TY - JOUR
T1 - Alkaline treatment as a means to boost the activity of TiO2in selective photocatalytic processes
AU - Yurdakal, Sedat
AU - Çetinkaya, Sidika
AU - Augugliaro, Vincenzo
AU - Palmisano, Giovanni
AU - Soria, Javier
AU - Sanz, Jesus
AU - Torralvo, Maria Jose
AU - Livraghi, Stefano
AU - Giamello, Elio
AU - Garlisi, Corrado
N1 - Funding Information:
The authors thank the Scientific Research Project Council of University of Afyon Kocatepe (BAP project no: 17.KARİYER.15) for financial support, Assoc. Prof. Dr. Levent Özcan for the photocurrent measurements (Biomedical Engineering, University of Afyon Kocatepe, Turkey) and Eng. Hakan Şahin (Teknoloji Uygulama ve Araştırma Merkezi (TUAM), University of Afyon Kocatepe) for the XRD and BET analyses. The authors are also grateful to Dr. Jacinto Sá (University of Uppsala, Sweden) for his support for IR characterization of the catalysts.
Funding Information:
The authors thank the Scientific Research Project Council of University of Afyon Kocatepe (BAP project no: 17.KAR?YER.15) for financial support, Assoc. Prof. Dr. Levent ?zcan for the photocurrent measurements (Biomedical Engineering, University of Afyon Kocatepe, Turkey) and Eng. Hakan ?ahin (Teknoloji Uygulama ve Ara\+t?rma Merkezi (TUAM), University of Afyon Kocatepe) for the XRD and BET analyses. The authors are also grateful to Dr. Jacinto S? (University of Uppsala, Sweden) for his support for IR characterization of the catalysts.*%blankline%*
Publisher Copyright:
© The Royal Society of Chemistry.
PY - 2020/8
Y1 - 2020/8
N2 - In this work, the activity enhancement of TiO2 photocatalysts by alkaline treatment has been investigated. Commercial (BDH, U.K., anatase phase) TiO2 samples, treated in alkaline solutions of NaOH at different concentrations and temperatures, were tested for the photocatalytic partial oxidation of 3-pyridinemethanol in water under UVA irradiation to form vitamin B3. Photocatalyst characterization has been carried out by XRD, BET, TEM, TGA, photoluminescence, FTIR, Raman, DRS, EPR and photocurrent measurements. The alkaline-treated samples showed an increased activity of up to 7 times (by considering first order rate constant values) compared to untreated BDH and the superior performance was maintained even after a thermal treatment at 400 °C, while the selectivity values were affected only marginally by the treatment (being ca. 40% and 15% for 3-pyridinemethanal and vitamin B3, respectively). The effect of NaOH concentration and treatment duration on the photocatalytic activity has also been studied extensively. The alkaline treatment has also proven to be effective in modifying the surface properties of another commercial catalyst, i.e., Merck, anatase, improving its reactivity in the conversions of both 4-methoxybenzyl alcohol and 3-pyridinemethanol. The NaOH treatment boosted the porosity and surface area, while lowering the percent crystallinity of the catalysts, due to a higher density of surface hydroxyl groups. It also enhanced the adsorption capability towards the reacting substrate, as shown by FTIR analysis. Despite the oxygen vacancies (or total abundance of Ti3+ centres) not being changed after the NaOH treatment, the process of hole trapping under irradiation is drastically affected due to the different water adsorption capabilities of the samples, as highlighted by EPR. The proposed simple treatment of commercial photocatalysts has the potential to support the development of effective photocatalysts, which do not require complex surface modification or doping to achieve high yields in reactions relevant to the chemical industry.
AB - In this work, the activity enhancement of TiO2 photocatalysts by alkaline treatment has been investigated. Commercial (BDH, U.K., anatase phase) TiO2 samples, treated in alkaline solutions of NaOH at different concentrations and temperatures, were tested for the photocatalytic partial oxidation of 3-pyridinemethanol in water under UVA irradiation to form vitamin B3. Photocatalyst characterization has been carried out by XRD, BET, TEM, TGA, photoluminescence, FTIR, Raman, DRS, EPR and photocurrent measurements. The alkaline-treated samples showed an increased activity of up to 7 times (by considering first order rate constant values) compared to untreated BDH and the superior performance was maintained even after a thermal treatment at 400 °C, while the selectivity values were affected only marginally by the treatment (being ca. 40% and 15% for 3-pyridinemethanal and vitamin B3, respectively). The effect of NaOH concentration and treatment duration on the photocatalytic activity has also been studied extensively. The alkaline treatment has also proven to be effective in modifying the surface properties of another commercial catalyst, i.e., Merck, anatase, improving its reactivity in the conversions of both 4-methoxybenzyl alcohol and 3-pyridinemethanol. The NaOH treatment boosted the porosity and surface area, while lowering the percent crystallinity of the catalysts, due to a higher density of surface hydroxyl groups. It also enhanced the adsorption capability towards the reacting substrate, as shown by FTIR analysis. Despite the oxygen vacancies (or total abundance of Ti3+ centres) not being changed after the NaOH treatment, the process of hole trapping under irradiation is drastically affected due to the different water adsorption capabilities of the samples, as highlighted by EPR. The proposed simple treatment of commercial photocatalysts has the potential to support the development of effective photocatalysts, which do not require complex surface modification or doping to achieve high yields in reactions relevant to the chemical industry.
UR - https://www.scopus.com/pages/publications/85090083985
U2 - 10.1039/d0cy00755b
DO - 10.1039/d0cy00755b
M3 - Article
AN - SCOPUS:85090083985
SN - 2044-4753
VL - 10
SP - 5000
EP - 5012
JO - Catalysis Science and Technology
JF - Catalysis Science and Technology
IS - 15
ER -