Nanofunctionalized Chlorella cells with photo stimulation for biological hydrogen production

• • The hybrid system of alkalized and Cu-doped g-C3N4 with Chlorella achieved a 3.7-fold increase in hydrogen production compared to bare Chlorella, demonstrating the efficacy of extracellular electron supply. • • Hydrothermal alkalization and copper ion doping of g-C3N4 expanded its light absorption range and enhanced photoresponse, optimizing the electronic structure for improved electron transfer. • • The g-C3N4 serves as an extracellular electron source independent of PSII, providing an alternative electron pathway to hydrogenase, which is critical under nutrient stress conditions where PSII activity is inhibited. • • This cell nanofunctionalization strategy offers a feasible route to enhance biological hydrogen production efficiency by regulating non-living components, with potential for scalable application in renewable energy.