在过渡金属催化剂上的C―C键断裂以实现生物质的升级

将当前能源生产和消费结构从过度依赖化石能源转变为高效利用可再生能源,是解决能源危机、实现碳中和的有效途径。生物质是最有前途的可再生能源之一,可以取代化石燃料以获得有价值的有机化合物。近年来,大力利用生物质能已成为一种必然趋势。用于生物质转化的传统热化学催化方法通常需要高温、高压等恶劣条件,甚至还需要外部氢或氧源。相比之下,在相对温和的条件下进行的生物质有机分子电催化转化为生产高价值化学品提供了一种绿色高效的策略。特别是,通过C―C键裂解将生物质衍生的分子转化为高价值的短链化学品至关重要。近年来,大量的研究证明过渡金属(TM)电催化剂由于其丰富的三维电子结构和独特的eg轨道增强了过渡金属-氧之间的共价键合,从而在有机物的C―C键断裂中起着至关重要的作用。此外,TM电催化剂的配位环境或电子结构会影响产物的选择性。毫无疑问,明确的反应活性位点和途径有助于深入理解催化剂结构与反应活性之间的构效关系。然而,TM电催化剂介导的生物质衍生有机分子的C―C键裂解反应用于生物质升级的研究目前尚处于起步阶段,其反应机理和催化反应过程尚不清楚。因此,有必要在原子水平上系统地了解电催化剂在C―C键裂解过程中的作用。在本综述中,我们首先依次介绍了广泛研究的TM电催化剂介导的生物质衍生有机分子(包括甘油、环己醇、木质素和糠醛)的C―C键裂解反应,并给出了一些典型的例子和相应的反应途径。然后,系统回顾了过渡金属化合物催化C―C键裂解的反应机理,揭示了界面行为,并构建了TM电催化剂的结构与裂解反应活性之间的构效关系。最后,我们简要总结了上述内容,并强调了在TM电催化剂上研究C―C键裂解的挑战和展望。我们期望这项工作可以为生物质的可控转化和合理设计C―C键裂解的TM电催化剂提供指导。

Trace Cobalt Doping and Defect Engineering of High Surface Area α-Ni(OH)_(2) for Electrocatalytic Urea Oxidation

Owing to the intrinsically sluggish kinetics of urea oxidation reaction(UOR)involving a six-electron transfer process,developing efficient UOR electrocatalyst is a great challenge remained to be overwhelmed.Herein,by taking advantage of 2-Methylimidazole,of which is a kind of alkali in water and owns strong coordination ability to Co^(2+)in methanol,trace Co(1.0 mol%)addition was found to induce defect engineering onα-Ni(OH)_(2)in a dual-solvent system of water and methanol.Physical characterization results revealed that the synthesized electrocatalyst(WM-Ni_(0.99)Co_(0.01)(OH)_(2))was a kind of defective nanosheet with thickness around 5-6 nm,attributing to the synergistic effect of Co doping and defect engineering,its electron structure was finely altered,and its specific surface a rea was tremendously enlarged from 68 to 172.3 m^(2)g^(-1).With all these merits,its overpotential to drive 10 mA cm^(-2)was reduced by 110 mV.Besides,the interfacial behavior of UOR was also well deciphered by operando electrochemical impedance spectroscopy.

CuO/Co_(3)O_(4)Bifunctional Catalysts for Electrocatalytic 5-Hydroxymethylfurfural Oxidation Coupled Cathodic Ammonia Production

The electrochemical coupling of biomass oxidation and nitrogen conversion presents a potential strategy for high value-added chemicals and nitrogen cycling.Herein,in this work,CuO/Co_(3)O_(4)with heterogeneous interface is successfully constructed as a bifunctional catalyst for the electrooxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and the electroreduction of nitrate to ammonia(NH_(3)).The open-circuit potential spontaneous experiment shows that more 5-hydroxymethylfurfural molecules are adsorbed in the Helmholtz layer of the CuO/Co_(3)O_(4)composite,which certifies that the CuO/Co_(3)O_(4)heterostructure is conducive to the kinetic adsorption of 5-hydroxymethylfurfural.In situ electrochemical impedance spectroscopy further shows that CuO/Co_(3)O_(4)has faster reaction kinetics and lower reaction potential in oxygen evolution reaction and 5-hydroxymethylfurfural electrocatalytic oxidation.Moreover,CuO/Co_(3)O_(4)also has a good reduction effect on NO_(3)^(-).The ex-situ Raman spectroscopy shows that under the reduction potential,the metal oxide is reduced,and the generated Cu_(2)O can be used as a new active site for the reaction to promote the electrocatalytic conversion of NO_(3)^(-)to NH_(3) synthesis.This work provides valuable guidance for the synthesis of value-added chemicals by 5-hydroxymethylfurfural electrocatalytic oxidation coupled with NO_(3)^(-)while efficiently producing NH_(3).

