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Abstract
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Three mixed metal iron-lanthanide isostructural clusters formulated, [Fe7Ln4(μ4-O)3(μ3-O)(μ3-OH)2(μ2-OH)
(mdea)6(κ1
-OAc)(κ2
-OAc)3(μ-OAc)6(H2O)].nH2O where {n = 1.0, 2.5 and 0.5 for Ln = Nd (1), Pr (2), and Eu (3),
respectively} are prepared by the reaction of FeCl2⋅4H2O and Ln(NO3)3⋅6H2O with N-methyldiethanolamine
(mdea) and CH3COO− . The core of these compounds is irregular tent-like clusters. In these structures, the central
Fe is bridged to another Fe in the cluster ball by (μ4-O)3(μ3-O) and with bridged Ln2 with two (μ3-OH) ions. All
these clusters were investigated as electrocatalysts for water oxidation. The results illustrate that 1 is the most
efficient material for water oxidation with overpotential of 309 mV and Tafel slope of 100 mV dec− 1 in neutral
media. This is due to the larger electrochemical active surface area and more active catalytic sites of this cluster
compared to Fe7Pr4 and Fe7Eu4 clusters. The electrocatalytic behavior of these clusters during bulk electrolysis is
similar. In all 1–3, a yellow thin film is formed on the surface of electrode during water oxidation. The analyses
show the presence of iron oxide and Ln oxide as the main components in this film. Long-term stability testing
confirms that the film is active in the reaction, but its level activity depends on the nature of lanthanides present.
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