrates a maximum pulsed peak power of 2.19 W at 298 K,which is 149%higher than that of the uncoated device.For continuous-wave(CW)operation,by optimizing the reflectivity of the Y_(2)O_(3)AR coating,the maximum output power reaches 0.73 W,which is 91%higher than that of the uncoated device.

F-doped orthorhombic Nb_(2)O_(5) exposed with 97% (100) facet for fast reversible Liþ-Intercalation

Orthorhombic Nb_(2)O_(5)(T-Nb_(2)O_(5))is attractive for fast-charging Li-ion batteries,but it is still hard to realize rapid charge transfer kinetics for Li-ion storage.Herein,F-doped T-Nb_(2)O_(5) microflowers(F-Nb_(2)O_(5))are rationally synthesized through topotactic conversion.Specifically,F-Nb_(2)O_(5) are assembled by single-crystal nanoflakes with nearly 97%exposed(100)facet,which maximizes the exposure of the feasible Li^(+)transport pathways along loosely packed 4g atomic layers to the electrolytes,thus effectively enhancing the Li^(+)-intercalation performance.Besides,the band gap of F-Nb_(2)O_(5) is reduced to 2.87 eV due to the doping of F atoms,leading to enhanced electrical conductivity.The synergetic effects between tailored exposed crystal facets,F-doping,and ultrathin building blocks,speed up the Li^(+)/electron transfer kinetics and improve the pseudocapacitive properties of F-Nb_(2)O_(5).Therefore,F-Nb_(2)O_(5) exhibit superior rate capability(210.8 and 164.9 mAh g^(-1) at 1 and 10 C,respectively)and good long-term 10 C cycling performance(132.7 mAh g^(-1) after 1500 cycles).

Surface deterioration dependent on the crystal facets of spinel LiNi_(0.5)Mn_(1.5)O_(4) cathode active material

The spinel LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode active materials(CAMs)are considered a promising alternative to commercially available cathodes such as layered and polyanion oxide cathodes,primarily due to their notable safety and high energy density,particularly in their single-crystal type.Nevertheless,the industrial application of the LNMO CAMs is severely inhibited due to the interfacial deterioration and corrosion under proton-rich and high-voltage conditions.This study successfully designed and synthesized two typical types of crystal facets-exposed single-crystal LNMO CAMs.By tracking the electrochemical deterioration and chemical corrosion evolution,this study elucidates the surface degradation mechanisms and intrinsic instability of the LNMO,contingent upon their crystal facets.The(111)facet,due to its elevated surface energy,is found to be more susceptible to external attack compared to the(100)and(110)facets.Our study highlights the electrochemical corrosion stability of crystal plane engineering for spinel LNMO CAMs.

Facet effects on bimetallic ZnSn hydroxide microcrystals for selective electrochemical CO_(2)reduction

Employing crystal facets to regulate the catalytic properties in electrocatalytic carbon dioxide reduction reaction(eCO_(2)RR)has been well demonstrated on electrocatalysts containing single metals but rarely explored for bimetallic systems.Here,we synthesize ZnSn(OH)_(6)(ZSO)microcrystals(MCs)with distinct facets and investigate the facet effects in eCO_(2)RR.Electrochemical studies and in situ Fourier Transform Infrared Spectroscopy(in situ-FTIR)reveal that ZSO MCs produce mainly C1 products of HCOOH and CO.The{111}facet of the ZSO MCS exhibits higher selectivity and faradaic efficiency(FE)than that of the{100}facet over a wide range of potentials(-0.9 V∼-1.3 V versus RHE).Density Functional Theory(DFT)calculations elucidate that the{111}facet is favorable to the adsorption/activation of CO_(2)molecules,the formation of intermediate in the rate-determining step,and the desorption of C1 products of CO and HCOOH molecules.

A review of energy and environment electrocatalysis based on high-index faceted nanocrystals

Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidation of small organic molecule(such as formic acid,methanol,and ethanol),oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),as well as the oxygen evolution reaction(OER).However,the practical applications of nanocrystals enclosed by HIFs still face many limitations in preparations of advanced electrocatalysts,including preparation strategy,limited life-time and stability.The development of advanced electrocatalysts enclosed with HIFs is crucial for solving these problems if the large-scale application of them is to be realized.Herein,we firstly detailedly demonstrate the identification methods of nanocrystals enclosed by HIFs,and then preparation strategies are elaborated in detail in this review.Current advanced nanocrystals enclosed by HIFs in electrocatalytic application are also summarized and we present representative achievements to further reveal the relationship of excellent electrocatalytic performance and nanocrystals with HIFs.Finally,we predict the remaining challenges and present our perspectives with regards of design strategies of improving electrocatalytic performance of Ptbased catalysts in the future.

Defect-density control of platinum-based nanoframes with high-index facets for enhanced electrochemical properties

Structure-engineered platinum-based nanoframes(NFs)at the atomic level can effectively improve the catalytic performance for fuel cells and other heterogeneous catalytic fields.We report herein,a microwave-assisted wet-chemical method for the preparation of platinum-copper-cobalt NFs with tunable defect density and architecture,which exhibit enhanced activity and durability towards the electro-oxidation reactions of methanol(MOR)and formic acid(FAOR).By altering the reduction/capping agents and thus the nucleation/growth kinetics,trimetallic platinum-copper-cobalt hexapod NFs with different density high-index facets are achieved.Especially,the rough hexapod nanoframes(rh-NFs)exhibit excellent specific activities towards MOR and FAOR,7.25 and 5.20 times higher than those of benchmark Pt/C,respectively,along with prolonged durability.The excellent activities of the rh-NFs are assigned to a synergistic effect,including high density of defects and high-index facets,suitable d-band center,and open-framework structure.This synergistic working mechanism opens up a new way for enhancing their electrocatalytic performances by increasing defect density and high-index facets in open-framework platinum-based NFs.

