Binary molten salt in situ synthesis of sandwich-structure hybrids of hollowβ-Mo2C nanotubes and N-doped carbon nanosheets for hydrogen evolution reaction

Focused exploration of earth-abundant and cost-efficient non-noble metal electrocatalysts with superior hydrogen evolution reaction(HER)performance is very important for large-scale and efficient electrolysis of water.Herein,a sandwich composite structure(designed as MS-Mo2C@NCNS)ofβ-Mo2C hollow nanotubes(HNT)and N-doped carbon nanosheets(NCNS)is designed and prepared using a binary NaCl–KCl molten salt(MS)strategy for HER.The temperature-dominant Kirkendall formation mechanism is tentatively proposed for such a three-dimensional hierarchical framework.Due to its attractive structure and componential synergism,MS-Mo2C@NCNS exposes more effective active sites,confers robust structural stability,and shows significant electrocatalytic activity/stability in HER,with a current density of 10 mA cm-2 and an overpotential of only 98 mV in 1 M KOH.Density functional theory calculations point to the synergistic effect of Mo2C HNT and NCNS,leading to enhanced electronic transport and suitable adsorption free energies of H*(ΔGH*)on the surface of electroactive Mo2C.More significantly,the MS-assisted synthetic methodology here provides an enormous perspective for the commercial development of highly active non-noble metal electrocatalysts toward efficient hydrogen evolution.

基于MO2C模式的高教园区校园电子服务平台研究

电子服务是电子商务发展的产物,是互联网的第三次浪潮。高教园区是大学生的主要聚集地,具备电子服务发展的有利环境。本文主要首先论述了校园电子商务和电子服务的区别,然后探讨了高教园区开展电子服务的必要性,最后提出一种基于MO2C模式的高教园区电子服务平台规划与设计方案。

沉积时间对非晶碳/Mo2C混合薄膜场发射性能的影响

在Al2O3衬底上采用微波等离子体增强化学气相沉积（MPCVD）系统中沉积薄膜,反应气体为CH4、H2。从样品的Raman谱中可以分析出薄膜中含有非晶碳成分。XRD有明显的晶态Mo2C衍射峰,所制备的薄膜为非晶碳/Mo2C混合膜。在高真空室中测量了样品的场发射特性,其开启场强为0.55 V/μm,在1.8 V/μm电场下测得样品的场发射电流密度为6.8 mA/cm^2。CCD图中可以看到样品有比较好的发光特性。研究了在一定反应条件下,沉积时间对样品场发射特性的影响,4 h制备的样品场发射性能最好。良好的场发射性能决定了所制备的样品是一种好的场致发射体。

N,P掺杂型C@Mo2C催化剂的制备及其催化CO2加氢反应研究

以三聚氰胺苯甲酸盐为碳源和氮源、以三聚氰胺磷钼酸盐为钼源、磷源和氮源,采用程序升温的方法制备了系列N,P掺杂型C@Mo_2C催化剂。采用XRD、SEM、TEM和XPS等对催化剂的结构、形貌和表面特性进行了表征,研究了三聚氰胺苯甲酸盐中n(三聚氰胺)/n(苯甲酸)、前驱体中n(C)/n(Mo)等因素对所制备催化剂的结构及其在二氧化碳加氢反应中催化性能的影响。在反应温度为220℃、反应压力为3.0 MPa、空速为3 600 m L/(g·h)的条件下,在N,P掺杂型C@Mo_2C的催化作用下,CO_2转化率可以达到12.2%,此时产物中CH_3OH的选择性达到52.2%。

Metal-doped Mo2C(metal=Fe,Co,Ni,Cu)as catalysts on TiO2 for photocatalytic hydrogen evolution in neutral solution