Highly selective electrosynthesis of imines via electroreduction coupling of nitroarenes with aryl aldehydes on Co_(9)S_(8)with positively charged sulfur vacancies

The electrocatalytic synthesis of imines through the reductive imination of nitroarenes with aldehydes is a facile,environmentally friendly,and valuable process.In this study,high selectivity electrosynthesis of imines was realized through the electrocatalytic C-N coupling reaction between nitroarenes and aryl aldehydes on Co_(9)S_(8)nanoflowers with rich sulfur vacancies(Co_(9)S_(8)-Vs).Comparative experiments revealed that positively charged sulfur vacancies play a pivotal role in boosting catalytic selectivity towards imines.Electron-deficient sulfur vacancies intensified the adsorption of negatively charged Ph-NO_(2),thereby enhancing the conversion rate of the electrochemical nitrobenzene-reduction reaction(eNB-RR).Simultaneously,sulfur vacancies augmented the adsorption capability of negatively charged Ph-CHO,enriching Ph-CHO species at the electrode interface and expediting the Schiff base condensation reaction rate.The experimental results show that the reaction conditions can satisfy the different nitroarenes and aryl aldehydes in the electrocatalytic aqueous-phase system under mild conditions to obtain the corresponding imine products in high selectivity.This study provides a facile and environmentally friendly pathway for future electrocatalytic synthesis of imine.

强化脱氢动力学实现超低电池电压和大电流密度下抗坏血酸电氧化

当今社会日益严峻的能源危机进一步加速了生物质资源多层次转化利用的发展,现代生物质能源技术已成为研究热点.抗坏血酸是生物质平台分子之一,脱氢抗坏血酸作为抗坏血酸的氧化产物,不仅与抗坏血酸一起组成了生物抗氧化系统,而且还发挥着重要的生物医学功能,例如人体抗癌、抗病毒和抗衰老等.在众多的脱氢抗坏血酸制备方法中,抗坏血酸的电催化氧化提供了在常温常压条件下使用水作为氧化剂和电能作为能量输入生产脱氢抗坏血酸的机会.另一方面,在水体系内,较低的抗坏血酸理论氧化电位(E理论=0.390 V)使得抗坏血酸氧化反应/氢析出反应(AAOR/HER)电对可以在低电池电压下工作,降低了因高电压带来的能源消耗和设备要求等成本,实现低能耗条件下的化学品转化和制氢.本课题组通过简单的氧气等离子体在碳材料表面引入含氧官能团(OCGs),并揭示了OCGs和抗坏血酸分子脱氢动力学之间的关系,利用提升反应动力学的策略提高AAOR的电催化活性.得益于OCGs对抗坏血酸分子脱氢动力学的调控作用,所设计的氧气等离子体处理碳纸电极(PO-CP)可以在0.65 VRHE下驱动100 mAcm^(–2)的电流密度,明显优于原始碳纸(CP)和其他金属基电催化剂.此外,在PO-CP电极表面抗坏血酸制备脱氢抗坏血酸的法拉第效率超过90%,并且具备较好的稳定性(20 h).X射线光电子能谱(XPS)结果表明,随着等离子体处理时间的延长,碳表面的含氧量增加,最终呈现饱和状态.进一步利用氢气退火作为对照组去除表面的OCGs,发现退火过程中所有类型的OCGs含量都明显下降,其中羧基和羰基的含量变化明显,说明退火处理可显著去除碳表面的C=O键,进而影响其AAOR性能.电化学测试表明,OCGs的引入提升了碳材料的AAOR本征活性,氢气退火对照组性能急剧下降,进一步表明了碳表面的含氧官能团对AAOR性能的提升至关重要.结合XPS结果,分析其中C=O键可能对AAOR本征活性的提升发挥重要作用.为降低三维电极带来的传质影响及等离子体处理对碳表面清洁影响等,进一步选用商业碳粉(XC72)作为模型材料并在玻碳电极表面探究OCGs的影响,同时选择氧气等离子体刻蚀和电化学氧化方法作为OCGs修饰策略.电化学测试表明,XC72表面的电化学性能规律和碳纸表面类似,进一步表明了碳表面的OCGs对AAOR的性能提升至关重要.最后,通过密度泛函理论来对AAOR的各基元步骤的吉布斯自由能(Gads)进行了研究.结果表明,OCGs修饰后,虽然AAOR的决速步骤没有发生变化(第一步脱氢过程),但是ΔGads变化明显.相比于原始碳晶格(G(ads(C))=1.36 eV),不同含氧官能团修饰下的碳表面的吉布斯自由能变化为ΔG(ads(-OH))=1.33 eV,ΔG(ads(C=O))=1.55 eV,ΔG(ads(-COOH))=1.24 eV.由此可见,含氧官能团特别是羧基的引入,可以显著降低AAOR过程中脱氢能垒,通过增强脱氢动力学来实现高效的抗坏血酸转化.此外,还将AAOR和HER集成到质子交换膜型电解槽中,当PO-CP阳极和Pt/C阴极组装时,在0.98 V(80℃)的超低电池电压下获得了1.00 Acm^(–2)的电流,这是目前电催化有机物转化反应的一个非常有优势的数据.而且系统每产生1 m^(3)的氢气只需要1.54 kWh的电能,几乎是传统电解水(4.95 kWh)的三分之一.综上,基于抗坏血酸在PO-CP表面高效率的电化学转化,这项工作为电化学生物质转化升级和制氢提供了更环保更经济的策略,并为适应规模化生产的电极设计提供了参考。

