Increasing the active surface area of an electrocatalyst is crucial for effective oxygen evolution reaction (OER). Here, a sophisticated electrode that uses the advantages of porous/hollow nanostructure, hierarchical nanostructure, and self-supported structure simultaneously is demonstrated for the first time. A self-supported porous hierarchical core–shell structure (PHCS) of cobalt oxide is synthesized by the combination of electrochemical deposition and electrochemical treatment. The treatment introduces numerous pores into the core of a core–shell structure, and it decreases the particle size of cobalt oxide to <5 nm, markedly increasing the surface area of the resultant structures. The electrochemical surface area of PHCS is 1.6 greater than that of hierarchical core–shell cobalt oxide, and is ∼20 times greater than that of cobalt oxide nanowires. The PHCS is extremely active in the OER, with the overpotential required for a current density of 100 mA cm^–2 being as small as 300 mV. The Tafel slope is 40.3 mV dec^–1, and the PHCS can work stably for more than 40 h.

中文翻译：

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氧化钴的自支撑多孔分层核-壳纳米结构，用于高效氧释放反应

对于有效的析氧反应（OER），增加电催化剂的活性表面积至关重要。在这里，首次展示了同时利用多孔/空心纳米结构，分层纳米结构和自支撑结构优势的复杂电极。通过电化学沉积和电化学处理相结合，合成了氧化钴的自支撑多孔分级核-壳结构（PHCS）。该处理将许多孔引入到核-壳结构的核中，并且将氧化钴的粒径减小至<5 nm，从而显着增加了所得结构的表面积。PHCS的电化学表面积比分层的核壳型氧化钴大1.6倍，比氧化钴纳米线大20倍左右。PHCS在OER中非常活跃，电流密度为100 mA cm时需要过电势^–2小至300 mV。塔菲尔斜率是40.3 mV dec ^–1，PHCS可以稳定工作40个小时以上。