Facet Effect On Noble Metal Nanometarials For CO₂ Electroreduction

With the development of the industrial revolution,the usage of fuel increases a lot,and leads to high level of CO₂ in atmosphere,which causes global warming.Decreasing the CO₂ concentration and converting CO₂ to useful carbon-containing fuels become hotspots of study.CO₂ electroreduction reaction is an effective method for CO₂ reutilization by converting electric energy to chemical energy.Up to now,the researches focus on morphology and particle size effect.However,the facets of catalysts with different particle sizes are complex,which make it difficult to study the facet effect of catalyst.In the first part of the thesis,we synthesize the Pd catalysts enclosed with{310},{100}and{111}facets,and keep the same particle sizes of catalysts to exclude the particle size effect.In this study,we demonstrate the facet effect on Pd nanocrystals with the same particle size for CO₂ electroreduction.The Pd concave cubes enclosed with high-index{310}facets show the highest CO Faradaic efficiency of 90.6%,higher than that of Pd octahedrons with{111}facets and Pd cubes enclosed with{100}facets.Density functional theory calculations and experiment reveal that Pd concave cubes enclosed with the{310}facets faciliate the*COOH formation and decrease the energy barrier of CO*desorption.In the second part of the thesis,we study the synergistic effect of Au-CeO₂ on CO₂electroreduction.The Ce³⁺concentration is high when the CeO₂ nanosheets are enclosed with{111}facets,and the Ce³⁺concentration increases with the NaBH₄pretreatment for CeO₂ nanosheets.The activity of CO₂ electroreduction is boosted with the Ce³⁺concentration increases,and the activity shows a linear relation with the fractions of Ce³⁺on Au-CeO₂ NSs.CO faradaic efficiency could reaches to 90.1%at-0.5 V on Au-CeO₂ nanosheets with NaBH₄ pretreatment,and the current is 3.6 times higher than that of catalyst without NaBH₄ pretreatment.In situ surface-enhanced infrared absorption spectroscopy and DFT indicates that Au-CeO₂ with high Ce³⁺concentration promotes CO₂ activation and enhances*COOH formation.