Electrocatalytic Properties Of Polymer-derived Porous Carbon-supported Non-noble Metal Compounds

In the scientific practice of exploring various kinds of energy storage devices and energy conversion devices,the metal zinc air battery stands out with its more considerable energy density,Reliable safety and ideal cycle life,and green environmental protection as many highlights,and has been praised as the 21st century environmental protection new energy.Zn-air batteries have a more promising application in the development of new energy materials.However,there is a fly in the ointment because Zn-air batteries,The maximum number of charge and discharge cycles,energy conversion rate and energy utilization rate of ZABs are all determined by the Oxygen reduction reaction（ORR）and Oxygen evolution reaction(Oxygen evolution reaction,OER is affected by slow hysteresis and poor stability.This restricts the exploration and utilization of potential advantages of zinc-air batteries to a certain extent.When we analyze the assembled devices of zinc-air batteries,it is not difficult to find that the composite preparation of materials involved in optimizing oxygen electrodes is a technical barrier to be overcome.Therefore,it is forward-looking to explore the development of high performance,considerable stability of oxygen electrode to improve the performance of zinc-air batteries.Rare precious metals such as Ruthenium dioxide（RuO₂）and platinum（Pt）are good catalysts for the reaction of OER and ORR.However,from the perspective of comprehensive consideration,the stock of precious metal electrocatalysts is small,economic cost and other reasons will limit its scale for commercial use to a certain extent.Therefore,finding a more suitable replacement is the main research direction of our scientific research.Carbon materials have been widely reported from many related catalytic literature fields due to their advantages such as large specific surface area,controllability of microscopic morphology,economical availability of synthetic materials and good conductivity.However,the catalytic performance provided by carbon materials alone is not considerable,and it will be of great exploring significance to build composite multifunctional materials by combining nano-scale carbon materials with various organic and inorganic materials through reasonable means.The ideal oxygen electrode material can be made by combining organic and inorganic materials with carbon materials with large specific surface area through scientific and creative design.In this paper,a simple conductive polymer polyp-phenylenediamine,poly-2,6-diamino-pyridine,poly-3-aminophenol and Zeolitic imidazolate frameworks（ZIFs）nitrogen-doped carbon precursors were used.As an excellent precursor of zinc-air batteries,zeolite imidazole skeleton has many advantages,such as regular morphology,controllable chemical composition,ideal pore size,etc.After being combined with CeO₂,FeS₂,Fe₃N nanoparticles,NiCo₂O₄and other materials,a series of oxygen electrode catalytic materials with reasonable cost and excellent catalytic activity were prepared.Firstly,a series of CeO₂/FeS₂/N-C composite catalytic materials were prepared by loading CeO₂and FeS₂on poly（p-phenylenediamine）nanospheres,and their catalytic properties related to OER were investigated.Then,the Co-N/C was obtained by carbonizing ZIF-67 as the symbiotic precursor,and poly（2,6-diamino-pyridine）was combined with it,and then Fe₃N nanoparticles were loaded on poly（2,6-diamino-pyridine）.Co-N@Fe₃N/C composite was easily obtained,and the ORR-related catalytic activity was explored.Finally,3-aminophenol as a nitrogen source and carbon source,poly-3-aminophenol is through the way of oxidation polymerization of 3-aminophenol monomer polymerization,and then NiCo₂O₄Mosaic in poly-3-aminophenol to prepare NiCo₂O₄/N-C.Then the application of oxygen electrode in Zinc-air battery was investigated.In addition,the structure of the catalyst is characterized by TEM,SEM,XRD,XPS,BET and Raman.The test results are given:Part Ⅰ CeO₂/FeS₂embedded in nitrogen doped carbon withmosaic structure:An effective catalyst for oxygen evolution reactionCeO₂/FeS₂/N-C electrocatalyst supported by CeO₂/FeS₂/N-C microspheres was prepared using simple conducting polymer p-phenylenediamine as nitrogen and carbon sources,and thio-acetamide was used as S source.The precursor of polyp-phenylenediamine nanospheres was cleverly prepared by a simple synthesis process of phenolic resin.The advantages of this resin are that small molecules are not released during the curing process,and the finished product has ideal pore size and other advantages.By solvothermal method.Ce（NO₃）₃·6H₂Oand Fe（NO₃）₃·9H₂O was loaded on the nanospheres in the form of CeO₂/FeS₂and pyrolyzed at 900℃to obtain CeO₂/Fe₃O₄/N-C.The resulting CeO₂/Fe₃O₄/N-C was obtained by solvothermal reaction under the action of thioacetamide to obtain CeO₂/FeS₂/N-C.Due to the unique