Enhancing oxygen evolution efficiency of multiferroic oxides by spintronic and ferroelectric polarization regulation

Xiaoning Li,Qingmei Wu,Zhengping Fu,Huan Liu,Zhenxiang Cheng,Zezhi Chen,Mengmeng Yang,Yalin Lu,Zheyin Yu,Xiaolin Wang

doi:10.1038/s41467-019-09191-0

Abstract

Regulating the electronic structure of catalysts is the most efficient strategy yet, despite its limitations, to improve their oxygen evolution efficiency. Instead of only adjusting the electronic structure, here we utilize ferroelectric polarization to accelerate the oxygen evolution reaction as well. This is demonstrated on a multiferroic layered perovskite Bi5CoTi3O15 with in-situ grown BiCoO3. Thanks to the superimposed effects of electronic regulation and ferroelectric polarization, the as-prepared multiferroic electrocatalysts are more efficient than the benchmark IrO2 (with a final 320 mV overpotential at the current density of 10 mA cm−2 and a 34 mV dec−1 Tafel slope). This work not only demonstrates a low-cost and high-efficient OER electrocatalyst, but also provides a strategic design for multi-component electrocatalytic material systems by consideration of both spin and polarization degrees of freedom.

Highlights

Regulating the electronic structure of catalysts is the most efficient strategy yet, despite its limitations, to improve their oxygen evolution efficiency
The fastest oxygen evolution reaction (OER) is observed on Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF), of which the magnetic ions are in the intermediate spin state, that is, the number of eg electrons is around 1.2
Four samples were prepared by the in situ hydrothermal method according to the designed composition of Bi4Ti3O12·(BiCoO3)n (n = 1, 2, 3, 4), and denoted as Co1, Co2, Co3, and Co4, respectively

Summary

Introduction

Regulating the electronic structure of catalysts is the most efficient strategy yet, despite its limitations, to improve their oxygen evolution efficiency. Instead of only adjusting the electronic structure, here we utilize ferroelectric polarization to accelerate the oxygen evolution reaction as well This is demonstrated on a multiferroic layered perovskite Bi5CoTi3O15 with in-situ grown BiCoO3. Inspired by the abovementioned spin state effects and the ferroelectric polarization function, we considered the multiferroic layered perovskite oxides as an excellent material matrix to combine the two strategies together to further improve the OER efficiency[22,23]. From considerations of structural tolerance and thermodynamic stability, only one layer of BCO can be inserted to form a four-layered perovskite oxide Bi5CoTi3O15 (BCTO), while the residual BCO would be deposited in situ on its surface as the secondary phase This configuration provides a suitable research platform to reveal the significance of the electronic regulation, as well as ferroelectric polarization on the OER performance. The electronic structure and the contribution of the ferroelectric polarization are studied in detail by various tests and measurements, and a possible enhanced mechanism is proposed

Methods

Results

Conclusion