Electrochemical Upcycling Of Waste Polyester Plastics And Biomass Coupled With Cathodic Small Molecule Reduction

As the most important polymer,the huge market demand has led to rapid growth in plastic production,and the massive accumulation of plastic waste has caused direct damage to water sources,soil,air,and ecosystems.The end-of-life management of plastic waste has not kept pace with the high-growth output,thereby arousing a strong desire to seek upcycling solutions.As a natural resource with abundant reserves,the comprehensive utilization of biomass has been a strategic high ground seized by countries around the world.In recent years,renewable energy has experienced vigorous development,but limitations such as intermittency,volatility,and regional dependence have greatly slowed down its pace of replacing traditional fossil fuels.Based on the above practical issues,electrochemical conversion technology driven by renewable energy is expected to offer novel breaking strategies for the optimization of power system load management,addressing both peak demand and off-peak surplus.Furthermore,it has the potential to mitigate the plastic crisis and enable high-value utilization of biomass.However,rare attention has been paid to the electrocatalytic conversion of waste plastics and biomass at present.The unclear reaction mechanisms and pathways,the absence of efficient and low-cost catalysts,as well as the limited industrial integration routes seriously impede the industrialization process in this field.This paper focuses on the electrochemical upcycling of polyester plastics and biomass glycerol,establishing a systematic research framework from catalyst synthesis,reaction mechanism disclosure,electron transfer path tracking,industrial integration route intensification,and technical and economic evaluation.Multiple environmentally friendly,energy-efficient,and economically viable electrochemical upcycling routes are proposed.The specific research work encompasses the following four aspects:（1）Two highly technically and economically feasible electrochemical routes have been proposed for the upcycling of waste polyethylene terephthalate（PET）plastic:1)PET upcycling coupled with green hydrogen production;2)PET upcycling coupled with carbon dioxide reduction（CO₂RR）to achieve bidirectional communist formate.A chromium-modified graded nickel sulfide catalyst was constructed to catalyze the electrooxidation of ethylene glycol monomer（EOR）.Thanks to the synergistic regulation of Cr and S on the Ni site,it only requires an oxidation potential of 1.378 V（vs.RHE）to drive a current density of 400 m A cm^-2,and the Faradaic efficiency（FE）of formate reaches95%.Specifically,the CO₂RR coupled EOR hybrid electrolysis strategy can drive a current density of 400 m A cm^-2 with only 2.582 V battery voltage,while also achieving bidirectional electrosynthesis of formate,surpassing most currently reported CO₂RR systems.Techno-economic evaluation confirms that the two technological routes can achieve attractive gross profit margins of 53.57%and 39.70%respectively,providing energy-saving and economical solutions for the electrochemical upcycling of PET plastic.（2）For the waste polybutylene terephthalate（PBT）plastic,a cation vacancies-enriched cobalt selenide nanoarray catalyst(Mo₁-Co Se-V_Co/NF)is constructed,which exhibites unprecedented catalytic activity for the oxidation of butane-1,4-diol（BDO）monomer(1.5 A cm^-2@1.477 V vs.RHE)and robust stability（170 h）,the highest FE of succinic acid product reached 94.0%.The mechanism and reaction pathways of BDO oxidation involved in the electrocatalytic process are revealed by the density functional theory calculations and in situ spectroscopic techniques.The universality of this novel approach is evidenced by the efficient electrocatalytic conversion of other plastics such as poly（butylene succinate）and PET.Finally,this upcycling electrocatalytic process can be extended to intelligent matching with cathodic small molecule reduction,leading to multiple energy-saving and highly economic potential hybrid electrolysis routes are proposed that are highly demanded by the zero-carbon economy.（3）Hydrogen peroxide（H₂O₂）electrosynthesis cannot rival traditional anthraquinone processes,which suffers seriously from the high potential of oxygen evolution reaction（OER）,low value of anode products,and the difficult extraction of H₂O₂ product.Herein,we present an electrosynthesis protocol involving coupling ORR-to-H₂O₂ with waste PET upcycling and the first H₂O₂conversion strategy.Ni-Mn bimetal-and onion carbon-based catalysts are designed to catalyze ethylene glycol electrooxidation and ORR-to-H₂O₂ with the Faradaic efficiency of 97.5%（H₂O₂）and 93.0%（formate）,respectively,demonstrating excellent catalytic performance.This electrolysis system runs successfully at only an ultra-low battery voltage of 0.927 V to achieve an industrial-scale current density of 400 m A cm^-2,surpassing all currently reported H₂O₂ electrosynthesis systems.Additionally,two direct downstream conversion schemes for H₂O₂ are proposed for the first time and upgraded to sodium perborate and dibenzoyl peroxide,thereby cleverly avoiding the difficulty of H₂O₂ separation.Techno-economic evolution highlights the gross profit of this hybrid electrolysis protocol has increased by 134.1%compared to the traditional H₂O₂ electrosynthesis system which provides an energy-saving and economical methodology for H₂O₂ electrosynthesis and plastics recycling.（4）We have pioneered a new membrane-free electrocatalysis protocol to achieve energy-saving CO₂RR.It bidirectionally coproduces formate through coupling CO₂RR with glycerol oxidation reaction（GOR）.Bismuth nanosheets and Ni,Co bimetallic organic skeleton catalysts are constructed for the highly selective conversion of CO₂RR and GOR to formate,respectively.Electrolyte cross experiments are conducted on both sides of the cathode and anode,confirming the possibility of conducting CO₂RR and GOR in a membrane free electrolytic cell.Subsequently,a membrane free flow cell is built to couple the anodic and cathodic reactions to achieve bidirectional collaborative production of formate,which was also the first case of membrane-free CO₂RR protocol.As predicted,the membrane-free design eliminates the mass transfer resistance at the membrane interface,significantly reducing the battery voltage,requiring only 2.487 V to drive an industry-level current density of 400 m A cm^-2,surpassing almost all currently reported CO₂ electrolysis configurations.This new membrane-free protocol serves as a general methodology for extending the classical principles of mass transfer and separation to the electrochemical field and provides an energy-saving platform for CO₂RR and other electrocatalysis technologies.