Metal Cobalt Loaded On Nitrogen-Doped Graphene Oxide For Oxygen Reduction Reaction Activity

New energy technology was developed vigorously to solve problems such as energy shortage and environmental pollution.Fuel cells are considered to be the most promising new energy technologies in the 21st century.The oxygen reduction reaction plays a key role in the energy conversion and fuel cells storage.It is very low that the oxygen reduction activity of non-precious metal materials in the cathode oxygen reduction of fuel cells.In this paper,the two-dimensional structure of graphene is modified to obtain a matrix.Cobalt loaded nitrogen-doped graphene oxide(Co/NGO)composite materials is prepared by magnetron sputtering.Aim of the paper is to increase oxygen reduction activity.The main research contents and conclusions are as follows:1)Four kinds of preparation samples were selected to prepare modified graphene.The morphological characteristics of graphene oxide(GO),nitrogen-doped graphene(NG),and nitrogen-doped graphene oxide(NGO)are maintained of the multilayer wrinkles.The order of oxygen reduction activity of the four samples is RGO<GO<NG<NGO.The NGO has the best oxygen reduction activity,because its electrochemical surface area is 86.5 cm2.The initial potential and the half-wave potential is 0.88 V and 0.78 V respectively.The structural characteristics of graphene oxide are retained in the NGO sample,moreover the doping of nitrogen plays a role in increasing the oxygen reduction activity.2)The effects of nitrogen content and reaction temperature on the oxygen reduction activity of NGO were further investigated.The composition of nitrogen content is observed.So the nitrogen content of NGO-20,NGO-30 and NGO-50 remaine between 3.8%and 4.2%.Since the variation of nitrogen content in this paper does not change the multi-layer fold morphology,the electrochemical surface areas of NGO-10,NGO-20,NGO-30,and NGO-50 are similar.Changing the preparation temperature has a great influence on the nitrogen-doped graphene oxide.The nitrogen doping content increases from 1.191%to 3.851%with increasing temperature.The order of oxygen reduction activity is NGO-35<NGO-55<NGO-75.So the oxygen reduction activity increases by nitrogen doping.3)The metal cobalt is loaded on the surface of the substrate by magnetron sputtering to further enhance the oxygen reduction activity of the NGO.From the topographical analysis,Co does not change the morphology of the matrix itself,which is caused by the low load of Co.The order of oxygen reduction activity is Co/C<Co/NG<Co/GO<Co/NGO.The electrochemical surface area and the initial potential of Co/NGO is 97.55cm2 and 0.86V respectively.The corresponding kinetic current is 1.17 mA·cm-2 at 0.8V The number of transferred electrons is 4.20.The Co/NGO sample changes the electronic structure of Co due to the interaction between the NGO matrix and Co in the reaction.Meanwhile,it increases the active site and the oxygen reduction activity.4)The effect of Co loading and sputtering power on the activity of Co/NGO oxygen reduction reaction is further investigated.The oxygen reduction activity of Co/NGO is increased,which is caused by an increase in the amount of loading due to an increase in sputtering time.The oxidogen reactivity is Co-10<Co-15<Co-20.The starting potential and the half-wave potential of Co-20 is 0.86V and 0.79 V respectively.For Co/NGO sputtered by different powers,the initial potential is from 0.87V to 0.86V The half-wave potential is from 0.79V to 0.78V.Because after changing the power,the particle size,load and oxygen reduction activity is similar to before.