Study On Composite Low-noble Metal Electrocatalytic Materials Derived From Prussian Blue Analogous Precursor

Electrocatalysts are the core components of renewable and environmentally friendly energy conversion devices such as fuel cells and metal air batteries.Precious metals Pt and Pd have good catalytic activity,but their high price,limited resources and poor anti-poisoning ability limit their large-scale application.Therefore,the development of new low-noble metal based elecctrocatalysts to reduce the amount of precious metals has been a research hot spot in recent years.Thereinto,metal organic frameworks(MOFs)materials are composed of various metal ions and diversified organic connectors,showing the advantages of porosity,high specific surface area,convenient functionalization,etc.have presented great potential in assisting preparation of electrocatalysts with low noble metal load and high catalytic activity and stability.The Prussian blue analogous(PBA)is a promising subclass of MOFs.Due to its low cost,easy preparation,large cavity,adjustable components and unique structural properties,it has been found with good electrocatalytic performance in the early stage.Moreover,its metal sites can be replaced by a variety of metals and the carbon and metal can be combined uniformly after carbonization.Therefore,it can be used as a precursor to prepare ideal porous carbon-metal composite electrocatalytic materials by introducing different electrocatalytic active centers.To reduce the amount of precious metals and improve the electrocatalytic activity and stability of precious metals,in this study,some low-noble metal electrocatalytic materials with low cost and good electrocatalytic performance were prepared with the help of Co3[Co(CN)6]2.Firstly,the well-dispersed binary PtCo/C alloy nanoparticles were prepared by in situ substitution method and the electrocatalytic activity and stability of the obtained low platinum electrocatalyst towards ethanol electrooxidation were studied.Subsequently,using precious metal Pd to modify carbonized Co3[Co(CN)6]2,which realizes the composited Co and Pd nanoparticles on the nitrogen-containing graphite carbon derived from Co3[Co(CN)6]2.The performance of the binary Pd-Co/C electrocatalyst towards ORR/OER reaction was studied.Moreover,its application as a cathode material of zinc-air battery devices was also investigated.In addition,in these two parts,the structures of as-prepared electrocatalysts were characterized by XRD,XPS,TEM,Raman,Element Mapping etc.,respectively.Specific research contents are as follows:Part I:Application of PBA-derived PtCo/C electrocatalysts towards electrocatalytic oxidation of ethanolCo3[Co(CN)6]2 precursor was synthesized by hydrothermal method.Then partially dispersed Co2+ metal sites were replaced by Pt4+ in situ substitution method.After annealing for 4 h at the optimal temperature of 600℃,PtCo/C electrocatalyst was prepared for electrocatalytic oxidation of ethanol.The results show that the electrocatalyst containing a small amount of precious metals(Pt,0.95wt.%),but greatly improves the mass electrocatalytic activity(840 mA mg-1Pt)of precious metals and presents good electrocatalytic oxidation performance of ethanol.C ompared to commercial Pt/C,it has lower initial potential(-0.590 V),lower apparent activation energy(38.90 kJ mol-1)and better stability and durability.This is mainly attributed to the combining of unique structural advantages of Co3[Co(CN)6]2 precursor and the excellent electrocatalytic properties of noble metal nanoparticles.This part of experiment shows that using Co3[Co(CN)6]2 to introduce noble metal nanoparticles has a considerable application prospect in greatly reducing the amount of precious metals and improving the electrocatalytic performance of precious metals.Part Ⅱ PBA-de rived Pd-Co/C composite bifunctional electrocatalysts applied to zinc-air batteryIn view of the good application of the former binary alloy PtCo/C on the anode.For further exploring the electrocatalytic performance of PBA derived metal complex as cathode material,PBA derived nitrogen rich graphite carbon material was firstly prepared through carbonizing Co3[Co(CN)6]2 precursor at 600℃ in the tube furnace for 3 h.Then adding a small amount of Pd2+,after reduction,Co,Pd nano particles were composited on PBA derived nitrogen-rich graphite carbon.The obtained PBA derived Pd-Co compound was investigated towards ORR/OER reactions and its application as cathode material of zinc air battery was also studied.The results show that the electrocatalyst has positive ORR half wave potential,low OER potential of 10 mA cm-2 current density,low ORR/OER tafel slope,good stability(retention rate:92.7%),high Zn-air battery power density(138.8 mW cm-2),and good constant-current charge-discharge cycle stability.This is mainly attributed to the composite synergistic effect of nitrogen-rich graphite carbon derived from Co3[Co(CN)6]2 as well as the composited Co and Pd nanoparticles on it.This part of the research is expanded and developed on the basis of the former part.Taking the two aspects of reducing the dosage of precious metal and ameliorating precious metal catalytic performance as the starting point,a binary complex with better bifunctional ORR/OER than that of single-component noble metal electrocatalyst was obtained and realized its good application in zinc air battery devices,indicating that MOF-based material is of great potential in constructing late-model electrocatalysts.