Molecular Photoelectrodes with Enhanced Photogenerated Charge Transport for Efficient Solar Hydrogen Evolution

Photoelectrocatalytic cells for seawater splitting have shown promise toward large-scale deployment; however, challenges remain in operation performances, which outline clear research needs to scale up photoelectrodes with small loss of efficiency. Here, we report an approach for scalable and robust solar H₂ evolution by enhancing photogenerated charge transport in a H₂-evolving molecular photoelectrode. The photoelectrode is based on p-type conjugated polymers that are homogeneously distributed in a polycarbazole network. With a self-assembled NiS₂ catalyst, the photoelectrode under solar irradiation (100 mW cm^-2, AM 1.5 G) is capable of evolving H₂ from seawater at an external quantum efficiency (EQE) of 34.4% under an applied bias of -0.06 V vs RHE. When scaling up from 1 cm² to 25 cm², the photoelectrode generates photocurrents stabilized at 0.4 A and maintains the high EQE at an efficiency loss of less than 1%. Investigation of the photogenerated charge-transport dynamics reveals that the kinetic basis for scaling up lies in the desirable hole diffusion length that far exceeds the spacing between adjacent conjugated-polymer chains due to interchain π-π interactions.