  Strain is known to greatly influence low temperature oxygen electrocatalysis
on noble metal films, leading to significant enhancements in bifunctional
activity essential for fuel cells and metal-air batteries. However, its
catalytic impact on transition metal oxide thin films, such as perovskites, is
not widely understood. Here, we epitaxially strain the conducting perovskite
LaNiO3 to systematically determine its influence on both the oxygen reduction
and oxygen evolution reaction. Uniquely, we found that compressive strain could
significantly enhance both reactions, yielding a bifunctional catalyst that
surpasses the performance of noble metals such as Pt. We attribute the improved
bifunctionality to strain-induced splitting of the eg orbitals, which can
customize orbital asymmetry at the surface. Analogous to strain-induced shifts
in the d-band center of noble metals relative to Fermi level, such splitting
can dramatically affect catalytic activity in this perovskite and other
potentially more active oxides.
