Enhancing the water oxidation electrocatalysis of correlated perovskite nickelates by disordering NiO6 octahedra

摘要

While distorting the octahedral structure is generally recognized to regulate the electronic structure and functionalities of correlated perovskite oxides such as rare-earth nickelates (ReNiO3), the potential influence of the alignment of these distorted octahedrons has not yet been studied. Herein, we demonstrate the improvement in the water oxidation (OER) electrocatalysis of rare-earth co-occupied SmxNd1−xNiO3, wherein the potential orbital reconfiguration owing to the disordering of NiO6 octahedra alignments was previously overlooked. The orbital reconfigurations of Ni-3d and O-2p for SmxNd1−xNiO3 owing to disordered NiO6 octahedral alignment is depicted by combining near-edge X-ray absorption fine structure analysis and density functional theory (DFT) calculations. The resultant centralized p–d hybridization largely enhances OER electrocatalytic activity; in particular, the current density of Sm0.5Nd0.5NiO3 is enhanced by ten times compared to the well investigated nickelate catalyst NdNiO3. The exploration of the OER mechanism using DFT calculation reveals the participation of the lattice oxygen (OL) in the OER, as is further confirmed through a probe reaction in TMAOH electrolyte. By quantifying the diffusion coefficient of OL, the highest OER electrocatalytic activity of Sm0.5Nd0.5NiO3 is demonstrated to be associated with a ∼300 enhancement in the diffusion coefficient of OL as compared to NdNiO3. The enhancement of OER electrocatalysis via rare-earth co-occupation is further demonstrated to be intrinsic by measuring the electrochemical surface area and reproducing such enhancement in rare-earth co-occupied bulk samples. We highlight the additional freedom in optimizing the electrocatalysis reactivity of ReNiO3 associated with the alignment in their NiO6 octahedra, in addition to the already known perspectives, such as iso-valent or aliovalent doping, defect controlling, and strain engineering.