Electronic structure regulation on layered double hydroxides for oxygen evolution reaction

Oxygen evolution reactions(OERs)as core components of energy conversion and storage technology systems,such as water splitting and rechargeable metal–air batteries,have attracted considerable attention in recent years.Transition metal compounds,particularly layered double hydroxides(LDHs),are considered as the most promising electrocatalysts owing to their unique two-dimensional layer structures and tunable components.However,heir poor intrinsic electrical conductivities and the limited number of active sites hinder their performances.The regulation of the electronic structure is an effective approach to improve the OER activity of LDHs,including cationic and anionic regulation,defect engineering,regulation of intercalated anions,and surface modifications.In this review,we summarize recent advances in the regulation of the electronic structures of LDHs used as electrocatalysts in OERs.In addition,we discuss the effects of each regulation type on OER activities.This review is expected to shed light on the development and design of effective OER electrocatalysts by summarizing various electronic structure regulation pathways and the effects on their catalytic performances.

Green Synthesis of Nitrogen-to-Ammonia Fixation: Past, Present, and Future

The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoelectrochemical approaches are developed as the next-generation NH3 synthesis technologies to substitute the Haber–Bosch method.However,the NH3 yield rate of nitrogen reduction reaction(NRR)by green approaches is extremely low,resulting in the current dilemma of NRR and contamination issues.Thus,in this mini review,the past advances on the sustainable NRR are briefly summarized in the three aspects as follows:the selectivity and adjustment of various catalysts,the type of electrolyte/solvent system,and the investigation of reaction conditions.Subsequently,the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply,and a perspective for rational and healthy development of this area is provided positively。

Transforming Co3O4 nanosheets into porous N-doped CoxOy nanosheets with oxygen vacancies for the oxygen evolution reaction

Cobalt oxides have been widely investigated as promising replacements for noble metal-based catalysts for oxygen evolution reaction(OER). Herein, we, for the first time, have obtained porous CoxOy nanosheets with N-doping and oxygen vacancies by etching Co3O4 nanosheets with NH3 plasma. Comparing with the pristine Co3O4 nanosheets(1.79 V), the porous CoxOy nanosheets with N-doping and oxygen vacancies have a much lower potential of 1.51 V versus RHE to reach the current density of 10 mA cm-2. The obtained sample has a lower Tafel slope of 68 m V dec-1 than the pristine Co3O4 nanosheets(234 mV dec-1).The disclosed Co^2+, which is responsible for the formation of active sites(CoOOH), N-doping and oxygen vacancies, gives rise to better performance of OER.

