Controllable Synthesis Of Metal Tellurides And Their Application In Electrochemistry

In recent years,transition metal dichalcogenides(TMD)have received extensive attention of the researchers due to their unique molecular structure,band structure and adjustable chemical and physical properties.They play important role in the fields of supercapacitor,ion battery,electrochemical catalysis and etc.Presently,the research of transition metal sulfides and selenides has been relatively mature while their low conductivity limits the carrier transmission in electrochemical reactions.Tellurium in the same group of sulfur and selenium owns strong metallic property.The corresponding transition metal tellurides exhibit superior metallic property to metal sulfides and selenides and are expected as novel electrode materials.Simultaneously,the small electronegativity differences between transition metals and tellurium make the chemical synthesis and application of transition metal telluride still face many challenges.First,we have developed a organic phase synthesis of 1T'-MoTe2 in ultra-thin nanosheet.The shapes and interlayer spacings of MoTe2 can be controlled by varying Mo precursors and the reaction atmosphere.According to the comparison of experimental conditions and the density functional theory(DFT)calculation results,it concluded that the existence of carbonyl group in the reaction system was essential to tune the interlayer distances and defects of MoTe2 nanosheets,which helped to improve the electrochemical performance.For the first time,MoTe2 was employed as the electrode material of supercapacitors,whose specific capacitance reached 1393 F g-1 at the current density of 1 A g-1.Next,as a typical two-dimensional carbon material,graphene(GO)is considered as an ideal electrode material due to its excellent conductivity and large surface area,which can attach other active materials easily.Here we developed an in-situ organic phase synthesis of 1T'-MoTe2 supported on graphene.The presence of graphene not only supported MoTe2 from agglomeration but also accelerate the electron transfer.The performance of the composite electrode was improved greatly.For example,it obtained high specific capacity(1791 F g-1 at the current density of 1 A g-1),good rate performance(1242 F g-1 at 50 A g-1)and excellent cycle stability(the specific capacity remained 98.6%after 2000 cycles test at 50 A g-1).Finally,we prepared a three-dimensional nanostructure of CoTe2 decorated porous nitrogen-doped graphitic carbon from ZIF-67 precursor via a heat treatment process of simultaneous carbonization and tellruization.The composite material exhibited excellent OER performance,which delivered a small overpotential of 300 mV at 10 mA Cm-2.The existing nitrogen-doped graphitic carbon could provide highly conductive network that afford fast electron transport and buffer the stress and volume changes during the long-term electrolysis.