Abstract
Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxy-hydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co0.54Fe0.46OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxy-hydroxide (FeOOH) catalysts, originate from the branch structure of Co0.54Fe0.46OOH on its surface so as to provide many active edge sites, enhanced mass/charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal−air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application.
Highlights
Gradually acknowledged and further explored for oxygen evolution reaction (OER) application[8,9]
The morphologies of FeOOH nanostructures were characterized by transmission electron microscopy (TEM) and high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM)
The main reason was that the Co-doping in FeOOH nanostructures constituted a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal−air batteries, regenerative fuel cells, and other important clean energy devices[41]
Summary
Gradually acknowledged and further explored for OER application[8,9]. the poor electrical conductivity of the FeOOH (~10−5 S cm−1) remains a major challenge and limits its mass-transfer kinetics[8]. Co doping in FeOOH nanostructure had shown excellent OER performance, because the Co ions could improve electron transfer enhance the electrical conductivity[13]. In the above cases, fabricate of high-quality FeOOH and Co-doped FeOOH nanostructures with pure phase, monodisperse and well-defined morphology, have not been demonstrated, which stimulate the continuous and systematic exploration. Gelatin as a water-soluble collagen, consisting of N-H functional groups, possesses many advantages to form inorganic-organic template for manipulating the growth of inorganic nanomaterials with diverse novel structures[14,15,16]. Owing to gelatin’s unique structural features and tunable properties, in the present work, we chose gelatin as the soft-template to synthesize high-quality FeOOH and Co-doped FeOOH nanostructures (CoxFe1−xOOH (x = 0.23, 0.54, 0.77)) (Fig. 1). The Co0.54Fe0.46OOH hybrid had lower onset potential of 1.52 V, lower overpotential of 390 mV at current density of 10 mA/cm[2], smaller tafel slope of 47 mV/dec and fairly longer time stability of 25000 s than other contrast catalysts, which can be attributed to more active edge sites, enhanced mass/charge transport capability and strong structural stability of the Co0.54Fe0.46OOH hybrid
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