二维材料最新研究进展

Research on two-dimensional(2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some major breakthroughs made in the field of 2D materials in last five years not only in developing novel synthetic methods and exploring new structures/properties but also in identifying innovative applications and pushing forward commercialisation. In this review, we provide a critical summary on the recent progress made in the field of 2D materials with a particular focus on last five years. After a brief backgroundintroduction, we first discuss the major synthetic methods for 2D materials, including the mechanical exfoliation, liquid exfoliation, vapor phase deposition, and wet-chemical synthesis as well as phase engineering of 2D materials belonging to the field of phase engineering of nanomaterials(PEN). We then introduce the superconducting/optical/magnetic properties and chirality of 2D materials along with newly emerging magic angle 2D superlattices. Following that, the promising applications of 2D materials in electronics, optoelectronics, catalysis, energy storage, solar cells, biomedicine, sensors, environments, etc. are described sequentially. Thereafter, we present the theoretic calculations and simulations of 2D materials. Finally, after concluding the current progress, we provide some personal discussions on the existing challenges and future outlooks in this rapidly developing field.

Rational construction of thermally stable single atom catalysts:From atomic structure to practical applications

As a new frontier in catalysis field,single-atom catalysts(SACs)hold unique electronic structure and high atom utilization,which have displayed unprecedented activity and selectivity toward a wide range of catalytic reactions.However,many reported SACs are susceptible to Ostwald ripening process in high temperature environment or long-term catalytic application,which will cause sintering and deactivation.This is due to the weak interaction between the metal atom and supports.The regeneration and recycling of deactivated catalysts will greatly increase the time and economic cost of industrial production.Therefore,it is necessary to develop SACs with excellent thermal stability to meet the industrial demands.Here,we discuss the fundamental comprehension of the stability of thermally stable SACs obtained from different synthesis methods.The influences of the speciation of metal centers and coordination environments on thermal stability are summarized.The importance of using novel in situ and operando characterizations to reveal dynamic structural evolution under synthesis and reaction conditions and to identify active sites of thermally stable SACs is highlighted.The mechanistic understanding of the unique role of thermally stable SACs in thermocatalytic application is also discussed.At last,a brief perspective on the remaining challenges and future directions of thermally stable SACs is presented.

Role of local coordination in bimetallic sites for oxygen reduction: A theoretical analysis

Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.

Surface BrØnsted-Lewis dual acid sites for high-efficiency dinitrogen photofixation in pure water

As is known to all, nitrogen not only plays an important role in the industrial development of human society but also plays an important part in the proteins that constitute the essence of life[1]. In 1910, the Haber-Bosch process was first used to synthesize ammonia.

Compressive strain in Cu catalysts:Enhancing generation of C_(2+) products in electrochemical CO_(2) reduction

Elastic strain in Cu catalysts enhances their selectivity for the electrochemical CO_(2)reduction reaction(eCO_(2)RR),particularly toward the formation of multicarbon(C_(2+))products.However,the reasons for this selectivity and the effect of catalyst precursors have not yet been clarified.Hence,we employed a redox strategy to induce strain on the surface of Cu nanocrystals.Oxidative transformation was employed to convert Cu nanocrystals to CuxO nanocrystals;these were subsequently electrochemically reduced to form Cu catalysts,while maintaining their compressive strain.Using a flow cell configuration,a current density of 1 A/cm^(2)and Faradaic efficiency exceeding 80%were realized for the C_(2+)products.The selectivity ratio of C_(2+)/C1 was also remarkable at 9.9,surpassing that observed for the Cu catalyst under tensile strain by approximately 7.6 times.In-situ Raman and infrared spectroscopy revealed a decrease in the coverage of K+ion-hydrated water(K·H_(2)O)on the compressively strained Cu catalysts,consistent with molecular dynamics simulations and density functional theory calculations.Finite element method simulations confirmed that reducing the coverage of coordinated K·H_(2)O water increased the probability of intermediate reactants interacting with the surface,thereby promoting efficient C–C coupling and enhancing the yield of C_(2+)products.These findings provide valuable insights into targeted design strategies for Cu catalysts used in the eCO_(2)RR.

