ABSTRACT
Nanoporous gold electrodes are of great interest in electroanalytical chemistry, because of their unusual activity and large surface area. The electrochemical activity can be further improved by coating with molecular catalysts such as the tetraruthenated cobalt-tetrapyridylporphyrazines investigated in this work. The plasmonic enhancement of the scattered light at the nanoholes and borders modifies the electrode's optical characteristics, improving the transmission through the surface-enhanced Raman scattering (SERS) effect. When monitored by hyperspectral dark-field and confocal Raman microscopy, this effect allows probing of the porphyrazine species at the plasmonic nanholes, improving the understanding of the chemically modified gold electrodes.
ABSTRACT
A new supramolecular electrocatalyst for Oxygen Evolution Reaction (OER) was synthesized from a central multibridging cobalt tetrapyridylporphyrazine (CoTPyPz) species by attaching four [Ru(bpy)2Cl]+ groups. Both CoTPyPz and the tetraruthenated cobalt porphyrazine species, TRuCoTPyPz, form very homogenous molecular films just by dropcasting their methanol solutions onto GCE electrodes. Such films exhibited low overpotentials for O2 evolution, e.g., 560 e 340 mV, respectively, displaying high stability, typically exceeding 15 h. The kinetic parameters obtained from the Tafel plots showed that the peripheral complexes are very important for the electrocatalytic activity. Hyperspectral Raman images taken along the electrochemical process demonstrated that the cobalt center is the primary active catalyst site, but its performance is enhanced by the ruthenium complexes, which act as electron-donating groups, in the supramolecular system.
