The Electrocatalytic Performance Optimizing Of Perovskites And Their Reactions Mechanism

In recent years,the electrocatalytic performances of perovskites have gained wide attention.Tailoring the elementary composition or ratio of perovskites with expect to optimize their ORR/OER activities become a common way for researchers.Here,we focus on how A-site deficiency influence the activities.Using a sol-gel method,we successfully synthesized LaNiO_3-??LNO?,La_0.95NiO_3-??L0.95NO?and La_0.9NiO_3-??L0.9NO?catalytics.Then XRD,SEM and XPS detections are used to systematically exploit the variation of crystal structures,microstructure and surface elementary composition.XRD results show the crystal of L0.9NO is distorted,and the lattice parameters shrink regularly.SEM images can not find any microstructure difference.The relative content of Ni³⁺on the surfaces of the three catalysts follow:L0.95NO>LNO>L0.9NO.And that of O₂^2-/O^-content follow:L0.9NO>L0.95NO>LNO.The ORR/OER activities are compared by LSV curves.The results show L0.95NO display the highest ORR limiting current and OER activity.L0.9NO's ORR onset potential is the most positive and the current density is higher than L0.95NO when the potential is more positive than 0.57 vs.RHE.OER activity is also higher than LNO when potential is more positive than 1.72 vs.RHE.These results show introducing A-site deficiency have positive effect to ORR/OER performance of LNO.But the transfer electron number calculated from Koutecky-Levich plots shows A-site deficiency did not optimize the ORR reaction mechanism.Tafel plot decreased imply the optimizing of the dynamic cause of OER reaction.A same method was used to study the influence of A-site deficiency to La_1-xCoO_3-?series.Results show the influence of crystal structure and lattice parameters is not clear,microstructure has no apparent difference,the relative content of Co³⁺on surface follows L0.95CO>LCO>L0.9CO,and the relative content of O₂^2-/O^-on surface follows L0.9CO>L0.95CO>LCO,then L0.9CO perform the best ORR/OER activity,and L0.95CO followed.The transfer electron numbers are close and tafel plots decrease also,shows introducing A-site deficiency is an advisable way to optimize the ORR/OER performances of perovskites.