Photoelectrochemical oxidation of p-nitrophenol on an expanded graphite—TiO2 electrode

Abstract

In the quest for more efficient photoanodes in the photoelectrochemical oxidation processes for organic pollutant degradation and mineralisation in water treatment, we present the synthesis, characterisation and photoelectrochemical application of expanded graphite-TiO2 composite (EG-TiO2) prepared using the sol-gel method with organically modified silicate. The Brunauer-Emmett-Teller surface area analyser, ultraviolet-visible diffuse reflectance, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, Raman spectrometry and X-ray photoelectron spectroscopy were employed for the characterisation of the composites. The applicability of the EG-TiO2 as photoanode material was investigated by the photoelectrochemical degradation of p-nitrophenol as a target pollutant in a 0.1 M Na2SO4 (pH 7) solution at a current density of 5 mA cm(-2). After optimising the TiO2 loading, initial p-nitrophenol concentration, pH and current density, a removal efficiency of 62% with an apparent kinetic rate constant of 10.4 × 10(-3) min(-1) was obtained for the photoelectrochemical process as compared to electrochemical oxidation and photolysis, where removal efficiencies of 6% and 24% were obtained respectively after 90 min. Furthermore, the EG-TiO2 electrode was able to withstand high current density due to its high stability. The EG-TiO2 electrode was also used to degrade 0.3 × 10(-4) M methylene blue and 0.1 × 10(-4) M Eosin Yellowish, leading to 94% and 47% removal efficiency within 120 reaction time. This confirms the suitability of the EG-TiO2 electrode to degrade other organic pollutants.

Graphene Quantum Dots Modified Screen‐printed Electrodes as Electroanalytical Sensing Platform for Diethylstilbestrol

“…This result can be explained since that H + ions are not a reagent in the reaction and when they are present in higher concentration the oxidation of DES requires more energy to occur. Slope value of 59.6 mV per pH unit indicates an equal number of electrons and protons transferred during the oxidation of DES as predicted in literature (Figure C). The sensitivity obtained for pH 4 was higher than that obtained for others pH values (Figure B) and therefore pH 4 was used for subsequent studies.…”

A Review on the Effects of Introducing CNTs in the Modification Process of Electrochemical Sensors

“…Therefore, different analytical methods have been developed for the improvement detection of BPA in real samples [71][72][73][74][75][76][77][78]. Polycarbonate plastic have various applications in packaging industry including food and beverages packaging, water and infant bottles.…”

The effect of different exposed facets on the photoelectrocatalytic degradation of o-chlorophenol using p-type Cu 2 O crystals

“…As a promising technology, photoelectrocatalytic degradation has attracted increasing attention for its ability to efficiently decompose refractory organic pollutants that cannot be eliminated biologically, due to its convenience, environmental compatibility, cost-effectiveness, versatility and safety [1][2][3][4][5][6][7]. Photoelectrocatalysis, as an enhanced photocatalytic technique, holds great promise for effective wastewater purification by decreasing the recombination of photogenerated electron-hole pairs via applying a bias potential.…”

“…Thus, the degradation efficiency of organic contaminants could be improved, and the toxic and refractory intermediates generated during electrochemical oxidation could be decomposed by photocatalysis-induced radicals. However, in conventional photoelectrocatalytic degradation, most of the studies have focused on the improvement of photocatalysts [1,8] or anodic electrode materials [2][3][4][5]7,9], while few studies have paid attention to cathodic electrode materials that also substantially influence both reaction selectivity and efficiency [6]. The reason is that some critical challenges still remain in the application of active cathodes for photoelectrocatalytic water treatment, including the low efficiency of photo-electric conversion under natural sunlight, short service life, high cost, secondary contamination, etc.…”