High-entropy catalysts for electrochemical water-electrolysis of hydrogen evolution and oxygen evolution reactions

High entropy materials (HEMs) have developed rapidly in the field of electrocatalytic water-electrolysis for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) due to their unique properties. In particular, HEM catalysts are composed of many elements. Therefore, they have rich active sites and enhanced entropy stability relative to single atoms. In this paper, the preparation strategies and applications of HEM catalysts in electrochemical water-electrolysis are reviewed to explore the stabilization of HEMs and their catalytic mechanisms as well as their application in support green hydrogen production. First, the concept and four characteristics of HEMs are introduced based on entropy and composition. Then, synthetic strategies of HEM catalysts are systematically reviewed in terms of the categories of bottom-up and top-down. The application of HEMs as catalysts for electrochemical water-electrolysis in recent years is emphatically discussed, and the mechanisms of improving the performance of electrocatalysis is expounded by combining theoretical calculation technology and ex-situ/in situ characterization experiments. Finally, the application prospect of HEMs is proposed to conquer the challenges in HEM catalyst fabrications and applications.

Selective Hydrodeoxygenation of Lignin-Derived Vanillin via Hetero-Structured High-Entropy Alloy/Oxide Catalysts

The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals.Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity.Herein,it is reported that a high-entropy alloy(HEA)on high-entropy oxide(HEO)hetero-structured catalyst for highly active,chemoselective,and robust vanillin hydrodeoxygenation.The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs(NiZnCuFeAlZrO_(x)),where exsolvable metals(e.g.,Ni,Zn,Cu)in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix.This catalyst exhibits excellent catalytic performance:100%conversion of vanillin and 95%selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120℃,which were attributed to the synergistic effect among HEO matrix(with abundant oxygen vacancies),anchored HEA nanoparticles(having excellent hydrogenolysis capability),and their intimate hetero-interfaces(showing strong electron transferring effect).Therefore,our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion,which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.

Boosting overall saline water splitting by constructing a strain-engineered high-entropy electrocatalyst

High-entropy materials(HEMs),which are newly manufactured compounds that contain five or more metal cations,can be a platform with desired properties,including improved electrocatalytic performance owing to the inherent complexity.Here,a strain engineering methodology is proposed to design transition-metal-based HEM by Li manipulation(LiTM)with tunable lattice strain,thus tailoring the electronic structure and boosting electrocatalytic performance.As confirmed by the experiments and calculation results,tensile strain in the LiTM after Li manipulation can optimize the d-band center and increase the electrical conductivity.Accordingly,the asprepared LiTM-25 demonstrates optimized oxygen evolution reaction and hydrogen evolution reaction activity in alkaline saline water,requiring ultralow overpotentials of 265 and 42 mV at 10 mA cm−2,respectively.More strikingly,LiTM-25 retains 94.6%activity after 80 h of a durability test when assembled as an anion-exchange membrane water electrolyzer.Finally,in order to show the general efficacy of strain engineering,we incorporate Li into electrocatalysts with higher entropies as well.

Study on the hydrogen absorption properties of a YGdTbDyHo rare-earth high-entropy alloy

This study investigated the microstructure and hydrogen absorption properties of a rare-earth high-entropy alloy(HEA),YGdTbDyHo.Results indicated that the YGdTbDyHo alloy had a microstructure of equiaxed grains,with the alloy elements distributed homogeneously.Upon hydrogen absorption,the phase structure of the HEA changed from a solid solution with an hexagonal-close-packed(HCP)structure to a high-entropy hydride with an faced-centered-cubic(FCC)structure without any secondary phase precipitated.The alloy demonstrated a maximum hydrogen storage capacity of 2.33 H/M(hydrogen atom/metal atom)at 723 K,with an enthalpy change(ΔH)of-141.09 kJ·mol^(-1)and an entropy change(ΔS)of-119.14 J·mol^(-1)·K^(-1).The kinetic mechanism of hydrogen absorption was hydride nucleation and growth,with an apparent activation energy(E_(a))of 20.90 kJ·mol^(-1).Without any activation,the YGdTbDyHo alloy could absorb hydrogen quickly(180 s at 923 K)with nearly no incubation period observed.The reason for the obtained value of 2.33 H/M was that the hydrogen atoms occupied both tetrahedral and octahedral interstices.These results demonstrate the potential application of HEAs as a high-capacity hydrogen storage material with a large H/M ratio,which can be used in the deuterium storage field.

