Influence of polar bridging molecules on the photoelectrocatalytic hydrogen production from perylene diimide network structures

Perylene diimide (PDI) photocatalysts are characterized by with broad spectral response, assemblability of molecules, and tunable energy band structure, but the slowness of their photogenerated carriers within the catalysts limits further applications. In this paper, PDI-based photoelectrodes with triazine-pyrimidine-PDI (TPP) and triazine-benzene-PDI (TBP) structures formed by triazine-, pyrimidine- and benzene-conjugated PDIs were designed and prepared in order to improve the overall carrier transport efficiency and reactivity of the catalysts. The interaction of the bridging molecules triazine, pyrimidine and benzene in the system generates a spatial electric field, as demonstrated by density-functional theory (DFT) calculations and detailed experiments. In addition, TPP exhibited the best photoelectrocatalytic performance, in which the current density of TPP reached 0.637 mA/cm2 at 1.23 V vs. RHE, which was 10.79 times higher than that of pure triazine-PDI (TP). This study will provide new ideas for the application of photocatalysts of PDI polymers in new energy fields.