Preparation Of Co-based Compounds/carbon Nanofibers And Its Application In Water Splitting

With the continuous growth of global energy demand,besides the increasing exhaustion of non-renewable energy sources such as coal and petroleum,and their negative impact on the environment,it is urgent to find efficient and low-cost clean and sustainable energy production and storage technologies.Among the known energy sources,hydrogen is regarded as the most promising energy source in the 21st century,due to its characteristics of highest energy density,simple preparation,clean products and easy storage.The technology for producing hydrogen from electrolyzed water is one of the most promising hydrogen production technologies in the future.For this technology,it can recycle and reuse water resources,low cost,simple equipment,and the only by-product is oxygen,which has no negative impact on the environment.Noble metal-based catalysts are the most excellent electrolytic water catalyst materials,but their scarcity limits their further applications.Transition metal-based catalysts have become widely used as electrode materials which are expected to replace precious metal-based catalysts due to their wide range of sources,good catalytic activity,and ease of preparation.Among them,cobalt is widely used in electrolytic water catalysts because of its excellent catalytic performance and easy modification.In this paper,a series of cobalt-based compounds/carbon nanofiber hybrid materials are prepared by electrospinning and high-temperature carbonization processes to study the growth and crystallization behavior of catalysts on carbon fibers,and their catalytic performance in electrolytic water.(1)Exploring the growth and crystallization behavior of single transition metal element(TM)on carbon nanofibers(CNFs).Cobalt-based nanoparticle-supported carbon fiber hybrid materials were prepared by electrospinning and high-temperature carbonization processes.The growth and crystallization behavior of single cobalt element on the fibers was studied.This research is generally applicable to transition metal nanocatalytic crystals such as Fe,Co,and Ni for their growth on carbon fiber.The prepared hybrid material is used in electrocatalytic hydrogen evolution to study its catalytic performance.(2)Cobalt and nickel are used to prepare alloy catalysts to improve the catalytic performance of cobalt-based nanoparticle-supported carbon fiber hybrid materials.The in-situ growth of cobalt-nickel alloys on carbon fibers(CNFs)can prevent the agglomeration of CoNi alloy nanoparticles,so that the hybrid material has a large number of uniformly distributed nano-catalytic crystals,which providing a large number of active sites for catalytic reactions.Compared with the Co-CoO/CNFs and Ni-NiO/CNFs hybrid materials prepared by the Co element or Ni element alone,the prepared CoNi alloys on carbon fibers are smaller in size and more uniformly distributed.Besides the oxidation state of some Co and Ni will change to the cobalt-nickel alloy state.The hybrid material was used in the electrocatalytic hydrogen evolution,and the influence of different proportions of cobalt and nickel on the hydrogen evolution performance of the hybrid material was studied.This study provide ideas for the preparation of high-performance transition metal hybrid materials.(3)Study on the preparation and catalytic performance of ternary carbide-supported carbon fiber hybrid materials prepared by double transition metal elements.Co6W6C/CNFs ternary hybrid materials were prepared by using PAN as the substrate and reaction raw materials through electrostatic spinning and high-temperature carbonization.During the high temperature process,Co,W and C in the carbon fiber are combined to form Co6W6C crystal.Here,PAN nanofibers serve as both a base material and a reaction vessel,and also provide a carbon element for the formation of catalytic crystals.The hybrid material was observed through morphological characterization.The diameters of Co6W6C nanoparticles were all within 20 nm and were evenly distributed on the carbon fibers.The Co6W6C nanoparticles were all wrapped by carbon layers,which could provide a large number of active sites for the electrocatalytic reaction.In the catalytic hydrogen evolution test,the catalytic crystal is protected from being attacked by the electrolyte and has excellent catalytic stability.