Synthesis of porous γ-Fe₂O₃ via alkaline treatment of size controlled scorodite particles synthesized using ultrasound irradiation and its evaluation as a cathode for lithium-ion battery

Abstract

Herein, we synthesized scorodite particles using ultrasound irradiation in a strong sulfuric acidic solution (pH 0.5) and investigated the scorodite particles' size and morphology. The highest crystallinity of scorodite (96%) was synthesized using 200 kHz ultrasonic treatment, and maximum yield of scorodite was obtained in three conditions: 200, 28 kHz, and stirrer. The oxidant generated through 200 kHz ultrasound irradiation enhanced Fe(II) oxidation in the solution resulting in crystal nuclei formation. The crystal nuclei were transformed to scorodite by oxidation with a supply of solute [Fe(III)] from the solution and ostwald ripening. Clustered scorodite (4 μm in size) was obtained via synthesis using 200 kHz ultrasound (pH 0.5). Arsenic could be separated from the clustered scorodite via alkaline treatment; scorodite was changed to porous γ-Fe 2 O 3 comprising nanosized particles. Porous γ-Fe 2 O 3 was evaluated as a cathode in a lithium-ion battery, which showed a 149 mAh g −1 discharge capacity with a 0.

Synthesis of porous γ-Fe2O3 from scorodite synthesized using ultrasound irradiation and evaluation of its battery performance

“…In our previous report, the arsenic leaching test results of highly crystalline (96%) clustered scorodite particles synthesized at pH 0.5 using 200 kHz ultrasound indicated an elution level of 29 ppm. 16) The amount of arsenic eluted from the scorodite obtained using ultrasound at pH 1.0 was smaller than this amount. This can be due to the scorodite's higher crystallinity, which enhanced the low solubility.…”

“…Maghemite made from clustered scorodite has the same initial discharge capacity as maghemite made from clustered amorphous iron arsenate (FeAsO 4 ), which was previously reported (161 mAh g −1 ). 16) Therefore, it was observed that the presence or absence of crystal water in scorodite had no effect on the battery performance of maghemite deposited by alkaline treatment. Furthermore, the battery performance of maghemite obtained in this study was compared with the reported values.…”

“…Synthesis of porous maghemite from scorodite and evaluation of its battery performance Maghemite was synthesized using three types (polyhedral, spindle and cluster) of highly crystalline (>95%) scorodite of various sizes and shapes as raw materials, including clustered scorodite previously synthesized using ultrasound at pH 0.5. 16) Polyhedral scorodite and spindle-shaped scorodite were synthesized using ultrasound in different acidic solutions of pH 2.0 and 1.0, respectively. For comparison, polyhedral scorodite with a diameter of less than 5 μm, synthesized using stirring (1,000 rpm) at 70 °C for 3 h with O 2 gas flow at pH 2.0 was also investigated.…”

“…The shape of the scorodite was a secondary particle of scorodite with clustered aggregation of primary particles, which has not been reported before. 16) However, the effect of ultrasound irradiation on clustered scorodite formation and the conditions for its formation are unclear. In this study, we investigate whether clustered particles are generated during scorodite synthesis using 200 kHz ultrasound at low temperature (70 °C) and short time (3 h) conditions in sulfuric acid solutions with pH values other than 0.5, and examine the effects of ultrasound on the crystallinity, yield, size, and shape of scorodite particles.…”

“…[18][19][20][21][22][23][24] The deposited clustered porous γ-Fe 2 O 3 was able to be charged and discharged as a cathode material for lithium-ion batteries. 16) In addition, porous maghemite produced from polyhedral scorodite particles (about 1 μm in diameter) showed potential as a cathode material. 25) In this study, scorodite of different sizes and shapes synthesized using ultrasound irradiation in different sulfuric acid solutions were also used as raw materials for the synthesis of γ-Fe 2 O 3 , and their battery performances were examined to see if they could be used as cathode materials.…”