| Wood biomass is a renewable resource with abundant reserves,and the residual wood waste after processing also contains rich chemical structure,and its high value utilization is significant to protect the environment and solve the energy shortage problem.In this study,wood powder of Fraxinus mandshurica was used as an example to construct a hydrogen generation and degradation system under three different redox media by PEMEC electrolysis technology.The system successfully performs energy recycling,converting biomass into potential chemical materials while converting electrical energy into green hydrogen energy.The specific studies are as follows:Firstly,an inexpensive manganese dioxide was used as the redox medium and electron transfer medium to construct a hydrogen generation and degradation system for Fraxinus mandshurica wood powder.The degradation rate was 50.9%,and the remaining solids were mainly cellulose,which could be further processed and reused.GC-MS analysis showed that the degradation products were mainly aromatic monomers（vanillin,acetophenone,etc.）and small amounts of long-chain alkanes.The manganese dioxide catalyst was successfully regenerated from liquid phase electrochemical oxidation using an H-type double electrolyzer,and the regenerated manganese dioxide was characterized by XRD as a good catalytic stability after four cycles of oxidation tests.In addition,hydrogen was simultaneously generated as clean energy at the cathode during electrolysis,and the hydrogen faraday efficiency of the hydrogen production from the Fraxinus mandshurica-Mn O2 system reached 91.6%at a current density of 40 m A/cm2.Secondly,in order to solve the problem of poor water solubility and low catalytic efficiency of manganese dioxide,soluble polyoxometalate（POM）were selected as catalysts to construct a new system.In this system,POM can directly reduce the wood powder in liquid homogeneous phase,which effectively accelerates the electron transfer rate.The degradation rate of Fraxinus mandshurica wood powder was improved by 10.2%compared with that of Mn O2 system,and the hydrogen Faraday efficiency of the system was 93.7%at 20 m A/cm2current density,which was about 40.0%less than that of aqueous electrolysis at 0.1 A/cm2.GC-MS analysis showed that the degradation products were mainly aromatic organic compounds and carbonyl compounds.In addition,POM can be regenerated under the action of electric potential,and the regenerated POM still maintains its original chemical structure as characterized by XPS,and the deviation of degradation rate is less than 1.3%in the four oxidation cycles experiment.Finally,POM is more expensive to use,and in order to reduce the reaction cost,inexpensive water-soluble Lewis acid Fe Cl3 was used as a catalyst.Compared to the POM system,this system reduces the cost of use,but the degradation rate of Fraxinus mandshurica is 55.6%,which is slightly lower compared to the POM system.With the Fe3+/Fe2+system,H2 generation can also be achieved,and its Faraday efficiency also exceeds 92.6%,which can save about 30.0%energy relative to the water electrolysis hydrogen production method at 0.1 A/cm2 current density.Fe3+/Fe2+can be cyclically regenerated in the electrolysis system and maintain good reactivity in the cyclic reaction,and the deviation of four times Fraxinus mandshurica degradation rate is less than 1.5%. |
