Cobaltitas de cálcio dopadas com Fe como eletrocatalisadores para a reação de evolução de oxigênio
The electrolysis of alkaline solutions is one of the most used strategies for producing hydrogen (H2). This process distinguishes itself by breaking the water molecule (water splitting) through two semi-reactions: Hydrogen Evolution Reaction (HER, cathodic reaction) and Oxygen Evolution Reaction (OE...
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| Yazar: | |
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| Diğer Yazarlar: | |
| Materyal Türü: | doctoralThesis |
| Dil: | pt_BR |
| Baskı/Yayın Bilgisi: |
Universidade Federal do Rio Grande do Norte
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| Konular: | |
| Online Erişim: | https://repositorio.ufrn.br/handle/123456789/45427 |
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| Özet: | The electrolysis of alkaline solutions is one of the most used strategies for producing
hydrogen (H2). This process distinguishes itself by breaking the water molecule (water
splitting) through two semi-reactions: Hydrogen Evolution Reaction (HER, cathodic
reaction) and Oxygen Evolution Reaction (OER, anodic reaction). The OER is
fundamental for several electrochemical technologies related to generate and storage
energy. New research for developing low-cost electrocatalysts with a good
electrochemical activity using more earth abundant elements has intensified in recent
years. The current work aims to study the effect of Fe doping on the OER of calcium
cobaltites, Ca3Co4-xFexO9 (x = 0, 0.1, 0.4, and 0.8). Powders were obtained by a proteic
sol-gel method using gelatin with calcination at 900 °C for 2 h. The resultant samples
were characterized by X-ray diffraction (XRD) and field emission scanning electron
microscopy (FESEM). X-ray photoelectron spectroscopy (XPS) provided information
on the chemical states of the surface, while Mössbauer spectroscopy confirmed the
presence of Fe+2, Fe+3 and Fe+4 ions. The Fe+2 ions replace the Co ions in the Ca2CoO3
layer and the Fe+4 ions are located in the CoO2 layer. While the Fe+3 ions are present
in the secondary phase Ca2Fe2O5 found in the samples. Fe has a strong preference
for occupying octahedral sites in the CoO2 layer over the Ca2CoO3 layer in the calcium
cobaltite maladjusted type structure. Linear scanning voltammetry (LSV), cyclic
voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to
analyze the electrochemical performance. The results indicated that Ca3Co3.2Fe0.8O9
needed the smallest overpotential of 320 mV to generate a current density of 10 mA cm-2. |
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