Preparation Of Nickel Based Materials And The Performance Of 5-Hydroxymethyl Furfural Electrooxidation

With the continuous development of industrial production,the problems of energy crisis and environmental pollution are becoming more and more serious.The substitution of renewable resources for traditional fossil energy has thus attracted extensive attentions.Biomass,as a kind of renewable resources with abundant reserves and wide distribution,has become the recent reseach object in the field of energy and chemical industry.As one of the important biomass platform compounds,5-hydroxymethylfurfural（HMF）can be oxidized to produce 2,5-furfuric acid（FDCA）which is a high value-added chemical that can replace petroleum-based terephthalic acid and act as a key compound in chemical and pharmaceutical fields.Thermal catalytic oxidation of HMF is widely used for preparing FDCA.However,this route usually involves the use of noble metal catalysts,high temperature,high pressure,oxygen and other harsh reaction conditions,and also produces many by-products.All the limitations will undoubtedly increase the cost of thermal catalytic oxidation of HMF.In comparison,electrocatalytic HMF oxidation reaction（HMFOR）represents a better choice,because the electrooxidation is completely driven by voltage,no additional oxidant is required.Meanwhile,HMFOR holds the advantages of high conversion and selectivity under mild reaction conditions.In addition,HMFOR has a much lower theoretical potential than the competitive oxygen evolution reaction（OER）.OER can be replaced by the HMFOR to couple cathode hydrogen evolution reaction for simualtaneously producing hydrogen and high value-added FDCA.Therefore,it is of great significance to design cost-effective and efficient HMFOR electrocatalysts to promote the utilization of biomass energy.In this thesis,vanadium doped nickel nitride and nickel phosphide-nickel sulfide heterojunction catalysts are designed and in situ grown on conductive nickel foam（NF）for the application in HMFOR.The main research contents are as follows:（1）A V-doped Ni₃N（5%V-Ni₃N）bifunctional catalyst is prepared by hydrothermal-calcination method,which shows excellent catalytic performance for both HMFOR and hydrogen evolution reaction（HER）.When 5%V-Ni₃N is used as catalyst for HMFOR,the conversion of HMF reaches 100%,the yield of FDCA and Faraday efficiency of reach 98%,and the production rate of FDCA reaches 403μmol cm^-2 h^-1 at the potential of 1.475 V vs RHE.After 10 cycles,5%V-Ni₃N still maintains good catalytic stability.X-ray photoelectron spectroscopy and in situ Raman spectroscopy demonstrate that the introduction of V accelerates the surface structural transformation of 5%V-Ni₃N to form active hydroxyl oxide species,thus accelerating HMFOR.DFT calculation further shows that the introduction of V makes the d band center closer to the Fermi level,thus enhancing the OH adsorption energy on the catalyst surface,and finally conducive to the surface reconstruction of the catalyst.When 5%V-Ni₃N is used as the cathode,HER overpotential is as low as 34.8m V.When 5%V-Ni₃N is used as both anode and cathode,the cell voltage required to achieve a current density of 50 m A cm^-2 in the HMFOR-HER system is 250 m V lower than that of the overall water splitting.These findings provide a new idea for the exploration of bifunctional catalysts.（2）A heterogeneous Ni₃P-Ni₃S₂ catalyst for HMFOR is prepared by hydrothermal and phosphorizaiton treatement.The catalyst exhibits excellent catalytic performance for HMFOR.At the potential of 1.425 V vs RHE,the current density reaches 110.0 m A cm^-2,far exceeding the 45.1 m A cm^-2 of precursor Ni₃S₂.The conversion of HMF reaches 97%,and the yield of FDCA and Faraday efficiency exceed 93%.FDCA production rate is 254.5μmol cm^-2 h^-1.The catalyst maintains robust catalytic stability during 8 cycles of electrolysis.The superior performance of HMFOR indicates that the construction of heterojunction could greatly promote the catalytic performance of the catalyst.