Since most of the polymers are synthesized by a coupling reaction in the presence of a Palladium(Pd)-catalyst , some Pd is typically trapped in the polymers and acts as cocatalysts. Kosco et al. have studied the effect of residual Pd remaining from synthesis on the performance of photocatalytic hydrogen evolution in (poly(9,9-dioctylfluorene-alt-1,2,3benzothiadiazole) (F8BT or PFBT) and found that the photocatalytic activity has been completely inhibited when the polymer has less than 1 ppm Pd in the systems with 30%V of diethyl amine (DEA) as the sacrificial donor (SD) . They also found that when the Pd content reached 40 ppm, the polymer could still produce a significant amount of hydrogen. However, the effect of the Pd co-catalyst seems to vary substantially from polymer to polymer. Some polymers with a decent amount of Pd, show very low or absent activity for photocatalytic hydrogen production . It implies that the polymer structure, especially the acceptor unit used in the polymer, should play an important role in the photocatalytic reaction even if the residual Pd is the catalytic site since the acceptor unit is where the electron is concentrated in an excited or reduced polymer.