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High Oxygen Evolution Activity of Tungsten Bronze Oxides Boosted by Anchoring of Co2+ at Nb5+ Sites Accompanied by Substantial Oxygen Vacancy
Advanced Science ( IF 14.3 ) Pub Date : 2020-09-29 , DOI: 10.1002/advs.202002242
Xiaoning Li 1 , Huan Liu 2 , Yanhua Sun 1 , Liuyang Zhu 2 , Xiaofeng Yin 3 , Shujie Sun 3 , Zhengping Fu 2 , Yalin Lu 2 , Xiaolin Wang 1 , Zhenxiang Cheng 1
Affiliation  

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 Sr0.5Ba0.5Nb2‐xCoxO6‐δ, with different ratios of Co to Nb to optimize the Co substitution proportion. It is found that the occupation of Co in the Nb5+ sites gives rise to the generation of massive surface oxygen vacancies (Ovac), while Co itself is stabilized in Co2+ by adjacent Ovac. The coexistence of Ovac and LS Co2+ 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.

中文翻译:

Co2+ 锚定在 Nb5+ 位点并伴随大量氧空位增强钨青铜氧化物的高析氧活性

尽管激活传统刚性结构中的晶格氧仍然是一个巨大的挑战,但在析氧反应(OER)过程中晶格氧的参与已被证明在动力学上比仅涉及金属的机制更快。在这项工作中,我们致力于探索一种新的柔性结构,该结构能够提供大量的氧空位,并提供操纵金属阳离子电子结构的自由。通过将低价态 Co 锚定在四方钨青铜 (TTB) 结构的 Sr 0.5 Ba 0.5 Nb 2- x Co x O 6- δ中的高价态 Nb 位点上,并使用不同的 Co 与 Nb 比例来优化Co替代比例。研究发现,Co在Nb 5+位点上的占据导致了大量表面氧空位(O vac )的产生,而Co本身则通过相邻的O vac稳定在Co 2+中。O vac和 LS Co 2+的共存使得最佳 SBNC45 中的氧嵌入机制成为可能,其在 1.7 V 下的比活性与可逆氢电极相比,比商用 IrO 2高 20 倍。这项工作为合理设计具有超快动力学的 OER 电催化剂开辟了一条全新途径。
更新日期:2020-11-19
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