Single Fe atom-anchored manganese dioxide for efficient removal of volatile organic compounds in refrigerator

The efficient and rapid removal of volatile organic compounds(VOCs)holds significant importance for ensuring food quality and human health,particularly within the low-temperature confined spaces in refrigerators.However,achieving effective VOCs degradation under such conditions poses challenges in terms of activating inert bonds and facilitating mass transfer.In this study,we propose a novel solution by designing a cleaner module that incorporates 1.07%single Fe atom-anchored manganese dioxide catalysts(FeSAs-MnO_(2)).The combination of single Fe atoms and defect-rich MnO_(2) substrate efficiently activates molecular oxygen,leading to enhanced generation of highly reactive oxygen species(ROS).Non-thermal plasma(NTP)and circulating fan are introduced to facilitate the regeneration of catalytic activity and improve mass transfer.The FeSAs-MnO_(2) cleaner module demonstrates exceptional performance in trimethylamine(TMA)removal,achieving a conversion efficiency of 98.9%for 9 ppm within just 9 min.Furthermore,accelerated aging tests predict an extended service life of up to 45 years for the FeSAs-MnO_(2) cleaner module,surpassing the expected lifespan of refrigerators significantly.

Integrating single Ni site and PtNi alloy on two-dimensional porous carbon nanosheet for efficient catalysis in fuel cell

The performance of catalyst depends on the intrinsic activity of active sites and the structural characteristics of the support.Here,we simultaneously integrate single nickel(Ni)sites and platinum-nickel(PtNi)alloy nanoparticles(NPs)on a two-dimensional(2D)porous carbon nanosheet,demonstrating remarkable catalytic performance in the oxygen reduction reaction(ORR).The single Ni sites can activate the oxygen molecules into key oxygen-containing intermediate that is further efficiently transferred to the adjacent PtNi alloy NPs and rapidly reduced to H_(2)O,which establishes a relay catalysis between active sites.The porous structure on the carbon nanosheet support promotes the transfer of active intermediates between these active sites,which assists the relay catalysis by improving mass diffusion.Remarkably,the obtained catalyst demonstrates a half-wave potential of up to 0.942 V,a high mass activity of 0.54 A·mgPt^(−1),and negligible decay of activity after 30,000 cycles,which are all superior to the commercial Pt/C catalysts with comparable loading of Pt.The theoretical calculation results reveal that the obtained catalyst with defect structure of carbon support presents enhanced relay catalytic effect of PtNi alloy NPs and single Ni sites,ultimately realizing improved catalytic performance.This work provides valuable inspiration for developing low platinum loading catalyst,integrating single atoms and alloy with outstanding performance in fuel cell.

Large-scale manufacturing of functional single-atom ink for convenient glucose sensing

Printing techniques hold great potential in the manufacture of electronics such as sensors,micro-supercapacitors,and flexible electronics.However,developing large-scale functional conductive inks with appropriate rheological properties and active components still remains a challenge.Herein,through optimizing the formulations of ink,iron single sites supported N-doped carbon black(Fe_(1)-NC)inks can serve as both conductive electrodes and high-reactive catalysts to realize convenient glucose detection,which pronouncedly reduces the dosage of enzyme and simplifies the sensors preparation.In detail,utilizing in-situ pyrolysis method,Fe_(1)-NC single-atom catalysts(SACs)are prepared in bulk(dekagram-level).The batched Fe_(1)-NC SACs materials can be uniformly mixed with modulated ink to realize the screen printing with high resolution and uniformity.Also,the whole scalable preparation and ink-functional process can be extended to various metals(including Co,Ni,Cu,and Mn).The introduction of highly active Fe_(1)-NC sites reduces the amount of enzyme used in glucose detection by at least 50%,contributing to the cost reduction of sensors.The strategy in harnessing the SACs onto the carbon inks thus provides a broad prospect for the low-cost and large-scale printing of sensitive sensing devices.

