Confocal microprobe Raman spectroscopic study of the electrochemical reduction of benzene on platinum and rhodium electrodes

Electrochemical Behaviour of Benzoic Acid on Platinum and Gold Electrodes

“…A negative band at 1690 cm -1 appears that is related to the stretching vibration of a CO group. This band can be due to the formation of cyclohexanecarboxylic acid by reduction of benzoic acid at the sample potential, which is obtained by cathodic reduction via the aromatic ring in a similar way as that for benzene or toluene reduction to the corresponding cyclohexane. ,− …”

“…2.b) the spectrum shows the positive band around 1387 cm -1 together with two negative bands at 2943 and 2863 cm -1 . These latter bands can be associated to the symmetric and asymmetric stretching vibration of C-H bonds of cycloalkanes (12) which indicates the reduction of the aromatic ring to cyclohexane as occurs with benzene (13)(14)(15)(16)). …”

“…At 0.02 V (Figure b) the spectrum shows the positive band around 1387 cm -1 together with two negative bands at 2943 and 2863 cm -1 . These latter bands can be associated with the symmetric and asymmetric stretching vibrations of C−H bonds of cycloalkanes, which indicates the reduction of the aromatic ring to cyclohexane, as occurs with benzene. − An additional negative band at 1730 cm -1 can be observed. However, this spectral region can be interfered with by the absorption of the solvent (water).…”

Electrochemical polymerization of acetylene on Rh electrodes probed by surface-enhanced Raman spectroscopy

“…In comparison, the surface Raman signal related to the electrochemical polymerization of acetylene on a roughened Rh electrode can be detected at potentials more negative than À0.3 V. Therefore, we may conclude that Pt has no catalytic activity towards the polymerization of acetylene. In our previous study, we found that Pt and Rh electrodes have different electrochemical catalytic activity towards the hydrogenation and halogenation of benzene: Rh shows a higher catalytic activity for the hydrogenation of benzene at negative potentials, whereas Pt is a better catalyst for the halogenation of benzene at positive potentials [43]. We pointed out that a higher electrochemical catalytic activity of Rh at negative potentials may be due to a stronger interaction of Rh with hydrogen, which may provide more active hydrogen radicals on the surface.…”

Espectroscopia vibracional e eletrônica de Diaminoantraquinonas como sondas de microambientes

“…Existem basicamente duas abordagens para o efeito Raman: a primeira envolve essencialmente o estado eletrônico fundamental e é conhecida como teoria da polarizabilidade sendo utilizada no contexto do efeito Raman normal. A segunda é aquela que faz uso das propriedades de estados eletrônicos excitados, conhecida como teoria vibrônica [69][70][71] Após a consolidação da técnica foram realizados muitos estudos visando identificar o maior número de substratos, porém, os trabalhos apontaram que as superfícies de prata, cobre e ouro promoviam uma maior intensificação e até hoje são as superfícies mais utilizadas seja na forma de eletrodos, colóides, filmes nanoestruturados etc, porém, é possível observar uma pequena intensificação em outras superfícies metálicas como platina, paládio, ródio [78][79][80][81] ferro e outros, ampliando a abrangência da técnica como ferramenta de estudo de superfícies 82 . Na tentativa de compreender o efeito foram realizados muitos estudos e alguns modelos foram propostos.…”