Water electrolysis on La(1-x)Sr(x)CoO(3-δ) perovskite electrocatalysts.

J Tyler Mefford,Keith J Stevenson,Sheng Dai,Alexie M Kolpak,William G Hardin,Xi Rong,Artem M Abakumov,Keith P Johnston

doi:10.1038/ncomms11053

Abstract

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr2+ substitution into La1−xSrxCoO3−δ. We attempt to rationalize the high activities of La1−xSrxCoO3−δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.

Highlights

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems
Inherent to these systems are the electrolysis of water (2H2O-O2 þ 4H þ þ 4e À ; oxygen evolution reaction (OER)) and the reduction of molecular oxygen (O2 þ 4H þ þ 4e À -2H2O; oxygen reduction reaction (ORR)), both of which require the use of an electrocatalyst due to their slow reaction kinetics
Using alkaline electrolytes opens up the possibility to use transition metal oxides as catalysts due to their structural stability, resistance to electrolytic corrosion and their high activities for both the OER and ORR5–7

Summary

Introduction

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. A major thrust in the field of renewable energy has been to develop higher power and more energy-dense storage devices, including low-temperature regenerative fuel cells and rechargeable metal–air batteries that function through the electrocatalysis of oxygen Inherent to these systems are the electrolysis of water (2H2O-O2 þ 4H þ þ 4e À ; oxygen evolution reaction (OER)) and the reduction of molecular oxygen (O2 þ 4H þ þ 4e À -2H2O; oxygen reduction reaction (ORR)), both of which require the use of an electrocatalyst due to their slow reaction kinetics. La3 þ , the amount of oxygen vacancy defects and the oxidation state of cobalt can be tuned through the relation[28]: LaCo3 þ O3 þ xSr2 þ À xLa3 þ

Methods

Results

Conclusion