To improve the photoproduction of hydrogen (H-2) by a green algae-based system, the effect of light/dark regimens on H-2 photoproduction regulated by carbonyl cyanide m-chlorophenylhydrazone (CCCP) was investigated. A fuel cell was integrated into a photobioreactor to allow online monitoring of the H-2 evolution rate and decrease potential H-2 feedback inhibition by consuming the generated H-2 in situ. During the first 15 h of H-2 evolution, the system was subjected to dark treatment after initial light illumination (L/D = 6/9 h, 9/6 h, and 12/3 h). After the dark period, all systems were again exposed to light illumination until H-2 evolution stopped. Two peaks were observed in the H-2 evolution rate under all three light/dark regimens. Additionally, a high H-2 yield of 126 +/- 10 mL L-1 was achieved using a light/dark regimen of L 9 h/D 6 h/L until H-2 production ceased, which was 1.6 times higher than that obtained under continuous illumination. H-2 production was accompanied by some physiological and morphological changes in the cells. The results indicated that light/dark regimens improved the duration and yield of H-2 photoproduction by the CCCP-regulated process of Tetraselmis subcordiformis.