Designing Bithiazole-Based Conjugated Polymers as Alternatives to Benzothiadiazole for Photocatalytic Hydrogen Evolution

Abstract

The photocatalytic hydrogen evolution on bithiazole (Tz)-based conjugated polymers were first demonstrated, establishing Tz as a new building block beyond conventional benzothiadiazole (BT) systems. Two Tz-based donor–acceptor polymers were synthesized: one consisting of fluorene and Tz units (PFOTz), and the other incorporating a thiophene π-spacer between Tz units (PFOTzT). The thiophene-incorporated PFOTzT leads to a more ordered nanostructure within the resulting nanoparticles, promoting stronger interchain interactions and red-shifted absorption. Photocatalytic nanoparticles were prepared via mini-emulsion and nanoprecipitation methods with various surfactants. The hydrogen evolution reaction (HER) performance was evaluated under visible-light irradiation using ascorbic acid as a sacrificial electron donor. Both Tz-based polymwers showed HER activity, but PFOTzT exhibited significantly higher HER activity. Time-resolved photoluminescence and transient absorption spectroscopy revealed that its superior performance arises from efficient exciton dissociation and suppressed charge recombination, resulting in prolonged carrier lifetimes. These results establish Tz as a alternative to BT in the design of high-performance organic photocatalysts and underscore the crucial impact of nanoscale morphology and interfacial engineering on photocatalytic efficiency.