[en] Here, we report a robust synthesis of iron oxide nanoparticles using a facile solvent deficient approach. The process involves only 2–3 simple steps, where, a hydrated ferric nitrate nonahydrate (Fe(NO₃)₃·9H₂O) salt is grinded with the ammonium bicarbonate (NH₄HCO₃) for 10 min without addition of any solvent to obtain a precursor. To form Fe₂O₃ nanoparticles this precursor was further annealed at 350 °C for 2 h in two different stages, (i) as prepared untreated and (ii) after rinsing by using deionized water. Single phase Fe₂O₃ particles formation was confirmed from X-ray diffraction pattern, Fourier transform infrared spectra and Raman spectra analysis. Scanning electron micrograph images shows, distinct morphology is achieved for two different samples. The N₂ adsorption-desorption measurement confirms the mesoporous nature with specific surface area of 40 and 85 m²g^-1 for samples obtained from untreated and rinsed precursors. Further, electrochemical performance determined using cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy shows the maximum improved specific capacitance for untreated and rinsed samples is 360 and 469 Fg^-1 at 2 mVs⁻¹ scan rate with a very less electrochemical series resistance of 4.12Ω and 2.34Ω, respectively. The maximum energy density of 12.38 and 18.32 Whkg⁻¹ and power density of 2531 and 2702 Wkg^-1 is achieved for Fe₂O₃ samples obtained from untreated and rinsed precursors. Also, it shows cyclic stability of 78% and 84% upto 2000 cycles for Fe₂O₃ obtained from untreated and rinsed precursors, respectively. - Highlights: • Facile, robust solvent deficient approach is used for synthesis of mesoporous Fe₂O_3. • Removal of spectator ions during synthesis and their size provides mesoporous nature. • Unimodal pore size distribution, high surface area is achieved for Fe₂O₃ nanoparticles. • The maximum improved specific capacitance obtained for rinsed sample is 469 Fg^-1. • Improved electrochemical stability of 84% after 2000 cycles is achieved.