| Zinc-air battery is a mature and promising energy technology due to its high energy density,large capacity,low price and pure product.The lag reaction kinetics of cathodic oxygen reduction seriously affects the performance of zinc-air battery,so the use of electrocatalysts is particularly important.At present,the most commonly used catalyst is Pt/C catalyst.But metal Pt is too expensive to put into large-scale commercial applications.In addition,under long-term and high-pressure working conditions,the carbon-based carrier is easily oxidized,resulting in inactivation of the battery powder,the agglomeration and shedding of nanoparticles.Then the titanium sub-oxide(TinO2n-1)based catalyst carrier with high catalytic activity,corrosion resistance,high oxidation resistance and wide electrochemical stable potential window attracted our attention.Among them,the performance of Ti4O7 is excellent and it has a very good application prospect which is necessary for improving the performance and cycle life of the zinc-air battery.In this paper,we focus on the preparation of Ag@Ti4O7 nanocomposite catalyst in order to improve the catalytic efficiency while reducing costs.The hydrothermal method was used to grow TiO2 precursor and Ti4O7 carrier was synthesized by high temperature carbon reduction method.The Ag nanoparticles were modified on Ti4O7 carrier by reduction method and finally electrochemical characterization test was performed.The main conclusions of this paper is following:(1)The TiO2 precursor grown by the hydrothermal method has high purity,uniform morphology with a size of 30-50 nm.Ti4O7 carrier was synthesized by high temperature reduction method with carbon black as reducing agent.Trial and error,single-phase pure Ti4O7 carrier can be produced with a size of 300-500 nm,when the molar ratio of C/TiO2 is 1.7:1,the reaction temperature is 1200℃,the reaction time is 3 h,and the gas flow rate is 500 mL/min.(2)Ag nanoparticles were modified on Ti4O7 carrier by chemical reduction method.In the preparation process,the selection of reducing agent type and reduction method has a great influence on the synthesis of Ag@Ti4O7.Experiments showed that NaBH4 was too reductive and not affected by temperature or other factors.1%trisodium citrate is the most suitable catalyst for the preparation of Ag@Ti4O7 nanocatalyst at 100℃ reaction condition.In the synthesis results,the Ag nanoparticles with uniformed and equiaxed size were coated well on the carrier.(3)The electrochemical properties of Ti4O7 carrier and Ag@Ti4O7 nanocatalyst were characterized.Ag@Ti4O7 nanocatalyst is 1.63 times more catalytically than Ti4O7 carrier.The catalytic reduction of oxygen by Ti4O7 and Ag@Ti4O7 is controlled by the diffusion process of O2.They all have excellent anti-alcoholic poisoning properties.The process of catalytic oxygen reduction reaction by Ti4O7 carrier has both 4e-path and 2e-path,while Ag@Ti4O7 nanocatalyst has only 4e-path.The synergistic effect between Ag and Ti4O7 changed the reaction path of oxygen reduction and improved the catalytic efficiency.Ag@Ti4O7 nanocatalyst also has a high cycle stability in the zinc-air battery. |
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