High Oxygen Evolution Activity of Tungsten Bronze Oxides Boosted by Anchoring of Co2+ at Nb5+ Sites Accompanied by Substantial Oxygen Vacancy. Issue 22 (29th September 2020)

• Record Type: Journal Article
• Authors: Li, Xiaoning; Liu, Huan; Sun, Yanhua; Zhu, Liuyang; Yin, Xiaofeng; Sun, Shujie; Fu, Zhengping; Lu, Yalin; Wang, Xiaolin; Cheng, Zhenxiang
• Is Part Of: Advanced science. Volume 7:Issue 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-29
• Subjects: oxygen intercalation mechanisms -- oxygen evolution reaction -- oxygen vacancies -- spin configuration -- tungsten bronze; Science -- Periodicals; 505
• DOI: 10.1002/advs.202002242
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: The participation of lattice oxygen in the oxygen evolution reaction (OER) process has been proved to be faster in kinetics than the mechanisms where only metal is involved, although activating the lattice oxygen in the traditional rigid structures remains a big challenge. In this work, efforts are devoted to exploring a new flexible structure that is competent in providing large amounts of oxygen vacancies as well as offering the freedom to manipulate the electronic structure of metal cations. This is demonstrated by anchoring low valence state Co at high valence state Nb sites in the tetragonal tungsten bronze (TTB)‐structured Sr0.5 Ba0.5 Nb2‐ x Co x O6‐ δ, with different ratios of Co to Nb to optimize the Co substitution proportion. It is found that the occupation of Co in the Nb 5+ sites gives rise to the generation of massive surface oxygen vacancies (Ovac ), while Co itself is stabilized in Co 2+ by adjacent Ovac . The coexistence of Ovac and LS Co 2+ enables an oxygen intercalation mechanism in the optimal SBNC45 with specific activity at 1.7 V versus reversible hydrogen electrode that is 20 times higher than for the commercial IrO2 . This work illuminates an entirely new avenue to rationally design OER electrocatalysts with ultrafast kinetics. Abstract : A cobalt‐doped tetragonal tungsten bronze structure Sr0.5 Ba0.5 Nb2‐ x Co x O6‐ δ is developed as a new oxygen evolution reaction electrocatalyst. This structure is competent in providing large amount of oxygen vacancies as well as the freedom to manipulate the electronic structure. The current density normalized by BET surface area of the optimal sample is 20 times higher than the commercial IrO2 .