Corn husk, a renewable biomass, has been successfully explored as a low-cost crude carbon source to prepare advanced higher-value 3D HPCs by means of KOH pre-treatment and direct pyrolysis, the synthesis route is simple, self-templating and easy to scale-up for industrialization. The CHHPCs present many advantages for supercapacitor applications, including higher surface area (928 m² g⁻¹), hierarchical porosity consisting of macro, meso, and micropores, a turbostratic carbon structure, uniform pore size, 3D architecture and rich O-doping (17.1 wt%). The supercapacitor performance of CHHPCs was evaluated in a 6 M KOH electrolyte and 1 M Na₂SO₄ electrolyte. The CHHPCs exhibit a high specific capacitance of 356 F g⁻¹ and 300 F g⁻¹ at 1 A g⁻¹, 20 A g⁻¹, respectively, ultra-high rate capability with 88% retention rate from 1 to 10 A g⁻¹ and outstanding cycling stability with 95% capacitance retention after 2500 cycles. The CHHPCs symmetric supercapacitor display a high energy density of 21 W h kg⁻¹ at a power density of 875 W kg⁻¹ and retains as high as 11 W h kg⁻¹ at 5600 W kg⁻¹ in 1 M Na₂SO₄ electrolyte. The facile, efficient and template-free synthesis strategy for novel 3D-HPCs from biomass sources may promote commercial application of 3D-HPCs in the fields of supercapacitors, lithium ion batteries, fuel cells and sorbents.