Chemical Flocculation-Based Green Algae Materials for Photobiological Hydrogen Production

Photobiological hydrogen production is among the most promising ways toward the mass production of hydrogen energy. The use of green algal aggregates to produce photobiological hydrogen has attracted much attention because it overcomes the limitations of sulfur deprivation and oxygen scavengers. However, the current preparation of green algal aggregates that are capable of hydrogen production is time-consuming and laborious, leading to a difficulty in large-scale applications. Here, we demonstrated that the chemical flocculation of green algae is able to generate aggregates for photobiological hydrogen production. We find that Chlorella pyrenoidosa can directly form aggregates in the original liquid cultures by a commercial chemical flocculant, cationic etherified starch, thereby achieving sustainable hydrogen production for 11 days under continuous light irradiation, and the average rate of photobiological production reaches 0.37 μmol H₂ (mg chlorophyll·h)^-1. This research provides a feasible approach for preparing a low-cost photobiological hydrogen production system helping to realize carbon neutrality.