Preparation And Performance Study Of Cobalt-based Electrocatalysts For The Oxidation Of Wood Derived 5-hydroxymethylfurfural

As one of the lignocellulosic biomass resources,accounting for about 30% of its total volume,wood residues are widely distributed,abundant in reserves,and have great potential for utilization.Fully utilizing these resources can not only significantly alleviate the pressure caused by energy shortage,but also effectively reduce the waste of resources and pollution of the environment.Compared with the utilization of wood residue in the traditional wood-based panel industry,the efficient refining of wood residue components into high value-added chemicals and downstream quality upgrading have also received much attention in recent years.The 5-hydroxymethylfurfural(HMF)prepared by converting cellulose fraction from wood residues is an important bio-based platform chemical that can be value-added into many high value-added products,among which 2,5-furandicarboxylic acid(FDCA)is an important monomer for the synthesis of green and degradable polymers.Therefore,the development of efficient conversion methods for the preparation of FDCA from wood-derived HMF is of great significance to improve the high-value utilization industry chain of wood residues.Among the many conversion methods,electrocatalysis can be performed at room temperature and pressure compared to the conventional methods,and the combination with efficient refining of wood residues is in line with the green chemistry concept.However,because of the inert reaction kinetics of electrodes,it is necessary to develop efficient electrocatalysts.To address the above problems,in this thesis,HMF prepared by cellulose conversion was used as raw material,and precious metal doped Pd-Co OOH and double transition metal Cu OCo OOH catalysts were prepared based on hydroxycobalt oxide(Co OOH)from two perspectives of enhanced adsorption and constructive defects,respectively,which were applied to electrocatalytic oxidation of HMF for efficient preparation of FDCA.in addition,the application of Cu OCo OOH electrocatalysts were applied to the oxidation of various hemicellulose and lignin-derived primary alcohols and aldehydes for the preparation of the corresponding carboxylic acids with excellent yields.The main studies and results of this paper are as follows:(1)Pd-CoOOH catalysts were prepared by depositing Pd on Co OOH nanosheets by in situ variable potential deposition.The cyclic voltammetric curve(CV)observed that the addition of Pd promoted the production of Co4+,which in turn promoted the oxidation of HMF.The open circuit potential(OCP)test confirmed that the addition of Pd enhanced the adsorption capacity of the catalyst to HMF,which in turn enhanced the catalytic performance.Applying high performance liquid chromatography(HPLC)to analyze the products,Pd doping greatly enhanced the yield of FDCA from 24.13% to 67.55%.The above tests showed that the doping of noble metal Pd successfully improved the catalytic ability of Co OOH.(2)The low crystallinity,oxygen-rich vacancy Cu OCo OOH catalyst was successfully prepared by co-deposition of non-precious metal CuCo precursor solution and electrochemical activation.High-resolution transmission electron microscopy(HRTEM)and X-ray diffraction(XRD)demonstrated the low crystallinity of the catalysts,and X-ray electron spectroscopy(XPS)and electron paramagnetic resonance(EPR)demonstrated the formation of oxygen vacancies.Linear voltammetric scanning curves(LSV)demonstrated a high current density for the electrocatalytic oxidation of HMF,and OCP confirmed that the addition of Cu greatly enhanced the adsorption capacity of the catalyst for HMF.The product analysis revealed that Cu OCo OOH could convert 100% of HMF after 42 min at 1.45 V potential,and the FDCA yield could reach 98%.Subsequent DFT calculations revealed the reason for the enhanced catalytic performance.In addition,the substrates were extended to 12 hemicellulose and ligninderived primary alcohols and aldehydes,all of which could be catalytically oxidized to the corresponding carboxylic acids by Cu OCo OOH with high efficiency.In conclusion,Cu OCo OOH has excellent catalytic performance for wood residue-based primary alcoholic aldehydes with good general applicability,and the electrocatalytic oxidation system developed in this study can be perfectly integrated with the current wood residue efficient refining industry.