Study On Hydrogen Production From Organic Molecule Electrooxidation Coupled With Electrolysis Of Water Catalyzed By Manganese Based Oxides

The need for a friendly environment and sustainable energy is growing due to resource constraints and environmental damage.The high energy density and cleanness of hydrogen energy make it a prime choice for the next generation of energy.The efficient acidic proton exchange membrane water electrolyzers（PEMWE）,as the most ideal device for hydrogen production,are severely limited by the slow anodic oxygen evolution reaction（OER）kinetics.At present,the commercial OER catalyst,which has the shortcomings of high cost and poor stability,promotes the development of alternatives and alternative reactions.Therefore,it is particularly significant to develop a low-cost,low-energy consumption,high-efficiency,and high value-added acid electrocatalytic electrolytic hydrogen production system.This study replaces OER with electrooxidation of various organic molecules,which is preferable to thermodynamics.It also focuses on various preparation techniques to design and increase catalytic activity and stability of Manganese-based oxides.Finally,it builds and develops an electrocatalytic system that can simultaneously perform the electrochemical synthesis of highly valuable products and cathode hydrogen evolution.The specific research contents and results are as follows:（1）The method of alcohol oxidation as an alternative to water oxidation for the production of ultra-durable H₂.The electronic structure of Mn O₂ can be optimized by adjusting its crystal phase,forδ-Mn O₂ phase,which has a high Mn³⁺content exhibits high activity.When the current density reaches 50 m A cm^-2,the overpotential is only1.48 V and the smaller Tafel slope is 176.22 m V dec^-1.In addition,theδ-Mn O₂ catalyst exhibits extremely high stability after 20 hours of ethylene glycol oxidation,but its activity rapidly loses within 0.5 hours of w ater oxidation.The results indicate that by increasing the Mn O₂ of the sea urchin-likeδphase in manganese oxide can improve the specific surface area of the catalyst and the activity and stability of acidic water decomposition catalysts.（2）The electrooxidation of glucose derived from biomass is coupled with ultra-durable hydrogen production in acidic media,and lanthanide elements are doped into Mn O₂.By adjusting the proportion of active Mn³⁺,the adsorption and desorption processes of alcohol aldehyde groups are effectively optimized and improve its electrooxidation activity,but not for OER.The catalyst exhibited extremely high activity and durability even after 50 hours of glucose oxidation.The electrooxidation reaction of glucose hindered the release of lattice oxygen and the formation of Mn O^4-,while the OER activity experienced a rapid decline within half an hour.Density functional theory（DFT）calculations further indicate that the activation energy of the intermediate formed in the glucose oxidation reaction in the first adsorption process is lower than that of OER,so that glucose oxidation is prioritized and the lattice oxygen mechanism in the catalyst oxidation process is avoided.This work indicates that biomass-derived glucose oxidation not only provides a low-cost and cost-effective method for producing high-value chemicals,but also exhibits great potential as an alternative reaction to acidic OER for ultra-durable hydrogen production.（3）The transition metal copper,cadmium and manganese were made into transition metal spinel oxide catalysts,and the active sites were increased to electro-oxidize monosaccharides and disaccharides.The goal is to explore the activity of catalysts enhanced by the introduction of more Mn³⁺through alloying.Research shows that manganese,copper,and cadmium can react as catalytic active sites.In the oxidation of fructose,the Cd Mn₂O₄ catalyst exhibits the best electrocatalytic activity,reaching a current density of 10 m A cm^-2 at only 1.25 V,which is much lower input voltage than traditional water decomposition under the same catalytic conditions and exhibits good stability.This work provides new ideas for constructing transition bimetallic active site catalysts,enhancing the synergistic effect of the two components in alloy catalysts,as well as long-term durable reactions in acidic solutions and achieving efficient electrochemical conversion.