Electrocatalytic reduction of diethyl oximinomalonate at a Ti/nanoporous TiO2 electrode

Enhanced mass transfer and service time of mesh Ti/Sb-SnO2 electrode for electro-catalytic oxidation of phenol

Titanium-based SnO₂ with Sb dopant (Ti/Sb-SnO₂) was of interest in the field of electro-catalytic oxidation due to its high organic oxidation rates. However, the relatively poor mass transfer performance and short service time limited its practical application. To overcome this problem, Ti/Sb-SnO₂ electrode was fabricated on mesh substrate and used as the anode for electrochemical oxidization of phenol. Compared to the anode prepared on planar Ti, the mesh anode with compact and uniform catalyst surface lowered electron transfer resistance and higher O_ads content (17.41%), which benefited the generation of hydroxyl radicals (·OH) (increment of 24.5%). In addition, this structure accelerated the fluid perturbation around electrode in microscopic scale as the COMSOL simulation result indicated; the electric potential on mesh anode varied regularly along the undulant terrain of electrode so that the mass transfer coefficient was enhanced by 1.67 times. These structure-dependent characteristics contributed to the superior electro-catalytic performance toward degradation of phenol. Experimental results showed that mesh anode had a higher TOC removal efficiency of 90.6% and mineralization current efficiency of 20.1% at current density of 10 mA cm^-2, which was 9.95% and 21.6% higher than the planar anode, and the service lifetime was 1.89 times longer than planar anode. This highly electro-catalytically active and stable Ti/Sb-SnO₂ mesh electrode showed a potential application prospect toward electro-catalytic degradation process.

Construction of TiO2 nanotube clusters on Ti mesh for immobilizing Sb-SnO2 to boost electrocatalytic phenol degradation

An efficient Sb-doped SnO₂ electrode featuring superior electrocatalytic characteristic and long stability was constructed by adopting clustered TiO₂ nanotubes-covered Ti mesh as substrate (M-TNTs-SnO₂). Compared with the electrodes prepared with mere Ti mesh or Ti plate grew with TiO₂ nanotube, the M-TNTs-SnO₂ exhibited higher TOC removal (99.97 %) and mineralization current efficiency (44.0 %), and longer accelerated service lifetime of 105 h for electrochemical degradation of phenol. The enhanced performance was mainly ascribed to the introduction of mutually self-supported TiO₂ nanotube clusters in different orientations. Such unique structure not only favored a compact and smooth surface of catalyst layer which improved the stability of electrode by reinforcing the binding force between substrate and catalyst layer, but also increased the loading capacity for catalysts, leading to 1.5-2.2 times higher of ·OH generation, the main active species for indirect electrochemical oxidation of phenol. Meanwhile, the transverse electron transfer from TiO₂ nanotube to catalyst layer was possibly achieved to further prompt the generation of ·OH. This study may provide a feasible option to design of efficient electrodes for electrocatalytic degradation of organic pollutants.

Dechlorination of pentachlorophenol (PCP) in aqueous solution on novel Pd-loaded electrode modified with PPy-SDBS composite film

Pentachlorophenol (PCP) is a persistent pollutant and a suspected human carcinogen. It can be found in the air, water, and soil and enters the environment through evaporation from treated wood surfaces, industrial spills, and disposal at uncontrolled hazardous waste sites. Ecotoxicity of PCP necessitates the development of rapid and reliable remediation techniques. Electrocatalytic hydrogenolysis (ECH) has been proven as a promising method for detoxification of halogenated wastes, due to its rapid reaction rate, low apparatus cost, mild reaction conditions, and absence of secondary contaminants. Challenge for the application of ECH is to prepare a Pd-coated cathode with high stability, high catalytic activity, and low Pd loading level. In this work, Pd/polypyrrole-sodium dodecyl benzene sulfonate/meshed Ti (Pd/PPy-SDBS/Ti) electrode was prepared and was characterized by cyclic voltammetry, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma-atomic emission spectrometry. Electrochemically reductive dechlorination of PCP on the Pd/PPy-SDBS/Ti electrode in aqueous solution was investigated. Pd microparticles were uniformly dispersed on PPy-SDBS film which was previously electrodeposited on the meshed Ti supporting electrode. The loading of Pd on the electrode was 0.72 mg cm(-2). Electrocatalytic dechlorination of PCP was performed in a two-compartment cell separated by cation-exchange membrane. The PCP removal on the Pd/PPy-SDBS/Ti electrode could reach 100 % within 70 min with dechlorination current 3 mA when PCP initial concentration was 10 mg L(-1) and initial pH was 2.4. Conversion of PCP on the Pd/PPy-SDBS/Ti electrode followed pseudo-first-order kinetics, and the apparent activation energy was 13.0 kJ mol(-1). The removal of PCP still kept 100 % after 70 min dechlorination when the Pd/PPy-SDBS/Ti cathode was reused ten times. The electrode exhibited promising dechlorination potential with high electrocatalytic activity, good stability, and low cost.

The electrochemistry of nanostructured titanium dioxide electrodes

Several of the multiple applications of titanium dioxide nanomaterials are directly related to the introduction or generation of charge carriers in the oxide. Thus, electrochemistry plays a central role in the understanding of the factors that must be controlled for the optimization of the material for each application. Herein, the main conceptual tools needed to address the study of the electrochemical properties of TiO(2) nanostructured electrodes are reviewed, as well as the electrochemical methods to prepare and modify them. Particular attention is paid to the dark electrochemical response of these nanomaterials and its direct connection with the TiO(2) electronic structure, interfacial area and grain boundary density. The physical bases for the generation of currents under illumination are also presented. Emphasis is placed on the fact that the kinetics of charge-carrier transfer to solution determines the sign and value of the photocurrent. Furthermore, methods for extracting kinetic information from open-circuit potential and photocurrent measurements are briefly presented. Some aspects of the combination of electrochemical and spectroscopic measurements are also dealt with. Finally, some of the applications of TiO(2) nanostructured samples derived from their electrochemical properties are concisely reviewed. Particular attention is paid to photocatalytic processes and, to a lesser extent, to photosynthetic reactions as well as to applications related to energy from the aspects of both saving (electrochromic layers) and accumulation (batteries). The use of TiO(2) nanomaterials in solar cells is not covered, as a number of reviews have been published addressing this issue.

Anode catalysts for direct ethanol fuel cells utilizing directly solar light illumination

Shine a light: A PtNiRu/TiO(2) anode catalyst for direct ethanol fuel cells shows photocatalytic activity. The peak current density for ethanol oxidation under solar light illumination is 2-3 times greater than that in the absence of solar light. Ethanol is oxidized by light-generated holes, and the electrons are collected by the TiO(2) support to generate the oxidation current.Novel PtNiRu/TiO(2) anode catalysts for direct ethanol fuel cells (DEFCs) were prepared from PtNiRu nanoparticles (1:1:1 atomic ratios) and a nanoporous TiO(2) film by a sol-gel and electrodeposition method. The performances of the catalysts for ethanol oxidation were investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results indicate a remarkable enhancement of activity for ethanol oxidation under solar light illumination. Under solar light illumination, the generated oxidation peak current density is 24.6 mA cm(-2), which is about 2.5 times higher than that observed without solar light (9.9 mA cm(-2)). The high catalytic activity of the PtNiRu/TiO(2) complex catalyst for the electrooxidation of ethanol may be attributed to the modified metal/nanoporous TiO(2) film, and the enhanced electrooxidation of ethanol under solar light may be due to the photogeneration of holes in the modified nanoporous TiO(2) film.