Solar Production of Hydrogen Using “Self-Assembled’’ Polyoxometalate Photocatalysts

Near-term and cost-effective production of solar hydrogen from inexpensive and readily available hydrogen containing compounds (HCCs) can boost the prospects of future hydrogen economy. In this paper, we assess the prospects of solar-assisted conversion of HCCs into hydrogen using polyoxometalate (POM) based photocatalysts, such as isopolytunstates (IPT) and silicotungstic acid (STA). Upon exposure to solar photons, IPT aqueous solutions containing various HCCs (e.g. alcohols, alkanes, organic acids, sugars, etc.) produce hydrogen gas and corresponding oxygenated compounds. The presence of small amounts of colloidal platinum increases the rate of hydrogen evolution by one order of magnitude. A solar photocatalytic flat-bed reactor, approximately 1.2 m × 1.2 m in size, was fabricated and tested for production of hydrogen from water-alcohol solutions containing IPT and STA and small amounts of colloidal Pt. The solar photoreactor tests demonstrated steady-state production of hydrogen gas for several days. IPT immobilized on granules of anion exchange resins with quaternary ammonium active groups show good photocatalytic activity for hydrogen production from water-alcohol solutions exposed to near-UV or solar radiation.