Carbon-based Electrodes And Their Structure-function Relationship In Electrocatalytic Biomass Conversion

Biomass is a new type of renewable non-fossil resource and the effective utilization of biomass resources will not change the carbon balance of the existing ecosystem.Therefore,it is considered as a potential substitution for fossil resources to mitigate climate risks and meet the requirements of sustainable development.At present,the synthesis of high value-added platform chemicals from biomass as raw materials has become a new green production mode.As one of the important representative platform products of biomass resources,5-hydroxy methyl furfural(HMF)can be used as raw materials to produce a variety of high value-added compounds,such as 2,5-furan dicarboxylic acid(FDCA)and 5-formyl-furan-2-formic acid(FFCA).They have been identified by the US Department of Energy as one of the 12 most valuable platform chemicals with the potential to replace terephthalic acid derived from fossil resources in the production of polyesters,polyamides and pharmaceuticals.The electrochemically catalyzed HMF oxidation process can be carried out under mild conditions,meeting the concept of green chemistry.However,the field of electrocatalytic HMF oxidation is still in the preliminary research stage,and facing many scientific challenges.For example,difficult product separation due to low yield and selectivity of the target product,high reaction overpotential leading to high energy consumption,the strongly alkaline electrolyte causing acid waste in the separation process,the unclear reaction mechanism of electrocatalytic process,the controversial reaction path,the difficulty in controlling the selective oxidation process,and the low reaction rate needing to be improved.Therefore,aiming at above problems,this study firstly prepared two Ni/Carbon paper(CP)catalysts by electrodeposition technology that could be used for exploration of structure-activity relationship and active site.The various physicochemical property characterization results confirmed that the active site for the electrocatalytic HMF oxidation is high-valenced Niδ+.The nanosheet-like Ni/CP catalyst was used to reduce the pH of electrolyte from 14 to 13,and FDCA with the yield of 99.4%and selectivity of 100%could be obtained under a lower overpotential.In addition,the reaction path was determined by theoretical calculation of the reaction energy barrier(Chapter 3).Secondly,Ni-based catalysts with more active sites were prepared by hydrothermal method,and the electronic structure of active sites was regulated by doping Cu atoms,which further improved the yield of FDCA and reduced the overpotential of the reaction(Chapter 4).Subsequently,non-metallic catalysts with mild and adjustable oxidation capacity were prepared by electrodeposition,and higher value-added FFCA intermediates were synthesized by electrochemical methods for the first time(Chapter 5).Finally,the proposed kinetic regulation strategy effectively increased the rate of product formation,and the use of pH asymmetric acid-base system not only improved the total Faraday efficiency,but also greatly reduced the reaction overpotential and saving energy consumption(Chapter 6).