Fabrication Of Transition Metal Composit Materials And Electrocatalytic Performance For Water Splitting

The huge consumption of fossil fuel,especially the urgency of traditional fossil and environmental pollution have become a focus of attention of the society.Therefore,it is urgent to find renewable energy as an alternative for fossil energy for whole world economic development.Recently,renewable energy?such as geothermal,wind and solar energy?is widely regarded as suitable substitutes by researchers.However,the spatial and temporal distribution of the energy severely limits their large-scale application.Hydrogen with earth-abundance,environmental friendly and high energy density is considered as a green and clean substitute of fossil energy,and abled to satisfy growing energy demand.Coal gasification and steam methane recombination are the main strategies of hydrogen production industry until now.These processes not only need large energy-wasting,but it is produced low purity hydrogen and huge carbon or pollutant emissions.Electrolysis of water is a clean and sustainable method to produce high purity hydrogen gas,which course includes two electrochemical reactions of hydrogen evolution reaction and oxygen evolution reaction.It is necessary to explore high-efficient catalysts to overcome the slowly dynamic of these two electrochemical reaction.This thesis describes the design and syntheses of a series of transition metal phosphides as electrocatalysts,and explores the performance of electrolysis of water to produce hydrogen under different conditions.This paper is mainly as follows:?1?The synthesis of Ni₃P/MnOOH catalytic materials and electrocatalytic performance for water splitting under simulated industrial environment.The design of bifuncational electrocatalyst with well activity at large-current density is the main motive force of promoting the development of industrial electrolytic water.This chapter used NiSO₄ and MnSO₄ as metal source,and take NaH₂PO₂ as phosphorus source.The Ni₃P/MnOOH hybrid film was prepared on Nickel foam?NF?by two-step method.This catalytic electrode requires only low overpotential of 268 and 341 mV at 1000 mA·cm^-2 under simulated industrial environment(6.0 mol·L^-1 NaOH,60 ^oC),respectively.An alkaline electrolyzer was consisted by Ni₃P/MnOOH electrode as the cathode and anode just need a cell voltage of 1.53 V at 10 mA·cm^-2 with good stability.This chapter not only improved the catalytic activity of oxygen evolution reaction,but also prepared bifuncational electrocatalyst with good electrocatalysis.It is provided broad prospect for the practical application of large-scale electrolysis water.?2?The synthesis of highly activity Ni₁₁?HPO₃?₈?OH?₆/Mn₃O₄ catalytic materials and electrocatalytic performance for hydrogen evolution reaction.The design of electrocatalysts with high-efficiently,cost-efficient and stable for hydrogen evolution reaction is important for alleviate energy crisis in the future.This chapter used the Ni₃P/MnOOH synthesis at chapter three as precursor,and prepared the Ni₁₁?HPO₃?₈?OH?₆/Mn₃O₄ composites?named as NiPi/Mn₃O₄?by electrochemical activation.The existence of the strong interface coupling between Ni₁₁?HPO₃?₈?OH?₆and Mn₃O₄ in this material,which accelerated the reaction dynamic of hydrogen evolution reaction.The nanowire and nanoparticle of material was greatly increased the contact area beween catalyst and electrolyte.Meanwhile,the existence of obvious interface between crystalline and amorphous,which make the NiPi/Mn₃O₄heterofeneous material with faster electron transfer and better stability.Owing to above characteristics,this catalyst electrode just need 84 mV to reach 100 mA·cm^-2 at alkaline solution.This research provide an efficient synthesis method to develop high efficient and stability electrocatalyst for hydrogen evolution reaction.?3?The synthesis of high activity double-deck CoP/CeO₂-FeO_xH bifunctional electrocatalyst and electrocatalytic performance for water splitting.Recently,the cobalt phosphides and FeOOH was respectively regarded as the active species of hydrogen and oxygen evolution reaction with low-cost,which was be widely discussed.The double-deck CoP/CeO₂-FeO_xH composite was prepared by sample two-step electrodeposition in this chapter.CoP as active material for hydrogen evolution reaction was deposited at underlying,and CeO₂-FeO_xH as active specie of oxygen evolution reaction was prepared at composite layer.Besides,the produce of the crack and nanosheet etc.microstructure in layer of CeO₂-FeO_xH was control by adjust parameters of electrodeposition.The introduction of ceria was produced amount interface,which improve the performance of oxygen evolution reaction and conductivity.This catalytic electrode requires only low overpotential of 27.6 and 248 mV at 10 mA·cm^-2 at alkaline medium,respectively.An alkaline electrolyzer was consisted by CoP/CeO₂-FeO_xH catalytic electrode as the cathode and anode just need a cell voltage of 1.53 V at 10mA·cm^-2.This chapter provide a new ideal to develop highly efficient and stability non-noble metal based bifunctional electrocatalyst for water splitting.