Zhuan Wang,Bo Yang,Xueying Zhao,Yushuai Chen,Dandi Wei,Lijuan Zhang,Xintai Su
Oxygen evolution reaction (OER) is the bottleneck of photocatalytic water splitting due to the slow four-electron transfer kinetics, and the construction of ultrathin materials is considered to be an effective means to solve the above problem. Herein, ultrathin γ-Fe 2 O 3 nanosheets (Fe 2 O 3 -NS) were prepared by a facile solution reduction-low temperature calcination method. The prepared photocatalyst has a leaf-like morphology with an average thickness of 2.0 nm and a large number of slit-like pores. Compared with γ-Fe 2 O 3 bulk, Fe 2 O 3 -NS exhibits excellent photocatalytic OER activity. The apparent quantum yield (AQE) and oxygen yield (measured at 420 nm) are 12.95% and 57.04%, respectively. The OER efficiency is superior to those reported iron oxide photocatalysts. This excellent performance may benefit from the ultrathin porous structure, appropriately narrow bandgap, and abundant oxygen vacancies . In addition, the photocatalyst shows good cycling stability, retaining 91.5% of the initial capacity in the fifth cycle test, which may be attributed to the magnetic cycling capability and good structural stability. This study confirms that Fe 2 O 3 -NS is a competitive candidate material for photocatalytic oxygen evolution and provides ideas for the design and construction of other defect-rich metal oxide nanosheets.
Iron-based nanostructured materials are desirable for various applications owing to their high magnetization. Herein, we presented a facile fabrication of free-standing γ-Fe 2 O 3 nanosheets by a molten salt method for microwave absorption. Furthermore, Al component was incorporated to serve as the template for hole production. The designed holey γ-Fe 2 O 3 nanosheets were effective to maximize the usage of nanomaterials, thereby providing larger surface area, richer defects, and more polarization centers. Both experimental measurements and electric field simulation showed an enhanced capability for microwave absorption using holey γ-Fe 2 O 3 when compared with its intact counterpart. Oxygen vacancy was generated during the hole evolution, which significantly improved the electrical conductivity and thus promoted the conductive loss mechanism. In addition, the holey configuration may extend the transmission path of microwave and confer it with multiple reflection and scattering within the absorbent matrix. Meantime, the polarization loss was strengthened owing to Al modulation associated with the induced defect sites. With the improvement in conductive loss, polarization, impedance matching, and attenuation constant, the as-synthesized holey γ-Fe 2 O 3 exhibited promising microwave absorbability, with a maximum reflection loss of 52.4 dB and an effective bandwidth of 5.12 GHz at a thickness of 2.2 mm, overperforming most pure Fe-based materials.
A facile method of synthesizing γ-Fe2O3 ultrathin nanoplates has been developed. These nanoplates are single crystalline and superparamagnetic at room temperature, with a thickness of only 1.4 nm. FTIR analysis has shown that the coordination mode between Fe and carboxyl group is dominated by bidentate configuration in the as prepared iron oleate complex, which is the key for producing the nanoplate morphology. By changing the reaction temperatures, the lateral size and thickness of nanoplates can be varied.
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