Carbon-based Electrocatalysts Derived From Self-assembled Conducting Polymers:Design,Synthesis And Applications

Electrocatalysis is catalytic process driven by electricity and electrocatalyst which accelerate charge transfer between electrode and electrolyte.Electrocatalysis processes are of vital importance to clean/renewable energy system and further enable carbon neutral cycle.Water and carbon dioxide based electrochemical reactions are the key to fuel cell,metal air battery,water splitting and carbon dioxide reduction system.Carbon materials possess unique features in elemental composition,microstructure and electronic state.Heteroatom doped carbons and metal/carbon composites are widely applicated in electrocatalysis.Conducting polymers are ideal precursors for carbon material.The highly conjugated nature offer suitable structure features for carbonization.Heteroatoms can be homogeneously distributed on conducting polymer precursors.Through proper molecular design and assembly,the composition and structure of conducting polymers can be tuned at different levels,which provide possibility in preparation of new carbon materials.All the above indicate the advantage of conducting polymer derived carbons in electrocatalysis.During my phD career,I mainly focused on carbon based electrocatalysts derived from self-assembled conducting polymers for oxygen reduction reaction(ORR),water splitting and carbon dioxide reduction(CO2RR).The main content is.1.An evaporation induced self-assembly method was developed to facile realize the assembly of graphene oxide(GO)and oxidized carbon nanotube(CNT)into hybrid nanospheres.The spontaneous segregation of oxidized CNT and GO in aerosolized droplets leads to formation of CNT/graphene hybrid nanospheres.After nitrogen and phosphorus doping,the hybrid nanospheres can effectively catalyze oxygen reduction reaction not only in alkaline but also in acidic media.The catalytic activity and layers of graphene can be tuned by varying the ratio of graphene oxide and oxidized CNT in the precursor solution.This method realize the optimization of surface area,degree of heteroatom doping,charge transfer ability,which is beneficial for mass and charge transport.It exhibit higher activity than Pt/C when used in alkaline zinc air battery and than other commonly used assembly method.This work offer new way for assembly of CNT and graphene and offer new concept for design of metal-free electrocatalyst.2.Novel iron/cobalt containing polypyrrole hydrogel is used as precursor for preparation of Fe/Co-nitrogen doped carbon material.It can be used to catalyze ORR/OER in alkaline media and can realize HER in wide pH range.Control experiments show that both Fe-N-C,Co-N-C and Co nanoparticles are essential to obtain trifunctional activity.Taking advantage of the trifunctional activity,a self-powered water splitting system was constructed by connecting two zinc-air batteries and an alkaline water splitting cell,using the obtained trifunctional electrocatalyst.Stable H2 and O2 evolution was observed with rates of 280 and 140 umol/h.This work demonstrates the application of conducting polymer derived carbon material in energy related applications and provide new insights for sustainable production of hydrogen energy.3.CO22 reduction is a promising way to solve the greenhouse effect.We develop a supramolecular crosslinked polypyrrole nanofiber derived Ni-N-C catalyst for electrocatalytic CO2 reduction.Aqueous CO2 reduction can be obtained with CO faradic efficiency up to 95%.At the same time,it can also catalyze OER in alkaline and neutral media.Based on the unique bifunctional electrocatalytic activity,we construct a full-cell CO2 reduction system using this catalyst which converts CO2/H2O into CO and O2.The activity exhibits no decay in 10 hours and CO faradic efficiency remains above 90%.Experiment results and DFT calculations indicate Ni-N center with lower N coordination numbers is the key to obtain the high activity.Control experiments show supramolecular crosslinking method is more proven to get uniformly distributed and effective Ni-N center.This work offer new idea for designing C02 reduction electrocatalysts,which is of great importance to realize carbon neutral cycle in the near future.