2026-04-19T13:35:55Zhttps://recercat.cat/oai/request

oai:recercat.cat:10256/286262026-04-14T10:47:31Zcom_2072_452955com_2072_2054col_2072_453073

Hydride transfer limits hydrogen evolution efficiency with Zn porphyrin photocatalysts El Bakouri, Ouissam Clausing, Simon T. Blancafort San José, Lluís photocatalysis Fotocatàlisi Mecanismes de reacció (Química) Reaction mechanisms (Chemistry) We performed a computational study on the photocatalytic hydrogen evolution mechanism using a Zn-based metalloporphyrin (ZnP), water, and a cheap sacrificial donor. Based on previous experiments, the active species is a Zn chlorin (ZnC), formed by photohydrogenation of ZnP. Our calculations favor an electron-proton-electron-hydride (EPEH) photocatalytic cycle that consists of one-electron photoreduction of ZnC followed by protonation of a bridge carbon and a second photoreduction, leading to a key ZnCH<inf>P4</inf>⁻ intermediate. One-electron photoreduction increases the aromaticity of the porphyrin rings, which explains the favorable photoreduction steps. The final step is a hydride transfer from ZnCH⁻ to a proton donor like an ammonium cation or water, resulting in hydrogen generation. Although this process is thermodynamically allowed, it has a high kinetic barrier and leads to loss of aromaticity, which limits catalytic efficiency. Hydrogen generation competes with ZnCH⁻ protonation and photohydrogenation. The poor activity of ZnCH<inf>P4</inf>⁻ as a hydride donor may be related to the loss of aromaticity associated with the hydride donation. The results have implications for electrocatalytic hydrogen production using porphyrins, which share a similar common intermediate. Therefore, our work will be useful to improve the molecular design of porphyrin-based photo- and electrocatalysts for hydrogen generation. 7 2026-04-14T10:47:31Z 2026-04-14T10:47:31Z 2026-04-14T10:47:31Z 2026-03-13 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion peer-reviewed https://hdl.handle.net/10256/28626 info:eu-repo/semantics/altIdentifier/doi/23578061 info:eu-repo/semantics/altIdentifier/doi/10.1002/asia.70665 info:eu-repo/semantics/altIdentifier/issn/1861-4728 info:eu-repo/semantics/altIdentifier/eissn/1861-471X Programa Estatal para Impulsar la Investigación Científico-Técnica y su Transferencia Attribution 4.0 International http://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess Elsevier Chemistry an Asian Journal, 2026, vol. 21 Articles publicats (D-Q)