Photoelectrochemical or electrophotochemical processes?

Abstract

Nos últimos anos, muitos estudos têm relatado a eficiente degradação de substratos de relevância ambiental por processos fotoeletroquímicos, sendo que, usualmente, admite-se que o sinergismo observado entre processos foto e eletroquímicos envolve o favorecimento eletroquímico dos processos de fotocatálise. Neste trabalho, algumas evidências experimentais são discutidas, visando demonstrar que, em certas situações, o efeito sinérgico envolve conceitos diferentes, isso é, processos fundamentalmente eletroquímicos, assistidos por reações fotoquímicas subseqüentes. De acordo com as nossas observações, a elevada capacidade de degradação apresentada por eletrodos do tipo DSA na presença de eletrólitos reativos, como cloreto de sódio, é devida à geração eletroquímica de oxidantes enérgicos, como cloro molecular, os quais podem ser fotoquimicamente transformados em espécies radicalares de maior reatividade, como radical cloro. Essa suposição se mostra evidente em estudos envolvendo ácido húmico, cânfora e um corante antraquinona (azul reativo 19).In recent years, many studies have related the efficient degradation of relevant substrates by photoelectrochemical processes. Usually, it is accepted that the synergy observed between photo and electrochemical processes involves the improvement of the photocatalytic efficiency as a result of a favorable electrochemical support. In this work some experimental observations are discussed with the aim of demonstrating that in several situations, the synergic effect involves a divergent concept. That is, an efficient electrochemical-based process assisted by subsequent photochemical reactions. As far as we know, the high degradation capacity shown by DSA electrodes used in the presence of reactive electrolytes, such us sodium chloride, is due to electrochemical generation of powerful oxidant agents, as molecular chlorine, followed by photochemical generation of active radicals, such chlorine radical. This assumption becomes clearly visible in degradation studies involving humic acid, camphor and an anthraquinone dye (reactive blue 19).

Recent Advances in Heterogeneous Photocatalytic Decolorization of Synthetic Dyes

“…The homogenous photocatalytic oxidation system employs various oxidants such as H 2 O, O 3 , Fenton reagent, NaOCl, and many others either alone or in combination with light [64] (Figure 2). Recently, heterogeneous photocatalysis has emerged as an important degradation technology leading to the total mineralization of organic pollutants, especially synthetic dyes [5, 37, 38, 65, 66]. …”

Determination of 3,4,5-Trihydroxybenzoic Acid Exploiting a Visible-Light-Driven Photoelectrochemical Platform: Application in Wine and Tea Samples

“…[23][24][25] The PEC methods exploit the ability of semiconductor materials to absorb radiated energy close to or greater than its bandgap energy, resulting in the formation of electron/hole pairs (e − /h + ). 23,26 Among the most interesting advantages of using PEC methods are high throughput analysis, userfriendliness, portability, high linear response range, low cost, and easy miniaturization. 25,27 For the PEC detection process, the irradiated light acts as a source of excitation to produce an electrical signal (photocurrent or photovoltage), which can be exploited as a detection signal.…”

Thermodynamic Consideration on Degradation of Humic Acids by Electrolysis

“…10,11 Thus, there have been many reports on the degradation and removal of HCs without the addition of oxidizing chlorine species. 2,3,[12][13][14][15][16][17][18][19][20][21][22][23][24][25] In particular, electrochemical methods are promising because of their general applicability. For example, Pinhedo and co-workers 2,3 reported an electrochemical degradation technique of HAs using dimensionally-stable anodes (DSA μ ).…”