Abstract
In artificial photocatalysis, sluggish kinetics of hole transfer and the resulting high-charge recombination rate have been the Achilles' heel of photocatalytic conversion efficiency. Here we demonstrate water-soluble molecules as co-catalysts to accelerate hole transfer for improved photocatalytic H2 evolution activity. Trifluoroacetic acid (TFA), by virtue of its reversible redox couple TFA·/TFA−, serves as a homogeneous co-catalyst that not only maximizes the contact areas between co-catalysts and reactants but also greatly promotes hole transfer. Thus K4Nb6O17 nanosheet catalysts achieve drastically increased photocatalytic H2 production rate in the presence of TFA, up to 32 times with respect to the blank experiment. The molecular co-catalyst represents a new, simple and highly effective approach to suppress recombination of photogenerated charges, and has provided fertile new ground for creating high-efficiency photosynthesis systems, avoiding use of noble-metal co-catalysts.
Highlights
In artificial photocatalysis, sluggish kinetics of hole transfer and the resulting high-charge recombination rate have been the Achilles’ heel of photocatalytic conversion efficiency
The inspiration gained from Mn4CaO5 clusters of photosystem II in natural photosynthesis stimulates the exploitation of O2-evolution catalysts[15]
K4Nb6O17 nanosheet catalysts were synthesized via a conventional solution method by anisotropic growth[19]
Summary
Sluggish kinetics of hole transfer and the resulting high-charge recombination rate have been the Achilles’ heel of photocatalytic conversion efficiency. Noble-metal oxides (such as RuO2 and IrO2) are usually used as co-catalysts for hole transport because they can effectively lower the overpotential for the oxidation reaction Subjected to their high costs of upscaling, several cost-effective and earth-abundant alternatives (primarily based on Co-Pi, NiOx, CoOx, and so on) have been exploited and achieve relatively high efficiency. This strategy through solid-state co-catalysts loading is potentially limited by finite contact areas between co-catalysts and reactants, lacking sufficient active sites for catalysis. Homogeneous co-catalyst, which is free from the limited contact areas between co-catalysts and reactants, provides sufficient active sites for catalysis, offering new opportunity to develop high-efficiency photosynthesis
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