| Electrochemical water splitting can transform intermittent renewable energy sources such as wind,solar and tidal energy into clean hydrogen with the highest thermogravimetric ratio and easier storage,thus providing a very effective way to solve the current energy crisis,environmental pollution,global warming caused by the massive consumption of fossil fuels.However,the application of noble metal based catalysts severely limits the application of water electrolysis technology.Therefore,the development of high activity and low-cost non-noble metal catalysts has become the focus of current research.Recently,transition metal sulfides have been considered the most promising catalysts to replace noble metals due to their controllable composition,rich synthesis strategies,and excellent catalytic activity,such as Mo S2,Co9S8,Co S2.However,these catalysts usually have high catalytic activity only for hydrogen evolution reaction（HER）or oxygen evolution reaction（OER）.This not only increases the complexity of the electrolysis water device,but also increases operating costs and reduces conversion efficiency.Based on this,this work is based on the design and preparation of highly active bifunctional electrolytic water catalyst.From the perspective of building heterostructure,taking advantage of its advantages in regulating electronic structure and promoting electron transfer efficiency,two kinds of non-noble metal sulfides Mo S2 and Co Sx with different catalytic functions are used as research objects,and the following research work is carried out:（1）Hierarchical flower-like heterointerface catalyst.Morphology and structure play an important role in the regulation of catalytic properties of catalysts.It is still a great challenge to construct heterointerface sulfide catalysts with regular morphology.Based on this,we successfully prepared a three-dimensional nanoflower-like Mo S2/Co S2 heterostructure catalyst formed by two-dimensional layer stacking using the strategy of combining hydrothermal with in-situ sulfuration and regulating the reaction conditions of the precursor.It is found that the existence of a large number of Mo S2/Co S2 interface structures optimizes the electronic structure of the material,which is more conducive to the adsorption and desorption of reaction intermediates,and at the same time,the electron transfer efficiency of the material is also greatly improved.In addition,the unique hierarchical flower-like three-dimensional structure facilitates the exposure of more catalytic active sites and promotes mass transfer.The synergistic effect of various advantages makes the material exhibit excellent HER and OER bifunctional catalytic activities in alkaline media.Mo S2/Co S2reaching a current density of 10 m A·cm-2 only requires an overpotential of 105 m V,Tafel slope of 71.02m V·dec-1,and exhibits excellent stability for HER.Mo S2/Co S2 reaching a current density of 10 m A·cm-2only requires an overpotential of 252 m V,with a Tafel slope of 51.78 m V·dec-1 for OER,which even surpasses commercial Ru O2.The current density of 10 m A·cm-2 can be obtained with a voltage of 1.56 V.This work provides a new strategy for the construction of heterogeneous catalysts with regular morphology,which is of great significance for the design of highly active bifunctional catalysts.（2）Self-supported electrode is used as conductive substrates to in-situ grow heterointerface catalysts.Considering the poor conductivity of sulfides,we used carbon cloth as a conductive substrate,grew Co Mo-precursors through hydrothermal method,and further in-situ vulcanized them to successfully prepare an excellent bifunctional heterostructure catalyst.By optimizing the vulcanization temperature,the morphology and crystal structure of the material were effectively controlled.It was found that the special structure of Co S nanoparticles with a large number of Mo S2 nanosheets inserted on the surface showed the best catalytic performance.Mo S2@Co S/CC exhibits low overpotentials of 94 and 205 m V at 10 m A·cm-2for HER and OER in alkaline media,respectively.Furthermore,for overall water splitting,the Mo S2@Co S/CC can afford a current of 10 m A·cm-2 at a voltage of 1.53 V with good stability.This work provides an effective strategy for the design and construction of highly active bifunctional catalysts. |
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