Study On The Preparation Of Molybdenum Disulfide-based Nanostructures And Its Catalytic Performance

Electrocatalytic and photocatalytic hydrogen evolution reaction can convert excess electrical energy or sunlight into chemical energy.They are green and sustainable methods for hydrogen production,and therefore have broad application potentials in the fields of fuel cells and energy storage.MoS2 has been demonstrated theoretically and experimentally to be a very promising HER catalyst owing to its high elemental abundance,high catalytic activity,and electrochemical stability.In comparison with semiconductor MoS2,the metallic phase MoS2 has high conductivity and its basal planes are active for electrocatalytic HER.However,the metallic MoS2 belongs to metastable phase,which renders great difficulty in its preparation.Therefore,the development of an approach that can effectively prepare high quality and stable metallic MoS2 is highly desired for the wide application of MoS2 in hydrogen evolution reaction.In this dissertation,I developed a new facile hydrothermal approach for the synthesis of metallic MoS2 in large scale and study their electrocatalytic and photocatalytic activity for HER.The specific contents of this dissertation are as follows:1.We have developed a new facile hydrothermal approach for the synthesis of metallic-MoS2 in large scale and studied their formation process and influencing factors.The concentration of S ions in the reaction solution is found to play a pivotal role on the formation of metallic-MoS2.When concentration of S ions is in excess,the metallic MoS2 is more easily obtained.The higher concentration of sulfur ions results in the formation of a large number of MoS2 nuclei.During the growth of these nuclei,the surplus S can bind at the edges of MoS2 and thus hinders the lateral growth of the MoS2 nanostructures.Such as facile and solid preparation method will be very helpful of the application metallic MoS2-based nanomaterials in catalysis,energy storage and other fields.2.The HER electrocatalytic performances of the prepared MoS2 was investigated.Both the metallic phase and abundant edges endow the metallic MoS2 nanopetals with superior electrocatalytic activity for HER.The very small overpotential of 210 mV is obtained at the geometric current density of 10 mA cm-2.The corresponding Tafel slope is 44 mV dec' The morphology affects the HER performance of the metallic MoS2.Since the petal-like metal phase MoS2 has a richer edge state,its catalytic activity is better than that of the sphere like metallic MoS2.At the same time,petal-like metallic MoS2 has excellent chemical stability and electrocatalytic hydrogen evolution stability.Therefore,the petal-like metal phase MoS2 synthesized by hydrothermal method has good catalytic activity for hydrogen evolution and is a potential substitute for platinum-based catalysts.3.The metallic MoS2 was utilized as the co-catalyst for the photocatalytic hydrogen production.First,the metastable TiO2(B)atomic thick nanosheets were prepared via a hydrothermal method.The flat facet of the prepared TiO2(B)are active(010)facet.TiO2(B)nanosheets display higher photocatalytic activity compared with P25,and the rate of hydrogen production is 10 times higher than that of P25.After the introduction of the metallic MoS2,the photocatalytic performance for hydrogen evolution of TiO2(B)is further improved by 14 folds.The enhancement of photocatalytic performance is found from the improvement of carrier separation efficiency and hydrogen evolution kinetics by metallic MoS2.