Study On The Preparation And Performances Of Co₃O₄ Based Catalysts For Oxygen Reduction In Alkaline Exchange Membrane Fuel Cell

Anion exchange membrane Fuel cells(AEMFC)can not only have advantages of environmental friendly and high conversion rate,but also can be used non noble metal cathode as catalyst.Thus,the manufacturing cost is greatly reduced.It become more concerned energy technologies of news.ORR catalyst is one of the key components of AEMFC,The development of new and low cost ORR catalyst has important theoretical and practical significance to promote the development of AEMFC.In the paper,first of all,Co3O4 was synthesized by liquid phase precipitation method,a series of carbon supported Co3O4 catalysts with different mass ratios was prepared by ultrasonic method.The synthetic method is simple and environmental protecting.The optimal condition(The optimal content of Co3O4 was 3%)of preparation of Co3O4/C catalyst specific surface area is 146.26 m2g-1,the polarized current density was 2.93 mA·cm’2(@-0.8 V),the electron transfer number of oxygen reduction reaction is 2.51.Based on this,core-shell catalyst of GO encapsulted Co3O4(Co3O4@GO)was synthesized as ORR catalyst by ultrasonic method.When content of GO was 5%of content of Co3O4,Co3O4@GO/C catalyst specific surface area is 220.54 m2g-1,which exhibited best activity for ORR,the polarized current density was 4.3 mA·cm-2(@-0.8 V).In order to further reduce cost,GO was instead of g-C3N4,Co3O4@g-C3N4/C catalysts was prepared by same method.The results show that with g-C3N4 content increasin,the polarized current density enlarged gradually,and then,they all reduced.When content of g-C3N4 was 3%of content of Co3O4,Co3O4@g-C3N4/C catalyst specific surface area is 172.31 m2g-1,which exhibited best activity for ORR,the polarized current density was 3.65 mA·cm-2(@-0.8 V).After the combination of g-C3N4 with the sulphur,the hybrid catalyst exhibited better catalytic activities for ORR.When the rate of S and g-C3N4 is 1:3,the specific surface area increases to 201.37 m2g-1,the polarized current density increases to 4 mA-cm’2(@-0.8 V).Noticed that the catalytic activity of the three catalysts for ORR was Co3O4@GO/C>Co3O4@S-g-C3N4/C>Co3O4@g-C3N4/C.Compared with Co3O4/C,the performance of and were increased by 48%,37%,26%,respectively.The electron transfer number of the optimal condition of preparation of three kinds of catalyst was 3.5,3.6,3.65,which indicates that the ORR occurred on catalyst was a diffusion controlled process related to an 4e-pathway.It showed that the three kinds of catalyst has good selectivity for oxygen.Therefore,after 1000 times of cyclic voltammograms test,the performance of the catalyst were not attenuation,demonstrating its excellent cycle stability.