Catalytic Performance of Carbon Smoke over Ag-LSCF Composite Catalysts

To improve the catalytic performance of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3)(LSCF)towards carbon soot,we utilized the impregnation method to incorporate Ag into the prepared LSCF catalyst.We conducted a series of characterization tests and evaluated the soot catalytic activity of the composite catalyst by comparing it with the LaCoO_(3) group,LaFeO_(3) group,and catalyst-free group.The results indicate that the Ag-LSCF composite catalyst exhibits the highest soot catalytic activity,with the characteristic temperature values of 376.3,431.1,and 473.9℃at 10%,50%,and 90%carbon soot conversion,respectively.These values are 24.8,20.2,and 23.1℃lower than those of the LSCF group.This also shows that LSCF can improve the catalytic activity of soot after compounding with Ag,and reflects the necessity of using catalysts in soot combustion reaction.XPS characterization and BET test show that Ag-LSCF has more abundant surface-adsorbed oxygen species,larger specific surface area and pore volume than LSCF,which also proves that Ag-LSCF has higher soot catalytic activity.

Bimetallic Single‑Atom Catalysts for Water Splitting

Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by single-atom catalysts(SACs),which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports.Recently,bimetallic SACs(bimSACs)have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports.BimSACs offer an avenue for rich metal–metal and metal–support cooperativity,potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges,substrate activation with reversible redox cycles,simultaneous multi-electron transfer,regulation of spin states,tuning of electronic properties,and cyclic transition states with low activation energies.This review aims to encapsulate the growing advancements in bimSACs,with an emphasis on their pivotal role in hydrogen generation via water splitting.We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs,elucidate their electronic properties,and discuss their local coordination environment.Overall,we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction,the two half-reactions of the water electrolysis process.

Catalyst–Support Interaction in Polyaniline‑Supported Ni_(3)Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn‑Air Batteries

Catalyst–support interaction plays a crucial role in improving the catalytic activity of oxygen evolution reaction(OER).Here we modulate the catalyst–support interaction in polyaniline-supported Ni_(3)Fe oxide(Ni_(3)Fe oxide/PANI)with a robust hetero-interface,which significantly improves oxygen evolution activities with an overpotential of 270 mV at 10 mA cm^(-2)and specific activity of 2.08 mA cm_(ECSA)^(-2)at overpotential of 300 mV,3.84-fold that of Ni_(3)Fe oxide.It is revealed that the catalyst–support interaction between Ni_(3)Fe oxide and PANI support enhances the Ni–O covalency via the interfacial Ni–N bond,thus promoting the charge and mass transfer on Ni_(3)Fe oxide.Considering the excellent activity and stability,rechargeable Zn-air batteries with optimum Ni_(3)Fe oxide/PANI are assembled,delivering a low charge voltage of 1.95 V to cycle for 400 h at 10 mA cm^(-2).The regulation of the effect of catalyst–support interaction on catalytic activity provides new possibilities for the future design of highly efficient OER catalysts.

Boosting Oxygen Evolution Reaction Performance on NiFe‑Based Catalysts Through d‑Orbital Hybridization

Anion-exchange membrane water electrolyzers(AEMWEs)for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant NiFe-based catalysts.By introducing a third metal into NiFe-based catalysts to construct asymmetrical M-NiFe units,the d-orbital and electronic structures can be adjusted,which is an important strategy to achieve sufficient oxygen evolution reaction(OER)performance in AEMWEs.Herein,the ternary NiFeM(M:La,Mo)catalysts featured with distinct M-NiFe units and varying d-orbitals are reported in this work.Experimental and theoretical calculation results reveal that the doping of La leads to optimized hybridization between d orbital in NiFeM and 2p in oxygen,resulting in enhanced adsorption strength of oxygen intermediates,and reduced rate-determining step energy barrier,which is responsible for the enhanced OER performance.More critically,the obtained NiFeLa catalyst only requires 1.58 V to reach 1 A cm^(−2) in an anion exchange membrane electrolyzer and demonstrates excellent long-term stability of up to 600 h.

