Atomic Dispersed Hetero‑Pairs for Enhanced Electrocatalytic CO_(2)Reduction

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)involves a variety of intermediates with highly correlated reaction and ad-desorption energies,hindering optimization of the catalytic activity.For example,increasing the binding of the*COOH to the active site will generally increase the*CO desorption energy.Breaking this relationship may be expected to dramatically improve the intrinsic activity of CO_(2)RR,but remains an unsolved challenge.Herein,we addressed this conundrum by constructing a unique atomic dispersed hetero-pair consisting of Mo-Fe di-atoms anchored on N-doped carbon carrier.This system shows an unprecedented CO_(2)RR intrinsic activity with TOF of 3336 h−1,high selectivity toward CO production,Faradaic efficiency of 95.96%at−0.60 V and excellent stability.Theoretical calculations show that the Mo-Fe diatomic sites increased the*COOH intermediate adsorption energy by bridging adsorption of*COOH intermediates.At the same time,d-d orbital coupling in the Mo-Fe di-atom results in electron delocalization and facilitates desorption of*CO intermediates.Thus,the undesirable correlation between these steps is broken.This work provides a promising approach,specifically the use of di-atoms,for breaking unfavorable relationships based on understanding of the catalytic mechanisms at the atomic scale.

Optimizing high-coordination shell of Co-based single-atom catalysts for efficient ORR and zinc-air batteries

Atom-level modulation of the coordination environment for single-atom catalysts(SACs)is considered as an effective strategy for elevating the catalytic performance.For the MNxsite,breaking the symmetrical geometry and charge distribution by introducing relatively weak electronegative atoms into the first/second shell is an efficient way,but it remains challenging for elucidating the underlying mechanism of interaction.Herein,a practical strategy was reported to rationally design single cobalt atoms coordinated with both phosphorus and nitrogen atoms in a hierarchically porous carbon derived from metal-organic frameworks.X-ray absorption spectrum reveals that atomically dispersed Co sites are coordinated with four N atoms in the first shell and varying numbers of P atoms in the second shell(denoted as Co-N/P-C).The prepared catalyst exhibits excellent oxygen reduction reaction(ORR)activity as well as zinc-air battery performance.The introduction of P atoms in the Co-SACs weakens the interaction between Co and N,significantly promoting the adsorption process of ^(*)OOH,resulting in the acceleration of reaction kinetics and reduction of thermodynamic barrier,responsible for the increased intrinsic activity.Our discovery provides insights into an ultimate design of single-atom catalysts with adjustable electrocatalytic activities for efficient electrochemical energy conversion.

The design and engineering strategies of metal tellurides for advanced metal-ion batteries

Owning various crystal structures and high theoretical capacity,metal tellurides are emerging as promising electrode materials for high-performance metal-ion batteries(MBs).Since metal telluride-based MBs are quite new,fundamental issues raise regarding the energy storage mechanism and other aspects affecting electrochemical performance.Severe volume expansion,low intrinsic conductivity and slow ion diffusion kinetics jeopardize the performance of metal tellurides,so that rational design and engineering are crucial to circumvent these disadvantages.Herein,this review provides an in-depth discussion of recent investigations and progresses of metal tellurides,beginning with a critical discussion on the energy storage mechanisms of metal tellurides in various MBs.In the following,recent design and engineering strategies of metal tellurides,including morphology engineering,compositing,defect engineering and heterostructure construction,for high-performance MBs are summarized.The primary focus is to present a comprehensive understanding of the structural evolution based on the mechanism and corresponding effects of dimension control,composition,electron configuration and structural complexity on the electrochemical performance.In closing,outlooks and prospects for future development of metal tellurides are proposed.This work also highlights the promising directions of design and engineering strategies of metal tellurides with high performance and low cost.

Diffusionless-Like Transformation Unlocks Pseudocapacitance with Bulk Utilization: Reinventing Fe_(2)O_(3) in Alkaline Electrolyte

Energy density can be substantially raised and even maximized if the bulk of an electrode material is fully utilized.Transition metal oxides based on conversion reaction mechanism are the imperative choice due to either constructing nanostructure or intercalation pseudocapacitance with their intrinsic limitations.However,the fully bulk utilization of transition metal oxides is hindered by the poor understanding of atomic-level conversion reaction mechanism,particularly it is largely missing at clarifying how the phase transformation(conversion reaction)determines the electrochemical performance such as power density and cyclic stability.Herein,α-Fe_(2)O_(3) is a case provided to claim how the diffusional and diffusionless transformation determine the electrochemical behaviors,as of its conversion reaction mechanism with fully bulk utilization in alkaline electrolyte.Specifically,the discharge productα-FeOOH diffusional from Fe(OH)2 is structurally identified as the atomic-level arch criminal for its cyclic stability deterioration,whereas the counterpartδ-FeOOH is theoretically diffusionless-like,unlocking the full potential of the pseudocapacitance with fully bulk utilization.Thus,such pseudocapacitance,in proof-of-concept and termed as conversion pseudocapacitance,is achieved via diffusionless-like transformation.This work not only provides an atomic-level perspective to reassess the potential electrochemical performance of the transition metal oxides electrode materials based on conversion reaction mechanism but also debuts a new paradigm for pseudocapacitance.

