Tailoring Spin State of Perovskite Oxides by Fluorine Atom Doping for Efficient Oxygen Electrocatalysis.

Abstract

Promoting the initially deficient but economical catalysts to high-performing competitors is important for developing superior catalysts. Unlike traditional nano-morphology construction methods, this work focuses on intrinsic catalytic activity enhancement via heteroatom doping strategies to induce lattice distortion and optimize spin-dependent orbital interaction to alter charge transfer between catalysts and reactants. Experimentally, a series of different concentrations of fluorine-doped lanthanum cobaltate (Fx -LaCoO3 ) exhibiting excellent electrocatalytic activity is synthesized, including a low overpotential of 390mV at j= 10mA cm-2 for OER and a large half-wave potential of 0.68V for ORR. Meanwhile, the assembled rechargeable Zn-air batteries deliver an excellent performance with a large specific capacity of 811 mAh/gZn under 10mA cm-2 and stability of charge/recharge (120h). Theoretically, taking advantage of density functional theory calculations, it is found that the prominent OER/ORR performance arises from the spin state transition of Co3+ (Low spin state (LS, t2g 6 eg 0 ) → Intermediate spin state (IS, t2g 5 eg 1 ) and the mediated d-band center upshift by F atom incorporation. This work establishes a novel avenue for designing superior electrocatalysts in perovskite-based oxides by regulating spin states.