A stratagem is implemented to widen the potential window in aqueous supercapacitors beyond the 1.23 V restrictions. The widening of the potential window is accomplished by a heterojunction design combining both negative and positive redox potential material. For the positive potential, VO(OH)₂ is employed and intentionally synthesized with a nanorod morphology to transform the battery's mechanistic behavior into extrinsic pseudocapacitive behaviour. Then, a VO(OH)₂ heterojunction is designed with low-cost activated carbon (HAC) derived from sustainable plant waste (hemp stem), which works in a negative potential window. The designed heterojunction not only harvested a large energy density (149.31 W h kg⁻¹ @ 1468.6 W kg⁻¹) in a symmetric cell, but also achieved a large voltage of 1.5 V. Here HAC, in addition to widening the potential window, also supports the VO(OH)₂ nanorods by preventing them from dissolution. The stabilization of the VO(OH)₂ phase was displayed in the attainment of a high rate capability (82.6% capacitance retention) upon a 5-fold current density increase. Supplementary to this, a stable cycling performance is also evaluated (96%, 10 000 cycle), which again precludes any doubt about the dissolution of VO(OH)₂. This work offers a distinctive approach and can also be applied to other charge storage materials to remove the 1.23 V limitation.