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Abstract
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Herein, a new ternary-component layered double hydroxide (LDH) consisting of Ca2+ was constructed using an
inexpensive bio-waste; eggshell, through a facile hydrothermal method (NiCaFe-LDH-H). The prepared material,
NiCaFe-LDH-H, was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM),
N2 adsorption-desorption; Brunauer-Emmett-Teller (BET), difference thermogravimetry (DTG) and thermogravimetric
analysis (TGA). Then, the NiCaFe-LDH-H was used as an electrocatalyst material to fabricate the
modified carbon paste electrode (CPE) for water oxidation at neutral solutions (pH = 7.0). The electrochemical
tests show that the NiCaFe-LDH-H modified CPE has efficient electrocatalytic activity towards the water oxidation
reaction in a neutral solution. The effect of the LDH preparation method, presence of Ca2+ (as a low-cost
material in comparison with transition metals), and its primary source was investigated on the electrocatalytic
activity of the NiCaFe-LDH-H modified CPE and compared with binary-component LDHs (without Ca2+). The
results of the electrochemical examinations indicate that the incorporation of Ca2+ from the eggshell source into
the LDH by the hydrothermal method improve water oxidation performance of the NiCaFe-LDH-H modified CPE:
lowering the onset potential to about 1.56 V vs. reversible hydrogen electrode (RHE) and overpotential to
373 mV in a neutral solution. The promoted electrocatalytic activity of the present modified CPE can be attributed
to the high active surface area of the NiCaFe-LDH-H modified CPE due to the high crystallinity of LDH
containing Ca2+.
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