Enhancing water-dissociation kinetics and optimizing intermediates adsorption free energy of cobalt phosphide via high-valence Zr incorporating for alkaline water electrolysis

Developing high-efficiency electrocatalysts for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) is required to enhance the sluggish kinetics of water dissociation and optimize the adsorption free energy of reaction intermediates.Herein,we tackle this challenge by incorporating high-valence Zr into CoP(ZrxCo_(1-x)P),which significantly accelerates the elementary steps of water electrolysis.Theoretical calculations indicate that the appropriate Zr incorporation effectively expedites the sluggish H2O dissociation kinetics and optimizes the adsorption energy of reaction intermediates for boosting the alkaline water electrolysis.These are confirmed by the experimental results of Zr_(0.06)Co_(0.94)P catalyst that delivers exceptional electrochemical activity.The overpotentials at the current density of 10 mA cm^(-2)(j10) are only 62(HER) and 240 mV(OER) in alkaline media.Furthermore,the Zr_(0.06)Co_(0.94)P/CC‖Zr_(0.06)Co_(0.94)P/CC system exhibits superior overall water splitting activity(1.53 V/j10),surpassing most of the reported bifunctional catalysts.This high-valence Zr incorporation and material design methods explore new avenues for realizing high-performance non-noble metal electrocatalysts.

Switching Optimally Balanced Fe-N Interaction Enables Extremely Stable Energy Storage

The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms.To address the notoriously significant volume changes accompanying intercalation or formation of alloy/compounds,we aim to introduce and utilize a weak,reversible Fe-N interaction during the(de)intercalation of ammonium ions(NH_(4)^(+))within iron(Ⅲ)hexacyanoferrate(FeHCF),inspired by manipulating the electrostatic adsorption between N and Fe in the early stages of ammonia synthesis(Bosch-Harber Process,Chemical Engineering)and steel nitriding processes(Metal Industry).Such strategy of switching well-balanced Fe-N interaction is confirmed in between the nitrogen of ammonium ions and highspin Fe in FeHCF,as observed by using X-ray absorption spectroscopy.The resulting material provided an extremely stable energy storage(58 mAh g^(-1) after 10000 cycles at current density of 1 A g^(-1))as well as high-rate performance(23.6 mAh g^(-1) at current density of 10 A g^(-1)).

Structure-catalytic functionality of size-facet-performance in pentlandite nanoparticles

As one of the pentlandites,Fe5Ni4S8(FNS) based materials have attracted increasing attention due to their excellent catalytic properties and promising applicability.The control over the catalyst surface structure often benefits its heterogeneous catalytic activity.However,this has not been investigated for FNS materials at the nanoscale regarding the catalytic activity related to high-index facets.Herein,FNS nanoparticles(FNSNPs) with enclosed continuous tunable high-index facets were prepared and studied to clarify the relationship between the structure and catalytic functionality.The results suggested strong dependence between exposed facets of FNSNPs and their sizes.The decline in the average size to5.8 nm led to enclosing by high-index facets(422) and(511) to yield optimal electrocatalytic activities toward the hydrogen evolution reaction.The catalytic activity of FNSNPs was closely related to the surface energy of the main exposed facets.These findings clarified the relationship between high-index-facet and high-surface-energy FNSNPs,as promising approaches in crystal surface control engineering.

Ultrathin origami accordion-like structure of vacancy-rich graphitized carbon nitride for enhancing CO_(2) photoreduction

Retaining the ultrathin structure of two-dimensional materials is very important for stabilizing their catalytic performances.However,aggregation and restacking are unavoidable,to some extent,due to the van der Waals interlayer interaction of two-dimensional materials.Here,we address this challenge by preparing an origami accordion structure of ultrathin twodimensional graphitized carbon nitride(oa-C_(3)N_(4))with rich vacancies.This novel structured oa-C_(3)N_(4) shows exceptional photocatalytic activity for the CO_(2) reduction reaction,which is 8.1 times that of the pristine C_(3)N_(4).The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects,which leads to modification of the electronic structure,regulation of the CO_(2) adsorption energy,and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction.This study provides a new avenue for the development of stable highperformance two-dimensional catalytic materials.

