Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity

Journal of Solid State Electrochemistry, Mar 2016

In this work, we were focused on the development of the electrochemical approach resulting in a stable boron doping of titania nanotubes. The doping procedure concerns anodic polarization of as-anodized titania in a H3BO3 solution acting as n boron precursor. The series of attempts were taken in order to elaborate the most beneficial doping conditions. The parameters of electrochemical doping allowing to obtain boron-doped titania characterized by the highest photoconversion efficiency are as follows: reaction voltage 1.8 V, process duration 0.5 h, and the concentration of boric acid 0.5 M. Spectroscopy techniques such as UV-vis, X-ray diffraction, photoluminescence emission, and X-ray photoelectron spectroscopy were used to characterize the absorbance capability and the crystalline phase, to confirm the presence of boron atoms and to study the nature of chemical compounds, respectively. The well-ordered structure of titania and resistance of its morphology toward electrochemical treatment in H3BO3 were confirmed by scanning electron microscopy images. However, cyclic voltammetry and electrochemical impedance spectroscopy studies showed the significant difference in conductivity and capacitance between doped and pristine titania. Moreover, the photocurrent densities of the B-doped sample were about seven times higher in comparison with those generated by the pure titania nanotube electrode.

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Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity

J Solid State Electrochem Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity Mariusz Szkoda 0 1 Anna Lisowska-Oleksiak 0 1 Katarzyna Siuzdak 0 1 0 Centre for Plasma and Laser Engineering, Szewalski Institute of Fluid Flow Machinery, Polish Academy of Science , Fiszera 14, 80-231 Gdańsk , Poland 1 Department of Chemistry and Technology of Functional Materials, Chemical Faculty, Gdańsk University of Technology , Narutowicza 11/12, 80-233 Gdańsk , Poland In this work, we were focused on the development of the electrochemical approach resulting in a stable boron doping of titania nanotubes. The doping procedure concerns anodic polarization of as-anodized titania in a H3BO3 solution acting as n boron precursor. The series of attempts were taken in order to elaborate the most beneficial doping conditions. The parameters of electrochemical doping allowing to obtain boron-doped titania characterized by the highest photoconversion efficiency are as follows: reaction voltage 1.8 V, process duration 0.5 h, and the concentration of boric acid 0.5 M. Spectroscopy techniques such as UV-vis, X-ray diffraction, photoluminescence emission, and X-ray photoelectron spectroscopy were used to characterize the absorbance capability and the crystalline phase, to confirm the presence of boron atoms and to study the nature of chemical compounds, respectively. The well-ordered structure of titania and resistance of its morphology toward electrochemical treatment in H3BO3 were confirmed by scanning electron microscopy images. However, cyclic voltammetry and electrochemical impedance spectroscopy studies showed the significant difference in conductivity and capacitance between doped and pristine titania. Moreover, the photocurrent densities of the B-doped sample were about seven times higher in comparison with those generated by the pure titania nanotube electrode. TiO2 nanotubes; Boron doping; Anodization; Photocurrent; Electrochemical doping - In the last decades, the development of photochemical systems capable of harnessing solar energy to produce electricity or chemical fuels has attracted significant interest [1, 2]. The most of research strategies focus on novel types of semiconductors exhibiting photocatalytic activity [3]. In particular, titanium dioxide is regarded as a promising semiconducting material for photoelectrochemical applications due to its low cost, non-toxicity, and stability against photocorrosion [4–6]. However, the activity of titania nanotubes in processes carried out under illumination is limited by their wide bandgap (Ebg = 3.2 eV) that corresponds to energy provided by ultraviolet light [7, 8]. For this reason, many approaches have been made to improve the activity of TiO2 that allows its efficient utilization under natural light source—sun. The vast majority of known strategies concerning material modification are based on metal [9–12] and non-metal doping [13–16], formation of organic-inorganic junctions [17], or surface sensitization by dye molecules [18]. To initiate the visible-light-driven activity of titania, doping with non-metal atoms (I, B, C, N, and S) has been considered as a one of the most effective approaches that results in stable material with improved photoactivity compared to the unmodified sample [19, 20]. Recently, doping of TiO2 with boron has been widely studied in terms of its effect on the surface and the bulk structure which changes the ability of tailoring the bandgap, suppresses electron-hole pairs from recombination, and improves electron conductivity [21–23]. Some papers have reported that B-doped TiO2 powders obtained by a modified sol-gel method showed a red-shifted absorption spectrum [24, 25], while other studies concern increase in the bandgap energy of TiO2 upon doping when H3BO3 was used as a boron precursor because of the decrease of the crystal size after incorporation of boron atoms [21]. According to Bettinelli et al. [21], boron used as a titania dopant could favor the transformation of anatase to rutile. On the other hand, Finazzi et al. [26] reported that B atoms in the anatase crystal could occupy different positions and promote changes in the electronic structure of boron-doped TiO2 that is in accordance to the results of density functional theory. In general, previous results on borondoped titania nanoparticles suggest that preparation method highly impacts on material properties, but simultaneous decrease of bandgap energy value is not always observed. In this work, we present a new boron doping of titania nanotube (TiO2 NT) approach realized during an electrochemical process carried out at constant voltage when as-anodized titanium plate is immersed in electrolyte containing boric acid as a boron precursor. This method could be regarded as a simple, cheap, and fast doping procedure that enables control of the photoactivity of obtained material. The series of attempts were undertaken (...truncated)


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Mariusz Szkoda, Anna Lisowska-Oleksiak, Katarzyna Siuzdak. Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity, Journal of Solid State Electrochemistry, 2016, pp. 1765-1774, Volume 20, Issue 6, DOI: 10.1007/s10008-016-3185-8