Engineered Microalgae‐Material Biohybrid Enhances Carbon‐Negative Hydrogen Production Under Emerging Contaminant Stress

Abstract In this study, a biohybrid composite (CS@PPy@Ca) is developed by encapsulating Chlorella sorokiniana (CS) with a polypyrrole (PPy) inner shell and a CaCO 3 outer layer. This hierarchical coating improved structural robustness and electron transfer, enabling stable performance under stress. Under 1 m M trichloroacetic acid (TCAA), CS@PPy@Ca achieved synergistic enhancement of CO 2 fixation (residual CO 2 <100 ppm) and H 2 production (341.8 ppm), ≈12‐fold higher than pristine CS (28.75 ppm) on day 3. Upon CO 2 supplementation (20% on Day 3), H 2 yield increased to 420 ppm by Day 6, accompanied by a drop in residual CO 2 to 90 ppm, indicating strong CO 2 tolerance and high CO 2 fixation efficiency under environmental stress. Transcriptomic analysis revealed upregulation of key photosynthetic genes, including those encoding photosystem II, ferredoxin, and cytochrome b₆f complex, thereby enhancing electron transport and Calvin cycle activity. Mechanistic studies confirmed that PPy facilitated charge transfer and CaCO 3 reinforced cellular integrity, jointly redirecting metabolism toward improved CO 2 fixation and H 2 production. This work highlights a robust material‐microbe synergy and provides a scalable strategy for CO 2 valorization and sustainable hydrogen production under environmental stress.