MXene-Based Quantum Dots Optimize Hydrogen Production via Spontaneous Evolution of Cl-to O-Terminated Surface Groups

MXene quantum dots(MQDs)offer wide applications owing to the abundant surface chemistry,tunable energy-level structure,and unique properties.However,the application of MQDs in electrochemical energy conversion,including hydrogen evolution reaction(HER),remains to be realized,as it remains a challenge to precisely control the types of surface groups and tune the structure of energy levels in MQDs,owing to the high surface energy-induced strong agglomeration in post-processing.Consequently,the determination of the exact catalytically active sites and processes involved in such an electrocatalysis is challenging because of the complexity of the synthetic process and reaction conditions.Herein,we demonstrated the spontaneous evolution of the surface groups of the Ti_(2)CT_(x)MQDs(x:the content of O atom),i.e.,replacement of the-Cl functional groups by O-terminated ones during the cathode reaction.This process resulted in a low Gibbs free energy(0.26 eV)in HER.Our steady Ti_(2)CO_(x)/Cu_(2)O/Cu foam systems exhibited a low overpotential of 175 mV at 10 mA cm^(-2)in 1 M aq.KOH,and excellent operational stability over 165 h at a constant current density of-10 mA cm^(-2).

非贵金属单原子催化剂的进展与展望（英文）

由于良好的催化活性和稳定性,贵金属催化剂已经被广泛应用于各种异相催化反应中,但是贵金属的稀有性和高成本无法满足未来日益增长的催化需求.2011年,张涛课题组成功地制备了高效、稳定的铂单原子催化剂.高效的单原子催化剂利用单个活性位点作为催化活性中心,可能会成为连接同相催化和异相催化的桥梁.然而从经济适用的长远角度考虑,将非贵金属催化剂缩小到原子尺度是否也会展现出优良的催化活性;是否有潜力替代目前已被广泛应用的贵金属催化剂?虽然现阶段非贵金属催化剂的催化性能仍无法达到贵金属催化剂的标准,但是已有相关研究从理论和实验上报道了非贵金属单原子催化剂及其优异的性能表明了其在未来发展中极其重要,因而,可以预见这两个疑问的答案都是肯定的.单原子概念的出现不仅为提高贵金属的催化性能及成本的降低指明了方向,同时也为制备具有高催化活性、甚至可与贵金属催化剂相媲美的非贵金属催化剂提供了可能性.我们在上述背景下,阐述了对单原子的概念日益加深的机制认知,并从理论和实验上概述了非贵金属单原子催化剂近期的发展情况,指出了目前的在单原子催化剂领域需要解决的一些问题,最后,针对研究现状,我们对未来单原子的发展提出了相应的展望.单原子催化剂具有较高的表面能,因而,如何寻找合适的基体与单原子相互作用,进而,使基体材料像一只手一样稳固地"抓紧"单原子,因而,降低其高表面能则是发挥优良催化性能的基础.强金属–基体相互作用(SMSI)不仅可以将单原子限制在基体表面,亦会影响整个催化过程.目前应用于单原子催化剂的基体种类很多,如金属氧化物、金属以及其他材料,而对SMSI认知则主要分两大类,一类是源自于基体表面的结构缺陷,另一类是源于其电子缺陷.从目前的发展状况来看SMSI机制仍有很多疑惑尚未解决,例如对电子转移影响的认知等.理论研究表明,在某些反应中非贵金属单原子展示出可替代贵金属的催化性质.比如,在一氧化碳优先反应(PROX)中,单原子钴和钛展示出的催化性能可与贵金属相媲美;理论计算同样证明单原子镍在一氧化碳还原中的催化活性比单原子铱优秀,甚至与单原子铂类似.大量的实验进展也报道了非贵金属单原子同样能在其他反应中展现出优异的性能,如氧析出反应(OER)、氢析出反应(HER)和氧还原反应(ORR).对于单原子催化剂,还有很多问题需要我们去解决,例如基体对于催化过程的具体影响、非贵金属的电子结构对于其催化性能的影响,以及单原子在基体上产生相互作用的位点等问题.纵然有许多问题需要更加深入的研究,但是单原子概念的出现,使得非贵金属催化剂材料取代传统贵金属催化剂成为了可能.

