Preparation And Electrochemical Properties Of Doped Carbon Materials Based On Supramolecular Precursor Design

Carbon materials show excellent application prospects in the field of energy,optoelectronics and bionics due to their high stability,wide abundance,and environmental friendliness.Control over the synthesis of carbon-based materials with specific morphology,structure and composition on the nanometer scale is of great significance for the improvement of their performances and the derivation of new properties.Doped carbon materials,owning to their outstanding physicochemical properties,are particularly effective in the application of fuel cell electrode catalysts.In this paper,heteroelement containing polymer assemblies were constructed through condensation polymerization or metal coordination reaction,which were then transformed into doped carbon materials by using a sintering process.With this method,the structure,morphology and composition of the doped carbon materials are controlled.Moreover,it can be used as a carrier to support the noble metal nanoparticles,so that the electrochemical performances are studied.Firstly,we synthesized the three-armed monomer named TBC terminated with three catechol groups.Polymer cross-linked network was prepared,based on the coordination between the catechol and ferric ion.When it was sintered at high temperature,accompanied with the effect of catalytic graphitization of iron,iron-supported,nitrogen-doped carbon nanomaterials(Fe/N/C)with ordered structure were obtained.Fe/N/C as non-noble metal catalysts own porous structure,large specific surface area and N,Fe co-doped component,thus exhibiting excellent catalytic performances,methanol resistance,and electrochemical stability.In addition,the influences of ferric salt type on the structure and properties of Fe/N/C were explored.The results revealed that the electrochemical performances of Fe/N/C treated with ferric sulafate or ferric chloride were superior to the others(Fe/N/C treated with ferric nitrate or ferric acetylacetonate).Subsequently,we synthesized the three-armed monomer named TBB terminated with three phenylboronic acid groups.Boronate polymer microspheres(BP)were formed via a self-assembly behavior accompanied with the condensation reaction between catechol and boric acid group.With the introduction of chloroplatinic acid,the boronate microspheres were etched by the coordination reaction between the chloroplatinic ions and catechol,leaving holes on the surface of the microspheres while Pt element was introduced into the polymer spheres,and BP-Pt hybrid particles were obtained.When they were sintered at high temperature,Pt nanoparticles were reduced and supported on the carbon materials.Finally,nitrogen,boron co-doped porous carbon nanospheres loaded with Pt nanoparticles(NBC-Pt)were prepared.The as-prepared NBC-Pt have spherical structure,loading with uniform Pt nanoparticles(diameter～2-3 nm),and N,B co-doped component.Thus these hybrid materials can act as noble metal catalyst for ORR catalysis and exhibit outstanding properties.Furthermore,the effects of chloroplatinic acid on the morphology,structure,and properties of the NBC-Pt were studied.The results show that NBC-Pt-2 and NBC-Pt-3 exhibit the best electrochemical performances,comparable to the commercial Pt/C catalyst.