High Fe‑Loading Single‑Atom Catalyst Boosts ROS Production by Density Effect for Efficient Antibacterial Therapy

The current single-atom catalysts(SACs)for medicine still suffer from the limited active site density.Here,we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron.The constructed iron SACs(h^(3)-FNC)with a high metal loading of 6.27 wt%and an optimized adjacent Fe distance of~4 A exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects.Attractively,a“density effect”has been found at a high-enough metal doping amount,at which individual active sites become close enough to interact with each other and alter the electronic structure,resulting in significantly boosted intrinsic activity of single-atomic iron sites in h^(3)-FNCs by 2.3 times compared to low-and medium-loading SACs.Consequently,the overall catalytic activity of h^(3)-FNC is highly improved,with mass activity and metal mass-specific activity that are,respectively,66 and 315 times higher than those of commercial Pt/C.In addition,h^(3)-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion(O_(2)·^(−))and glutathione(GSH)depletion.Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h^(3)-FNCs in promoting wound healing.This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

Preparation of Co/S co-doped carbon catalysts for excellent methylene blue degradation

S and Co co-doped carbon catalysts were prepared via pyrolysis of MOF-71 and thiourea mixtures at 800℃at a mass ratio of MOF-71 to thiourea of 1:0.1 to effectively activate peroxymonosulfate(PMS)for methylene blue(MB)degradation.The effects of two different mixing routes were identified on the MB degradation performance.Particularly,the catalyst obtained by the alcohol solvent evaporation(MOF-AEP)mixing route could degrade 95.60%MB(50 mg/L)within 4 min(degradation rate:K=0.78 min^(-1)),which was faster than that derived from the direct grinding method(MOF-DGP,80.97%,K=0.39 min^(-1)).X-ray photoelectron spectroscopy revealed that the Co-S content of MOF-AEP(43.39at%)was less than that of MOF-DGP(54.73at%),and the proportion of C-S-C in MOF-AEP(13.56at%)was higher than that of MOF-DGP(10.67at%).Density functional theory calculations revealed that the adsorption energy of Co for PMS was -2.94 eV when sulfur was doped as C-S-C on the carbon skeleton,which was higher than that when sulfur was doped next to cobalt in the form of Co-S bond(-2.86 eV).Thus,the C-S-C sites might provide more contributions to activate PMS compared with Co-S.Furthermore,the degradation parameters,including pH and MOF-AEP dosage,were investigated.Finally,radical quenching experiments and electron paramagnetic resonance(EPR)measurements revealed that ^(1)O_(2)might be the primary catalytic species,whereas·O~(2-)might be the secondary one in degrading MB.

De novo-design of highly exposed Co−N−C single-atom catalyst for oxygen reduction reaction

The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.

High-entropy alloy catalysts:From bulk to nano toward highly efficient carbon and nitrogen catalysis

High-entropy alloys(HEAs)have attracted widespread attention as both structural and functional materials owing to their huge multielement composition space and unique high-entropy mixing structure.Recently,emerging HEAs,either in nano or highly porous bulk forms,are developed and utilized for various catalytic and clean energy applications with superior activity and remarkable durability.Being catalysts,HEAs possess some unique advantages,including(1)a multielement composition space for the discovery of new catalysts and fine-tuning of surface adsorption(i.e.,activity and selectivity),(2)diverse active sites derived from the random multielement mixing that are especially suitable for multistep catalysis,and(3)a high-entropy stabilized structure that improves the structural durability in harsh catalytic environments.Benefited from these inherent advantages,HEA catalysts have demonstrated superior catalytic performances and are promising for complex carbon(C)and nitrogen(N)cycle reactions featuring multistep reaction pathways and many different intermediates.However,the design,synthesis,characterization,and understanding of HEA catalysts for C-and N-involved reactions are extremely challenging because of both complex high-entropy materials and complex reactions.In this review,we present the recent development of HEA catalysts,particularly on their innovative and extensive syntheses,advanced(in situ)characterizations,and applications in complex C and N looping reactions,aiming to provide a focused view on how to utilize intrinsically complex catalysts for these important and complex reactions.In the end,remaining challenges and future directions are proposed to guide the development and application of HEA catalysts for highly efficient energy storage and chemical conversion toward carbon neutrality.

