Preparation Of Carbon-based Catalysts And The Performance Study On Cathodic Oxygen Reduction Reaction For The Synthesis Of Hydrogen Peroxide

As an important green product and chemical raw material,hydrogen peroxide is one of the 100 most important chemicals in the world.The current industrial synthesis of hydrogen peroxide by anthraquinone method uses precious metals as catalysts,and the high concentration of hydrogen peroxide synthesized by this method poses a challenge to post-transportation.The direct hydrogen-oxygen synthesis method has the risk of explosion,and the electrochemical method is a green and non-polluting hydrogen peroxide synthesis method developed in the last two years,which can directly synthesize low concentration of hydrogen peroxide in situ for direct use.Carbon materials are abundant and inexpensive,the surface structure and properties are relatively unique and can be fine-tuned,therefore they are considered as promising alternatives to noble metal catalysts in hydrogen peroxide electrochemical synthesis.Both mesoporous hollow carbon nanospheres and graphene oxide,as common used carbon materials,which have large specific surface area,excellent electrical and thermal conductivity,and are widely used in catalysis.Firstly,this thesis presents mesoporous hollow carbon nanospheres with different specific surface areas and surface compositions prepared by soft template method with different molar ratios of tetrapropyl orthosilicate and tetraethyl orthosilicate,and their surface surface structures and compositions were analyzed by SEM,TEM,XPS,BET,Raman and other characterization methods.The mesoporous structure is favorable for the adsorption of O₂ molecules and the desorption of H₂O₂ molecules,which effectively prevents further reduction of*OOH;the large specific surface area is favorable for the dispersion of active sites;Graphitic N on the surface is the active site of the reaction.The oxygen reduction reaction test by rotating ring-disk electrode showed that it has a high selectivity of hydrogen peroxide proves this,but the activity is very low.Then,loaded with transition metal Co and doped heteroatoms N/P on mesoporous hollow carbon nanospheres by impregnation method.The Co-N_x coordination promoted the atomic dispersion of Co;the high electronegativity of P modulated the adsorption properties of Co,and the performance tests showed that the activity was substantially increased.Secondly,in this thesis,graphene oxide was prepared by electrochemical method,which is a simple and non-pollution method without introducing metal ions on graphene oxide compared with the common Hummers method.SEM,TEM,and XPS characterization methods showed that the structure and composition were similar to those of commercial graphene oxide.The synthesized EC GO was tested with low activity in oxygen reduction reaction using a rotating ring-disk electrode.The graphene oxide was then loaded with transition metal Co and doped with heteroatom by impregnation method the N used to anchor Co to form monodisperse Co-N_x active sites,and the performance tests for the oxygen reduction reaction showed a significant increase in activity compared to the unloaded graphene oxide.