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The development of bioelectrochemical systems requires careful selection of both their biotic and abiotic components to obtain sustainable devices. Herein, we report a biophotoelectrode obtained with polyhydroxybutyrate (PHB), a biopolymer, which purple non-sulphur bacteria produce as an energy stock under specific environmental conditions. The electrode was obtained by casting a mixture composed of PHB and carbon fibers in a 3:2 mass ratio. Following, the composite material was modified with polydopamine and thermally treated to obtain a hydrophilic electrode with improved electrochemical behavior. The bio-based electrode was tested with metabolically active cells of Rhodobacter capsulatus embedded in a biohybrid matrix of polydopamine. The system achieved enhanced catalytic activity under illumination, with an 18-fold increase in photocurrent production compared to biophotoelectrodes based on glassy carbon, reaching a current density of 12 ± 3 μ A cm−2, after 30 min of light exposure at +0.32 V. The presented biocompatible electrode provides a sustainable alternative to metal-based and critical raw material-based electrodes for bioelectrochemical systems. [ABSTRACT FROM AUTHOR]

We report the preparation of mono and bi-enzymatic bioanodes immobilizing dehydrogenase enzymes at the surface of a carbon support aiming to follow the 2 and 4 electron transfer of ethanol oxidation by HPLC. Enzymatic immobilization of ADH and AlDH enzymes at the bioanodes was performed using Nafion membranes modified with tetrabutylammonium salt. Themonoenzymatic film with immobilized alcohol dehydrogenase (ADH) provided, at pH 8.50, power densities of 29.5 ± 3.4 μW cm-2; however, addition of the second enzyme (AlDH) aiming to transfer 4 electrons furnished values as high as 186.0 ± 19.4 μW cm-2. These results indicate that as the product of the first oxidation is consumed by the second enzyme it inhibits the first enzyme less thus, furnishing better performance for the bienzymatic electrodes. Long-term electrolysis (12 hours) of ethanol followed by HPLC-UV/RID system confirms our electrochemical finding demonstrating formation of 2 and 4 electrons products, e.g., acetaldehyde (6.6 mmol L-1) and acetate (0.72 mmol L-1) when a two dehydrogenase enzyme system was employed. The faradaic efficiency was above 60% for the bi-enzymatic system. We demonstrate that simultaneous product identification and mass balance analysis is an important tool to follow the synergy between the enzymes within the enzymatic cascade. [ABSTRACT FROM AUTHOR]

We prepared a W/WO3/TiO2 bicomposite photoanode by simple electrochemical anodization of W foil, followed by cathodic electrodeposition of TiO2 and annealing at 450°C for 30min. This photoanode shows good photoactivity under irradiation with UV and visible light. In optimized conditions, it promotes complete photoelectrocatalytic oxidation of 3.33×10−5 molL−1 basic red 51 solution (which is used in hair dye) at 0.1molL−1 Na2SO4, pH 2.0, under a current density of 1.25mAcm−2 and ultraviolet and visible radiation–total organic carbon removal is 94 and 88%, respectively. This effect paves the way for the sustainable solar-assisted remediation of water bodies contaminated with organic components of hair dyes. [ABSTRACT FROM AUTHOR]

Magnetic molecularly imprinted polymers (MMIPs) have become a research hotspot due to their two important characteristics: target recognition and magnetic separation. This paper presents the preparation, characterization, and optimization of an MMIP for the preconcentration of disperse red 73 dye (DR73) and its subsequent efficient degradation by photoelectrocatalytic treatment. The MMIPs were characterized by scanning electron microscopy (SEM), which revealed homogeneous distribution of the particles. Excellent encapsulation of magnetite was confirmed by transmission electron microscopy (TEM). A study of dye binding showed that the dye was retained more selectively in the MIP, compared to the NIP. The release of DR73 from the imprinted polymers into methanol and acetic acid was analyzed by UV-Vis spectrophotometry. The extracts showed higher absorbance values for MMIP, compared to MNIP, confirming greater adsorption of dye in the MMIP material. The extracts were then subjected to photoelectrocatalytic treatment. LC-MS/MS analysis following this treatment showed that the dye was almost completely degraded. Hence, the combination of MMIP extraction and photoelectrocatalysis offers an alternative way of selectively removing an organic contaminant, prior to proceeding with its complete degradation.