Photocatalytic reduction of carbon dioxide to formic acid at porphyrin and phthalocyanine adsorbed Nafion membranes

The metal porphyrin (MP) and phthalocyanine (MPC) adsorbed Nafion membranes are prepared (Nf/MP and Nf/MPC) and used as photocatalysts for the photoreduction of carbon dioxide (CO2). The formation of formic acid (HCOOH) is observed when the Nf/MP and Nf/MPC membranes are dipped in CO2 saturated solution and irradiated in the presence of a sacrificial electron donor such as triethanolamine (TEA). The turnover number of the photocatalysts are very high in the presence of a sacrificial electron donor. The Nf/MP and Nf/MPC membranes behave as a p-type semiconductor. The irradiation of these membranes leads to the formation of holes (MP.(+) or MPC.(+)) and HCOOH by electron transfer. The TEA acts as sacrificial electron donor and scavenges the holes. (C) 1997 Elsevier Science S.A.