Locating the cocktail and scaling-relation breaking effects of high-entropy alloy catalysts on the electrocatalytic volcano plot

High entropy alloys(HEAs)have been the star materials in electrocatalysis research in recent years.One of their key features is the greatly increased multiplicity of active sites compared to conventional catalytic materials.This increased multiplicity stimulates a cocktail effect and a scaling-relation breaking effect,and results in improved activity.However,the multiplicity of active sites in HEAs also poses new problems for mechanistic studies.One apparent problem is the inapplicability to HEA catalysts of the currently most popular mechanistic study method,which uses the electrocatalytic theoretical framework(ETF)based on the computational hydrogen electrode(CHE).The ETF uses a single adsorption energy to represent the catalyst,i.e.,a catalyst is represented by a'point'in the volcanic relationship.It naturally does not involve the multiplicity of active sites of a catalyst,and hence loses brevity in expressing the cocktail effect and scaling-relation breaking effect in HEA catalysis.This paper attempts to solve this inapplicability.Based on the fact that the adsorption energy distribution of HEAs is close to a normal distribution,the mean and variance of the adsorption energy distribution are introduced as descriptors of the ETF,replacing the original single adsorption energy.A quantitative relationship between the variance and the cocktail and scaling-relation braking effects is established.We believe the method described in this work will make the ETF more effective in mechanistic studies of HEA electrocatalysis.

Solution combustion synthesis of high-entropy metal spinel oxide as oxygen evolution reaction catalyst

High-entropy metal spinel oxide(HEO)is proved to be a promising oxygen evolution reaction(OER)catalyst with high catalytic performance and stability.A short routine synthesis process based on solution combustion synthesis was proposed to prepare(Co_(0.25)Ni_(0.25)Mn_(0.25)Zn_(0.25))Fe_(2)O_(4)spinel HEO in this work.During the process,the products were rapidly synthesized and melted due to the high-temperature reaction,and then quickly crystallized on the surface of nickel foam to form a nano-structure coating.With the aid of nano-scale spinel structure,the overpotential of non-activation HEO electrode reaches 276 mV at the current density of 10 mA·cm^(-2),and after 100 h i-t test,it can be further reduced to 230 mV,which proves the high activity of OER catalysis.The promotion of OER catalytic performance can be attributed to the surface reconstruction caused by the selective element leaching and the boost of oxygen vacancy,leading to the formation of nano-scale flocculation around spinel core after the long-term OER process.This work indicates a special casting process for functional materials and explores the application of rapid crystallization.

Synergistic coupling of Ni_(3)ZnC_(0.7)decorated with homogeneous multimetal CoNiCuFe nitrogen-codoped carbon matrix as high-entropy catalysts for efficient overall water splitting

Due to unique electrical properties and high catalytic efficiency,transition metal nitrogen-codoped car-bide(TM-N-C)has attracted tremendous interest as a multifunctional electrocatalyst for water splitting.Unlike traditional single-source modification,herein a novel pomegranate-like high-entropy(HE)elec-trocatalyst of Ni_(3)ZnC_(0.7)decorated with homogeneous multimetal(Fe,Co,Cu,and Ni)nitrogen-codoped carbon matrix(Ni_(3)ZnC_(0.7)@CoNiCuFe-NC)is reported.It can be implemented by the simple thermal an-nealing method of multimetal codoped zeolitic imidazolate framework(ZIF).Benefiting from the syn-ergistic effects of plentiful TM-N-C species,template effect of ZIF and distinct nanoporous structure,HE electrocatalyst Ni_(3)ZnC_(0.7)@CoNiCuFe-NC exhibits outstanding electrocatalytic performance.When ap-plied in strong alkaline electrolyte(1.0 M KOH),the overpotentials of Ni_(3)ZnC_(0.7)@CoNiCuFe-NC present as low as 202 and 97 mV for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)at 10 mA cm^(−2)current density.Surprisingly as a bifunctional electrode,it can achieve the low cell voltage of 1.53 V at 10 mA cm^(−2)current density for overall water splitting,which is comparable to conventional IrO_(2)||Pt/C electrode and superior to the recently reported analogous bifunctional catalysts.Thus,the work proposes the direction for the rational design of homogeneous distribution of TM-N-C material for water splitting in the green hydrogen energy industry.

