Local Hydroxide Ion Enrichment at Inner Surface of Lacunaris Perovskite Nanotubes Facilitates Oxygen Evolution Reaction

Abstract

Numerous strategies have been devised to optimize the intrinsic activity of perovskite oxides for oxygen evolution reaction (OER). However, conventional synthetic routes typically yield limited active sites and low mass activities. More critically, the sluggish mass transfer poses a huge challenge, particularly at high polarization conditions, which impedes the overall reaction kinetics. Herein, lacunaris La0.5Pr0.25Ba0.25Co0.8Ni0.2O3−δ nanotubes (LPBCN-NTs) were prepared via electrospinning and post-annealing, which exhibited a small overpotential of 358.8 mV at 10 mA cm−2 and a lower Tafel slope of 71.46 mV dec−1, superior to the same stoichiometric LPBCN nanoparticles and solid nanofibers, the state-of-the-art counterparts and the commercial IrO2. Density functional theory calculations revealed that the surface oxygen vacancies in LPBCN-NTs significantly lowered the OH− adsorption energy, while finite element analysis indicated that the precisely-constructed lacunaris NT structure enriched an order of magnitude higher OH− concentration at its inner surface, both of which collectively resulted in the accelerated OER kinetics. This study clarifies clearly the underlying mechanism of how the lacunaris nanotubular architecture and the surface oxygen vacancy of perovskite oxides affect the heterocatalysis, which undoubtedly paves an avenue to handle the long-standing issues of sluggish mass transfer rate and poor intrinsic catalytic activity.