New molecule-based catalyst to produce H2 by metallo-porphine dispersed into polymer membrane

Electrocatalytic proton reduction was studied with metallo-tetraphenylporphine (MTPP) incorporated into a Nafion membrane (Nf[MTPP]) coated on a basal-plane pyrolytic graphite (BPG) electrode or a Pt electrode. It was found that when M = Mn and Fe, Nf[MTPP] can work as a highly active catalyst to produce dihydrogen. Especially in a Pt base electrode system, it was shown that the electrocatalytic H+ reduction by the electrode-coated Nf[MTPP] takes place even at the theoretical H+/H-2 redox potential (- 0.25 V vs. Ag/AgCl, at pH 1.0), and that its catalytic activity is much higher than that of a neat MTPP and a conventional Pt catalyst. When the catalysis of the Pt/Nf[MnTPP] system was investigated with respect to MnTPP concentration in the membrane ([MnTPP](Nf)), the amount of the dihydrogen produced decreased with the increase of [MnTPP](Nf). The catalysis was discussed in terms of the electron transfer process to generate the electroactive species for H-2 production as well as the characteristics around the catalyst site in the membrane. (C) 1999 Elsevier Science B.V. All rights reserved.