Study On The Regulation Of Structure And Properties Of Electrocatalytic Materials By Ce

The problem of environment and energy has gradually become a worldwide problem faced by human beings.It is extremely urgent to research and develop renewable clean energy.Electrocatalytic water splitting is an important means to obtain clean hydrogen energy and alleviate environmental pollution,while electrocatalytic oxygen evolution reaction?OER?involves multiple proton coupled electron transfer process,resulting in slow oxygen evolution kinetics and becomes the bottleneck of water splitting technology.Therefore,the development of efficient,stable and cheap OER electrocatalysts to reduce overpotential and improve energy efficiency is a key scientific problem urgently solved.Cerium is one of the largest rare earth elements in the earths crust,which prone to Ce⁴⁺?Ce³⁺conversion and the formation of oxygen vacancy with the influence of the surrounding environment,and cerium element itself is not only a catalytic activity at the same time,but also can be used as cocatalyst to improve the performance of catalyst,so development of efficient,stable and cheap Ce-based catalyst has good application prospect.In this paper,the effect of cerium on the microstructure and properties of electrocatalytic materials is studied.The main contents are as follows:1.The research background of this thesis is introduced,with the emphasis on the layered structure of hydrotalcite-like compounds,MOFs derivatives and cerium-based electrocatalysts for water oxidation.In addition,the aim and research significance of the work are summarized.2.Study on the regulation of Ce doping on the structure and properties of hydrotalcite-like electrocatalytic materials.Developing convenient doping to build highly active oxygen evolution reaction?OER?electrocatalysts are practical processes for solving the energy crisis.Herein,a facile and low cost in-situ self-assembly strategy for preparing Ce-doped NiFe-LDH Nanosheets/Nanocarbon?denoted as NiFeCe-LDH/CNT,LDH=layered double hydroxide,CNT=carbon nanocube?hierarchical nanocomposite is established for enhanced OER,in which the novel material provides its overall advantageous structural features,including the high intrinsic catalytic activity,the rich redox properties and high,flexible coordination number of Ce³⁺and the strongly coupled interface.Further experimental results indicate that doped Ce into NiFe-LDH/CNT nanoarrays bring about the reinforced specific surface area,electrochemical surface area?ECSA?,lattice defects,and the electron transport between the LDH nanolayered structure and the framework of CNTs.The effective synergy prompt the NiFeCe-LDH/CNT nanocomposite possessing superior OER electrocatalytic activity with an low onset potential?227 mV?and Tafel slope(33 mv dec^-1),better than most non-noble metal based OER electrocatalysts reported.Therefore,the combination of remarkable catalytic ability and the facile normal temperature synthesis conditions endows the Ce-doped LDH nanocomposite as a promising catalyst to expand the field of lanthanide-doped layered materials for efficient water splitting electrocatalysts with scale-up potential.3.Study on the synergistic effect of encapsulated CeO₂ nanoparticles on the performance of MOF-derived cobalt sulfide electrocatalytic materials.Using ZIF-67 as sacrificial template,a novel core-shell structure composite CeO₂@CoS was designed.CeO₂ NPs were successfully encapsulated in ZIF-67-derived hollow CoS.The core-shell structure CeO₂@CoS nanomaterials make full use of the synergistic effect of internal CeO₂ NPs and outer CoS with adjusting the electronic structure of CoS,accelerating the electron transfer rate and inducing vacancy defect,which significantly improve the catalytic activity and reaction kinetics of OER.Thus,the strategy of combining CeO₂ NPs with functionalized MOFs derivatives provides a new idea for the design of highly efficient cerium-based electrocatalysts.4.Study on the performance regulation of MOF-derived cobalt sulfide electrocatalytic materials by CeO_x nanoparticles.Transition metal sulfides?TMSs?have emerged as one of the important candidates for oxygen evolution reaction?OER?electrocatalysts to solve the energy crisis.Herein,we develop a novel hybrid nanostructure with conveniently decorating CeO_x nanoparticles on the surface of ZIF-67-derived hollow CoS through in-situ generation.In this case,proper control of the amount of CeO_x on the surface of CoS can achieve precise tuning of Co²⁺/Co³⁺ratio,especially for the induced defects,further boosting the OER activity.Meanwhile,the formation of protective CeO_x thin layer effectively inhibits the corrosion by losing cobalt ion species from the active surface into the solution.It thus represents a rare example of a hybrid hetero-structural electrocatalyst with CeO_x NPs to improve the performance of the hollow TMS nanocage.5.Lattice stress and high energy interface were constructed to enhance the electrocatalytic performance of CeO_x/CoS nanocomposites.Metal-organic frameworks?MOFs?derived materials have recently emerged as promising eletrocatalysts for oxygen evolution reactions?OER?.And integrating multi-active sites into the MOF-derivatives still remains a significant challenge in the renewable energy area,thus to greatly improve the functions of the materials.Herein,we developed an effective strategy to construct the lattice strain and high-energy interfaces by fabricating bunched MOF-derived CeO_x/CoS along long CeO₂ nanorods?L-CeO₂NRs?,which can be used as efficient OER electrocatalyst.Our design principle involves the formation of lattice strain between the units through the epitaxial compression growth of MOF-derived hollow CoS nanocages along CeO₂NRs,and the further generation of high-energy interfaces by the interaction between each two CeO_x/CoS polyhedron with high active heterostructure,lattice defects and grain boundaries.This work afforded a novel approach to tune the lattice strain and interface-catalysis engineering,thus unlocking the hidden potential of MOF-derived materials for effective catalytic applications.