It is an urgent challenge to develop low-cost and high-performance catalysts for the oxygen evolution reaction (OER). We synthesized nanoparticulate electrocatalysts consisting of cobalt-doped goethite-type iron oxyhydroxide (α-FeOOH) with controlled Co/Fe ratios [Co x Fe 1– x OOH ( x ≤ 0.20)] based on our own wet process. A Co 0.20 Fe 0.80 OOH-coated glassy carbon electrode generated a current density ( j ) of 10 mA cm –2 at an overpotential (η) as small as 383 mV (1.61 V vs the reversible hydrogen electrode) in an alkaline electrolyte, with a small Tafel slope of 40 mV dec –1 and excellent durability, whereas pure α-FeOOH required η = 580 mV to reach the same current density. This can be ascribed to the effect of Co doping, which resulted in an increase in electrochemically active surface area and a decrease in charge-transfer resistance. The content of cobalt, a scarce resource, in the catalyst is much smaller than those in most of the other Fe-based catalysts reported so far. Thus, this study will provide a new strategy of designing cost-effective and high-performance catalysts for the OER in alkaline solution.

This paper reports a facile means of fabricating nitrogen-doped carbon cloth (CC) via a hydrothermal process in the presence of hydrazine and ammonia. The resulting N-doped CC can be used directly as an electrode for a supercapacitor, requiring no polymeric binder or current collector. X-ray photoelectron spectroscopy (XPS) revealed that the surface of oxidized CC was nitrogen-doped concurrently with reduction; in other words, the oxygen-containing groups were replaced with nitrogen species of different types depending on the composition and temperature of the hydrothermal bath. The highest areal capacitance was estimated to be 136 mF cm −2 at a current density of 0.5 mA cm −2 for a N-doped CC electrode treated at 160 • C, while the capacitance remained at 81% of its original value when the applied current density was increased from 0.5 to 15 mA cm −2 . We explored the role of different nitrogen species in the capacitive process based on a combination of XPS and electrochemical measurements. High hydrothermal temperatures and the presence of NH 3 yielded pyridinic nitrogen atoms, leading to fast electron transfer during charge/discharge cycles.

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