Electrochemical Investigation of Doped Titanium Dioxide

Thin films of transition-metal doped (0.2, 1.0, and 5.0 atom%) TiO2 were prepared on titanium foil using a sol-gel route catalyzed by ammonium acetate. Dopants investigated were the fourth-period transition metals. The prepared films were characterised by Raman spectroscopy, Auger electron spectroscopy, and photoelectrochemical methods. The films doped with transition metals showed a lower photocurrent response than undoped samples. No major red shift in the photocurrent response spectra of the doped films was observed. A photocurrent response was observed under visible light irradiation of the samples and was potential dependent peaking around −0.3 V (SCE), which is indicative of electron promotion from a filled defect level. Examination of the defect level potential dependence by analysis of the current-time response under chopped illumination at fixed potential (−0.8 V–+1.07 V) gave a good correlation with the potential dependence observed in the visible light irradiation studies

Heterogeneous Electro-Fenton as “Green” Technology for Pharmaceutical Removal: A Review

The presence of pharmaceutical products in the water cycle may cause harmful effects such as morphological, metabolic and sex alterations in aquatic organisms and the selection/development of organisms resistant to antimicrobial agents. The compounds’ stability and persistent character hinder their elimination by conventional physico-chemical and biological treatments and thus, the development of new water purification technologies has drawn great attention from academic and industrial researchers. Recently, the electro-Fenton process has been demonstrated to be a viable alternative for the removal of these hazardous, recalcitrant compounds. This process occurs under the action of a suitable catalyst, with the majority of current scientific research focused on heterogeneous systems. A significant area of research centres working on the development of an appropriate catalyst able to overcome the operating limitations associated with the homogeneous process is concerned with the short service life and difficulty in the separation/recovery of the catalyst from polluted water. This review highlights a present trend in the use of different materials as electro-Fenton catalysts for pharmaceutical compound removal from aquatic environments. The main challenges facing these technologies revolve around the enhancement of performance, stability for long-term use, life-cycle analysis considerations and cost-effectiveness. Although treatment efficiency has improved significantly, ongoing research efforts need to deliver economic viability at a larger scale due to the high operating costs, primarily related to energy consumption.Xunta de Galicia | Ref. ED481B-2018/096Ministerio de Economía y Competitividad | Ref. CTM2017-87326-

An Experimental Investigation of Hydrogen Production Through Biomass Electrolysis

This work investigated hydrogen production from biomass feedstocks (i.e. glucose, starch, lignin and cellulose) using a 100 ml h-type proton exchange membrane electrolysis cell. Biomass electrolysis is a promising process for hydrogen production, although low in technology readiness level, but with a series of recognised advantages: (i) lower temperature conditions (compared to thermochemical processes), (ii) minimal energy consumption and low-cost post-production, (iii) potential to synthesis high volume H2 and (iv) smaller carbon footprint compared to thermochemical processes. A Lewis acid (FeCl3) was employed as a charge carrier and redox media to aid in the depolymerisation/oxidation of biomass components. A comprehensive analysis was conducted, measuring the H2 and CO2 emission volume and performing electrochemical analysis (i.e. linear sweep voltammetry and chronoamperometry) to better understand the process. For the first time, the temperature's influence on current density and H2 evolution was studied under a temperature ranging from ambient temperature (i.e., 19 °C) to 80 °C. The highest H2 volume was 12.1 mL, which was produced by FeCl3-mediated-electrolysis of glucose at ambient temperature, which was up to two times higher than starch, lignin and cellulose at 1.20 V. Of the substrates examined, glucose also showed the maximum power to H2 yield ratio of 30.99 kWh/kg. Results show that hydrogen can be produced from biomass feedstock at ambient temperature when Lewis acid (FeCl3) is employed and with a higher yield rate and a lower electricity consumption compared to water electrolysis

Electrochemical Enhancement of Photocatalytic Disinfection on Aligned TiO2 and Nitrogen Doped TiO2 Nanotubes

TiO2 photocatalysis is considered as an alternative to conventional disinfection processes for the inactivation of waterborne microorganisms. The efficiency of photocatalysis is limited by charge carrier recombination rates. When the photocatalyst is immobilized on an electrically conducting support, one may assist charge separation by the application of an external electrical bias. The aim of this work was to study electrochemically assisted photocatalysis with nitrogen doped titania photoanodes under visible and UV-visible irradiation for the inactivation of Escherichia coli. Aligned TiO2 nanotubes were synthesized (TiO2-NT) by anodizing Ti foil. Nanoparticulate titania films were made on Ti foil by electrophoretic coating (P25 TiO2). N-doped titania nanotubes and N,F co-doped titania films were also prepared with the aim of extending the active spectrum into the visible. Electrochemically assisted photocatalysis gave higher disinfection efficiency in comparison to photocatalysis (electrode at open circuit) for all materials tested. It is proposed that electrostatic attraction of negatively charged bacteria to the positively biased photoanodes leads to the enhancement observed. The N-doped TiO2 nanotube electrode gave the most efficient electrochemically assisted photocatalytic inactivation of bacteria under UV-Vis irradiation but no inactivation of bacteria was observed under visible only irradiation. The visible light photocurrent was only a fraction (2%) of the UV response