The neutral hydrogen evolution reaction(HER)is vital in the chemical industry,and its efficiency depends on the interior character of the catalyst.Herein,work function(WF)engineering is introduced via 3d metal(Fe,Co,Ni,and Cu)doping for modulating the Fermi energy level of Mo2C.The defective energy level facilitates the free water molecule adsorption and,subsequently,promotes the neutral HER efficiency.Specifically,at a current density of 10 mA/cm2,Cu-Mo2C exhibits the best HER performance with an overpotential of 78 mV,followed by Ni-Mo2C,Co-Mo2C,Fe-Mo2C,and bare Mo2C with 90,95,100,and 173 mV,respectively,and the corresponding Tafel slope values are 40,43,42,56,and 102 mV/dec.The modified WF can also lead to an enhanced photocatalytic efficiency owing to the lowered Schottky barrier and excellent carrier transition across the electrocatalyst–solution interface.When coupling the metal-doped Mo2C samples with TiO2,enhanced photocatalytic neutral HER rates are obtained in comparison to the case with bare TiO2.Typically,the HER rates are 521,404,275,224,147,and 112μmol/h for Cu,Ni,Co,Fe,bare Mo2C,and bare TiO2,respectively.Time-resolved photoluminescence spectroscopy(TRPS)and ultrafast transient absorption(TA)measurements are carried out to confirm the recombination and migration of the photogenerated carriers.The fittedτvalues from the TRPS curves are 22.6,20.5,10.1,4.7,4.0,2.5,and 1.9 ns for TiO2,TiO2-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,and TiO2-Pt,respectively.Additionally,the fittedτvalues from the TA results are 31,73,and 105 ps for the TiO2-Mo2C,TiO2-Cu-Mo2C,and TiO2-Pt samples,respectively.This work provides in-depth insights into the WF modulation of an electrocatalyst for improving the HER performance.

Pt/Mo2C heteronanosheets for superior hydrogen evolution reaction

One of the most primary challenges to achieve large-scale hydrogen generation from water electrolysis is the sluggish kinetics and noble metal dependence of cathodic hydrogen evolution reaction(HER).By considering the excellent water dissociation catalytic activity of Mo2C, abundant Pt/Mo2C interfaces were facilely engineered via galvanic replacement(gr) by using Mo/Mo2C nanosheets as self-sacrificed templates to alter the alkaline HER mechanism on Pt based catalyst. The rational designed interface-rich gr-Pt/Mo2C catalyst exhibited excellent activity with the overpotential to drive 10 mA/cm2 current density decreased by 18.5 mV compared with the commercial Pt/C catalyst. 34.3 mV/dec Tafel slope confirms the Volmer-Tafel HER route on gr-Pt/Mo2C in alkaline condition. Platinum utilization is calculated to be improved by 9.7 times by considered the low Pt loading in the gr-Pt/Mo2C catalyst. With its satisfied stability, the scalable gr-Pt/Mo2C catalyst shows promising application potential in industrial electrolysis systems.

锂离子电池Mo2C/N-C复合材料的制备及性能研究

以三氧化钼、草酸、盐酸多巴胺为原料,通过水热和高温煅烧的方法制备了碳化钼与氮掺杂碳纳米管(Mo2C/N-C)复合材料。采用X射线衍射仪、热重分析仪、扫描电子显微镜、透射电子显微镜、拉曼光谱等表征手段研究了Mo2C/N-C复合材料的化学组成、结构与形貌,并使用电池测试系统对材料进行了电化学性能测试。结果表明:Mo2C/N-C复合材料具有棒状碳纳米管结构,长径比较大,Mo2C纳米微晶均匀分布在氮掺杂的碳基质中。Mo2C的纳米微晶缩短了Li+离子的扩散路径,纵横比较大的棒状结构缩短了电解质中离子迁移路径,且氮掺杂的碳基质加速了电子转移并在放电/充电循环期间缓冲了Mo2C的体积变化。用Mo2C/N-C作为锂离子电池的负极材料,电流密度为100mA/g时,复合材料初始放电比容量为1146.5mAh/g,充电比容量为855.2mAh/g,库伦效率为74.59%。经过100次充放电循环后,复合材料放电比容量为574.2mAh/g,库仑效率为98.08%,表现出优异的电化学性能。

Fabrication and application of hierarchical mesoporous MoO2/Mo2C/C microspheres

Hierarchical mesoporous MoO2/Mo2C/C microspheres,which are composed of primary nanoparticles with a size of about 30 nm,have been designed and synthesized through polymer regulation and subsequent carbonization processes.The as-synthesized microspheres were characterized by XRD,Raman,SEM,TEM,XPS measurements and so on.It was found that polyethylene glycol acted as a structure-directing agent,mild reducing agent and carbon source in the formation of these hierarchical mesoporous Mo O2/Mo2C/C microspheres.Moreover,the electrochemical property of the microspheres was also investigated in this work.Evaluated as an anode material for lithium ion batteries,the hierarchical mesoporous Mo O2/Mo2C/C electrode delivered the discharge specific capacities of 665 and 588 m Ah/g after 100 cycles at current densities of 100 and 200 m A/g,respectively.The satisfactory cycling performance and controllable process facilitate the practical applications of the hierarchical mesoporous Mo O2/Mo2C/C as a potential anode material in high-energy density lithium-ion batteries.

