Preparation And Application Of DES-based Pretreated Lignin-based Carbon Nanomaterials

The production of high value-added products from lignocellulosic biomass resources is a highly promising technological route,but there are still many problems,among which the underutilization of high value-added lignin is a major obstacle.In this paper,we pretreated two types of lignocelluloses,pennisetum and beer lees,using deep eutectic solvent（DES）pretreatment method,and explored the most suitable pretreatment environment by optimizing different conditions.The separated cellulose residues were analyzed by crystallinity analysis and enzymatic digestion of the separated cellulose from pennisetum,and the extracted lignin from pennisetum and beer lees were analyzed by IR and thermogravimetric analysis,SEM analysis,particle size analysis and GPC analysis.Then,we compared different raw materials,screened different heteroatoms,optimized calcination temperature,mass ratio of dicyandiamide to precursor,heteroatom doping and other factors to prepare catalyst materials with the best performance for Zinc-Air Batteries.The main results of the study are as follows:（1）The lignin yield of beer lees treated with DES of 4﹕1 lactic acid（LA）﹕choline chloride（Ch Cl）at a liquid-to-solid ratio of 20﹕1 and a reaction temperature of 160℃for 4 h was 71.35%,while the lignin yield of pennisetum was 77.77%at a reaction of 2﹕1 LA﹕Ch Cl DES at a liquid-to-solid ratio of 20﹕1 and a reaction temperature of 140℃for 3 h.The characterization of lignin revealed that the lignin extracted by DES method maintained the basic active functional groups and kept close to the most original structure.（2）The carbon nanomaterials prepared by adding Fe to lignin in 10 wt%doping amount by hydrothermal method to form Fe doped precursors with 5times mass of dicyandiamide at 850℃had the best redox effect with half wave potential of 0.846 V vs.RHE,starting potential of 0.972 V vs.RHE and limiting current density of-6.071 m A cm^-2.（3）Fe₂-5N/CNTs-850℃Zinc-Air Batteries have an open-circuit voltage of 1.47 V,which is similar to that of 20%Pt/C Zinc-Air Batteries with an open-circuit voltage of 1.49 V.The good performance of Fe₂-5N/CNTs-850℃batteries after 45 hours proves that they have good application prospects.