Effect of Aluminium (Al)-doping on electrochemical performance of hydrothermally synthesized hematite (α-AlxFe2−xO3) nanospheres for supercapacitor application

• Published in: Journal of energy storage 2025-01, Vol.107, Article 114987
• Main Authors: Irshad, Iqra, Nazir, Asif, Tahir, Asma, Lone, A.G., Want, Basharat
• Format: Article
• Language: English
• Subjects: Capacity retention; Cole-cole plots; Electrochemical stability; Nanospheres; Specific capacitance
• ISSN: 2352-152X
• DOI: 10.1016/j.est.2024.114987

This study explores the detailed impacts of Al3+ substitutional doping on the structural, dielectric and electrochemical characteristics of α-Fe2O3. Rietveld refinements of X-ray diffraction patterns confirmed the rhombohedral corundum-type structure within the R3c space group. Evaluation of the unit cell indicated contraction due to replacing the significantly smaller Al3+ ions with octahedrally coordinated Fe3+ ions. Morphological characterization through FESEM and TEM revealed the presence of finely dispersed nanospheres exhibiting particle size within the range of 18-32 nm. Through X-ray photoelectron spectroscopy (XPS), definitive evidence has been identified for incorporating Al3+ ions into the crystalline structure of hematite, providing insight into the complex interactions between Fe3+ and Al3+ ions. BET analysis assessed the surface area and pore structure of nanostructures. The adoption of nanospheres is justified by their intrinsically elevated surface-to-volume ratio, amplifying electroactive sites for enhanced charge storage. The results reveal promising prospects for improved supercapacitor performance and increased energy storage efficiency in nanosphere-based electrode materials. Using galvanostatic charge-discharge and cyclic voltammetry for electrochemical evaluations, the 40 % Al-doped hematite electrode performed exceptionally well electrochemically, exhibiting a specific capacitance of 891 Fg−1 at a scan rate of 10 mV/s. The Al-doped hematite nanoparticles are engineered specifically, as demonstrated by our results, thereby rendering attractive candidates for the next generation of supercapacitor devices with improved electrochemical stability and increased performance metrics. Dielectric characteristics and AC conductivity of Al-doped α-Fe2O3 were systematically analyzed via impedance spectroscopy utilizing a comprehensive frequency range extending from 100 kHz to 300 MHz. AC conductivity decreased as Al3+ ion concentration increased, indicating a hopping mechanism for charge transport. Deviations in tan δ and ε’ with frequency and temperature were explained by Maxwell-Wagner interfacial polarization and charge hopping among Fe3+ and Fe2+ ions. Nyquist plots provided insights into the conduction mechanism in Al-doped α-Fe2O3, making it a potential candidate for advanced electronic components, telecommunications devices, and biomedical sensors. •Hydrothermally synthesized Al doped hematite nanospheres with an average diameter of 18–32