Phosphorus-doping-tuned PtNi concave nanocubes with high-index facets for enhanced methanol oxidation reaction

Surface engineering has been found to be an efficient strategy to boost the catalytic performance of noble-metal-based nanocatalysts.In this work,a small amount of P was doped to the surface of PtNi concave cube(P-PtNi CNC).Interestingly,the P-PtNi CNC nanocatalyst shows an enhanced methanol oxidation reaction(MOR)performance with achieving 8.19 times of specific activity than that of comercial Pt/C.The electrochemical in situ Fourier transform infrared spectroscopy(FTIR)results reveal that the surface P doping promotes the adsorption energy of OH,enhancing the resistance against CO poisoning.Therefore,the intermediate adsorbed CO(COads)reacted with adsorbed OH(OHads)through the Langmuir–Hinshelwood(LH)mechanism to generate CO_(2)and release surface active sites for further adsorption.This work provides a promising strategy via the incorporation of non-metallic elements into the PtNi alloys bounded with high-index facets(HIFs)as efficient fuel cell catalysts.

Catalytic PtPd bimetal nanocrystals with high-index facets for radiation injury repair

Radiotherapy is one of the most important clinical cancer treatments,which works mainly by delive ring a prescribed radiation dose to the tumor tissues.However,high doses of radiation may also lead many irreversible damages to the surrounding normal tissues.Thereby,how to effectively reduce these sideeffects has been a significant factor in influencing cancer therapeutic effect.In this work,we synthesized the hollow PtPd nanocubes with high-index facets,and investigated the radiation protection capability in vitro and in vivo.Our results showed the PtPd nanocrystals can decrease the ROS level and improve the survival rate of radiated cells.Meanwhile,survival rate of radiated mice can significantly increase from 0 to 30%after PtPd treatment.Consequently,the enzyme and ROS level in radiated mice can be recovered.

Interfacial synergistic effect in SnO_(2)/PtNi nanocrystals enclosed by high-index facets for high-efficiency ethylene glycol electrooxidation

Strengthening the oxide-metal interfacial synergistic interaction in nanocatalysts is identified as potential strategy to boost intrinsic activities and the availability of active sites by regulating the surface/interface environment of catalysts.Herein,the SnO_(2)/PtNi concave nanocubes(CNCs)enclosed by high-index facets(HIFs)with tunable SnO_(2)composition are successfully fabricated through combining the hydrothermal and self-assembly method.The interfacial interaction between ultrafine SnO_(2)nanoparticles and PtNi with HIFs surface structure is characterized by analytical techniques.The as-prepared 0.20%SnO_(2)/PtNi catalyst exhibits extraordinarily high catalytic performance for ethylene glycol electrooxidation(EGOR)in acidic conditions with specific activity of 3.06 mA/cm^(2),which represents 6.2-fold enhancement compared with the state-of-the-art Pt/C catalyst.Additionally,the kinetic study demonstrates that the strong interfacial interaction between SnO_(2)and PtNi not only degrades the activation energy barrier during the process of EGOR but also enhances the CO-resistance ability and long-term stability.This study provides a novel perspective to construct highly efficient and stable electrocatalysts for energy conversions.

Highly active zigzag-like Pt-Zn alloy nanowires with high-index facets for alcohol electrooxidation

The development of highly efficient Pt-based alloy nanocatalysts is important but remains challenging for fuel cells commercialization.Here,a new class of zigzag-like platinum-zinc (Pt-Zn) alloy nanowires (NWs) with rough surface and controllable composition is reported.The merits of anisotropic one-dimensional nanostructure,stable high-index facets and coordinatively unsaturated Pt sites endow the composition-optimal Pt94Zn6 NWs with a mass activity of 7.2 and 6.2 times higher than that of commercial Pt black catalysts toward methanol/ethanol oxidation,respectively.Alloying-induced d-band electron modulation and lattice strain effects weaken the adsorption strength of poisoning species,which originally enhances the catalytic activity of Pt-Zn NWs.This study provides a new perspective of Pt-Zn electrocatalysts with intrinsic mechanism for enhanced catalytic performance.

Synthesis of polyhedral iron oxide nanocrystals bound by high-index facets

High surface energy of high-index facets endows nanocrystals with high activities and thus promotes potential applications such as highly efficient catalysts,special optical,electrical and magnetic devices.But the high surface energy of the high-index facets usually drives them to grow faster than the other facets and finally disappear during the crystal growth,which leads the synthesis of nanocrystals with high-indexed facets exposed to be a great challenge.Herein,we introduced two routes to control the synthesis of-Fe2O3polyhedrons with different sets of high-index facets,one using different metal ions(Ni2+,Cu2+or Zn2+)as structure-directing agents and the other applying polymer surfactant sodium carboxymethyl cellulose(CMC)as additive.The growth process of high-index-Fe2O3polyhedrons was also discussed and possible growth mechanism was proposed.