Structural Desigen And Nitrate Reduction Performance Study Of Iron-based Electrocatalysts

Nitrate is highly stable and persistent in water,endangering human health and aquatic ecosystems.Due to its high reliability and efficiency,electrochemical nitrate reduction reaction（NO₃RR）is considered to be the best choice for mitigating excess nitrate in water.Iron-based nanocatalysts stand out in replacing traditional noble metals due to their non-toxicity,easy availability,recyclability,low cost,and high reduction ability.Despite the fact that researchers have carried out various iron particle modification designs such as loading,doping,and assembly,most studies still suffer from scientific difficulties such as poor durability,slow electron transfer rate,and low catalytic efficiency of iron-based electrocatalysts,making it difficult to achieve satisfactory nitrate reduction performance.Thus,in this thesis,we prepared a series of iron-based electrocatalysts by loading with conductive substrates,interfacial modification,and heteroatom doping,and investigated the relationship between the structure of iron-based electrocatalysts and the nitrate reduction performance in detail.The specific contents are as follows:（1）Conductive materials such as graphite felt,carbon cloth,carbon paper,nickel foam,copper foam,and iron foam were used as carriers in the hydrothermal reaction and thermal reduction strategy to grow iron particles in situ.A series of self-supported iron-based composite electrocatalysts were developed to achieve varying degrees of nitrate reduction performance,with needle-like iron particles（Fe/GF）loaded on a graphite felt matrix achieving the best nitrate reduction performance,which was attributed to improved dispersion and electrical conductivity of Fe nanoparticles on the graphite felt matrix to avoid agglomeration between active sites,and 67.7%nitrate removal.（2）The performance and mechanism of this cathode material for electrochemical NO₃RR were thoroughly investigated using a graphene nanochainmail-protected iron nanoparticle catalyst（Fe@Gnc）.This encapsulation structure can protect Fe nanoparticles from being easily attacked by other ions in the electrolyte solution as well as oxygen,and it can also reduce Fe nanoparticle leakage.After up to 40 cycles,Fe@Gnc can achieve 72.7%nitrate removal and 99.6%nitrogen selectivity,with retention of 96%nitrate removal and nitrogen selectivity.（3）In order to increase the electron transfer rate,the surface modification design of iron nanoparticles protected by graphene nanochainmail via B atoms（Fe@BG）was used.Boron enters the graphene lattice,and the local electron deficient environment at the doping position alters the original electronic structure,allowing for fast electron transfer between the iron-carbon interface.Among these,Fe@BG-3 has an excellent nitrate removal rate and nitrogen selectivity,as well as a fast removal rate and long-term stability.In only 12 hours,72.5%nitrate removal and 97.2%nitrogen selectivity can be achieved.When the reaction time is increased to 24 hours,the nitrate removal rate meets national water purification standards.