Time-Resolved Spectroscopy and High-Efficiency Light-Driven Hydrogen Evolution of a {Mo₃ S₄ }-Containing...

Area of Science:

• Inorganic Chemistry
• Materials Science
• Photocatalysis

Background:

• Polyoxothiometalate ions (ThioPOM) are emerging catalysts for the hydrogen evolution reaction (HER).
• Their activity is typically associated with electrophilic {MoSx} clusters and vacant polyoxotungstates.
• Previously, exposed disulfido ligands were thought to be crucial for HER activity.

Purpose of the Study:

• To investigate the light-driven hydrogen evolution reaction (HER) activity of a novel dumbbell-like ThioPOM anion.
• To elucidate the role of the {Mo3S4} active cores and the {PW11O39} subunits in the catalytic process.
• To understand the mechanism of electron transfer in the photocatalytic system.

Main Methods:

• Synthesis and characterization of the dumbbell-like ThioPOM anion [{(PW11O39)Mo3S4(H2O)3(OH)}2]8-.
• Photophysical studies, including transient absorption spectroscopy and electrochemical measurements.
• Evaluation of light-driven hydrogen evolution reaction (HER) activity using a photosensitizer and sacrificial donor.

Main Results:

• The dumbbell-like ThioPOM anion exhibited very high light-driven HER activity.
• The active {Mo3S4} cores were found to lack exposed disulfido ligands, contradicting prior hypotheses.
• {PW11O39} subunits acted as oxidant-resistant protecting groups and electron-collecting units.
• Reductive quenching mechanism confirmed for the photosensitizer [Ir(ppy)2(dtbbpy)]+ by triethanolamine (TEOA).
• A very high rate constant for electron transfer from the reduced photosensitizer to the ThioPOM catalyst was observed.

Conclusions:

• The study demonstrates a novel ThioPOM catalyst with exceptional light-driven HER activity.
• The findings challenge the necessity of exposed disulfido ligands for HER activity in ThioPOMs.
• The results offer new insights into the design principles of molecular catalytic systems for efficient hydrogen production.