Utilizing ion leaching effects for achieving high oxygen-evolving performance on hybrid nanocomposite with self-optimized behaviors

Daqin Guan,Alexander C Komarek,Xinhao Wu,Chien-Te Chen,Zhiwei Hu,Ming Zhu,Wei Zhou,Kaifeng Zhang,Zongping Shao,Yu-Cheng Huang,Chung-Li Dong,Jing Zhou,Hong-Ji Lin,Chung-Kai Chang,Yijun Zhong,Gihun Ryu,Chih-Wen Pao

doi:10.1038/s41467-020-17108-5

Abstract

Ion leaching from pure-phase oxygen-evolving electrocatalysts generally exists, leading to the collapse and loss of catalyst crystalline matrix. Here, different from previous design methodologies of pure-phase perovskites, we introduce soluble BaCl2 and SrCl2 into perovskites through a self-assembly process aimed at simultaneously tuning dual cation/anion leaching effects and optimizing ion match in perovskites to protect the crystalline matrix. As a proof-of-concept, self-assembled hybrid Ba0.35Sr0.65Co0.8Fe0.2O3-δ (BSCF) nanocomposite (with BaCl2 and SrCl2) exhibits the low overpotential of 260 mV at 10 mA cm-2 in 0.1 M KOH. Multiple operando spectroscopic techniques reveal that the pre-leaching of soluble compounds lowers the difference of interfacial ion concentrations and thus endows the host phase in hybrid BSCF with abundant time and space to form stable edge/face-sharing surface structures. These self-optimized crystalline structures show stable lattice oxygen active sites and short reaction pathways between Co–Co/Fe metal active sites to trigger favorable adsorption of OH− species.

Highlights

Ion leaching from pure-phase oxygen-evolving electrocatalysts generally exists, leading to the collapse and loss of catalyst crystalline matrix
Decades of efforts have been devoted to understanding the oxygen evolution reaction (OER) mechanisms (4OH− → O2 + 2H2O + 4e−) on oxides and the mechanism systems have been successfully established, including conventional adsorbate evolution mechanism (AEM) on active transition-metal sites[10], lattice oxygen oxidation mechanism (LOM) on active oxygen sites[32], and cooperative AEM and LOM on metal and oxygen active sites[16,33], respectively
Based on prior studies[5,8,18,21,22,23,24,34,35], we propose the possible basic models for the variations of electrocatalyst surface triggered by ion leaching effects during OER in alkaline solutions here

Summary

Introduction

Ion leaching from pure-phase oxygen-evolving electrocatalysts generally exists, leading to the collapse and loss of catalyst crystalline matrix. Multiple operando spectroscopic techniques reveal that the pre-leaching of soluble compounds lowers the difference of interfacial ion concentrations and endows the host phase in hybrid BSCF with abundant time and space to form stable edge/face-sharing surface structures These self-optimized crystalline structures show stable lattice oxygen active sites and short reaction pathways between Co–Co/Fe metal active sites to trigger favorable adsorption of OH− species. Different from prior design methodologies of pure-phase perovskites, we introduce soluble foreign compounds (namely BaCl2 and SrCl2) into high-valence perovskite structures via a self-assembly synthesis method for simultaneous achievement of positive anion/cation leaching effects and the protection of perovskite crystalline matrix. Our design principle based on operando changes of catalysts during electrocatalysis paves a new way to the rational design of hybrid materials for efficient energy conversions

Methods

Results

Conclusion