Synthesis Of Co_0.85Se Supported By Nitrogen Doped Carbon/graphene As ORR/OER Bifunctional Catalysts And Their Properties

This thesis aims to explore the bifunctional catalytic activity of the Co_0.85Se supported by nitrogen doped carbon/graphene.The bifunctional catalysts were synthesized respectively by hydrothermal method and calcining method.The structures,morphologies and properties of the catalysts were tested by XRD,SEM,XPS,Raman and electrochemical measurements.The main results are as follows.?1?Products with different content of impurity phase and different grain size were synthetized under different hydrothermal conditions.Analysis showed that less impurity in the product,smaller grain size,and better dispersion of the product,led to better OER catalytic activity.And the test showed that the pure Co_0.85Se had no ORR activity;?2?Combining graphene oxide with ZIF8,the nitrogen doped carbon/graphene was obtained by calcination method.Changing the distribution of the polyhedron formed by ZIF8 on the surface of graphene makes the best sample NGC-80.Measurements showed the porous structure and different forms of nitrogen,which is the essential cause of its better ORR catalytic activity;?3?Nitrogen doped carbon/graphene support Co_0.85Se was obtained by hydrothermal reaction in the presence of hydrazine hydrate by mixing nitrogen doped carbon/graphene with cobalt source and selenium source.The catalyst's bifunctional activity was observed.Hydrothermal reaction could not only increase the degree of disorder,it also changed the form of nitrogen.And the Co_0.85Se had the role of anchoring for graphene.When the ratio of Co and carrier carbon was 1mmol:80mg,the reaction time was 12h,the product had the best performence;?4?The products under the ZIF67 system was synthesized by one-step selenylation method.Measurement showed selenylation damaged the morphology of ZIF polyhedron structural unit,and the existence of graphene could increase the dispersion.Through multiple groups of experiments,it can be found that when the addition of cobalt was 2.5mmol,the temperature of selenylation was 700?,and the ratio of 2-methylimidazole:Co was 16:1,the sample had the best bifunctional activity.Its bifunctional activity was analyzed,and the ?E was calculated at 0.751V,the transfer electron number was about 3.2.Chronoamperometry and chronopotentiometry showed the catalyst had much better stability than commercial catalysts.