Correlating the electronic structure of perovskite La1-xSrxCoO3 with activity for the oxygen evolution reaction:The critical role of Co 3d hole state

• 作者: Zechao Shen Mei Qu Jueli Shi Freddy E.Oropeza Victor A.de la Pe(n)a O'Shea Giulio Gorni C.M.Tian Jan P.Hofmann Jun Cheng Jun Li Kelvin H.L.Zhang
• 来源期刊: 能源化学
• 年，卷（期）: 2022,（2）
• 页码范围: 637-645
• 页数: 9页
• 语种: 英文

摘要

Perovskite LaCoO3 is being increasingly explored as an effective low-cost electrocatalyst for the oxygen evolution reaction (OER).Sr doping in LaCoO3 (La1-xSrxCoO3) has been found to substantially increase its catalytic activity.In this work,we report a detailed study on the evolution of the electronic structure of La1-xSrxCoO3 with 0 ≤ x ≤ 1 and its correlation with electrocatalytic activity for the OER.A combination of X-ray photoemission spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) was used to unravel the electronic density of states (DOS) near the Fermi level (EF),which provide insights into the key elec-tronic structure features for the enhanced OER catalytic activity.Detailed analysis on the Co L-edge XAS suggest that LaCoO3 has a low spin state with t62ge0g configuration at room temperature.This implies that the high OER catalytic activity of LaCoO3 should not be rationalized by the occupancy of eg =1 descriptor.Substituting Sr2+ for La3+ in LaCoO3 induces Co4+ oxidation states and effectively dopes hole states into the top of valence band.A semiconductor-to-metal transition is observed for × ≥ 0.2,due to the hole-induced electronic DOS at the EF and increased hybridization between Co 3d and O 2p.Such an electronic modulation enhances the surface adsorption of the *OH intermediate and reduces the energy barrier for interfacial charge transfer,thus improving the OER catalytic activity in La1-xSrxCoO3.In addition,we found that the La1-xSrxCoO3 surface undergoes amorphization after certain period of OER measurement,leading to a partial deactivation of the electrocatalyst.High Sr doping levels accelerated the amorphiza-tion process.