부산대학교 도서관

Perovskite oxides (AB[O.sub.3]) have been widely recognized as a class of promising noble-metal--free electrocatalysts due to their unique compositional flexibility and structural stability. Surprisingly, investigation into their size-dependent electrocatalytic properties, in particular barium titanate (BaTi[O.sub.3]), has been comparatively few and limited in scope. Herein, we report the scrutiny of size-and dopant-dependent oxygen reduction reaction (ORR) activities of an array of judiciously designed pristine BaTi[O.sub.3] and doped BaTi[O.sub.3] (i.e., La- and Co-doped) nanoparticles (NPs). Specifically, a robust nanoreactor strategy, based on amphiphilic star-like diblock copolymers, is employed to synthesize a set of hydrophobic polymer-ligated uniform BaTi[O.sub.3] NPs of different sizes ([less than or equal to]20 nm) and controlled compositions. Quite intriguingly, the ORR activities are found to progressively decrease with the increasing size of BaTi[O.sub.3] NPs. Notably, La- and Co-doped BaTi[O.sub.3] NPs display markedly improved ORR performance over the pristine counterpart. This can be attributed to the reduced limiting barrier imposed by the formation of -OOH species during ORR due to enhanced adsorption energy of intermediates and the possibly increased conductivity as a result of change in the electronic states as revealed by our density functional theory--based first-principles calculations. Going beyond BaTi[O.sub.3] NPs, a variety of other AB[O.sub.3] NPs with tunable sizes and compositions may be readily accessible by exploiting our amphiphilic star-like diblock copolymer nanoreactor strategy. They could in turn provide a unique platform for both fundamental and practical studies on a suite of physical properties (dielectric, piezoelectric, electrostrictive, catalytic, etc.) contingent upon their dimensions and compositions. star-like diblock copolymer | perovskite nanocrystals | oxygen reduction reaction | density functional theory