The Preparation Of Biomass Carbon-based Composites And The Studies On Their Catalytic Performance For Oxygen Reduction Reaction

Biomass is a natural resource with a wide range of sources,low prices and renewables.Due to the rich carbon content and unique microstructure of biomass,the development and utilization of biomass has received more and more attention in recent years to prepare biomass carbon-based composite materials,whose application in energy,environment and catalysis are able to effectively reuse biomass resources.More importantly,the preparation of biomass carbon-based composites from biomass can improve the economic value of the biomass itself.In this paper,a series of biomass glucose,starch and chitosan were used as raw materials for successful preparation of carbon-based nanocomposites,which were employed to catalyze oxygen reduction reaction and vinyl acetate synthesis reaction.The relevant research contents are as follows:?1?Preparation of nitrogen-doped carbon-supported Zn-vacancy ZnS composite and studies on its catalytic oxygen reduction reaction.With glucose as the resource,nitrogen-doped carbon-supported ZnS composite with Zn vacancy?ZnS/N-C-900?was prepared by a one-step carbon bath method with the heat treatment at 900°C.The test results showed that the prepared composite ZnS/N-C-900 had a specific surface area of 1056.2 m²/g and the composite contained Zn vacancies.The electrochemical test results displayed that in the alkaline electrolyte,when Ag/AgCl was used as the reference electrode,the onset potential of the ZnS/N-C-900 electrode was 0.95 V_RHE,which was significantly higher than that of Pt/C(0.92 V_RHE).When the graphite electrode was employed as the reference electrode,the ZnS/N-C-900electrode also showed the onset potential of 0.95 V_RHE,which was also much higher than that of Pt/C(0.92 V_RHE),so whether Pt wire or graphite was used as a reference electrode,the prepared ZnS/N-C-900 had good ORR catalytic activity in alkaline electrolyte.The results of density functional theory?DFT?calculations indicated that the Zn vacancy in ZnS/N-C-900 as the active site required only a lower reaction energy?O₂?*OOH?in the catalytic ORR process?0.92 eV?.Therefore,the Zn vacancies as active sites promised the prepared ZnS/N-C-900 catalyst to exhibit excellent ORR catalytic activity,stability and methanol resistance in an alkaline electrolyte.?2?Preparation of N-doped carbon-supported Co-CoO_x composite and studies on its catalytic oxygen reduction reaction.Using soluble starch as resource,Co-CoO_x/N-C?SBM?,a composite of nitrogen-doped carbon supported partially oxidized Co-CoO,was prepared via a sand-bath method?SBM?.Compared with the half-wave potential(E_1/2=0.82 V vs.RHE)of Co-CoO/N-C?CHT?prepared by conventional high temperature pyrolysis,the results of the ORR test in alkaline electrolyte confirmed that the Co-CoO_x/N-C?SBM?prepared by the sand-bath method exhibited a more excellent half-wave potential(E_1/2=0.85 V vs.RHE).Furthermore,Co-CoO_x/N-C?SBM?had high catalytic activity and also exhibited excellent stability and methanol tolerance as compared with the commercial Pt/C.?3?Preparation of copper-nitrogen co-doped carbon-supported metal-copper composites and studies on their catalytic oxygen reduction reactions.Using biomass chitosan as raw material,the composite Cu/Cu-N-C was prepared by a simple one-step carbon bath method.The results showed that Cu/Cu-N-C had a high specific surface area(S_BET=607.3 m²/g).Compared with the onset potential(E₀=0.92 V_RHE)of the commercial 20wt%Pt/C,Cu/Cu-N-C displayed the onset potential?E₀?of 0.96V_RHE during electrocatalytic ORR,indicating that Cu/Cu-N-C has a higher ORR catalytic activity.At the same time,Cu/Cu-N-C also exhibited good stability and resistance to methanol.?4?Preparation of zinc-nitrogen co-doped carbon-supported ZnO composites and studies on their catalytic oxygen reduction reactions.Using chitosan as the precursor,a single-step carbon bath pyrolysis method was used to prepare a composite material?ZnO@Zn-N-C?,in which ZnO nanoparticles were in situ encapsulated within zinc and nitrogen-doped carbon,without any further treatment.The results showed that in the electrocatalytic test of oxygen reduction reaction?ORR?,due to the presence of Zn-N structure,the initial potential of ZnO@Zn-N-C electrode was 0.93 V_RHE,which were significantly higher than commercial Pt/C(E₀=0.92 V_RHE),indicating that the prepared composite ZnO@Zn-N-C possessed good ORR catalytic activity.