This investigation involves the synthesis of Cu doped alpha-MnO2 nanoparticles through modified Chemical route. Obtained nanoparticles (diameter_(similar to)5 nm to (similar to)18 nm) are found mostly stable at high temperature and its size can be modulated by Cu doping and post sintering temperature variation. Cyclic voltammetry and galvanostatic charge-discharge performance indicate the excellent cycling stability along with a maximum capacitance of 229.5 F/g for current density of 1 A/g. Our fabricated device is also capable to power up 73 numbers of LED for 10 min after being charged for 10 s. From the photocatalytic experiment, degradation efficiency of 73.1% has been achieved by using even ultra diluted aqueous solution (0.0025 g/L) of active material to degrade the pollutant dye like Brilliant Green of 5 ppm concentration. Entire results suggest that the synthesized materials are the promising candidate to be used in photocatalysis and supercapacitive application purpose.