Coaxial ultrathin Co_1-yFe_yO_x nanosheet coating on carbon nanotubes for water oxidation with excellent activity

The rational design of high-performance and non-precious metal electrocatalysts is highly important for energy technologies. Herein, for the first time, a coaxial ultrathin Co_1-yFe_yO_x nanosheet coating on carbon nanotubes (denoted as Co_1-yFe_yO_x/CNTs) is prepared by a one-step pyrolysis method. The fabrication procedure is ultrafast and uncomplicated, furthermore, it does not need any reducing agent, alkali, or surfactant. In 1.0 M KOH, the obtained optimal hybrids Co_0.8Fe_0.2O_x/CNTs_{25 wt%} catalyze oxygen evolution reactions (OER) with a very sharp onset potential (∼1.45 V) and an exceptional over-potential (0.28 V, at 10 mA cm^-2) for more than 14 h, benefiting from the abundant active sites of ultrathin Co_0.8Fe_0.2O_x nanosheets, the hierarchical tubular architecture, and the strong cooperative effect among Co, Fe and CNTs. Remarkably, the excellent activity and durability of Co_0.8Fe_0.2O_x/CNTs_{25 wt%} for the OER is superior to commercial RuO₂ and many other highly active precious-metal/transition-metal catalysts reported to date. The design concept for tubular iron-group binary metal nanosheet hybrids creates new pathways for energy technologies.