Resourcification Of Waste Shrimp And Crab Crusts And Its Application In Zinc Ion Hybrid Capacitors

Shrimp,crab,and other crustacean biological resources are plentiful in our country and they have significant development potential.According to publicly available data,Chinese annual production of seawater shrimp and crab farming for domestic consumption totals 60million tons.Every year,ten million tons of crustacean food waste are produced based on the total weight of shrimp and crabs.For a long time,this crustacean food waste has been piling up with other garbage.Landfills and piles of food waste decay and emit foul-smelling leachate,which depletes oxygen in surface water,resulting in the deteriorating water quality and eutrophication of water.Moreover,they also seriously affect drinking water sources,damage soil,and breed bacteria.These simple and crude treatments are extremely hazardous to the environment and human life.Discarded shrimp and crab shells account for a significant portion of crustacean food waste.Although a small portion of waste shrimp and crab shells are currently used as feed additives for the livestock industry,raw materials for chitosan production,and heavy metal sewage treatment agents,significant portion is still disposed by landfill.Most landfill shrimp and crab shells pollute the environment and waste resources.Therefore,the utilization and application of waste shrimp and crab shells will be benefit for environmental protection and carbon-neutral planning.Furthermore,it will generate economic benefits while improving the environment and people’s living standards,which is critical in socioeconomic and environmental protection.Herein,this research will concentrate on the resource utilization of food waste chitosan,by extracting the chitosan material,which is the main useful component in shrimp and crab shells collected from food waste,and investigating the optimal optimization conditions through high-temperature carbonization to obtain carbon-based materials with three-dimensional structure.We also investigated the potential of these materials for zinc ion hybrid capacitors.Firstly,food waste shrimp and crab crusts were directly carbonized and activated to produce hierarchical porous carbon functional materials with multiple adsorption sites and a large specific surface area.The annealing temperature was investigated for its effect on material structure and electrochemical properties.Food waste shrimp and crab crusts will be creatively repurposed and used to support environmental protection and carbon neutrality programs.It will generate economic benefits while improving the environment and people’s living standards,which is critical in socioeconomic and environmental protection.1.Waste shrimp and crab shells contain a large amount of calcium（Ca CO₃）that can be used directly as an activator,and proteins and chitosan in shrimp and crab shells can also be used directly as carbon sources.Considering its characteristics,we obtained a hierarchical porous carbon functional material（CSC-X）with multiple adsorption sites by directly carbonizing and activating the waste shrimp and crab shells.After 20,000 cycles at a current density of 5 A g^-1,the cycling stability was 91%.2.CTSK-X was extracted from chitosan,a fibrous material of shrimp and crab shells,and activated by carbonization of chitosan at different temperatures to obtain CTSK-X.The material characterization and electrochemical characterization of CTSK-X show that CTSK-700 has the best rate performance among CTSK-X cathodes.Furthermore,the CTSK-700 cathode material has the highest zinc ion hybrid capacitor cathode material stability.CTSK-700 has the best cycling performance of CTSK-X after 20,000 cycles at a charge/discharge current density of 1 A g^-1,with a 63%capacity retention rate.57%capacity retention is still achieved after 20,000 cycles at a high current density of 5 A g^-1,and Coulomb efficiency is close to 100%.3.CTSAc K-700,a material with a unique layered pore structure and ultra-high surface area,was obtained by replacing the solvent water in the above preparation process and optimizing the carbonization and activation processes.CTSAc K-700 has a larger specific surface area,more defects,and similar nitrogen and oxygen atom contents than CTSK-700.At a charge/discharge current density of 1 A g^-1,the zinc ion hybrid capacitors built on the CTSAc K-700 platform have a specific capacitance of up to 100 m Ah g^-1.After 20,000 cycles at a current density of 5 A g^-1,113%of the specific capacity was retained,indicating a more stable cycling performance.With feasibility and excellent stability,a one-step carbon-activated,direct resource recovery scheme for food waste shrimp and crab crusts was realized and successfully applied to zinc ion hybrid capacitors.