Controllable Colloidal Synthesis Of Nanostructured Metal Oxides And Metal Composites For Photo-/Electro-Catalysis

Environmental pollution and energy crisis are two major issues faced by nankind in the 21st century.In order to solve the crisis of environment and energy,researchers have made great efforts and gained a lot of research results.In the aspect of solving environmental problems,titanium dioxide(TiO2)is used as an effective photocatalyst.The exposure(001)facets of TiO2 can effectively degrade organic pollutants under light conditions.In addition,in order to effectively solve the energy problem,fuel cells work as the high efficient equipment in energy conversion and have the low pollution emissions,which have drawn researchers' attention.Catalysts play an important role in accelerating the photodegradation of pollutants and the electrochemical oxidation of fuels.It has been considered as a great approach to enhance the catalytic activity and stability by adjusting the interface properties and electronic structure of catalysts.In this paper,the photocatalytic degradation of organic pollutants was firstly achieved by adjusting the(001)facet of TiO2.Then,non-noble metals were introduced to tune the nanostructures and electronic structures of Pt and Pd,which has effectively improved the electrocatalytic activity and stability of the catalysts.In this work,we have successfully prepared TiO2 nanoparticles with exposed(001)facet,PtBi alloy,Pt-Bi(OH)3 and PdBi-Bi(OH)3 composite nanomaterials by liquid phase synthesis.On the one hand,the formation mechanism of the(001)facets and their application in the photodegradation of organic pollutants has been discussed.On the other hand,the incorpration of Bi into Pt and Pd has been studied systematically.The main work is as follows:1.To investigate the formation mechanism of TiO2(001)facet and its photocatalytic application,TiO2 nanorods with exposed(001)facets at both ends were employed as the template.The results indicated that the F ion not only could play a role in decreasing the surface energy of(001)facets,which prevented their decrease and disappearance during the growth of(001)facets,but also can continuously etch the(001)facet.The generated TiO2 by etching could react with HF to form the unstable titanium tetrafluoride(TIF4)and then decompose into TiO2,which would deposit on the(001)facet of TiO2 nanoparticles and make the(001)facet grow larger.Moreover,with the increasement of(001)facet,the degradation rate of methylene blue(MB)was significantly enhanced.2.We employed a polyol method to prepared core-shell Pt2Bi hexagonal nanoplates using diethylene glycol(DEG)as a reducing agent and solvent,polyethylene pyriloxone(PVP)as the surfactant.The inner Pt-Bi core was a stable intermetallic compound,which could generate a stress effect with the Pt shell.Therefore,core-shell PtZBi catalyst can effectively improve their activity and stability for the oxidation of methanol and ethanol,which will be of important significance to the development of fuel cells.3.In order to improve the utilization rate of Pt catalyst and its anti-poisoning,we have designed a two-step method.First of all,we used a polyol method to synthesize the butterfly-like Pt-Bi nanoparticles,and subsequently the Bi in Pt-Bi nanoparticles was leached out using the electrochemical method.After the leaching process,the butterfly-like nanoparticles were transformed into the porous Pt nanoframes.It was because that most of the Bi elements would be dissolved by the electrooxidation,and the remained Bi would form bismuth hydroxide(Bi(OH)3 and decorate on the surface of porous Pt nanofames.The generated Bi(OH)3 could promote water to decompose and generate adsorbed OH around the Pt active site,which can enhance CO anti-poisoning ability of Pt.The in situ ATR-SEIRAS measurements and CO striping experiments revealed that the incorporation of Bi(OH)3 in Pt facilitated the oxidative removal of intermediates and contributed to the higher actvity and stability of ethanol oxidation reaction(EOR).4.For EOR in alkaline solution,poor activity and stability still limit the development of Pd in direct alkaline ethanol fuel cells(DEFCs).Therefore,a two-step method has been designed to prepare high activity and stability of PdBi-Bi(OH)3 catalyst in EOR.First,we used the DEG system to prepare necklace-like PdBi nanowires,and then the necklace-like PdBi nanowires were activated in alkaline solution.After the activation,the Bi(OH)3 modified PdBi nanowires can be obtained.the nanowires manifested an exceptional mass activity(5.30 A mgPd-1),and a current density of?1.00 A mgPd-1 can be retained after operating for 20,000 s CA tests,suggesting the outstanding EOR activity and durability.In conclusion,this paper has designed and synthesized metal oxides,noble metal alloys or compounds with different shapes and structures based on the existing issues in the their field.The formation mechanism of TiO2 crystal facets has been deeply studied and discussed,which has the guiding significance to the preparation of metal oxides.The design and control of noble metal alloy materials or compounds,such as Pt and Pd based catalysts exhibit the significance to the development of fuel cells.