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

Abstract

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(SO 3H) 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 2×10 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(SO 3H) 4. The electron propagation through the polymer 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(SO 3H) 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.