**Abstract**

This book chapter discusses the topochemical synthesis of blue titanium oxide (b-TiO2) and their application as electrode material for supercapacitor devices in aqueous and organic electrolytes. The formation mechanism of b-TiO2 via topochemical synthesis and their characterization using X-ray diffraction, UV–visible, photoluminescence, electron spin resonance spectroscopy, laser Raman spectrum, X-ray photoelectron spectroscopy, and morphological studies (FESEM and HR-TEM) are discussed in detail. The supercapacitive properties of b-TiO2 electrode were studied using both aqueous (Na2SO4) and organic (TEABF4) electrolytes. The b-TiO2 based symmetric-type supercapacitor (SC) device using TEABF4 works over a wide voltage window (3 V) and delivered a high specific capacitance (3.58 mF cm−2), possess high energy density (3.22 μWh cm−2) and power density (8.06 mW cm−2) with excellent cyclic stability over 10,000 cycles. Collectively, this chapter highlighted the use of b-TiO2 sheets as an advanced electrode for 3.0 V supercapacitors.

**Keywords:** blue TiO2, topochemical synthesis, electron-spin resonance, photoluminescence, supercapacitors