2D titanium carbide(MXene) electrodes with lower-F surface for high performance lithium-ion batteries

MXene has shown distinctive advantages as anode materials of lithium-ion batteries. However, local surface chemistry, which was confirmed that can block ion transfer and limit redox reaction, has a significant effect on electrochemical performance. Herein, annealing MXene under hydrogen was employed for removing-F and turning-OH to-O terminations. We demonstrate that it improves the kinetics of Li-ion transport between the electrolyte and electrode. As a result, a lower interfacial charge transfer impedance was obtained. The electrochemical measurement exhibited that a nearly 2-fold increase of specific capacity was achieved for the annealed MXene.

Revealing the Intrinsic Peroxidase-Like Catalytic Mechanism of Heterogeneous Single-Atom Co-MoS2

The single-atom nanozyme is a new concept and has tremendous prospects to become a next-generation nanozyme.However,few studies have been carried out to elucidate the intrinsic mechanisms for both the single atoms and the supports in single-atom nanozymes.Herein,the heterogeneous single-atom Co-MoS2(SA Co-MoS2)is demonstrated to have excellent potential as a high-performance peroxidase mimic.Because of the well-defined structure of SA Co-MoS2,its peroxidase-like mechanism is extensively interpreted through experimental and theoretical studies.Due to the different adsorption energies of substrates on different parts of SA Co-MoS2 in the peroxidase-like reaction,SA Co favors electron transfer mechanisms,while MoS2 relies on Fenton-like reactions.The different catalytic pathways provide an intrinsic understanding of the remarkable performance of SA Co-MoS2.The present study not only develops a new kind of single-atom catalyst(SAC)as an elegant platform for understanding the enzyme-like activities of heterogeneous nanomaterials but also facilitates the novel application of SACs in biocatalysis.

Integrated Co3O4/carbon fiber paper for high-performance anode of dual-ion battery

In dual-ion batteries (DIBs), energy storage is achieved by intercalation/de-intercalation of both cations and anions. Due to the mismatch between ion diameter and layer space of active materials, however, volume expansion and exfoliation always occur for electrode materials. Herein, an integrated electrode Co3O4/carbon fiber paper (CFP) is prepared as the anode of DIB. As the Co3O4 nanosheets grow on CFP substrate vertically, it promotes the immersion of electrolyte and shortens the pathway for ionic transport. Besides, the strong interaction between Co3O4 and CFP substrate reduces the possibility of sheet exfoliation. An integrated-electrode-based DIB is therefore packaged using Co3O4/CFP as anode and graphite as cathode. As a result, a high energy density of 72 Wh/kg is achieved at a power density of 150 W/kg. The design of integrated electrode provides a new route for the development of high-performance DIBs.

Optimizing the micropore-to-mesopore ratio of carbon-fiber-cloth creates record-high specific capacitance

The application of commercial carbon fiber cloth(CFC) in energy storage equipment is limited by its low specific capacitance and energy density. By a simple one-step activation treatment, the specific surface area of CFCs with porous structure can be increased considerably from 3.9 up to 875 m^2/g and the electrochemical properties of CFCs can be improved by three orders of magnitude(1324 mF/cm^2). Moreover,the hydrophobicity of CFCs can be transformed into superhydrophilicity. However, the electrochemical performance of CFCs does not show a positive correlation with specific surface area but have a strong relationship with the hierarchical pore distribution forged by the annealing treatment. Only moderate micropore and mesoporous ratio enables optimizing the electrochemical performance of CFCs.

Unlock the potential of Li4Ti5O(12) for high-voltage/long-cycling-life and high-safety batteries: Dual-ion architecture superior to lithium-ion storage

Li4Ti5O(12)(LTO)has drawn great attention due to its safety and stability in lithium-ion batteries(LIBs).However,high potential plateau at 1.5 V vs.Li reduces the cell voltage,leading to a limited use of LTO.Dual-ion batteries(DIBs)can achieve high working voltage due to high intercalation potential of cathode.Herein,we propose a DIB configuration in which LTO is used as anode and the working voltage was 3.5 V.This DIB achieves a maximum specific energy of 140 Wh/kg at a specific power of 35 W/kg,and the specific power of 2933 W/kg can be obtained with a remaining specific energy of 11 Wh/kg.Traditional LIB material shows greatly improved properties in the DIB configuration.Thus,reversing its disadvantage leads to upgraded performance of batteries.Our configuration has also widened the horizon of materials for DIBs.

