Hydrogen Evolution by Polymer Photocatalysts; a Possible Photocatalytic Cycle

We propose, supported by ab-initio calculations, a possible photocatalytic cycle for hydrogen evolution by a prototypical polymer photocatalyst, poly(p-phenylene), in the presence of a sacrificial electron donor. As part of that cycle we also introduce a family of related sites on the polymer that in the absence of a noble metal co-catalyst can facilitate the evolution of molecular hydrogen when the polymer is illuminated. The bottlenecks for hydrogen evolution, electron transfer from the sacrificial electron donor and hydrogen-hydrogen bond formation, are discussed, as well as how they could potentially be improved by tuning the polymer properties and how they change in the presence of a noble-metal co-catalyst.