oxygen affinity of CeO₂itself,the existence of oxygen vacancy and the unique electronic structure of the synthesized CeO₂/N-C catalyst endowed the ideal oxygen precipitation reaction activity.The experimental conditions were further optimized to explore the influence of different metal doping ratios between metals on the catalyst.Through the coordination of the proportion regulation between different metals,It is found that when the ratio of two metals is the same,the catalytic activity will be insufficient.When the ratio of transition metal to rare earth element metal is enlarged,the agglomeration will occur when the metal doping amount is too large,which to some extent prevents the exposure of the active site of oxygen precipitation.Therefore,a large number of experiments have verified that CeO₂/FeS₂/N-C is obtained when the intermediate metal ratio of Fe:Ce=5:1 and the sulfide reagent TAA is 10 times of CeO₂/Fe₃O₄/N-C.Considering the benign transformation between Ce⁴⁺and Ce³⁺,rare earth oxides have ideal oxygen storage capacity and conductivity,which ensures effective charge transfer and efficient formation ofO₂^2-/O^-.It is worth noting that the relatively low OER overpotential（340 m V）measured at the current density of 100m A/cm²under the condition of 1 M KOH alkaline solution is better than commercial RuO₂（380 m V）.Part Ⅱ Fe₃N-modified Co-N/C was used as oxygen reduction electrocatalyst in wearable zinc air batteriesZIF-67 as the precursor after 900℃high temperature pyrolysis reaction successfully get a Co-N/C,the conductive polymer 2,6-2-amino-pyridine polymerization into a composite material,again through the solvent thermal A series of Co-N@Fe₃N/C electrocatalysts were prepared using Fe（NO₃）₃·9H₂O supported on a polymer in the form of Fe₃N.The influence of different pyrolysis temperatures on catalytic performance was explored.Pyrolysis was conducted at 800℃,900℃and1000℃respectively.It was found that with the increase of temperature,the degree of graphitization of catalysts tended to be complete,while the conductivity of catalysts also increased,and the catalytic performance also showed a trend of steady improvement.Considering that the catalytic performance at 1000℃is not as good as that at 900℃,it may be that some parts of rhomboidal dodecahedron with regular morphology have collapsed carbon matrix under high temperature pyrolysis,and the irregular morphology leads to the inability of orderly conduction of electrons.Simultaneously,the sintering phenomenon occurred in the process of cracking polymer at high temperature.It is even possible that the high temperature caused the agglomeration between different metals Fe and Co.Therefore,we tested the electrochemical performance of the optimized Co-N@Fe₃N/C,and the test results showed that the catalyst had a positive initial potential（0.949 V）,and the half-wave potential could also reach（0.863 V）.When we creatively used Co-N@Fe₃N/C as the oxygen electrode catalyst of zinc-air battery,The ideal open circuit potential（1.416 V）and peak power density(175.2 m W cm^-2)were obtained.Part Ⅲ NiCo₂O₄embedded in nitrogen doped carbon with Mosaic structure:a kind of effective oxygen evolution reaction electric catalystConducting polymers using simple 3-amino phenol as source of nitrogen and carbon source,the preparation of the NiCo₂O₄embedded in the Mosaic structure of nitrogen doped carbon as effective catalysts for oxygen precipitation reaction,Poly-3-aminophenol is a monomer polymerization of 3-aminophenol by the way of oxidation polymerization,and then NiCo₂O₄inlaid in poly-3-aminophenol to prepare NiCo₂O₄/N-C.The prepared product not only has the characteristics of ideal pore porosity,large surface area and multiple selective binding sites of poly（3-aminophenol）,but also has excellent oxygen precipitation ability of NiCo₂O₄.As a conductive polymer providing nitrogen and carbon sources,3-aminophenol has the characteristics of excellent conductivity,low price,portability,and considerable capacity and energy storage.After optimizing the experimental conditions,the influence of different metal doping ratios between metals on catalysts was explored.Through the coordination between metals,it was found that when the ratio of two metals was the same,the catalytic activity would be insufficient,because when different metals were doped in,the presence of metals would promote the redistribution of carbon atoms to the surrounding charge and improve the conductivity of the catalyst.At the same time,the catalytic active sites of oxygen reduction and oxygen precipitation are enriched.Doping metal in different forms can reasonably modify the morphology and catalytic properties of carbon precursors using ZIF-67 or conductive polymer.It is worth noting that the relatively low OER overpotential（283 m V）measured at the current density of 10m A/cm²under the condition of 1 M KOH alkaline solution is better than commercial RuO₂（340 mV）.