Design And Synthesis Of Cathode Catalysts With High Activity For Oxygen Reduction And Their Performance In Microbial Fuel Cells

As green technologies,microbial fuel cells?MFCs?can not only directly convert the organic energy in wastewater into electricity,but also can treat wastewater simultaneously,which can be used to help meet our energy needs and improve the nexus between water and energy.One of the main challenges is the development of efficient and stable cathode catalysts for MFCs,the application of traditional Pt catalysts has been restricted due to its rare reserves and high cost.Thus,this project synthesized aseries of low Pt catalyst and non-pt catalysts with different structure,morphology and composition by controlling the synthesis condition,and discussed it's application in MFC type of BOD sensors.First,we successfully fabricated nanostructured Pt-Ru alloy catalysts by NaBH₄reduction at room temperature.The electrochemical measurement results indicated that the Pt-Ru alloys possess 2.3-times greater mass activity of Pt towards the ORR compared to the commercial Pt/C catalyst.The open circuit voltage increased 0.05V,compared to that of MFC with Pt/C as cathode catalyst.The Pt-Ru/C catalyst exhibited a higher activity owing to the synergistic effects from the decrease in Pt loading and doping with Ru.The above results clearly demonstrate that Pt-Ru/C is a promising substitute for Pt nanoparticles for ORR in single chamber MFCs.Next,a simple arginine-assisted hydrothermal route to produce Pd-nanochains?Pd-NCNs?in the presence of PVP has been firstly reported.The asprepared catalyst with uniform distribution shows excellent electrocatalytic activity and stability for the oxygen reduction reaction in neutral solution,which is attributed to the unique structure and abundant surface atom defects on Pd-NCNs.The maximum power density of MFC with Pd nanochains as cathode catalyst is 14.10 W/m³ increase by50%in comparison to commercial Pd black,Therefore,the Pd-NCNs.are promising cathode catalyst in MFCs.Third,bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions.In this study,we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in MFCs,which represent a promising technology for wastewater treatment,while directly generating electrical energy.In specific,in comparison with the hollow structured Pt nanoparticles,a benchmark for the electrocatalysis,the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains.The maximum power density generated in a membraneless single-chamber MFC running on wastewater with core-shell Au-Pd as cathode catalysts is ca.16.0 W/m³ and remains stable over 150days,clearly illustrating the potential of core-shell nanostructures in the applications of MFCs.Finally,we developed a simple single-chamber MFC-type biochemical oxygen demand sensor with Au-Pd/C nanoparticles as cathode catalyst,and demonstrated its feasibility in the construction of a real-time BOD measurement system,such as the simple structure,easy operation and shorter testing time.Our study successfully examined the effect of different factors that affected the performance of the BOD sensor,namely,the anodic pH?pH=7.0?,organic matter concentration?5¹10mg/L?,and the response time?120 min?.Subsequently,the optimized biosensor was tested with real wastewater.When real wastewater was fed into the biosensor,the BOD values presented a standard deviation from 1.5%to 7.75%,thus demonstrating the practical applicability of this system to real treatment effluents.This will provide theoretical support and technical guidance for the expansion of MFCs.