Preparation Of Transition Metal Oxide Electrocatalysts By Atomic Layer Deposition And Performance Of Oxygen Reduction And Evolution Reaction

Energy and environment are two major problems in the world today.The increasing scarcity of petroleum resources and the aggravation of the greenhouse effect caused by the excessive emission of polluting gases have made the development and utilization of new energy and technology of green environmental protection a very urgent research topic for the sustainable development of the world.Hydrogen-oxygen fuel cells have important application prospects because of their large specific capacity.Cathode electrode reaction has high overpotential,which significantly affects the battery,so improving the electrode reaction efficiency and reducing the overpotential of the electrode to increase the energy efficiency of the battery has become a key scientific problem to be solved in the development and application of hydrogen oxygen fuel cells.Inaddition,hydrogen and oxygen are the fuels for the cells,so the source and acquisition are of great significance.The results show that the over-potential of water splitting can be reduced and the reaction process can be accelerated by using appropriate electrocatalysts,resulting in reduced energy.?1?N-CoOx/CNTs electrocatalysts were in situ prepared by plasma-enhanced atomic layer deposition?PE-ALD?for oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?.The preparation method is simple and easy to operate,and at relatively low temperature.The results show that:1.The N-CoO grew uniformly on carbon nanotubes and have good dispersibility;2.The oxygen reduction and oxygen evolution tests using RDE and RRDE in alkaline system had better performance.The results showed that the oxygen reduction reaction is a 4-electron reaction,and the performance is similar to that of commercial Pt/C.3.The toxicity test of N-CoOx/CNTs and commercial Pt/C showed that the current density decreased by only 4%and 20%for Pt/C after adding methanol.4.After cyclic stability test,the current of N-CoOx/CNTs decreased by 5%and that of Pt/C decreased by 11%after 10000 s under the same conditions.5.The overpotential of the OER after N doping was 420 mV,which was similar to that of the most transition metal oxide catalysts reported at present,compared with the CoOx/CNTs without N doping,which was 455mV.6.The stability test showed that the current had not decayed after 4.5 hours at the current density of 10 mA cm^-2.It can be concluded that both for ORR and OER,N-CoOx/CNTs showed excellent electrocatalytic performance.?2?The electrocatalyst of CoOx/FeOx/CNTs was prepared by PE-ALD.The results show that:1.Two layers of metal oxides grew uniformly on carbon nanotubes,and had good dispersion.2.OER tests showed excellent electrocatalytic performance under alkaline conditions.The overpotential of CoOx/FeOx/CNTs at current density of 10 mA cm^-2 was only 308 mV,which was higher than that of single metal oxide?84mV?CoOx/CNTs?and 98 mV?FeOx/CNTs?,respectively?.3.The stability of CoOx/FeOx/CNTs at 10 mA cm^-2 was tested.After 9 h,the current still did not attenuate,while the commercial catalyst RuO₂ decreased by 10%.It can be concluded that the OER stability of the two metal oxides is better.It has been proved by characterization that the composite metal oxides with heterojunctions had excellent OER properties and stability.?3?The samples of TiO₂/Co₃O₄/Ti were prepared by atomic layer deposition and hydrothermal method.Ti foil with strong stability was used as the matrix material,on the one hand,it can be applied as a free-binder matrix material;on the other hand,it will accelerate the electron conduction rate and improve the performance of electrocatalytic reaction.At the same time,an amorphous layer of titanium dioxide can be grown on the surface of the material to ensure that the material does not fall off and agglomerate in the catalytic process.The results show that:1.Through XRD,SEM and TEM characterization,Co₃O₄ nanowire arrays were successfully grown on Ti foil by hydrothermal method and an amorphous layer of titanium dioxide was grown on the surface of the arrays by atomic layer deposition.2.Under the condition of 0.1 M KOH electrolyte,the OER performance of the material were characterized by electrochemical characterization.The prepared catalyst had excellent electrocatalytic performance,especially for the cyclic stability.After 18 h cyclic test,the performance of the electrocatalysts coated with titanium dioxide did not decrease.While the current density of the electrocatalysts without titanium dioxide decreased to75%of the initial current density after 5 h.