Graphene/Mo2C heterostructure directly grown by chemical vapor deposition

Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo2C heterostructure by using chemical vapor deposition（CVD）. The composition and structure of the heterostructure are characterized through energydispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo2C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.

Controlled growth of Mo2C pyramids on liquid Cu surface

Precise spatial control of 2D materials is the key capability of engineering their optical,electronic,and mechanical properties.However,growth of novel 2D Mo2C on Cu surface by chemical vapor deposition method was revealed to be seed-induced 2D growth,limiting further synthesis of complex Mo2C spatial structures.In this research,we demonstrate the controlled growth of Mo2C pyramids with numerous morphologies,which are characterized with clear terraces within the structures.The whole evolution for Mo2C pyramids in the coursed of CVD process has been detected,posing significant potential in probing growth mechanism.The formation of the Mo2C pyramids arises from the supersaturation-induced nucleation and concentration-gradient driven diffused growth of a new Mo2C layer on the edged areas of intrinsic ones,as supported by STEM imaging.This work provides a novel Mo2C-based pyramid structure and further reveals a sliding growth mechanism,which could offer impetus for the design of new 3D spatial structures of Mo2C and other 2D materials.

Electronic tattoos based on large-area Mo2C grown by chemical vapor deposition for electrophysiology

Tattoo electronics has attracted intensive interest in recent years due to its comfortable wearing and imperceivable sensing,and has been broadly applied in wearable healthcare and human-machine interface.However,the tattoo electrodes are mostly composed of metal films and conductive polymers.Two-dimensional(2D)materials,which are superior in conductivity and stability,are barely studied for electronic tattoos.Herein,we reported a novel electronic tattoo based on large-area Mo_(2)C film grown by chemical vapor deposition(CVD),and applied it to accurately and imperceivably acquire on-body electrophysiological signals and interface with robotics.High-quality Mo_(2)C film was obtained via optimizing the distribution of gas flow during CVD growth.According to the finite element simulation(FES),bottom surface of Cu foil covers more stable gas flow than the top surface,thus leading to more uniform Mo_(2)C film.The resulting Mo_(2)C film was transferred onto tattoo paper,showing a total thickness of~3μm,sheet resistance of 60-150Ω/sq,and skin-electrode impedance of~5×10^(5)Ω.Such thin Mo_(2)C electronic tattoo(MCET in short)can form conformal contact with skin and accurately record electrophysiological signals,including electromyography(EMG),electrocardiogram(ECG),and electrooculogram(EOG).These body signals collected by MCET can not only reflect the health status but also be transformed to control the robotics for human-machine interface.

Mo2C/WC对金属陶瓷组织和性能的影响

以TiC、TiN、Mo2C、WC、Co、Ni为原料,采用粉末冶金法制备Ti(C,N)基金属陶瓷。结合XRD物相检测、显微组织分析以及力学性能测试研究了Mo2C/(WC+Mo2C)对Ti(C,N)基金属陶瓷显微组织和力学性能的影响。结果表明:随着Mo2C/(WC+Mo2C)的增加,Ti(C,N)基金属陶瓷的硬度逐渐增加,抗弯强度先降低后增加。当Mo2C/(WC+Mo2C)=0.8时,Ti(C,N)基金属陶瓷的显微组织细化明显,综合力学性能最佳,维氏硬度(HV)为1 411.15,抗弯强度为1 053.7 MPa。

Mo2C添加量对Ti(C,N)-Ni-Co金属陶瓷组织及其切削性能的影响

本文制备了不同Mo2C含量的Ti(C,N)-Ni-Co金属陶瓷,对比分析了其微观组织和机械性能以及对304不锈钢切削性能的影响。通过扫描电镜观察分析了微观组织的变化以及切削试验刀具后刀面磨损情况。利用阿基米德排水法、洛氏硬度计、维氏硬度压痕法、三点弯曲法分别测试了金属陶瓷的相对密度、硬度、断裂韧性以及横向断裂强度。结果显示,随着Mo2C含量的增加,金属陶瓷的晶粒度减小,当添加量(质量分数,下同)为18%时出现小晶粒团聚扎堆;硬度和密度增加;断裂韧性和横向断裂强度先增加后减小,在添加量为12%时达到最大值;当添加量为12%时,刀具后刀面磨损量在100 m/min和80 m/min的切削速度下均为最低。

