Synthesis Of TiO_x/rGO Composites And Their Electrocatalytic Properties For Oxygen Reduction Reaction

In recent years,fuel cells and their related materials have become research hotspots in the field of energy materials beeause of its environmental protection,zero emission and high fuel efficiency.Oxygen reduction reaction(ORR)is one of the key reactions in the development of fuel cell technology.Pt and its alloys have been considered as the excellent electrocatalysts for ORR because of their high efficient direct four-electron transfer process.However,their high cost,slow kinetic reaction and low stability hinder their largescale practical applications.Therefore,it is necessary to design non-noble metal catalysts with low-cost,efficient and simple synthesis method.In this our research,we have prepared a series of reduced graphene oxide(rGO)supported titanium oxides with different morphologies via electrochemical method,hydrothermal method and thermal reduction and studied their electrocatalytic performance for ORR in fuel cells.The main contents are as follows:Firstly,the TiO2NTs/rGO composite was fabricated by simple anodic oxidation and electrochemical method.It showed excellent ORR catalytic activity.Most importantly,it displayed much better long-term stability and methanol tolerance than Pt/C.Its excellent ORR catalytic activity and stability are mainly attributed to the synergistic effect of regular arrangement TiO2NTs and high conductive rGO.Secondly,we have successfully synthesized TiO2/rGO composites with different morphologies(octahedral,truncated octahedral and elliptical)through a facile hydrothermal strategy and ammonium titanate as a precursor.Among TiO2/rGO composites with different morphologies,the TiO2/rGO(octahedral)composite exhibited the best electro-catalytic activity in alkaline solution.This indicated that the catalytic activity of TiO2/rGO composites are affected by different morphologies of TiO2,which may attribute to the rate of electron transfer or oxygen adsorption is different in the exposed grain.Thirdly,the Ti2O3/rGO composite has been prepared by a facile thermal reduction method.The as-prepared TiZO3/rGO composite showed very superior ORR activity with the onset potential of 0.90V vs.RHE,nearly four electron transfer number and the highest energy conversion efficiency.Moreover,it demonstrates much better long-term stability and resistance to methanol crossover than Pt/C.