Study On Crystal Surface Engineering Modification And Electrochemical Properties Of Cerium Dioxide Nanomaterials

As a common metal oxide nanomaterial,CeO2 has been widely used in catalysis,energy storage,sensing,and fuel cells due to its ease of preparation,perfect morphology,multivalent states of Ce element,presence of surface oxygen vacancies and excellent redox ability.However,CeO2 still faces problems such as low intrinsic conductivity and deficiency of active sites,resulting in its intrinsic catalytic activity still needs to be improved,and therefore further enhancement of the reactivity is urgently needed.Surface engineering,an important modification strategy,has been widely used to enhance the catalytic activity of nanomaterials.In this thesis,surface engineering methods such as crystalline surface engineering,defect engineering and doping engineering were used to introduce defects and doping into CeO2 nanomaterials with different crystal facets exposures,and their H2O2 non-enzymatic electrochemical sensing and electrocatalytic hydrogen evolution reaction properties were investigated.Finally,the mechanism of the effect of surface engineering modification on electrochemical performance was explored as follows:(1)Using the idea of combining crystal facet engineering and defect engineering,CeO2 nanocrystals with different exposed crystal facet enriched with oxygen vacancies and Ce3+were prepared by a hydrothermal reaction combined with an aluminothermic reduction modification method,and the nanocrystals were characterized for oxygen vacancies and Ce3+/Ce4+content and combined with DFT theoretical calculations for mechanistic analysis of the H2O2 sensing performance.It is shown that the synergistic effect of the crystal facet and surface defects increases the surface active sites while being able to reduce the energy required for the redox reaction,resulting in excellent non-enzymatic H2O2 electrochemical sensing performance.The aluminothermic reduced CeO2 octahedra exhibited the best H2O2 sensing performance among all samples,with a wide linear range(20 ?M?13.61 mM),high sensitivity(128.83?A/(mM·cm2))and low detection limit(13.09 ?M).It also has good selectivity and stability.and its practicability is verified in the sensing test of H2O2 in medical disinfectant.This work will provide a new method for the modification of electrochemically active materials and uncover a non-enzymatic H2O2 electrochemical sensor with practical applications in food,medical and environmental applications.(2)N-doped porous CeO2 nanosheets were obtained by surface modification of ultrathin CeO2 nanosheets using NH3/Ar plasma etching.The optimum modification parameters were obtained by regulating the plasma etching time and temperature,and the best sample exhibited significantly enhanced HER activity at a current density of 10 mA/cm2,with the overpotential reduced from 370 mV to 65 mV and the Tafel slope reduced from 159.5 mV/dec to 105.2 mV/dec after modification.The excellent HER performance was found to result from the synergistic coupling between the porous structure formed by the NH3/Ar plasma and the N element doping when compared with the pure Ar plasma treated samples.The present work will open up a new avenue for the preparation of high performance CeO2-based electrocatalysts by low temperature and rapid surface modification.