The Development And Applications Of Novel Nano-Electrodes In Electro-Catalysis Systems

Electro-catalysis technology takes advantages of energy conservation and environmental protection.Also,it is facile to control in precise,and couple with other technologies like photo-catalysis.So that it is widely used in the conversion and storage of clean energy,as well as the treatment of organic pollutants.How to select appropriate electrode material and design specific morphology and structure to optimize its performance in corresponding application is the emphasis in current electro-catalysis work.In this thesis,two efficient electro-catalysts were synthesized through simple and mild solution-phase methods,and their mechanisms were studied in-depth to provide scientific basis for practical applications.On one hand,for electro-catalytic oxygen reduction reaction,commercialized Pt nano-polyhedra single crystal electrode as precious metal is the first choice.The exposed facets of Pt electrode are simply modified and then the nucleation and growth mechanism is discussed.Next,TiO2 nano-polyhedra single crystal electrode as transitional metal oxide is a more cost-effective choice.The integrated modification is made by adjusting the exposed facets,doping defects and complexing with substrates.And a two-electrons transfer mechanism with the generation of hydrogen peroxide is explored.For electrochemical detection of trace bisphenol A,the exposed facets of TiO2 electrode are modified,and further functionalized with molecular imprinting,in order to match the standards as an analytical method.On the other hand,inspired by the generation of H2O2 with TiO2 cathode,the in-situ organic Fenton system for synergistically electro-catalytic degradation of phenol with the commercialized carbon felt,is surveyed.A novel mechanism for phenolic degradation with remarkable improvement is proposed.The main contents and achievements of this thesis are as follows:1.Conducting the controllable synthesis of sub-5 nm Pt nano-polyhedra.Sub-5 nm Pt cuboctahedra with superior purity and uniformity were synthesized through polyol reduction under thermodynamic control with adequately high temperature.The use of K2PtCl4 as precursor,PVP as colloidal stabilizer,KBr as capping agent and EG as both reductant and solvent,is responsible for the formation of the high-quality products.The active precursor and mild reductant make the size decrease to 4.06 nm and the yield increase to 56.6%,due to the fast kinetics of reduction.Meanwhile,the appropriate amounts of colloidal stabilizer and capping agent ensure the high dispersion.Furthermore,this method is demonstrated to be facile and robust within rational adjustment of kinetics.So that the products can be easily reproduced and enlarged.This work not only provides possible high-activity electrocatalyst for commercialization,but also for systematically comprehension of the influence of low-index facets on electrocatalytic performance.2.Exploring defective TiO2-x single crystals exposed by high-energy {001}facets for electro-catalytic oxygen reduction reaction.Nano-structured TiO2,self-doped by oxygen vacancies and selectively exposed with the high-energy {001} facets,were synthesized through alcoholthermal method,which exhibits competitive oxygen reduction activity,durability and tolerance to methanol.Combining the electrochemical tests with density-functional theory calculations,we elucidate the defect-centred oxygen reduction reaction mechanism for the superiority of the reductive {001}-TiO2-x nanocrystals.Our findings may provide an opportunity to develop a simple,efficient,cost-effective and promising catalyst for oxygen reduction reaction in energy conversion and storage technologies.3.Realizing facet-tailored TiO2 single crystals engineered by inorganic-framework molecular imprinting sites for electrochemical sensing of trace bisphenol A.The high-energy {001} facets exposed TiO2 single crystals with specific inorganic-framework molecular recognition ability were prepared through hydrothermal method as the electrode material to detect bisphenol A,a typical and widely present organic pollutant in the environment.The oxidation peak current was linearly correlated to the BPA concentration from 10.0 nM to 20.0 μM(R2=0.9987),with a low detection limit of 3.0 nM(S/N=3).Furthermore,it exhibited superior discriminating ability,high anti-interference capacity,and good long-term stability.Its good performance for BPA detection in real environmental samples,including tap water,lake and river waters,domestic wastewater,and municipal sludge,was also demonstrated.This work extends the electro-catalytic applications of TiO2 and suggests that this material could be used as a highly active,stable,low-cost,and environmentally benign electrode material for electrochemical sensing.4.Developing in-situ organic Fenton catalytic reactions triggered by anodic polymeric intermediates for water purification.An in-situ organic Fenton catalytic approach triggered by the aromatic intermediates,e.g.,benzoquinone and hydroquinone,which formed in the electrochemical oxidation of phenol as organic activator of H2O2 is developed.By taking phenol as a target pollutant,we demonstrate that the developed approach not only improves the pollutant degradation performance,but also refreshes the anode with a better catalytic stability.Our findings might provide a new opportunity to develop a simple,efficient and cost-effective approach for water purification.