Photoinduced Surface-Generated Pt Complexes on Delayed-Fluorescent Benzothioxanthene Imide Nanoparticles for Photocatalytic Hydrogen Evolution.

Abstract

Photocatalytic hydrogen evolution (HER) using organic photosensitizers and platinum co-catalysts offers opportunities for sustainable hydrogen production, although operational stability and efficient Pt utilization remain challenging. Here, we investigate BTI-TPA, a donor-acceptor benzothioxanthene imide derivative, as a photoactive scaffold for Pt-based HER catalysts. Using unique photoreaction of imide fragment, BTI-TPA nanoparticles were functionalized with Pt complexes via in situ formation of mono- and binuclear Pt species. Photophysical studies revealed delayed fluorescence in such systems, which confirmed storing of the excitation energy for a few microseconds. Both prompt fluorescence (PF) and delayed fluorescence (DF) undergo dynamic quenching upon Pt coordination in the presence of sacrificial electron donors, suggesting energy transfer towards catalyst. The optimal catalyst with 10 mol% Pt relative to the BTI dye achieved a turnover frequency (TOF) of 55 h-1, while a 20 mol% Pt loading yielded the highest H2 production rate of 2.9 mmol g-1 h-1. With a HER activity retained over 50% after 4 days of continuous irradiation, this particular Pt based hybrid photocatalytic systems represent a rare type of surface-anchored molecular catalyst, in which mononuclear Pt species outperform their di- or oligonuclear derivatives.

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