An option for green and sustainable future: Electrochemical conversion of ammonia into nitrogen

Green and sustainable options are needed to ease the current energy and environmental crisis, and alleviate the greenhouse effect and energy shortage. As an alternative carbon–neutral synthetic fuel, ammonia shows great potential due to its high energy density, non-toxic by-products, and mature related infrastructures. However, related practical applications have been severely hampered on ammoniaoxidation due to the high cost of catalysts and immature energy utilization systems. Here, we comprehensively summarized the efforts which have been made in recent years with the aim of providing a deep sight into the development and deficiencies in this territory and trying to establish a simple framework of basic knowledge for researchers. The exploration of mechanism is discussed first and then the relevant catalysts studied in recent years are summarized. Besides, the progress of direct ammonia fuel cells(DAFCs) is also presented and the challenges as well as perspectives on future developments of electrocatalysts for ammonia electro-oxidation and its practical application are provided at the end.

Sulfonic groups functionalized Zr-metal organic framework for highly catalytic transfer hydrogenation of furfural to furfuryl alcohol

The highly selective catalytic transfer hydrogenation(CTH)of furfural(FF)to furfuryl alcohol(FOL)is a significant route of biomass valorization.Herein,a series microporous Zr-metal organic framework(ZrMOF)functionalized by sulfonic groups are prepared.Based on the comprehensive structural characterizations by means of X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),N2 physisorption,Thermogravimetric(TG)and Fourier transformed infrared spectroscopy(FTIR),we find that sulfonic acid(–SO_(3)H)functional groups are tethered on the UIO-66 without affecting the structure of the framework.Systematic characterizations(NH_(3)-TPD,CO_(2)-TPD,and in-situ FTIR)demonstrate that modifying of sulfonic groups on UIO-66 results in the formation of stronger Lewis acidic-basic and Brnsted acidis sites.The cooperative role of the versatile Lewis acidic-basic and Brnsted acidic sites in 60%mol fraction of sulfonic acid-containing UIO-66(UIO-S_(0.6))retain high surface area and exhibit excellent catalytic performance of 94.7%FOL yield and 16.9 h^(-1).turnover number(TOF)under mild conditions.Kinetic experiments reveal that the activation energy of the CTH of furfural(FF)over UIO-S_(0.6) catalyst is as low as 50.8 k J mol^(-1).Besides,the hydrogen transfer mechanism is investigated through isotope labeling experiments,exhibiting that theβ-H in isopropanol is transferred to the a-C of FF by forming six-membered intermediates on the Lewis acidic-basic and Brnsted acidic sites of the UIO-S_(0.6),which is the rate-determining step in the formation of FOL.

The Co_3O_4 nanosheet array as support for MoS_2 as highly efficient electrocatalysts for hydrogen evolution reaction

The electrochemical hydrogen evolution reaction（HER） on a non-precious electrocatalyst in an alkaline environment is of essential importance for future renewable energy. The design of advanced electrocatalysts for HER is the most important part to reduce the cost and to enhance the efficiency of water splitting. MoSis considered as one of the most promising electrocatalysts to replace the precious Pt catalyst.Herein, for the first time, we have successfully loaded MoSelectrocatalysts onto the CoOnanosheet array to catalyze HER with a low onset potential of6 mV. The high hydrogen evolution activity of MoSsupported on the CoOnanosheet array may be attributed to the increased active sites and the electronic interactions between MoSand CoO.

Balancing sub‐reaction activity to boost electrocatalytic urea synthesis using a metal‐free electrocatalyst

Electrocatalytic urea synthesis via coupling of nitrate with CO_(2)is considered as a promising alternative to the industrial urea synthetic process.However,the requirement of sub-reaction(NO_(3)RR and CO_(2)RR)activities for efficient urea synthesis is not clear and the related reaction mechanisms remain obscure.Here,the construction,breaking,and rebuilding of the sub-reaction activity balance would be accompanied by the corresponding regulation in urea synthesis,and the balance of sub-reaction activities was proven to play a vital role in efficient urea synthesis.With rational design,a urea yield rate of 610.6 mg h−1 gcat.−1 was realized on the N-doped carbon electrocatalyst,superior to that of noble-metal electrocatalysts.Based on the operando SRFTIR measurements,we proposed that urea synthesis arises from the coupling of^(*)NO and^(*)CO to generate the key intermediate of^(*)OCNO.This work provides new insights and guidelines into urea synthesis from the aspect of activity balance.

