Li Xinzhe, Fang Yiyun, Wen Lixin, Li Feng, Yin Guanlin, Chen Wanmin, An Xingcai, Jin Jun, Ma Jiantai
State Key Laboratory of Applied Organic Chemistry, The Key Laboratory of Catalytic Engineering of Gansu Province and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China.
Dalton Trans. 2016 Apr 7;45(13):5575-82. doi: 10.1039/c6dt00102e. Epub 2016 Feb 25.
Cobalt-based nanomaterials are promising candidates as efficient, affordable, and sustainable alternative electrocatalysts for the oxygen evolution reaction (OER). However, the catalytic efficiency of traditional nanomaterials is still far below what is expected, because of their low stability in basic solutions and poor active site exposure yield. Here a unique hybrid nanomaterial comprising Co@Co3O4 core-shell nanoparticle (NP) encapsulated N-doped mesoporous carbon cages on reduced graphene oxide (denoted as Co@Co3O4@NMCC/rGO) is successfully synthesized via a carbonization and subsequent oxidation strategy of a graphene oxide (GO)-based metal-organic framework (MOF). Impressively, the special carbon cage structure is very important for not only leading to a large active surface area, enhanced mass/charge transport capability, and easy release of gas bubbles, but also preventing Co@Co3O4 NPs from aggregation and peeling off during prolonged electrochemical reactions. As a result, in alkaline media, the resulting hybrid materials catalyze the OER with a low onset potential of ∼1.50 V (vs. RHE) and an over-potential of only 340 mV to achieve a stable current density of 10 mA cm(-2) for at least 25 h. In addition, metallic Co cores in Co@Co3O4 provide an alternative way for electron transport and accelerate the OER rate.
钴基纳米材料有望成为高效、经济且可持续的析氧反应（OER）替代电催化剂。然而，传统纳米材料的催化效率仍远低于预期，这是因为它们在碱性溶液中的稳定性较低且活性位点暴露率较差。在此，通过基于氧化石墨烯（GO）的金属有机框架（MOF）的碳化及后续氧化策略，成功合成了一种独特的杂化纳米材料，该材料由包覆在还原氧化石墨烯上的N掺杂介孔碳笼中的Co@Co3O4核壳纳米颗粒（NP）组成（记为Co@Co3O4@NMCC/rGO）。令人印象深刻的是，这种特殊的碳笼结构不仅对于形成大的活性表面积、增强质量/电荷传输能力以及易于气泡释放非常重要，而且还能防止Co@Co3O4 NPs在长时间电化学反应过程中发生聚集和剥落。结果，在碱性介质中，所得的杂化材料催化OER时具有约1.50 V（相对于可逆氢电极，RHE）的低起始电位和仅340 mV的过电位，以实现至少25小时的10 mA cm(-2)稳定电流密度。此外，Co@Co3O4中的金属Co核为电子传输提供了一条替代途径，并加速了OER速率。
