Panchromatic ternary polymer dots
(Pdots) consisting of two conjugated
polymers (PFBT and PFODTBT) based on fluorene and benzothiadiazole
groups, and one small molecular acceptor (ITIC) have been prepared
and assessed for photocatalytic hydrogen production with the assistance
of a Pt cocatalyst. Femtosecond transient absorption spectroscopic
studies of the ternary Pdots have revealed both energy and charge
transfer processes that occur on the time scale of sub-picosecond
between the different components. They result in photogenerated electrons
being located mainly at ITIC, which acts as both electron and energy
acceptor. Results from cryo-transmission electron microscopy suggest
that ITIC forms crystalline phases in the ternary Pdots, facilitating
electron transfer from ITIC to the Pt cocatalyst and promoting the
final photocatalytic reaction yield. Enhanced light absorption, efficient
charge separation, and the ideal morphology of the ternary Pdots have
rendered an external quantum efficiency up to 7% at 600 nm. Moreover,
the system has shown a high stability over 120 h without obvious degradation
of the photocatalysts.
Artificial
photosynthesis is seen as a path to convert and store
solar energy into chemical energy for our society. In this work, highly
fluorescent aspartic acid-based carbon dots (CDs) are synthesized
and employed as a photosensitizer to drive photocatalytic hydrogen
evolution with an [FeFe] hydrogenase (CrHydA1). The direct interaction
in CDs from l-aspartic acid (AspCDs)/CrHydA1 self-assembly
systems, which is visualized from native gel electrophoresis, has
been systematically investigated to understand the electron-transfer
dynamics and its impact on photocatalytic efficiency. The study discloses
the significant influence of the electrostatic surrounding generated
by sacrificial electron donors on the intimate interplay within the
oppositely charged subunits of the biohybrid assembly as well as the
overall photocatalytic performance. The system reaches an external
quantum efficiency of 1.7% at 420 nm and an initial activity of 1.73
μmol(H2) mg–1(hydrogenase) min–1 under favorable electrostatic conditions. Owing to
the ability of the synthesized AspCDs to operate efficiently under
visible light, in contrast to other materials that require UV illumination,
the stability of the biohybrid assembly in the presence of a redox
mediator extends beyond 1 week.
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