<p>Covellite (CuS) nanostructures were synthesized via a chelation-assisted hydrothermal route using EDTA and PEG, followed by annealing at 100 and 200&#xa0;°C, to regulate their structural, optical, and electrochemical properties for organic pollutant degradation and energy storage applications. X-ray diffraction confirms a hexagonal covellite phase for all samples, with chelating agents promoting preferential (110) growth. PEG-assisted annealing induces a morphological transition from irregular aggregates to uniform nanoflower architectures, most pronounced for PEG–CuS annealed at 200&#xa0;°C. BET analysis shows that CuS–PEG has a higher surface area (28.70 m²&#xa0;g⁻¹, 15.7&#xa0;nm pores) than CuS–EDTA (27.58 m²&#xa0;g⁻¹, 23.30&#xa0;nm), with uniform mesopores that enhance active sites and ion diffusion. XPS verifies&#xa0;availability of Cu and S. The bandgap is tunable from 1.1 to 1.4&#xa0;eV and correlates with crystallite size, enabling strong visible-light absorption, while suppressed electron–hole recombination enhances charge separation. Under natural sunlight, methyl orange acts as a photosensitizer, injecting excited electrons into the CuS conduction band and significantly improving photocatalytic activity. Scavenger studies and DFT-based Fukui function analysis confirm a dominant photo-sensitized charge-transfer pathway, with hydroxyl radicals as secondary reactive species. Beyond photocatalysis, PEG-derived CuS nanoflowers demonstrate excellent electrochemical performance as the positive electrode in an asymmetric supercapacitor, delivering 415 F g⁻¹ at 1 A g⁻¹, an energy density of 147 Wh kg⁻¹ at 856 W kg⁻¹, and 98% capacitance retention after 10,000 cycles. Three-electrode tests reveal pseudo-capacitance with up to 716 F g⁻¹ (1 A g⁻¹), a low Rct (2.15 Ω), and ideal EIS. The enhanced performance originates from the PEG-directed hierarchical CuS nanoflower architecture, which facilitates rapid electron transport and efficient ion diffusion.</p>