The aim of this study is to prepare a two-dimensional (2D) WO3·H2O nanostructure assembly into a flower shape with good chemical stability for electrochemical studies of catalyst and energy storage applications. The 2D-WO3·H2O nanoflowers structure is created by a fast and simple process at room condition. This cost-effective and scalable technique to obtain 2D-WO3·H2O nanoflowers illustrates two attractive applications of electrochemical capacitor with an excellent energy density value of 25.33 W h kg-1 for high power density value of 1600 W kg-1 and good hydrogen evolution reaction results (low overpotential of 290 mV at a current density of 10 mA cm-2 with a low Tafel slope of 131 mV dec-1). A hydrogen evolution reaction (HER) study of WO3 in acidic media of 0.5 M H2SO4 and electrochemical capacitor (supercapacitors) in 1 M Na2SO4 aqueous electrolyte (three electrode system measurements) demonstrates highly desirable characteristics for practical applications. Our design for highly uniform 2D-WO3·H2O as catalyst material for HER and active material for electrochemical capacitor studies offers an excellent foundation for design and improvement of electrochemical catalyst based on 2D-transition metal oxide materials.