Carbon-based Non-noble Metal Materials:Synthesis And Applications In Electrochemistry

Recently,the urgent need for the transformation of traditional fossil energy and the concept of developing an environment-friendly society have been deeply rooted in people's minds.It is extremely urgent to develop clean energy.Researches on efficient conversion and utilization of clean energy,such as fuel cell,metal-air battery,water splitting technology,CO2 conversion technology and N2 fixation technology,et al.)have become hot and difficult points in this field.At present,the above technologies mainly rely on noble metal based catalysts,such as Pt,Ru,Ir,et al,which have remarkable catalytic activity,but the high price and limited reserves cannot support the long-term application.Toward this end,new catalysts should be designed.Carbon supported non-noble metal single-atom electrocatalysts,especially the family of metal-nitrogen complexed carbon(MNC)materials,have high conductivity and unique metal-ligand interaction,which render?100%atom utilization and stimulate strong quantum effects.However,it is still a challenge to obtain single-atom electrocatalysts with high activity,high stability and large-scale preparation.Based on this,this work focuses on the development of non-platinum catalysts,mainly including two aspects:one is the selection of carbon substrate;the other is the regulation of metal or non-metal components.As for the substrate materials,low toxicity and cost formamide is selected to prepare nitrogen doped carbon materials using for chelating metals by solvent thermal method.Calcium carbide(CaC2)is selected to converse topologically into high-crystalline few-layer graphene in water,which can be used as conductive substrate.As for the adjustment of metal component,the influence of metal and non-metal on the ORR performance were studied by using the flexibility of formamide system.And then the synchrotron radiation and electron microscopy technique were used to verify the structure-activity relationship.The specific research content are as follows:(1)Formamide was used to prepare nitrogen-doped carbon materials by the self-polymerization reaction.Then two-dimensional molecular template(melamine)was introduced into the system for dimensional regulation of carbon materials.Also we managed to fabricate high crystalline few-layered graphene from commercialized CaC2.The structure of obtained materials were further studied by TEM,XPS and AFM et al..These two examples of the preparation of carbon materials under mild conditions broaden the idea of the preparation of carbon materials.(2)A scalable and general synthetic method for the fabrication of atomically dispersed formamide-converted transition metal-nitrogen-carbon materials(named as f-MNCs)has been developed through metal-mediated formamide-condensation and carbonization.The method has the advantages of simple operation,strong controllability,low cost and has great potential in practical application.(3)All the f-MNCs single-atom electrocatalysts prepared can be thinly coated onto various carbon and oxide supports to increase conductivity and even production scale.For instance,simply depositing thin layer of f-FeNC and f-NiNC on commercially available oxydic CNT delivered excellent catalytic performance towards oxygen reduction reaction(ORR)and CO2 reduction reaction(CO2RR),respectively.Moreover,due to the flexible applicability of the system to metal types and substrate materials,this method can be extended to the preparation of AC@f-MnNC and SiO2@f-ZnNC,opening avenue for the subsequent development of materials with high specific surface area and high metal utilization.(4)The as-prepared f-MNC materials were pyrolyzed to further crosslink or solidify the structure,and to increase the conductivity at the same time.Assistance of Zn was found of significant role for single-site or dual-sites f-MNC electrocatalysts to further enhance the performance of f-MNC.After high temperature pyrolysis,the treated f-FeCoNC exhibited outstanding ORR activity and stability which were higher than commercial Pt/C in both alkaline and acid media under the same catalyst loading.More importantly,the extraordinary ORR performance was well retained after the f-FeCoNC900 being deposited on an inexpensive activated carbon(AC).Furthermore,the catalytic performance of atomically dispersed MNC materials can be improved through regulating the local electronic structure of M-N4 by neighboring S doping.In summary,a scalable and general synthetic method for the fabrication of atomically dispersed transition metal-decorated formamide-converted nitrogen-carbon materials(f-MNCs)has been developed through metal-mediated formamide-condensation and carbonization.Considering the capability of accommodating various metallic and non-metallic components,the developed methodology provides numerous new possibilities for the large-scale synthesis of single atom catalysts with isolated single-,dual-,triple-metallic sites,or even heteroatom sites for relevant electrocatalysis applications in energy technologies.