Construction And Electrocatalysis Of Metal Dichalcogenides-based Nanocrystals With Phase Engineering

Transition metal dichalcogenides（TMDs）have been regarded as one of the most significant materials for energy conversion catalysis due to unique and tunable electronic structures as well as physical and chemical properties.The phase of this category of material can be engineered for investigation purposes,demonstrates that metallic 1T phase possesses high intrinsic activity for hydrogen evolution reaction（HER）,and superb electrical conductivity facilitates charge transfer during electrocatalysis.While semiconducting 2H phase identifies remarkable performance of edge sites for electrochemical CO₂ reduction reaction（CO₂RR）,impeding the competing HER reaction.However,compared to noble metal-based electrocatalysts,TMDs show poorer performances and their stability can be considered as the key scientific fundamental in the process of practical applications.Mo S₂ and Ni Se₂ are the main investigation objectives and utilized for the construction of hybrid nanostructures and compositions through novel solvothermal synthetic strategies with phase engineering.The enhancement of electrocatalytic performance has been achieved by the design of complicated structures and compositions.A variety of characterizations for synergistic effects of multi-components,interfacial properties and etc.have been carried out to elucidate the structure-function relationship,thus contributing to optimization of electrocatalytic performances.These achievements play an essential role in tackling energy crisis and environmental issues.（1）We firstly proposed a novel solvothermal strategy to realize complete phase transition of Mo S₂ and obtained porous hybrid nanostructure comprised of 1T Mo S₂ and amorphous Ni-Co complexes with Ni-Co hydroxides as precursors through electron-donating effect of hydrazine hydrate.The hybrid electrocatalyst exhibited splendid catalytic performances for overall water splitting（OWS）as both anode and cathode.In this system,amorphous Ni-Co complexes can stabilize 1T Mo S₂ during electrocatalysis,which opens up a new road for the stabilization on metastable phase of TMDs materials.（2）Based on the above synthetic strategy,we systematically designed and constructed a hybrid nanotube-array electrode constituted by 1T’Mo S₂ and（Co,Fe,Ni）₉S₈.The advantages of this hybrid electrode for OWS electrocatalysis are demonstrated as follows.The synergistic effects of multi-components improve the intrinsic activity for OWS.The metallic feature of 1T’Mo S₂ promotes the electrical conductivity of the electrode.Porous nanostructures and uneven surface of the nanotubes enhance the density of catalytic active sites.Besides,superaerophobicity and superhydrophilicity of the surface of the nanoarray architectures facilitate the mass transfer process of water splitting electrocatalysis.The hybrid nanotube arrays show ultrahigh efficiency and excellent stability for OWS.In situ structural characterizations demonstrate the fascinating electrochemical stability of as-prepared 1T’Mo S₂.（3）The hierarchical hollow cages comprised of edge-exposed 2H Mo S₂ and N-doped carbon have been synthesized by thermal reduction with ZIF-67 rhombic dodecahedrons as template and carbon source at a high temperature.A large quantity of exposed edges of 2H Mo S₂ provide active centers for CO₂RR and charge transfer between the two components promotes the intrinsic activity of the hybrid electrocatalyst.Carbon hybridization improves electrical conductivity.Porous hollow structure enhances specific surface area and facilitates mass transfer process of electrocatalysis.We have acquired highly active and robust hybrid electrocatalyst for CO₂RR,which can achieve 92.68%of Faradaic efficiency for CO production.（4）We successfully prepared amorphous Ni O_x nanoparticles（NPs）decorated Ni Se₂ultrathin nanowires（UNWs）in ethylene glycol solvent system with two-step hot-injection method in an atmospheric pressure reaction system and subsequent high-pressure solvothermal method in a sealed system.The secondary component,amorphous Ni O_x NPs,did not only provides more catalytic active sites for OWS,but it also protects the inherent active center,Ni Se₂ UNWs,from further oxidation during electrocatalysis for avoiding inactivation.The hybrid electrocatalyst displayed highly active and ultra-stable performances for OWS,which expands the applied range of transition metal diselenides.This work mainly explores the functionality of secondary component in the hybrid material,bringing new opportunities of this category of material in electrocatalysis.