Preparation Of Three Transition Metal Nanomaterials And Their Application In Supercapacitors And CO Preferential Oxidation In H₂-rich Stream

In recent years,transition metal based nanomaterials have been widely used in energy storage and energy conversion due to their large surface area,abundant active sites and outer shell electrons.This research is committed to solving the existent problems of supercapacitors and proton membrane fuel cells from the perspective of the design and synthesis of transition metal based nanomaterials:（I）The supercapacitors are restricted by the narrow voltage window and low energy density.The transition metal phosphorus sulfides and their composites were prepared by doping with nickel,cobalt and vanadium transition metals and applied to supercapacitors.（II）The promotion of proton membrane fuel cell applications was hindered by the short lifetime and low activity of CO preferential oxidation in H₂-rich steam.A tube/rod like Cu-Ce catalyst with resistance of CO₂ was fabricated by design and modulation of morphology of the transition metal Cu-Ce catalyst and applied to the reaction.The main research contents are provided as follows:（1）Transition metal phosphorous sulfide has excellent electrochemical performance,however,the complex preparation route hindered its further application.In this study,a simple one-step electrodeposition method was used to deposit interconnected nano wall nickel cobalt phosphorus sulfide（Ni-Co-P-S）nano sheets on the surface of carbon cloth.Ni-Co-P-S nano sheet with multi-component synergistic effect provides rich active sites and improves the reversible capacitance.The prepared Ni-Co-P-S electrode materials showed excellent electrochemical performance in the three electrode system,and the specific capacitance was up to 2744 F/g at 4 A/g.The supercapacitor based on Ni-Co-P-S positive electrode and active carbon negative electrode shows high specific capacitance of 110.9 F/g（at a current density of 1 A/g）,excellent energy density of 39.4 Wh/kg（at a power density of 797.5 W/kg）,and good cycle stability（capacity retention rate is 91.87%after 10000 cycles）.（2）V₂O₃ has the disadvantages of low specific capacitance and poor cycle stability.Improving the electrochemical performance of V₂O₃ is a challenge for vanadium based pseudocapacitor materials.In this study,a V₂O₃/carbon nanospheres（H-V₂O₃/C）electrode for supercapacitors was designed and synthesized.The introduction of carbon improves the conductivity and stability of the electrode,and the hollow structure makes it with high specific surface area and fast ion transport.H-V₂O₃/C integrated electrode can work in the positive and negative potential window at the same time.The specific capacitance of H-V₂O₃/C integrated electrode is up to708.6 F/g under-1.1～1.3 V wide voltage window.The electrode used in the SC device of water system integration provides a 2.4 V wide voltage window,energy density of96.8 Wh/kg,power density of 1204.6 W/kg,and excellent cycle stability.（3）In CO preferential oxidation in H₂-rich steam,the induced redox sites of Cu-Ce based catalysts can be easily affected by the competitive adsorption of CO₂.In this research,a fine nanotube/rod like Cu O/Ce O₂-T was prepared.The surface regenerated tubular structure accelerates the separation of CO₂ and the formation of carbonate.The catalyst has significant resistance of CO₂.Compared with rod and amorphous Cu O/Ce O₂ catalysts,the crystal surface characteristics,endowed by the special morphology,can highly promote the dispersion of Cu species.In addition,the interaction of active Cu-O-Ce interface shows rich metal valence states,oxygen vacancies and 100%CO conversion at 100℃.Hollow structure can promote metal dispersion and CO₂separation,and effectively facilitate activity and stability of the catalyst.