Research On Humidity Sensitivity And Catalytic Hydrogen Evolution Of Two-Dimensional Layered Material MX₂

The few-layer/thin-layer sheet structure of the two-dimensional layered material gives it a large specific surface area and a large number of exposed active sites of surface,which makes its applications in electrochemical catalysis,gas/moisture sensing and other fields attract much attention.In this thesis,the transition metal compounds Molybdenum disulfide?MoS₂?,tungsten disulfide?WS₂?and molybdenum disselenide?MoSe₂?were taken as the research objects.Thin-layer nanosheets were obtained by liquid-phase ultrasonic stripping method,and the catalytic hydrogen evolution electrode and humidity sensor were prepared by inkjet printing technology.The performance of hydrogen evolution reaction and moisture sensitivity were studied respectively.The main research work and results are as follows:?1?In a mixed solvent system of absolute ethanol and deionized water,polyvinyl pyrrolidone and reduced graphene oxide were added.The MX₂-PVP-rGO ink containing MoS₂,WS₂,MoSe₂ thin-layer nanosheets were obtained by liquid phase ultrasonic stripping method.UV-Vis absorption spectrum test results show that the concentration of MX₂-PVP-rGO ink increased with the increase of the peeling time;the results of scanning electron microscope and X-ray diffraction showed that the peeled body material formed lamellar structure,which had better crystallinity.The water contact angle test of the functional layers formed by different inks after inkjet printing showed that the hydrophilicity of the MX₂-PVP-rGO functional layer was greatly improved compared to the pure MX₂ functional layer,which was conducive to promoting the process of hydrogen evolution reaction and moisture-sensitive mass transfer.?2?Nanoflakes with different levels of stripping could be obtained by controlling the liquid phase ultrasonic stripping time,and printed onto the copper electrode via inkjet to obtain a hydrogen evolution reaction electrode.The result of the linear scanning voltammetry test showed that the performance of catalytic hydrogen evolution was enhanced with the increase of peeling degree;The catalytic hydrogen evolution electrode was prepared by liquid-phase ultrasonic stripping for 48 h,and when the cathode current density was 10 mA cm^-2,the overpotentials of hydrogen evolution reaction of MoS₂,WS₂and MoSe₂ were 56 mV,88 mV and 214 mV,respectively.The cyclic voltammetry characteristics of the three electrodes were tested,and their electrochemical double-layer capacitance values were calculated to be 44 mF cm^-2,34.4 mF cm^-2 and 26 mF cm^-2,which indicated that the MoS₂-based hydrogen evolution reaction electrode had a larger electrochemical active area,which corresponded to its lower catalytic hydrogen evolution reaction overpotential.?3?The ink obtained after ultrasonication for 48 h and centrifugation was ink-jet printed on copper interdigitated electrodes to prepare a moisture-sensitive sensor.The I-V characteristics of the device showed that the device is a resistive sensor;The results of humidity sensitivity test showed that the device had wide humidity range?11%RH-95%RH?and fast response-recovery speed;The WS₂ based humidity sensor had the best comprehensive humidity sensing performance of the three material systems.The moisture sensing mechanism of the MX₂ humidity sensor was investigated by measuring the impedance characteristics of the humidity sensor under different relative humidity and combining with bode diagram analysis.