Corrosion engineering on AlCoCrFeNi high-entropy alloys toward highly efficient electrocatalysts for the oxygen evolution of alkaline seawater

Seawater splitting is a prospective approach to yield renewable and sustainable hydrogen energy.Complex preparation processes and poor repeatability are currently considered to be an insuperable impediment to the promotion of the large-scale production and application of electrocatalysts.Avoiding the use of intricate instruments,corrosion engineering is an intriguing strategy to reduce the cost and presents considerable potential for electrodes with catalytic performance.An anode comprising quinary AlCoCrFeNi layered double hydroxides uniformly decorated on an AlCoCrFeNi high-entropy alloy is proposed in this paper via a one-step corrosion engineering method,which directly serves as a remarkably active catalyst for boosting the oxygen evolution reaction(OER)in alkaline seawater.Notably,the best-performing catalyst exhibited oxygen evolution reaction activity with overpotential values of 272.3 and 332 mV to achieve the current densities of 10 and100 mA·cm^(-2),respectively.The failure mechanism of the obtained catalyst was identified for advancing the development of multicomponent catalysts.

光学体表成像设备Catalyst的故障维修案例及日常保养方法

本文介绍了光学体表成像设备Catalyst HD的工作原理,以及处理常见的硬件和软件故障的方法,并提供了日常维护保养方法。其中,对于硬件故障,利用Catalyst HD系统的MutilZsn软件来判断Catalyst投影器和摄像头故障,对于软件故障方面,探讨了Catalyst HD系统在医用直线加速器上常见的Authorization Pending联锁问题的触发原因。本文为科室更好地开展光学体表引导放疗技术,高效地运用好设备提供参考意见。

Relationship between the unique microstructures and behaviors of high-entropy alloys

High-entropy alloys(HEAs),which were introduced as a pioneering concept in 2004,have captured the keen interest of nu-merous researchers.Entropy,in this context,can be perceived as representing disorder and randomness.By contrast,elemental composi-tions within alloy systems occupy specific structural sites in space,a concept referred to as structure.In accordance with Shannon entropy,structure is analogous to information.Generally,the arrangement of atoms within a material,termed its structure,plays a pivotal role in dictating its properties.In addition to expanding the array of options for alloy composites,HEAs afford ample opportunities for diverse structural designs.The profound influence of distinct structural features on the exceptional behaviors of alloys is underscored by numer-ous examples.These features include remarkably high fracture strength with excellent ductility,antiballistic capability,exceptional radi-ation resistance,and corrosion resistance.In this paper,we delve into various unique material structures and properties while elucidating the intricate relationship between structure and performance.

Strong synergy between physical and chemical properties:Insight into optimization of atomically dispersed oxygen reduction catalysts

Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.

Boric Acid-Assisted Pyrolysis for High-Loading Single-Atom Catalysts to Boost Oxygen Reduction Reaction in Zn-Air Batteries

The emerging of single-atom catalysts(SACs)offers a great opportunity for the development of advanced energy storage and conversion devices due to their excellent activity and durability,but the actual mass production of high-loading SACs is still challenging.Herein,a facile and green boron acid(H_(3)BO_(3))-assisted pyrolysis strategy is put forward to synthesize SACs by only using chitosan,cobalt salt and H_(3)BO_(3)as precursor,and the effect of H_(3)BO_(3)is deeply investigated.The results show that molten boron oxide derived from H_(3)BO_(3)as ideal high-temperature carbonization media and blocking media play important role in the synthesis process.As a result,the acquired Co/N/B tri-doped porous carbon framework(Co-N-B-C)not only presents hierarchical porous structure,large specific surface area and abundant carbon edges but also possesses high-loading single Co atom(4.2 wt.%),thus giving rise to outstanding oxygen catalytic performance.When employed as a catalyst for air cathode in Zn-air batteries,the resultant Co-N-B-C catalyst shows remarkable power density and long-term stability.Clearly,our work gains deep insight into the role of H_(3)BO_(3)and provides a new avenue to synthesis of high-performance SACs.