Total conversion of centimeter-scale nickel foam into single atom electrocatalysts with highly selective CO_(2)electrocatalytic reduction in neutral electrolyte

To improve the atomic utilization of metals and reduce the cost of industrialization,the one-step total monoatomization of macroscopic bulk metals,as opposed to nanoscale metals,is effective.In this study,we used a thermal diffusion method to directly convert commercial centimeter-scale Ni foam to porous Ni single-atom-loaded carbon nanotubes(CNTs).As expected,owing to the coating of single-atom on porous,highly conductive CNT carriers,Ni single-atom electrocatalysts(Ni-SACs)exhibit extremely high activity and selectivity in CO_(2)electroreduction(CO_(2)RR),yielding a current density of>350 mA/cm^(2),a selectivity for CO of>91%under a flow cell configuration using a 1 M potassium chloride(KCl)electrolyte.Based on the superior activity of the Ni-SACs electrocatalyst,an integrated gas-phase electrochemical zero-gap reactor was introduced to generate a significant amount of CO current for potential practical applications.The overall current can be increased to 800 mA,while maintaining CO Faradaic efficiencies(FEs)at above 90%per unit cell.Our findings and insights on the active site transformation mechanism for macroscopic bulk Ni foam conversion into single atoms can inform the design of highly active single-atom catalysts used in industrial CO_(2)RR systems.

Surface modification of MoS_(2) nanosheets by single Ni atom for ultrasensitive dopamine detection

Single atom catalysts have been recognized as potential catalysts to fabricate electrochemical biosensors,due to their unexpected catalytic selectivity and activity.Here,we designed and fabricated an ultrasensitive dopamine(DA)sensor based on the flower-like MoS_(2) embellished with single Ni site catalyst(Ni-MoS_(2)).The limit of detection could achieve 1 pM in phosphate buffer solution(PBS,pH=7.4),1 pM in bovine serum(pH=7.4),and 100 pM in artificial urine(pH=6.8).The excellent sensing performance was attributed to the Ni single atom axial anchoring on the Mo atom in the MoS_(2) basal plane with the Ni-S_(3) structure.Both the experiment and density functional theory(DFT)results certify that this structural feature is more favorable for the adsorption and electron transfer of DA on Ni atoms.The high proportion of Ni active sites on MoS_(2) basal plane effectively enhanced the intrinsic electronic conductivity and electrochemical activity toward DA.The successful establishment of this sensor gives a new guide to expand the field of single atom catalyst in the application of biosensors.

Cu_(2+1)O/CuO_(x)heterostructures promote the electrosynthesis of C^(2+)products from CO_(2)

Manipulating the oxidation state of Cu catalysts can significantly affect the selectivity and activity of electrocatalytic carbon dioxide reduction(CO_(2)RR).However,the thermodynamically favorable cathodic reduction to metallic states typically leads to catalytic deactivation.Herein,a defect construction strategy is employed to prepare crystalline/amorphous Cu_(2+1)O/CuO_(x)heterostructures(c/a-CuO_(x))with abundant Cu0 and Cuδ+(0<δ<1)sites for CO_(2)RR.The C^(2+)Faradaic efficiency of the heterostructured Cu catalyst is up to 81.3%,with partial current densities of 406.7 mA·cm−2.Significantly,real-time monitoring of the Cu oxidation state evolution by in-situ Raman spectroscopy confirms the stability of Cuδ+species under long-term high current density operation.Density functional theory(DFT)calculations further reveal that the adjacent Cu0 and Cuδ+sites in heterostructured c/a-CuO_(x)can efficiently reduce the energy barrier of CO coupling for C^(2+)products.

Three-Dimensional Welded Mn_(1) Site Catalysts with nearly 100% Singlet Oxygen Fabrication for Contaminant Elimination

Reactive oxygen species(ROS)have a significant part in the elimination of recalcitrant organic pollutants and commonly coexist in one advanced oxidation system.It is difficult for us to make clear the effect of the co-instantaneous generation of radicals and nonradicals,which would cover and obscure the transformation pathway.Herein,a coordinate welding process is presented for fabricating accessible Mn1 site catalysts(Mn SSCs)in order to clarify the nonradical(singlet oxygen/^(1)O_(2))generated pathway and transformation in oxidative removal of contaminants.The Mn SSCs achieve nearly 100%^(1)O_(2) fabrication by activating peroxymonosulfate,which displays an excellent sulfamethoxazole elimination performance,super anti-anion interference,and extraordinary stability.As revealed by density functional theory calculations,the Mn SSCs with a special welded three-dimensional nanostructure could significantly boost the activation process by oxidizing the peroxymonosulfate at the interlayer of Mn SSCs and reducing dissolved oxygen on the surface of Mn SSCs.This design of Mn SSCs with a three-dimensional welded nanostructure might offer a potential approach for employing single site catalysts for environmental remediation.

