Tailoring electronic structure of stretchable freestanding single-crystal LaNiO3 thin film for enhanced oxygen evolution reaction

The comprehension of the electronic structure of an electrochemical catalyst, as a fundamental core content, has significantly accelerated advancements in competitive catalyst engineering since the adsorption and desorption abilities of an electrode are governed by its surface energy profile. However, achieving precise control over the electronic structure poses a significant challenge. Nanoporous materials, high-entropy systems, and layered double hydroxides frequently induce stoichiometric changes, leading to complexity such as electronic reconstruction, energy degeneracy disruption, and impurity energy levels. Here, we have successfully developed a stretchable freestanding single-crystal LaNiO3 thin film electrocatalyst enabling the accurate manipulation of the electronic structure on a large scale. Different from the rigid epitaxial heterostructure catalyst, we observed that with every 1 % increase in strain, the OER current of freestanding LaNiO3 is enhanced by ∼238 % compared to the pristine state. This is attributed to the dx2-y2 orbital occupation increasing by ∼7 %, and the eg-center decreasing by ∼0.05 eV, resulting in a weakened Ni-O adsorption. [Display omitted] •A stretchable freestanding single-crystal LaNiO3 (LNO) catalyst is developed.•The d orbital polarization and center are tuned by the in-plane biaxial strain.•Every 1 % increase in strain facilitates a ∼238 % improvement in OER current.•LNO with 4 % tensile strain offers an ultrahigh OER activity of 6.3 mA cm-2 at 1.63 V.