Local hydroxide ion enrichment at the inner surface of lacunaris perovskite nanotubes facilitates the oxygen evolution reaction.

ABSTRACT

Numerous strategies have been devised to optimize the intrinsic activity of perovskite oxides for the oxygen evolution reaction (OER). However, conventional synthetic routes typically yield limited numbers of active sites and low mass activities. More critically, the sluggish mass transfer poses a huge challenge, particularly under 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 values for the same stoichiometric LPBCN nanoparticles and solid nanofibers, state-of-the-art counterparts and 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 the OH- concentration at its inner surface by an order of magnitude, both of which collectively resulted in accelerated OER kinetics. This study clarifies the underlying mechanism of how the lacunaris nanotubular architecture and the surface oxygen vacancies of perovskite oxides affect heterocatalysis, which undoubtedly paves the way to handling the long-standing issues of sluggish mass transfer rates and poor intrinsic catalytic activity.