Study On The Overall Water Splitting Performance Of Iron-based Metal Compound Electrocatalysts Supported By Vertically Aligned Heteroatom-doped Graphene Array

The goal of carbon peak and carbon neutralization has forced people to vigorously develop green and low-carbon energy.Among various green energy sources such as solar energy and wind energy,hydrogen energy has become a promising low-carbon energy source due to its high combustion calorific value and no strict requirements for hydrogen production sites.In various hydrogen production methods,water splitting is only one that no pollution to the environment,but it requires the use of catalysts to reduce additional energy consumption and increase the reaction rate.Currently noble metal-based electrocatalysts exhibit the most excellent electrocatalytic performance,but the low reserves and high cost limit their large-scale applications in industry.Therefore,it is necessary to develop low-cost and high-performance non-noble metal-based electrocatalysts to replace the noble metal-based electrocatalysts.In this work,a series of composite electrocatalysts is prepared by using different heteroatoms doped vertically aligned graphene arrays to support iron group metal phosphides（IMPs）and iron group metal borides（IMBs）for overall water splitting in a wide p H range.The following two aspects are mainly studied:（1）A variety of heteroatom-doped vertical graphene arrays（X-r GO,X=N,P,B,S,O）are successfully prepared by a one-step directional freezing process and heat treatment method.Graphene has a good vertical structure and has sufficient mechanical strength to serve as a substrate for self-supporting materials;Fe Co Ni P nanoparticles are supported on the above heteroatom-doped vertical graphene arrays by chemical deposition（Fe Co Ni P@X-r GO,X=N,P,B,S,O）.The surface morphology and microstructure of the samples are studied by SEM,TEM and other characterization methods,founding that Fe Co Ni P nanoparticles have uniform particle size and uniform distribution on the graphene substrate;Catalytic performance of Fe Co Ni P@X-r GO（X=N,P,B,S,O）is studied by LSV,CV and EIS in a wide p H range,and Fe Co Ni P@P-r GO has the best performance,which is very close to Pt/C@P-r GO and Ir O₂@P-r GO;The intrinsic mechanism of the excellent catalytic performance of Fe Co Ni P@P-r GO is investigated by DFT calculations,and found that there is a synergistic effect between P in Fe Co Ni P and P in P-r GO.This work studies the synergistic effect between IMPs and different heteroatom doped graphene,finds a suitable substrate for IMPs composite electrocatalyst,gives an enlightenment for design of other transition metal based electrocatalysts.（2）The heteroatom-doped graphene vertical array-supported Fe Co Ni B nanoparticle composite electrocatalyst（Fe Co Ni B@X-r GO,X=N,P,B,S,O）is prepared by the same chemical deposition method using the X-r GO（X=N,P,B,S,O）of the above experiments.The surface morphology and structure of the samples are studied by SEM,TEM and other characterization methods.Fe Co Ni B@B-r GO has a good vertical structure,and the Fe Co Ni B nanoparticles are evenly distributed on the graphene substrate with the particle size is uniform;The overall water splitting performance of Fe Co Ni B@X-r GO（X=N,P,B,S,O）in a wide p H range is studied by various electrochemical testing methods such as LSV,CV,EIS;The catalytic performance is even higher than that of Pt/C@B-r GO and Ir O₂@B-r GO.XPS results show that the reason why the excellent performance of Fe Co Ni B@B-r GO is that B in B-r GO also transfers electrons to metal sites.Compared with Fe Co Ni P@P-r GO in the previous chapter,the performance of Fe Co Ni B@B-r GO is further improved,which may be due to the high electron density of metal sites and defect-rich amorphous structure of Fe Co Ni B@B-r GO.This work provides an enlightenment for the rational design of non-noble metal-based electrocatalysts,promotes the application of non-noble metal-based electrocatalysts in the water electrolysis industry,boosts the development of electrolytic water hydrogen production industry and the use of low-carbon environmental protection energy.