This study presents a novel approach to efficiently convert solar energy into hydrogen peroxide (H₂O₂) using a polyimide aerogel photocatalyst. The photocatalyst, designated PI-BD-TPB, features photoreductive carbonyl groups that facilitate the formation of anion radical intermediates, which play a crucial role in the photocatalytic redox cycle. Under photoexcitation, the carbonyl groups are reduced to anion radicals, which are then oxidized by O₂ to produce H₂O₂. This process is mediated by a redox cycle involving the anion radical, which enhances O₂ adsorption and lowers the energy barrier for the O₂ reduction reaction, significantly improving the overall efficiency of H₂O₂ production. The PI-BD-TPB aerogel exhibits a high quantum yield of 14.28% at 420 ± 10 nm and a solar-to-chemical conversion efficiency of 0.92%. Additionally, the aerogel demonstrates excellent scalability, with a 0.5 m² self-supported sample producing 34.3 mmol m⁻² of H₂O₂ under natural sunlight. The study also includes detailed characterization and theoretical calculations to elucidate the photocatalytic mechanism, confirming the effectiveness of the anion radical intermediate in enhancing the efficiency of H₂O₂ production.This study presents a novel approach to efficiently convert solar energy into hydrogen peroxide (H₂O₂) using a polyimide aerogel photocatalyst. The photocatalyst, designated PI-BD-TPB, features photoreductive carbonyl groups that facilitate the formation of anion radical intermediates, which play a crucial role in the photocatalytic redox cycle. Under photoexcitation, the carbonyl groups are reduced to anion radicals, which are then oxidized by O₂ to produce H₂O₂. This process is mediated by a redox cycle involving the anion radical, which enhances O₂ adsorption and lowers the energy barrier for the O₂ reduction reaction, significantly improving the overall efficiency of H₂O₂ production. The PI-BD-TPB aerogel exhibits a high quantum yield of 14.28% at 420 ± 10 nm and a solar-to-chemical conversion efficiency of 0.92%. Additionally, the aerogel demonstrates excellent scalability, with a 0.5 m² self-supported sample producing 34.3 mmol m⁻² of H₂O₂ under natural sunlight. The study also includes detailed characterization and theoretical calculations to elucidate the photocatalytic mechanism, confirming the effectiveness of the anion radical intermediate in enhancing the efficiency of H₂O₂ production.