Acid-stable antimonate based catalysts for the electrocatalytic oxygen evolution reaction

Acid-stable and highly active catalysts for the electrocatalytic oxygen evolution reaction(OER)are paramount to the advancement of electrochemical technologies for clean energy conversion and utilization.In this work,based on the density functional theory(DFT)calculations,we systematically investigated the MSb_(2)O_(6)(M=Fe,Co,and Ni)and transition metal(TM)doped MSb_(2)O_(6)(TM-MSb_(2)O_(6),TM=Mn,Fe,Co,Ni,Cu,Zn,Ru,Rh,Pd,Ir,and Pt)as potential antimonate-based electrocatalysts for the OER.The stability and OER activity of these considered electrocatalysts were systematically studied under acidic conditions.It was found that Rh-NiSb_(2)O_(6),Pt-CoSb_(2)O_(6),Rh-FeSbO4,and Co-NiSb_(2)O_(6)can serve as efficient and stable OER electrocatalysts,and their OER catalytic activities are better than that of the current state-of-the-art OER catalyst(IrO2).Our findings highlight a family of promising antimonate-based OER electrocatalysts for future experimental verification.

Atomically dispersed Au_1 catalyst towards efficient electrochemical synthesis of ammonia

Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au_1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH＋4 Faradaic efficiency of 11.1 % achieved by our Au_1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH＋4 yield rate of 1,305 μg h-1 mg-1Au has been reached, which is roughly 22.5 times as high as that by sup- ported Au nanoparticles. We also demonstrate that by employing our Au_1 catalyst, NH＋4 can be electro- chemically produced directly from N_2 and H_2 with an energy utilization rate of 4.02 mmol kJ-1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies.

Porous bimetallic Pt-Fe nanocatalysts for highly efficient hydrogenation of acetone

Porous Pt-Fe bimetallic nanocrystals have been synthesized via self-assembly and can effectively facilitate the synthesis of 2-propanol from acetone. The bimetallic catalyst has three--dimensional channels and shows turnover frequencies （TOFs） of up to 972 h^-1 for a continuous process more than 50 h. Preliminary mechanistic studies suggest that the high reactivity is related to the interface consisting of a bimetallic Pt-Fe alloy and Fe2O3-x. An understanding of real catalytic behavior and the catalytic mechanism based on model systems has been shown to help fabricate an improved Pt/Fe3O4 catalyst with increased activity and lifetime which has great potential for large-scale industrial applications.

Multicarbons generation factory:CuO/Ni single atoms tandem catalyst for boosting the productivity of CO_(2)electrocatalysis

Tandem electrocatalysis is an emerging concept for effective electrochemical CO_(2) reduction reaction(CO_(2)RR)towards multicarbons(C_(2+)).This decouples the multiple steps of CO_(2)-to-C_(2+)into two steps of CO_(2)-to-CO and CO-to-C_(2+)catalyzed by individual catalysts,to improve the Faradic efficiency(FE).However,due to the mass-transport limitation of CO from the generation site to the long-distance consumption site,such a strategy still remains challenge for high-rate production of C_(2+)products.Herein,we designed CuO/Ni single atoms tandem catalyst,which made the catalytic sites of Ni and Cu for independently catalyzing CO_(2)-to-CO and CO-to-C_(2+)compactly neighbored,enabling the in-situ generation and rapid consumption of CO.The CuO/Ni SAs tandem catalyst achieved a particularly high partial current density of C_(2+)products(1220.8 mA/cm^(2)),while still maintained outstanding C_(2+)products FE(81.4%)and excellent selectivities towards ethylene(FE 54.1%)and ethanol(FE 28.8%),enabling the profitable production of multicarbons by CO_(2)RR.