A semiconductor-electrochemistry model for design of high-rate Li ion battery

For designing batteries with high-rate and long-life, electronic/ionic transport and reaction must be unified for metal oxide electrodes. However, it remains challenging for effectively integrating the whole substrate/active materials/electrolyte interfaces. Herein by taking Li ion battery as example, we propose a semiconductor-electrochemistry model by which a general but novel insight has been gained into interfacial effect in batteries. Different from those traditional viewpoints, this derived model lies across from physics to electrochemistry. A reaction driving force can be expressed in terms of Fermi energy change,based on the tradeoff between electronic and ionic concentration at the reaction interfacial region. Therefore, at thermodynamic-controlled interface I of substrate/electrode, increasing contact areas can afford higher activity for active materials. Whereas at kinetically-governed interface II of electrode/electrolyte or inside active materials, it is crucial to guarantee high-reaction Li ionic concentration, with which some sufficient reaction degrees can reach.

MOFs fertilized transition-metallic single-atom electrocatalysts for highly-efficient oxygen reduction: Spreading the synthesis strategies and advanced identification

Metal-organic frameworks(MOFs) have been widely used in oxygen reduction reaction(ORR) of fuel cells and metal-air batteries, attributed to their unique structures and compositions. Recently, the preparation of transition-metallic single-atom electrocatalysts(TM-SACs) using MOFs as precursors or templates has made great progress. Herein, the development history of SACs prepared based on MOFs and their characterization are overviewed firstly, and then several strategies are summarized for preparing TM-SACs using MOFs and further modification. Finally, the challenges and opportunities confronted by TM-SACs are fully discussed. Consequently, our work can guide the realization of TM-SACs abundant with high activity, high loading and high stability.

Quantum Dots Compete at the Acme of MXene Family for the Optimal Catalysis

It is well known that two-dimensional(2D)MXene-derived quan-tum dots(MQDs)inherit the excellent physicochemical properties of the parental MXenes,as a Chinese proverb says,“Indigo blue is extracted from the indigo plant,but is bluer than the plant it comes from.”Therefore,0D QDs harvest larger surface-to-volume ratio,outstanding optical properties,and vigorous quantum confinement effect.Currently,MQDs trigger enormous research enthusiasm as an emerging star of functional materials applied to physics,chemistry,biology,energy conversion,and storage.Since the surface properties of small-sized MQDs include the type of surface functional groups,the functionalized surface directly determines their performance.As the Nobel Laureate Wolfgang Pauli says,“God made the bulk,but the surface was invented by the devil,”and it is just on the basis of the abundant surface functional groups,there is lots of space to be thereof excavated from MQDs.We are witnessing such excellence and even more promising to be expected.Nowadays,MQDs have been widely applied to catalysis,whereas the related reviews are rarely reported.Herein,we provide a state-of-the-art overview of MQDs in catalysis over the past five years,ranging from the origin and development of MQDs,synthetic routes of MQDs,and functionalized MQDs to advanced characterization techniques.To explore the diversity of catalytic application and perspectives of MQDs,our review will stimulate more efforts toward the synthesis of optimal MQDs and thereof designing high-performance MQDs-based catalysts.

Architecture of Co-layered double hydroxide nanocages/graphene composite electrode with high electrochemical performance for supercapacitor

A facile hydrolysis method was applied to fabricate high-performance Co-layered double hydroxide（LDH）nanocages/graphene composites for supercapacitors. The materials exhibit enhanced rate capability than the counterpart electrode free of graphene while maintaining a high specific capacitance. In addition,such Co-LDH nanocages/graphene composites display an excellent cycling stability; the capacitance retention of Co-LDH nanocages/graphene composite electrode remains 90.4% after 10000 cycles at a current density of 2 A g（-1）. The integration of high capacity of double hydroxide and outstanding conductivity of graphene makes the delicately-designed composites promising candidates for electrode materials for supercapacitors.

Boosting the kinetics of PF_(6)^(-) into graphitic layers for the optimal cathode of dual-ion batteries:The rehearsal of pre-intercalating Li^(+)

Large anions exhibit slow diffusion kinetics in graphite cathode of dual-ion batteries(DIBs);particularly at high current density,it suffers severely from the largely-reduced interlayer utilization of graphite cathode,which as a bottleneck limits the fast charge application of DIBs.To maximize interlayer utilization and achieve faster anion diffusion kinetics,a fast and uncrowded anion transport channel must be established.Herein,Li^(+)was pre-intercalated into the graphite paper(GP)cathode to increase the interlayer spacing,and then hosted for the PF_(6)^(-)anion storage.Combined with theoretical calculation,it shows that the local interlayer spacing enlargement and the residual Li^(+)reduce the anion intercalation energy and diffusion barrier,leading to better rate stability.The obtained GP with Li^(+)pre-intercalation(GP-Li)electrode exhibits a discharge capacity of 23.1 m Ah g^(-1) at a high current of 1300 m A g^(-1).This work provides a facile method to efficiently improve the interlayer utilization of graphite cathode at large currents.