Ultrathin defective high-entropy layered double hydroxides for electrochemical water oxidation

One of the fundamental driving forces in the materials science community is the hunt for new materials with specific properties that meet the requirements of rapidly evolving technology.

Recent advances in defect electrocatalysts: Preparation and characterization

the types and strategies used to prepare defect electrocatalysts will continue to be studied and developed as new defective materials are generated.4. Characterization of defectsThis review briefly summarizes recent progress in defect electrocatalysts, and the synthesis strategies and characterization techniques for defects are systematically discussed. Although challenges in the characterization of defect structures in the electrocatalytic reaction process remain, the dynamic evolution of defect sites is predicted to be helpful for designing and preparing high-performance electrocatalysts for commercial applications. Furthermore, due to an insufficient understanding of the defect-structureproperty relationships, future possibilities for the reasonable design of defect electrocatalysts to obtain desirable performance are suggested.

Recent Progress on Electrocatalytic Valorization of Biomass-Derived Organics

Electrocatalytic valorization of biomass derivatives can be powered by electricity generated from renewable sources such as solar and wind energy.A shift from centralized,high-temperature,and energy-intensive processes to decentralized,low-temperature conversions is achieved,which meets the requirement of sustainable energy generation.This approach provides an efficient,green,and additive-free strategy for biomass derivative valorization,in which product selectivity could be easily regulated by the applied potential and electrocatalyst utilized.However,a scale-up application is still far from being completed due to the inability of conversion rates and selectivity to meet the industrialization requirements.A better understanding of the reaction mechanism and the development of highefficiency and high-selectivity electrocatalysts are required to pave the path toward larger industrialization applications.Herein,we summarize the recent research progress in the electrocatalytic oxidation and hydrogenation of platform compounds such as furanic compounds and glycerol.In the literature,these three research areas are integrated to realize the scale-up application of the processes as mentioned above.The investigations of the mechanism are based on in situ techniques,theoretical calculations,and advanced electrocatalyst studies.Finally,the challenges and prospects in this topic are described.We expect that this review will provide the fundamental understanding and design guidelines to achieve efficient and high-selectivity catalysts and further facilitate the scale-up application of the electrocatalytic conversion of biomass derivatives.

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries

Sodium-ion batteries(SIBs)are considered to be attractive candidates for large-scale energy storage systems because of their rich earth abundance and consistent performance.However,there are still challenges in developing desirable anode materials that can accommodate rapid and stable insertion/extraction of Na+and can exhibit excellent electrochemical performance.Herein,the self-assembled hairball-like VS4 as anodes of SIBs exhibits high discharge capacity(660 and 589 mAh g−1 at 1 and 3 A g−1,respectively)and excellent rate property(about 100%retention at 10 and 20 A g−1 after 1000 cycles)at room temperature.Moreover,the VS4 can also exhibit 591 mAh g−1 at 1 A g−1 after 600 cycles at 0°C.An unlike traditional mechanism of VS4 for Na+storage was proposed according to the dates of ex situ characterization,cyclic voltammetry,and electrochemical kinetic analysis.The capacities of the final stabilization stage are provided by the reactions of reversible transformation between Na2S and S,which were considered the reaction mechanisms of Na–S batteries.This work can provide a basis for the synthesis and application of sulfur-rich compounds in fields of batteries,semiconductor devices,and catalysts.

Etching oxide overlayers of NiFe phosphide to facilitate surface reconstruction for oxygen evolution reaction

Transition-metal phosphides have been of concern as efficient electrocatalysts for oxygen evolution reaction(OER)due to its high conductivity and earth-abundance reserves.However,oxide overlayers formed on their surface by spontaneously atmospheric oxidation are usually neglected,thus confusing the establishment of structure–performance relationship.Herein,we successfully etched the oxide overlayers of NiFe phosphide(NiFeP)by a dielectric barrier discharge(DBD)plasma technique,aiming to reveal the influence of the oxide overlayers on its electrocatalytic performance for OER.It is found that etching the oxide overlayers can accelerate the surface reconstruction process of NiFeP and facilitate the formation of metal hydroxides,which are key intermediate phases for OER.Consequently,the etched NiFeP-DBD material shows remarkably enhanced OER activity with an overpotential of 265 mV at a current density of 10 mA cm^(-2).The finding of this work probably brings a significant impact to understand the structure–performance relationship of metal phosphide in electrooxidation reaction.

