Structural Regulation Of Binary Transition Metal Electrocatalytic Materials To Directionally Oxidate Biomass

Biomass,especially lignocellulose,which is rich in renewable carbon resources,provides the most viable alternative feedstock for the green and sustainable production of bio-derived chemicals.Currently,the value-added process of biomass demands a shift from centralized and rigorous to decentralized and green.And the production of fine chemicals by electrooxidation to replace the sluggish oxygen evolution reaction（OER）offers new opportunities and challenges for the high-value utilization of biomass and its derived compounds.Among them,efficient construction of highly active,selective and stable electrocatalysts and investigation of the conversion mechanism therein have become the focus of research.Therefore,in this thesis,two binary transition metal（Co,Ni）-based electrocatalytic materials were developed using structural modulation strategies to explore the advantages of targeted breaking of lignin C_α-C_βbonds and 5-hydroxymethylfurfural conversion,respectively.First,in the study of lignin oxidative bond breaking,2-phenoxy-1-phenylethanol（PPE,a typical ligninβ-O-4 model compound）was chosen as the starting point for this thesis.PPE oxidation reaction（POR）and hydrogen evolution reaction（HER）were exploited to obtain benzoic acid esters and promote cathodic hydrogen production.The oxidative breakage of the C_α-C_βbond is an essential part of lignin depolymerization to platform chemicals and is largely dependent on electrocatalysts.Herein,a synthesis strategy is proposed using metal-organic framework（MOF）encapsulation and sulfuration on the nickel foam（NF）substrate.The robust bimetallic sulfides heterostructures,named Co₃S₄/（α,β）-NiS,showed selectively and efficiently oxidize C_α-C_βin 2-phenoxy-1-phenylethanol（PPE）,a typicalβ-O-4 model.An ultralow potential of 0.954 V vs RHE is exhibited by NF@Co₃S₄/（α,β）-NiS for 10 m A cm^-2 in alkaline solutions containing PPE,owing to the multiphase active interface and smooth pore channels.A PPE conversion of93.6%and benzoate yield of 83.8%were reached from the electrooxidation of PPE at1.414 V vs RHE.Meanwhile,lignin can be effectively cleaved to the main product vanillin.Secondly,nanoflower-sphere-like cobalt-nickel bimetallic MOF（Co₁Ni₃-MOF-1）with multilayer cleavage-like pore structures were successfully prepared by ionic liquid（[Bmim][BF₄]）-assisted solvothermal method in the study of 5-hydroxymethylfurfural（HMF）oxidation to prepare 2,5-furandicarboxylic acid（FDCA）Through coordinated diatomic control,the synthesized Co₁Ni₃-MOF-1 has the best selectivity and kinetic advantage in the HMF oxidation reaction（HMFOR）when the n（Co/Ni）is 1:3.During alkaline electrolyte for HMFOR,close to 100%HMF conversion and 95.8%FDCA selectivity can be achieved at 1.464 V vs RHE,and exhibits good cycling durability.Further studies revealed that[Bmim][BF₄]was the structural template and its anion acted as a charge compensator to modulate the electronic structure of the cobalt-nickel MOF and enables Co₁Ni₃-MOF-1 to acquire a porous structure with a high specific surface area,thus enhancing the high catalytic activity of HMFOR.This study developed two inexpensive and stabilized binary transition metal-based electrocatalysts for the value-added utilization of lignin and 5-hydroxymethylfurfural,respectively.In addition,coupling with the HER can successfully achieve lower electricity consumption of water splitting.