Investigation on Template Etching Process of SBA-15 Derived Ordered Mesoporous Carbon on Electrocatalytic Oxygen Reduction Reaction

摘要

Ordered mesoporous carbon(OMC)is a promising material for oxygen reduction reaction(ORR)in fuel cells owing to its high surface area and more number of catalytic active sites.Herein,OMC was synthesized by hard template method,i.e.,nanocasting of sacrificial silica template(SBA-15)and then the sacrificial template was abolished using three different etching chemicals namely,hydrofluoric acid(HF),sodium hydroxide(NaOH)and polyvinylidene fluoride(PVDF)respectively,in order to study the etching effect.The etched OMCs derived from the SBA-15 template was confirmed by various characterization techniques.In OMC,the porous nature,surface morphology and defect density changes with respect to etching chemicals were evidently determined.From the electrochemical studies,it has been concluded that the NaOH etched OMC showed higher electrocatalytic activity than others by exhibiting more positive onset(0.83 V),half-wave potential(0.75 V),high current density(3.3 mA/cm~2),Tafel slope(83 mV/dec)and n-value(2.4).Eventually,the electrochemical impedance study(EIS)was performed to determine the charge transfer resistance(R_(ct))of various etched OMCs and has been found that NaOH etched OMC shows the lowest R_(ct)value due to the presence of more defective sites and result in enhancing oxygen adsorption during ORR.