Controlled Preparation Of Carbon-Based Atomically Dispersed Transition Metal Catalysts And Electrocatalytic Performance Investigation

Hydrogen energy as an important secondary energy has great significance for building low-carbon society.An ideal pathway to develop hydrogen energy is converting the intermittent and difficult-utilized solar or wind energy to hydrogen energy and storing it.And hydrogen can convert to electric energy through hydrogen fuel cell when it is needed.However,both hydrogen fuel cell and electrocatalytic water splitting require expensive noble metal based catalysts to improve energy conversion efficiency,which restrict the development of related technique.Focusing on the challenge that amounts of expensive platinum-based catalysts are needed in hydrogen evolution reaction and oxygen reduction reaction,this thesis aims to develop low-cost,high efficiency and high durability electrocatalysts,and systemically investigate carbon based atomically dispersed transition metal catalysts,and obtain several high-performance catalysts.The main content and conclusion are as follows:(1)Iron,copper dual metal single atom catalyst is prepared through ligandmediated method using commercial carbon black as substrate.Compared with individual iron single atom catalyst or copper single atom catalyst,Iron,copper dual metal single atom catalyst exhibits better oxygen reduction reaction performance.Density function theory calculations indicate that there exists synergistic effect between adjacent iron and copper atoms,which increase the electron density of iron atoms and optimize the binding energy of oxygen reduction intermediates,thereby increasing the oxygen reduction performance.Besides,the influence of different carbon substrates for oxygen reduction reaction is also investigated,and it is found that high surface area carbon substrates with hierarchical pores are more suitable for oxygen reduction reaction which attributes to it can fully expose active sites and facilitate reactants mass transfer.This work provides basis for rationally designing high performance oxygen reduction electrocatalyst and investigating the relationship between structure and function.(2)A macropore-rich carbon material with ultrahigh surface area is prepared through pyrolyzing MOF-5 at negative pressure.Then several single atom catalysts containing chromium,manganese,iron and cobalt are prepared using this macropore-rich carbon material as carbon substrate.The electrocatalytic oxygen reduction performance and durability in perchloric acid electrolyte are compared,and it is found that chromium single atom catalyst exhibit the best oxygen reduction performance and durability.Accelerated durability test find that durability of transition metal single atom catalyst strong related to dissolved metal percentage.The lower metal dissolution,the higher durability will be obtained.This work provides a new idea for developing high performance,high durability non-noble metal oxygen reduction electrocatalyst in acid condition.(3)Platinum-loaded vertical graphene array electrodes with different platinum dispersion degree are prepared through atomic layer deposition method.The hydrogen evolution reaction performance of this self-supported electrode is increasing with the increase of platinum content,but the platinum mass activity firstly increased and then decreased with the increase of platinum content,and it achieves the highest mass activity when platinum single atoms and clusters coexisted in electrode.Besides,it is clarified by control experiment that the vertical array structure can expose more active sites,increase the electrochemical active surface area and facilitate reactants mass transfer,thereby boost hydrogen evolution reaction performance efficiently.This work provides new idea for designing lowcost and high-efficient hydrogen evolution reaction catalysts.