Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution.
Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution.
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DOI：
10.1038/ncomms9625
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发表时间：
2015-10-12
影响因子：
16.6
通讯作者：
Strasser P
中科院分区：
文献类型：
--
作者：
Bergmann A;Martinez-Moreno E;Teschner D;Chernev P;Gliech M;de Araújo JF;Reier T;Dau H;Strasser P
由地球丰富的材料催化的水裂解对于全球规模的非化石燃料生产至关重要，但我们对活性催化剂结构和反应性的理解仍然不足。在这里，我们报告在析氧反应过程中使用先进的原位X射线技术确定的晶体Co 3 O 4电催化剂的结构可逆演变。在电极电位促进析氧时，Co 3 O 4的亚纳米壳层转变为X射线无定形CoOx（OH）y，其包含二-μ-氧代桥联的Co 3 +/4+离子。与不可逆的非晶化不同，在这里，催化活性层的形成在返回到非催化电极条件时通过重结晶而逆转。由于其活性非晶氧化物的结构灵活性，Co 3 O 4材料因此结合了可控、稳定晶体材料的稳定性优势和高催化活性。我们建议，结晶氧化物可以定制用于在催化电位下产生反应性非晶表面层，只是为了在静止条件下返回到其稳定的结晶状态。 了解催化剂的结构和反应活性对于水裂解催化剂的开发是重要的。在这里，作者报告了可逆的结构转变的近表面的结晶Co 3 O 4电催化剂的非晶CoOx（OH）y在析氧。
Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co3+/4+ ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions. Understanding of catalyst structure and reactivity is important for the development of water splitting catalysts. Here, the authors report reversible structural transformation of the near-surface of crystalline Co3O4 electrocatalysts to an amorphous CoOx(OH)y during oxygen evolution.