Synthesis Of Silver-based Nanomaterials And Its Electrocatalytic Performance For Oxygen Reduction Reaction In Alkaline Media

To cope with energy shortage and environmental pollution,the development and utilization of various new energy technologies have received extensive attention.The fuel cell is a promising energy conversion device due to its high conversion efficiency,cleanness,and eco-friendly.However,the use of expensive Pt-based catalysts and the slow kinetics of cathodic reaction limit the development of fuel cells.Therefore,it is essential to develop efficient and low-cost oxygen reduction reaction（ORR）electrocatalysts.The development of anion exchange membrane fuel cells makes it possible to use non-Pt catalysts.Ag has good ORR performance in alkaline conditions,and its price is less than 3%of Pt,suggesting that Ag-based catalyst is a promising low-cost alternative.However,the ORR performance of Ag is still far behind that of precious metals such as Pt.Therefore,this article mainly synthesizes binary and ternary Ag-based catalysts and improves the ORR activity and stability by adjusting the composition,structure,and morphology of Ag-based catalysts.The main research contents of this paper can be described as follows:（1）A series of binary Ag-based catalysts doped with 3d transition metals were prepared by the same synthesis method.After preliminary screening of electrochemical test results,Ag-Mn with better ORR activity and Ag-Cu binary composites with better stability were obtained.Subsequently,different Ag-Mn and Ag-Cu binary composite materials were synthesized by room temperature ultrasonic method,solvothermal method and other methods,and their ORR activity and stability were explored.The test results found that Ag-Mn/C-V（V represents reduction using ascorbic acid）has a half-wave potential(E_1/2)of 0.820 V,while Ag-Cu/C-N（N represents reduction using hydrazine hydrate）after scanning 2000 cycles of CV,E_1/2half-wave potential drops only 2 m V.（2）The ternary flake Ag-based catalyst Ag Cu Mn/C-NS is synthesized on the basis of the binary Ag-based catalyst by a low-temperature synthesis method,its ORR activity and stability has been improved.The E_1/2 of the catalyst is 0.820 V.After 8000 cycles of voltammetry,the E_1/2 of the catalyst dropped by only 9 m V,the ternary catalyst shows activity similar to Ag-Mn/C-V and stability similar to Ag-Cu/C-N,indicating that the synergy between metals has a positive impact on its performance improvement.And by comparing the ORR performance of the flake Ag Cu Mn/C-NS catalyst and the granular Ag Cu Mn/C-NP,it can be seen that the structure of the catalyst is also beneficial to the improvement of its performance.In addition,the influence of various factors on the performance and morphology of the Ag Cu Mn/C-NS catalyst during the synthesis process was also explored.（3）A ternary Ag-based catalyst with a unique morphology of Ag nanowires and Cu Mn O_x nanosheets coated with Ag NW@Cu Mn O_x NS/C composite structure was further synthesized.The catalyst exhibits excellent ORR electrocatalytic performance:in 0.1 M KOH,its E_1/2 is 0.837 V,after cyclic voltammetry scans 30,000 cycles,the catalyst’s E_1/2 only dropped by 6m V.In addition,the use of the catalyst as a cathode to assemble the membrane electrode of an alkaline membrane fuel cell exhibits a peak power density of 1.4 W/cm²,which proves that the catalyst has excellent ORR electrocatalytic performance.Its high activity comes from the unique core-shell nanowire structure of the catalyst and the synergistic effect between multiple metals.