Photoelectrocatalytic reduction of CO2 to formate using immobilized molecular manganese catalysts on oxidized porous silicon

초록

The reduction of carbon dioxide (CO2) to formate using molecular catalysts immobilized on high surface area porous silicon is described. Manganese complexes of the type ((R) bpy)Mn(CO)(3)Br (bpy = 2,2 '-bipyridine) were prepared with silatrane groups on the bpy ligand for attachment to oxide-coated porous silicon (SiOx-porSi). SiOx-porSi wafers were formed by heating hydrogen-terminated p-type porous silicon wafers under air, and the manganese complexes were immobilized on SiOx-porSi by heating at 80 degrees C. The resulting hybrid photoelectrodes are photoelectrocatalysts for CO2 reduction in acetonitrile containing 2.0 M triethylamine and 2.0 M isopropanol, yielding formate with high selectivity (>96%) and current density (similar to 0.6 mA/cm(2)), excellent reproducibility, and a photovoltage of 280 mV at -1.75 V (versus ferrocenium/ferrocene) under 1 sun illumination. The applied potential is close to the equilibrium potential for CO2 reduction to formate. This work presents rare examples of immobilized molecular catalysts for CO2 reduction to formate and the first on semiconducting silicon.

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