Surface Modifications and Growth of Titanium Dioxide for Photo-Electrochemical Water Splitting

Abstract

This study investigates photo-anodes based on titanium dioxide (TiO 2 ) that can be used to produce hydrogen by the photo-electrochemical decomposition of water. TiO 2 is a wide band gap semiconductor that absorbs only the UV region of the solar spectrum. Sensitization of TiO 2 to visible light by the addition of gold nanoparticles (AuNPs) was studied. AuNPs sustain localized surface plasmon resonance (LSPR) that results in the absorption of light at the resonant energy. The evidence for water splitting by Au-TiO 2 systems is discussed critically. Fabrication of arrays of AuNPs was done by; annealing sputtered gold thin films, micellar nanolithography, and nano-sphere lithography. The optical characteristics and photo-electrochemical 'water splitting' performance of AuNP coated rutile (110) electrodes were determined. Nbdoped crystals coated in AuNPs of ca. 20 nm exhibited a small photocurrent that was not present with the bare rutile electrode. Reduced un-doped rutile (110) with AuNPs did not exhibit the 'plasmonic photocurrent'. Some Nb-doped electrodes did not exhibit an effect. Batches of Nb-doped and reduced rutile were examined using voltammetry and impedance spectroscopy and it was found that the 'inactive' Nb-doped TiO 2 was partially reduced.Thin films of TiO 2 were fabricated by pulsed laser deposition (PLD) onto amorphous and single crystal substrates.The effect of growth conditions on the phase and orientation of the film were studied, and procedures to grow anatase films oriented with (100), (001), and (101) were developed. The temperature and heating regime of TiO 2 films fused silica affected the orientation of film growing. Nb doping of the films also affected the temperature of the anatase-rutile phase transition and the orientation of the films, acting to stabilize anatase at higher temperatures. Surprisingly, highly doped films were found to be non-conductive. The importance of the oxygen partial pressure in producing conductive films for use as electrodes is discussed.

Controllable Anchoring of Graphitic Carbon Nitride on MnO2 Nanoarchitectures for Oxygen Evolution Electrocatalysis

“…The above observations account for the activity increase brought about by composite systems, but how does one explain the different performances of MnO 2 + g-CN­(CM) electrocatalysts obtained using different EPD durations? To attain a deeper insight into this issue, flat band potential values were estimated by the intercept of the square photocurrent density curves with the potential axis (Figure b). , The Fermi level potentials reported in Figure c are the electrode potentials at which no band bending occurs . An inspection of the obtained results reveals that the Fermi level position is directly dependent on the target electrocatalyst, with an increase according to the order MnO 2 –CM-600 < MnO 2 –CM-180 < MnO 2 –CM-20 < MnO 2 –CM-45.…”

Electrochemical Strategy for Eradicating Fluconazole-Tolerant Candida albicans Using Implantable Titanium

“…For example, C. albicans can achieve a relatively higher tolerance to ROS through the secretion of superoxide dismutase, an enzyme able to convert some ROS into less damaging chemical species. 48 However, it is possible that oxidation products such as hydroperoxyl (HO 2 ), superoxide (O 2 -), and hypochlorous acid (HOCl), commonly generated at the interface of anodic Ti electrodes under a positive potential, 38,49 could be present in our electrochemical condition and have more profound impacts on C. albicans. For instance, by testing the effects of hypochlorous acid on planktonic C. albicans cells, we found that the cells were totally killed (∼7 logs) with 100 mM NaOCl (Supporting Information, Figure S7).…”

Production and Structural Characterization of Some Magnesium Matrix Composites Reinforced with Amorphous/Nanocrystalline NiTi Particulates

“…Formation of NiTi 2 and Mg 3 Ni 2 Ti phases in the Mg + 10% A1 sample takes place in the sintering process and is due to titanium oxides and nickel and titanium oxides, respectively, present in the reinforcement powder. The point defects present in the oxides represent an oxygen source according to the reduction reaction [19]:…”