Electrocatalytic proton reduction by phthalocyanine cobalt derivatives incorporated in poly(4-vinylpyridine-co-styrene) film

The electrocatalytic proton reduction by phthalocyanine cobalt derivatives such as non-substituted phthalocyanine cobalt(II) (CoPc), octcyanophthalocyanine cobalt(II) (CoPc(CN)(8)), and tetrasulfonatophthalocyanine cobalt(II) (CoPc(SO3H)(4)) incorporated in a poly(4-vinylpyridine-co-styrene) (P(VP-St)) film coated on a graphite electrode has been studied. Under the applied potential of -0.90 V (Ag/AgCl), the turnover number of the catalyst for hydrogen production reached 2x10(5) h(-1) for the P(VP-St)[CoPc] system. The catalytic efficiency of the three complexes is in the order, CoPc > CoPc(CN)(8) > CoPc(SO3H)(4). The electron propagation through the matrix has been studied by the potential-step chronoamperospectrometry (PSCAS). The result demonstrated that the electron transfer occurs through a physical diffusion mechanism. The apparent diffusion coefficient decreased in the order of CoPc > CoPc(CN)(8) > CoPc(SO3H)(4) which is in accordance with that of the catalytic efficiency. The catalytic proton reduction was strongly suggested to be dominated by the electron transfer within the matrix. (C) 1999 Elsevier Science B.V. All rights reserved.