A hierarchical heterostructure of CdS QDs confined on 3D ZnIn_(2)S_(4) with boosted charge transfer for photocatalytic CO_(2) reduction

Metal sulfide based materials as photocatalysts for energy conversion are essential to produce value-added chemical fuels,but their intrinsically slow carrier dynamics and low activity are yet to be resolved.Herein,we developed a unique heterogeneously nanostructured ZnIn_(2)S_(4)-CdS heterostructure that involves zero-dimensional(0D)CdS quantum dots uniformly confined on three-dimensional(3D)ZnIn_(2)S_(4)nanoflowers,which achieves an excellent catalytic performance of CO_(2) photoconversion under visible-light irradiation.The obtained hierarchical heterostructure can significantly enhance the light harvesting,shorten the migration distance of carriers,and obviously accelerate the transport of electrons.As evidenced by the ultrafast transient absorption spectroscopy,the formed interface can effectively facilitate charge separation and transport.This work opens up a new avenue to carefully design the elaborate heterostructures for achieving optimal charge separation efficiency by lowering interfacial kinetic barriers and energy losses at the interface.

Highly sensitive ethanol gas sensor based on ultrathin nanosheets assembled Bi_2WO_6 with composite phase

Bismuth tungstate(Bi2 WO6) has many intriguing properties and has been the focus of studies in a variety of fields, especially photocatalysis. However, its application in gas-sensing has been seldom reported.Here, we successfully synthesized assembled hierarchical Bi2 WO6 which consists of ultrathin nanosheets with crystalline-amorphous composite phase by a one-step hydrothermal method. X-ray diffraction(XRD), X-ray photoemission spectroscopy(XPS), field-emission scanning electron microscopy(FESEM),and high-resolution transmission electron microscopy(HRTEM) techniques were employed to characterize its composition, morphology, and microstructure. By taking advantage of its unique microstructure,phase composition, and large surface area, we show that the resulting Bi2 WO6 is capable of detecting ethanol gas with quick response(7 s) and recovery dynamic(14 s), extremely high sensitivity(Ra/Rg= 60.8@50 ppm ethanol) and selectivity. Additionally, it has excellent reproducibility and long-term stability(more than 50 d). The Bi2 WO6 outperform the existing Bi2 WO6-based and most of the other state-of-the-art sensing platforms. We not only provided one new member to the field of gas sensor,but also offered several strategies to reconstruct nanomaterials.

Exposing Cu-rich {110} active facets in PtCu nanostars for boosting electrochemical performance toward multiple liquid fuels electrooxidation

In catalysis,tuning the structural composition of the metal alloy is known as an efficient way to optimize the catalytic activity.This work presents the synthesis of compositional segregated six-armed PtCu nanostars via a facile solvothermal method and their distinct composition-structure-dependent performances in electrooxidation processes.The alloy is shown to have a unique six arms with a Cu-rich dodecahedral core,mainly composed of {110} facets and exhibit superior catalytic activity toward alcohols electrooxidation compared to the hollow counterpart where Cu was selectively etched.Density functional theory (DFT) calculations suggest that the formation of hydroxyl intermediate (OH^*) is crucial to detoxify CO poisoning during the electrooxidation processes.The addition of Cu is found to effectively adjust the d band location of the alloy catalyst and thus enhance the formation of ^*OH intermediate from water splitting,which decreases the coverage of ^*CO intermediate.Our work demonstrates that the unique compositional anisotropy in alloy catalyst may boost their applications in electrocatalysis and provides a methodology for the design of this type catalyst.

Hollow cobalt-nickel phosphide nanocages for efficient electrochemical overall water splitting

A low-cost,highly efficient and strong durable bifunctional electrocatalyst is crucial for electrochemical overall water splitting.In this paper,a self-templated strategy combined with in-situ phosphorization is applied to construct hollow structured bimetallic cobalt-nickel phosphide(CoNiP_(x))nanocages.Owing to their unique hollow structure and bimetallic synergistic effects,the as-synthesized CoNiP_(x)hollow nanocages exhibit a high electrocatalytic activity and stability towards hydrogen evolution reaction in all-pH electrolyte and a remarkable electrochemical performance for oxygen evolution reaction in 1.0 mol L^(-1)KOH.Meanwhile,with the bifunctional electrocatalyst in both anode and cathode for overall water splitting,a low voltage of 1.61 V and superior stability are achieved at a current density of 20 mA cm^(-2).