Constructing Nanostructure Of Co-based And Mo-based Efficient Electrocatalysts And Investigating Their Water Splitting Behaviors

With the rapid consumption of fossil energy due to the fast increasing demand,the world is facing energy shortage and environmental pollution,forcing us to develop new sustainable clean energies.Electrocatalysis energy conversion technology has advantage of simple operation,high energy conversion efficiency,which is a hotspot in the field of clean energy research.In this thesis,we direct electrolysis of water as oriented applications,and aim at developing high efficiency electrocatalyst.At present,the energy consumption in these reactions is high,which greatly limits the efficiency of energy conversion.Electrode materials plays a very important role in the whole catalytic reaction process,which is the transfer medium of electrons in electrocatalytic process and also the place where electrocatalytic reaction occurs.Reasonable construction of electrode materials is an important factor to enhance electrocatalytic performance.Precious metal materials are a kind of excellent electrocatalytic materials,but their rarity and high price limit their large-scale application in industry.Therefore,the development of cheap and efficient electrocatalysts is an important task in the field of electrochemical energy conversion.Based on this,this paper aims to effectively regulate non-noble metal nanocomposites by doping with heteroatom and introduction of pore structure and so on,and to construct a high-performance electrocatalytic electrode interface.The main research contents of this paper are summarized as follows:1.Combining with the precursor morphology oriented method,Co₃S₄ nanobrush was firstly prepared and further introduced different levels of P atoms by low temperature phosphorization.And then the Co₃S_4-x P_x nanobrush successfully constructed,which delivers remarkably extraordinary HER catalytic performance in all pH electrolytes with low overpotentials of 58,106,89 mV at 10 mA/cm²and 116,201,148 mV at 100 mA/cm² in 0.5 M H₂SO₄,1.0 M phosphate and 1.0 M KOH,respectively.Theoretical calculation further proves that P element doping improved electronic structure of Co₃S₄,making it transition from semiconductor state to conducting state property,which is more conducive to the rapid electron transmission in the electrocatalytic reaction process.Besides,P doping regulates the free energy of H_adsds absorption and desorption on the surface and accelerates the kinetics of hydrogen evolution reaction.This work demonstrates a method to synthesize a high-performance non-noble catalyst while shedding a light on the fundamental insight of P-modification and effect of P/S ratio.2.Hydrogen evolution catalyst has better catalytic kinetics in acidic electrolyte,while oxygen evolution catalyst has better catalytic performance in alkaline electrolyte.Therefore,it is challenging to design the same catalyst to achieve full water splitting in the same electrolyte.Herein,we describe our recent finding that Co₃S₂P₂ nanobrush integrated on Ti mesh behaves as a robust monolithic full water splitting catalyst.When used as a 3D water-splitting electrode,such electrode drives 10 mA/cm² at overpotential of 230 mV for the oxygen evolution reaction in 1.0 M KOH,and the corresponding two-electrode electrolyser needs a cell voltage of 1.60 V for 10 mA/cm² water-splitting current at room temperature.The excellent electrocatalytic performance is mainly attributed to its self-supporting Co₃S₂P₂ nanobrush interface,which not only effectively improves the electron transfer capacity and gas precipitation rate,but also reduces the degradation of catalyst performance caused by catalyst agglomeration in the catalytic reaction process.3.SiO₂ nanospheres template-based synthesis strategies are proposed for preparation of porous molybdenum carbide nanocrystals embedded within nitrogen-doped carbon foams?p-Mo₂C/NC?.The composite synthesized by in-situ pyrolysis increases the strong coupling interaction between Mo₂C and high-conductive substrate,which is conducive to the rapid transfer of electrons in the catalytic process,thus accelerating the reaction kinetics.The p-Mo₂C/NC hybrid electrocatalyst shows high catalytic activity in acidic medium.The reaction pathways and mechanism have been studied by Tafel analysis.4 At the third work,although,p-Mo₂C/NC hybrid electrocatalyst shows high catalytic activity,its catalytic performance needs to be further improved.Due to the transition metal phosphides have excellent electrical conductivity and phosphorus atoms have more efficiency free energy of H_ads,it is a kind of excellent electric catalyst of catalytic activity of hydrogen evolution.In view of this,one-step pyrolysis of ammonium molybdate,phytic acid and melamine was developed for the first time in this work,and nitrogen-doped carbon coated MoP nanoparticles were successfully synthesized.Its catalytic activity was significantly better than that of the Mo₂C composite catalyst.In this work,the author developed a method to prepare phosphide by using phytic acid as a phosphorus source.