Synthesis and physicochemical properties of oxides based on lanthanum and transitions metals

Fawzi, HADJI (2023) Synthesis and physicochemical properties of oxides based on lanthanum and transitions metals. Doctoral thesis, Université Mohamed Khider (Biskra - Algérie).

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Abstract

Developing economical and highly efficient electrode material is crucial for water electrolysis and supercapacitors associated with energy conversion and storage. For this purpose, we successfully elaborated a new series of LaCo1 xZnxO3 oxides (x = 0, 0.03, 0.05, 0.1, 0.2, 0.3 and 0.4) via a facile sol gel route. We investigated, for the first time, their structural, morphological and electrochemical properties for possible use as electrode material toward oxygen evolution reaction and supercapacitor in a basic solution. Among the developed materials, the LaCo0.9Zn0.1O3 electrocatalyst displays a remarkable performance; an overpotential of merely 327 mV is needed to generate a specified current density of 10 mA.cm 2geo; a current density of around 73.41 mA.cm−2 at 450 mV, almost twice as high compared to the pristine electrocatalyst; a faster reaction kinetic with a lower Tafel slope of ~92 mV.dec−1 and an activity loss of less than 4 % after 24 hours of utilization. On the other hand, the LaCo0.95Zn0.05O3 electrode provides the best specific capacitance (300.47 F/g); this is almost four times higher compared to the undoped electrode (75.36 F/g). The electrode material also shows excellent capacitance retention of 85.73% after 5000 cycles at 5 A/g. In addition, a hybrid supercapacitor with high energy density was constructed by combining LaCo0.95Zn0.05O3 with activated carbon. The LaCo0.95Zn0.05O3//activated carbon hybrid device offers a high energy density of 36.12 Wh.kg 1 at a power density of 390.35 W.kg 1. The device is characterized by outstanding retention of the capacitance of 81% after being subjected to 5000 successive charge discharge cycles.

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