A proper design of organic dyes may own the archetypical light-harvesting characteristic while conferring at the same time anchoring groups to be bonded to specific surfaces.[1] In this way, controversial topics such as the thiol conjugation of 2D transition metal dichalcogenides (TMDCs) with organic molecules [2] shall be rationally tackled for the development of ground-breaking photocatalytic systems. We have synthesized thiolated tetraphenyl porphyrins, with and without hydroxyl groups in the phenyl substituents, which have been covalently attached to chemically exfoliated two-dimensional MoSe2 (ce-MoSe2) nanosheets. [3] We detected the formation of sulfo-selenide bridges, specifically on the edges of the ce-MoSe2, as confirmed by first principle calculations, and we investigated the modified TMDCs’ electrocatalytic activity in the hydrogen evolution reaction (HER) after conjugation with the dyes. The HER activity is suppressed or enhanced according to the presence of mildly acid hydroxyls groups in the attached molecules, since they provide a local proton relay boosting the production of H2, especially in mildly acidic conditions (pH=4.3). Moreover, the well-known light-harvesting properties of porphyrins have been exploited to improve significantly the light-assisted HER activity. Due to the formation of a type II heterojunction or Schottky contact between the molecules and the 2H and 1T MoSe2 nanosheets respectively, [4] the hybrid materials showed an improvement of the HER onset potential under illumination compared to the pristine material or dark conditions, without activity loss for more than 16 h.
References:
[1] Y. Zeng et al. Angew. Chem. Int. Ed. 2015, 54, 52.
[2] X. Chen, A. R. McDonald, Adv. Mater. 2016, 28, 5738.
[3] M. Blanco et al. J. Mater. Chem. A, 2020, 8, 11019.
[4] Y. Zang et al. Nat. Nanotechnology, 2014, 9, 111.