Photoelectrochemical Oxidation of Ethanol under Visible Light Irradiation on TaON-Based Catalysts

Abstract

The ethanol photoelectro-oxidation reaction was investigated under visible irradiation on TaON-based catalysts modified with Pd and IrO 2 . Prepared catalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Electrochemical investigations were conducted in 0.2 mol L −1 NaOH solution, by voltammetric multi-cycling experiments for dark and illuminated electrodes. Product and intermediate distribution analyses were carried out by differential electrochemical mass spectrometry and high-resolution liquid chromatography aiming at establishing the photoelectrocatalytic reaction pathways. The presence of small amounts of palladium (ca 2 atom% Pd in TaON) is essential to obtain enhanced ethanol photoelectro-oxidation under visible light in alkaline medium. Photocatalytic reaction promotes formation of molecular hydrogen, carbon dioxide, acetate ions, and acetaldehyde (the last one subsequently converted into crotonaldehyde and acetaldol), while the main product formed by the ethanol photoelectro-oxidation is only acetate ion.

Monitoring Charge Transfer Dynamics of Surface Trapped Holes in ZnO Surface Utilized for Ethanol Oxidation Using Heterodyne Transient Grating Spectroscopic Techniques

“…Because the decay of the component was accelerated when either the concentration of ethanol increased or the solvent was changed to methanol, we could conclude that the decay of the additional component we observed in this study was related to the charge transfer dynamics between the photoexcited charge carriers trapped at the surface of ZnO and ethanol. Based on our observations and the former studies about the reaction mechanism of the photodegradation of ethanol on the photocatalyst surface, − it could be attributed to the charge transfer of the long-lived holes from the ZnO surface to ethanol, associated with its photooxidation. However, the component arising from the recombination of surface trapped holes competing with the charge transfer was not found.…”

Synthetic Photoelectrochemistry

“…Several reports of oxidation of simple organic molecules by iPEC exist, for example,a lcohol oxidations. [58] However, such reactions generally occur in aqueous solvent systems, and certain photoanode materials are known to undergo photocorrosion in aqueous solvent systems. [59] Sammis,B erlinguette and co-workers reported oxidations of tetralin (60), benzyl alcohol (3), and cyclohexene (62)i nM eCN under iPEC using aBiVO 4 photoanode and a100 WXelamp fitted with an AM1.5G filter as simulated sunlight, to give products 61, 4,a nd 63,r espectively ( Figure 14).…”

“…Thus far, the synthetic photoelectrochemistry examples reported herein have been conducted in custom-built (transparent) electrochemical reaction vessels.T hese generally fall into two categories ( Figure 16): a) an undivided glass "pot cell"/"beaker cell"/undivided glass voltammetry setup, [35,47,53,58,61,63] or b) ad ivided glass "H-type" cell with ag lass or membrane frit. [39,49,52,63] These are all standard academic reactors used for SOE, [66] which can be easily irradiated with visible light.…”

Basic comprehension and recent trends in photoelectrocatalytic systems

“…Some pioneering studies describe ethanol [211][212][213] and glucose 214 photoelectrocatalytic oxidation. One of the most interesting valorization processes involves glycerol as the raw organic molecule.…”