CN_x-(Si/Sn) Oxide Nano-composite Supported For Oxygen Reduction Reaction

Fuel cells are clean and efficient electrochemical power device that have a widevariety of potential applications.However,the commercialization of fuel cell needovercome a lot of barriers,such as high catalyst cost,low activity and stability.Thegreat efforts have been devoted to developing new kind catalyst of fuel cell.Atpresent,the most effective catalysts for oxygen reduction reaction （ORR） kinetics forlow temperature fuel cells include Pt/C.However,their electrocatalytic activity andstability need to be improved.Some researchers through improved catalyst support toimproved catalysts activity,such as,carbon nanotubes （CNTs）,graphite nanofibers,carbon spherules instead of tradition support carbon.These studies have made asignificant impact on the electrocatalysts.However,these carbon materials in terms ofactivity,cost and durability still do not satisfy the requirements of thetarget.Nitrogen-doped carbon （CN_x） have strong valence bonds between nitrogenatoms and carbon atoms,which can improve the activity and durability ofcatalysts.Nitrogen atoms can promote the formation of electrochemical active sitesand fixed metal atoms.To match this requirements,we have focused on the preparation of CN_xcoatedoxide for supports.The new catalysts are found to exhibit high electrocatalyticactivities and good stabilities during recation.The structural and chemical propertiesof samples were characterized by Fourier-Transform infrared,X-ray diffraction （XRD）,and transmission electron microscopy （TEM）,etc.Additionally,the catalysts weretested in a micro fuel cell system by measuring the performance for ORR,which weremade from our lab-made catalysts.It was found that these catalysts showed quite goodactivity for ORR in polymer fuel cells.The thesis is consists of two parts and theresearch details are as follows:Part Ⅰ: Nitrogen-doped carbon coated SiO₂as an efficientelectrocatalyst support for ORRAn electrocatalyst support,nitrogen-doped graphitic layer （CN_x） oxide （SiO₂）（donated as CN_x-SiO₂） is synthesized by carbonizing the polypyrrole （PPy） coated SiO₂and is explored for the first time as a cathode electrocatalyst support in protonexchange membrane fuel cell.The structural and chemical properties of the CN_x-SiO₂are investigated using Fourier-Transform infrared,X-ray diffraction and transmissionelectron microscopy.The electrocatalytic activity and stability of Pt/CN_x-SiO₂towardsORR are studied by cyclic voltammetry （CV） and steady state polarizationmeasurements.Upon loading20%Pt metal,the catalysts exhibit superior catalyticperformance during ORR,surpassing the conventional Pt/C （Vulcan XC-72） catalysts.Part Ⅱ: Nitrogen-doped carbon coated SnO₂as an efficientelectrocatalyst support for ORRAn electrocatalyst support,nitrogen-doped graphitic layer （CN_x） oxide （SnO₂）（donated as CN_x-SnO₂） is synthesized by carbonizing the polypyrrole （PPy） coatedSnO₂and is explored for the first time as a cathode electrocatalyst support in protonexchange membrane fuel cell.The structural and chemical properties of the CN_x-SnO₂are investigated using FTIR,XRD and TEM.The electrocatalytic activity and stabilityof Pt/CN_x-SnO₂towards ORR are studied by CV and steady state polarizationmeasurements.Upon loading20%Pt metal,the catalysts exhibit superior catalyticperformance during ORR,surpassing the conventional Pt/C （Vulcan XC-72） catalysts.