基于Mo2C的新型电化学传感器用于色氨酸的检测

开发了一种基于Mo2C的高灵敏度高催化性新型电化学传感器并用于色氨酸(Trp)的检测。水热一锅法制备Mo2C,通过扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)和X射线衍射(XRD)对Mo2C纳米复合材料进行表征。在PBS缓冲液中,采用循环伏安法和差分脉冲伏安法研究了Trp在修饰电极上的电化学行为,并对影响实验结果的滴涂量、pH和扫描速度等进行了优化。最佳条件下,色氨酸浓度在10.0~100μmol/L和400~800μmol/L的范围内与Mo2C/GCE电流响应呈良好的线性关系,检测限为3.3μmol/L。

Solid-state template-free fabrication of uniform Mo2C microflowers with lithium storage towards Li-ion batteries

Herein,we first report one-step synthesis of uniform Mo2 C microflowers(MCMFs)from low-cost precursors via industrialized solid-state strategy.With fine optimization in precursor ratio and pyrolysis temperatures,the as-fabricated MCMFs are assembled well with interconnected single-crystalline nanosheet subunits.More encouragingly,the resultant MCMFs are further highlighted as a competitive anode with robust and long-duration lithium-storage behaviors towards high-performance Li-ion batteries.

华西医院疾病系统遗传研究院龚萌团队与麻醉手术中心李涛团队揭示Mo2C纳米酶治疗纤维肌痛能量代谢分子机制

近日,华西医院疾病系统遗传研究院/疾病分子网络前沿科学中心/蛋白组学-代谢组学平台龚萌副研究员团队与麻醉手术中心/线粒体与代谢研究室李涛研究员团队合作,在Biomaterials (IF:15.304)发表文章"Integrated metabolomics revealed the fibromyalgia-alleviation effect of Mo2C nanozyme through regulated homeostasis of oxidative stress and energy metabolism",首次发现Mo2C纳米酶对利血平诱导产生的纤维肌痛具有治疗作用,并首次借助综合代谢组学技术揭示了纤维肌痛治疗过程中的能量代谢分子机制.该研究认为Mo2C纳米酶具有作为纤维肌痛治疗药物的潜力,为纤维肌痛的临床治疗提供了新思路.

Mo_2C负载量对甲烷二氧化碳重整制合成气催化剂Mo_2C/γ-Al_2O_3的影响

用浸渍法制备了不同M o2C负载量的M o2C/-γA l2O3系列催化剂,采用微型固定床连续反应器对其甲烷和二氧化碳重整制合成气反应进行了活性评价,并采用XRD方法对催化剂进行了结构表征。活性测试结果表明,M o2C负载量在15%~30%时,催化剂具有较好的CH4转化率和CO、H2选择性,但M o2C担载量过高和过低时催化剂活性均不高。XRD结果表明,催化剂的活性的差别与活性组分的碳化程度有关,也与部分碳化钼转化成二氧化钼有关。

Mo_2C含量对Ti(C,N)基陶瓷力学性能和显微结构的影响

采用热压烧结工艺制备了添加微量Cr3C2 的Ti(C0 5N0 5) (Ni Co) Mo2 C -Cr3C2 系Ti(C ,N)基金属陶瓷。分析三种不同Mo2 C含量材料的力学性能、断口形貌和磨削表面压痕裂纹扩展情况 ,研究表明 :材料的断裂均以沿晶断裂为主 ;材料的抗弯强度与Rim相有关 ,8wt%Mo2 C含量的金属陶瓷Rim相厚度适中 ,抗弯强度高 ;1 6wt%Mo2 C含量的金属陶瓷的扩展裂纹短 ,裂纹扩展发生偏转 。

WC和Mo_2C添加对Ti(C,N)基金属陶瓷切削性能的影响

传统的Ti(C,N)基金属陶瓷刀具材料广泛采用Mo2C来改善粘结相对硬质相的润湿性,近年来Mo的价格不断上涨,寻找低成本金属代替Mo已成为Ti(C,N)基金属陶瓷的发展趋势。为了探讨WC代替Mo2C添加的可行性及其效果,研究了WC和Mo2C添加对Ti(C,N)基金属陶瓷切削性能的影响,采用电子扫描显微镜(SEM)观察刀具的磨损形貌,通过能谱分析(EDS)分析磨损表面的元素分布,并对刀具的主要磨损机理进行分析。实验结果表明,添加WC的金属陶瓷的切削长度和添加Mo2C的相当,将原始WC粉末粒度细化后,不仅切削长度显著增加,切屑也由带状缠乱型变为螺旋型,并且大大减少积屑瘤的形成,有利于切削的进行。切削磨损机理主要为扩散磨损和氧化磨损,伴有轻微的磨粒磨损。