Design And Optimization Of Transitional Metal Sulfides As Efficient Catalysts For Hydrogen Evolution Reaction

Two of the most serious challenges in the world are environment pollution and energy crisis. Environment and energy problems are related to the economy development of each country in the world. Many countries take care of the development of clean and renewable energy use. Hydrogen is the most popular clean energy in the 21st century. The most well-known electrocatalyst for hydrogen evolution reaction ?HER? is Pt. The reserve of Pt is limited and the price of Pt is extremely high. Hence, these problems have restricted the large-scale application of Pt in water splitting. To develop earth-abundant, low-cost and highly efficient non-noble metal catalysts has become the hot points of new energy study. This thesis focuses on improving HER performance of transitional metal sulfides by morphology optimization, hereatoms doping and incorporation of interface. The main parts are as follow:Firstly, we successfully synthesized hierarchically Ni3S₂ nanorod arrays foam through a simple hydrothermal process assisted by the pre-treatment with HCl. The pre-treatment by HCl is proved to be critically important to achieve high density of hierarchically Ni3S₂ nanorod arrays on Ni foam surface. The resulting hierarchical Ni3S₂ nanostructures exhibits excellent catalytic activity and stability towards HER with low overpotential of 200 mV at current density of 10 mA cm'2, which are among the best non-nobel metal HER electrocatalysts reported in literatures.Then, for the first time, we synthesized phosphorus-doped cobalt disulfide nanosheets ?CoS₂/P? as highly advanced electrocatalysts for HER. Through P doping, the surface properties of CoS₂ could be optimized to more efficiently catalyze HER with promoted charge transfer and facilitated proton adsorption. The P doping strategy could improve the electrocatalytic performance for HER, with an onset potential of 25 mV and low overpotential ?67 mV? to achieve current density of 10 mA cm^-2. The catalytic ability towards HER of CoS₂/P even beyond that on CoP.Finally, this paper combined higher stability MoS₂ and high activity CoS₂ into a bybrid ?MoS₂@CoS₂?, acting as promising HER catalysts. Compared with pure MoS₂ and CoS₂, the resulting hierarchical concentric MoS₂@CoS₂ exhibits significantly enhanced electrocatalytic activity towards HER, with an onset potential of 20 mV and low overpotential ?69 mV? to achieve current density of 10 mA cm^-2.