Preparation And Electrocatalytic Properties Of Two-dimensional ReS₂ And Its Composites

Hydrogen not only has high calorific value,but also has zero pollution.It is one of the ideal clean energy.Hydrogen evolution from water electrolysis is a low-cost,pollution-free and easy-to-operate method for hydrogen production.However,electrolysis of water for hydrogen evolution requires catalysts to assist in improving the efficiency.Non-precious metal catalysts gradually replace expensive precious metal catalysts.Among them,transition metal sulfide catalysts are playing a greater role due to their low price,simple preparation,and excellent catalytic performance.In this work,a novel transition metal sulfide two-dimensional ReS₂ catalyst was designed and prepared to investigate its catalytic performance for hydrogen evolution reaction(HER)under alkaline conditions.First,the carbon cloth(CC)with good conductivity was used as the catalyst carrier,and ReS₂ nanosheets were synthesized on it,so that the nanosheets were vertically arranged and interconnected,and the surface area and conductivity were increased to obtain excellent catalytic performance.Then,the ReS₂/CC catalyst was modified to replace the carbon cloth with carbon cloth-supported carbon nanotubes with a larger surface area,exposing more active area and edge active sites;introducing Mo element,using the synergistic effect of Mo and Re,Improve the electron transport speed for better electrocatalytic performance.The main findings are summarized as follows:1.Two-dimensional ReS₂ nanosheets were grown on carbon cloth substrates using a hydrothermal synthesis technique using CS(NH₂)₂,NH₄ReO₄ and deionized water as precursor solutions.The influence of the molar ratio of CS(NH₂)₂ to NH₄ReO₄ in the precursor solution and the hydrothermal reaction time on the morphology,structure and catalytic performance of ReS₂ nanosheets were studied.The results show:When the molar ratio of CS(NH₂)₂ to NH₄ReO₄ is in the range of 10:1 to 6:1,the distribution density of ReS₂nanosheets on CC substrates decreases with the decrease of the molar ratio of CS(NH₂)₂ to NH₄ReO₄ and decrease.When the molar ratio of CS(NH₂)₂ to NH₄ReO₄ was less than 4:1,no ReS₂ nanosheets were grown on CC substrates.The distribution density of ReS₂ nanosheets grown with different reaction times did not change greatly within 12-24 h.The electrocatalytic performance of ReS₂/CC showed that the molar ratio of CS(NH₂)₂ to NH₄ReO₄ in the precursor solution had a significant effect on the electrocatalytic performance of ReS₂/CC.The growth time had no obvious effect on the morphology,structure and electrocatalytic performance of ReS₂ nanosheets.When the molar ratio of CS(NH₂)₂ to NH₄ReO₄ was 10:1and the growth time was 20 h,the ReS₂ nanosheets/CC exhibited the best HER catalytic performance.The overvoltage at 10 mA/cm~2,Tafel slope,electric double layer capacitance,ECSA and charge transfer resistance were 99 mV,222 mV/dec,135 mF/cm~2,3375 cm~2 and6.90?,respectively.The long-term stability test results show that during the HER reaction lasting for 20 hours,the current density basically does not decrease,and the overpotential corresponding to the current density of 10mA/cm2 is shifted by 22mV.The ReS₂/CC catalyst has good stability.From the variation of ECSA with distribution density and growth time,we infer that the active sites of 2D ReS₂ nanosheets exist on the edge and basal planes.Active sites on the basal plane are caused by Revacancies and defects.2.Mo_xRe_1-xS₂ composites were synthesized on carbon cloth-supported carbon nanotubes(CNT@CC)as HER catalysts by hydrothermal synthesis technique.The results show:The carbon nanotubes are all wrapped by Mo_xRe_1-xS₂ nanosheets,exposing a large amount of surface area and edge sites.Mo_0.4Re_0.6S₂/CNT@CC exhibits the best catalytic performance.The overvoltage at 10 mA/cm2,Tafel slope,electric double layer capacitance,and ECSA were87 mV,67 mV/dec,220 mF/cm2,and 5500 cm2,respectively.Mo_xRe_1-xS₂/CNT@CC can maintain good stability during the continuous HER process.Compared with ReS₂/CC,the catalytic performance of Mo_xRe_1-xS₂/CNT@CC is greatly improved.The main reason is that the surface area and active sites are greatly increased,and the electron transport ability is improved,so the catalytic performance has been greatly improved.