A bifunctional perovskite oxide catalyst:The triggered oxygen reduction/evolution electrocatalysis by moderated Mn-Ni co-doping

ABO-type perovskite oxides(e.g.,LaCoO) with flexible and adjustable A-and B-sites are ideal model catalysts to unravel the relationship between the electronic structure and electrocatalytic activity(e.g.,oxygen reduction/evolution reactions,ORR/OER).It has been well understood in our recent work that the secondary metal dopant at B-site(e.g.,Mn in LaMnCoO) can regulate the electronic structure and improve the ORR/OER activity.In this work,the Mn-Ni pairs are employed as the dual dopant in LaMnNiCoO(x+y+z=1) catalysts toward bifunctional ORR and OER.The structure-property relationships between the triple metal B-site(Mn,Ni and Co) and the electrochemical performance are particularly investigated.Compared to the individual Mn doping(e.g.,LaMnCoO(Mn:Co=1:3) catalyst),the dual Mn-Ni doping significantly improves the ORR mass activity@0.8 V by 1.54 times;meanwhile,the OER overpotential@10 mA cmis reduced from 420 to 370 mV,and the OER current density at 1.55 V is increased by 2.43 times.Reasonably,the potential gap between EDRR@-1 mA cmand E@10 mA cmis achieved as only 0.76 V by using the optimal LaMnNiCoO(x:y:z=1:2:3) catalyst.It is revealed that the dual Mn-Ni dopant efficiently optimizes electron structures of the LaMnNiCoO(1:2:3) catalyst,which not only decreases the eg orbital electron number,but also modulates the O 2 p-band closer to the Femi level,accounting for the enhanced bifunctional activity.