Promoting surface reconstruction of NiFe layered double hydroxides via intercalating[Cr(C_(2)O_(4))_(3)]^(3-)for enhanced oxygen evolution

Rationally manipulating surface reconstruction of catalysts for water oxidation,inducing formation and dynamic accumulation of catalytically active centers still face numerous challenges.Herein,the introduction of[Cr(C_(2)O_(4))_(3)]^(3-)into NiFe LDHs by intercalation engineering to promote surface reconstruction achieves an advanced oxygen evolution reaction(OER)activity.In view of the weak electronegativity of Cr^(3+) in[Cr(C_(2)O_(4))_(3)]^(3-),the intercalation of[Cr(C_(2)O_(4))_(3)]^(3-)is expected to result in an electron-rich structure of Fe sites in NiFe LDHs,and higher valence state of Ni can be formed with the charge transfer between Fe and Ni.The optimized electronic structure of NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs with more active Ni^(3+) species and the expedited dynamic generation of Ni^(3+) (Fe)OOH phase during the OER process contributed to its excellent catalytic property,revealed by in situ X-ray absorption spectroscopy,Raman spectroscopy,and quasi-in situ X-ray photoelectron spectroscopy.With the modulated electronic structure of metal sites,NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs exhibited promoted OER property with a lower overpotential of 236 mV at the current density of 10 mA cm^(-2).This work illustrates the intercalation of conjugated anion to dynamically construct desired Ni^(3+) sites with the optimal electronic environment for improved OER electrocatalysis.

Activity origin and alkalinity effect of electrocatalytic biomass oxidation on nickel nitride

Electro-oxidation of 5-hydroxymethylfurfural(HMFOR)is a promising green approach to realize the conversion of biomass into value-added chemicals.However,considering the complexity of the molecular structure of HMF,an in-depth understanding of the electrocatalytic behavior of HMFOR has rarely been investigated.Herein,the electrocatalytic mechanism of HMFOR on nickel nitride(Ni3 N)is elucidated by operando X-ray absorption spectroscopy(XAS),in situ Raman,quasi in situ X-ray photoelectron spectroscopy(XPS),and operando electrochemical impedance spectroscopy(EIS),respectively.The activity origin is proved to be Ni^(2+δ)N(OH)ads generated by the adsorbed hydroxyl group.Moreover,HMFOR on Ni3 N relates to a two-step reaction:Initially,the applied potential drives Ni atoms to lose electrons and adsorb OH-after 1.35 VRHE,giving rise to Ni^(2+δ)N(OH)ads with the electrophilic oxygen;then Ni^(2+δ)N(OH)ads seizes protons and electrons from HMF and leaves as H_(2) O spontaneously.Furthermore,the high electrolyte alkalinity favors the HMFOR process due to the increased active species(Ni^(2+δ)N(OH)ads)and the enhanced adsorption of HMF on the Ni3 N surface.This work could provide an in-depth understanding of the electrocatalytic mechanism of HMFOR on Ni3 N and demonstrate the alkalinity effect of the electrolyte on the electrocatalytic performance of HMFOR.

Three-dimensional hierarchical MoS_2/CoS_2 heterostructure arrays for highly efficient electrocatalytic hydrogen evolution

Developing non-expensive, highly active and highly stable electrocatalysts for hydrogen evolution has aroused extensive attention, owing to the necessity of novel clean and sustainable energy carriers. In this paper, we report a synthesis of free-standing three-dimensional hierarchical MoS_2/CoS_2 heterostructure arrays through a convenient process. The investigation of electrocatalytic HER performance suggests that the MoS_2/CoS_2 hybrid catalyst exhibits significant enhancement in HER(onsetpotential and potential at a current density of 100 mA cm^(-2) are 20 mV and125 mV, respectively) and superior durability(no shift of current density is observed after a continuous scanning of 3000 times) compared with individual CoS_2 and MoS_2. The superior HER performance was attributed to the formation of the interface between CoS_2 and MoS_2 through the electrochemical characterization, Raman, XPS analysis, and the control experiment. The lower onsetpotential, higher current density, excellent durability, and the free-standing structure of the three-dimensional hierarchical MoS_2/CoS_2 heterostructure array make it a promising cathode catalyst suitable for widespread application.