طراحي و سنتز فوتوكاتاليست‌هاي بر پايه اكسيدهاي فلزي (TiO2، CaTiO3، SrTiO3) با ايجاد جاي خالي اكسيژن و تلفيق آن‌ها با كالكوژنيد¬ها (MoS2 و CdTe) براي توليد هيدروژن و تخريب نوري رودامين B

In this thesis, to prepare suitable photocatalysts for hydrogen evolution reaction an‎d photodegradation, nanoparticles based on metal oxides an‎d chalcogenides were synthesized by the hydrothermal method. To characterization the synthesized photocatalysts, methods such as FESEM, EDX, Map, XRD, DRS, FTIR, Raman, TEM, XPS, BET, an‎d contact angle measurement were also utilized. To investigate the photoelectrochemical properties of the synthesized photocatalysts, techniques such as linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, open-circuit voltage measurement, chronoamperometry, an‎d Mott-Schottky analysis were used. First work devised an efficient hydrothermal method to synthesize a TiO2-MoS2 heterostructure with an oxygen vacancy on FTO. The strategy of oxygen vacancy resulted in a photocurrent density of 0.6 mA cm-2, which is 3 times higher than pure TiO2. Also, the TiO2-x-MoS2 heterostructure exhibits a photocurrent density of 2.6 mA cm-2 an‎d higher O2 evolution than pure TiO2 in a 1.0 M KOH solution under UV–Vis irradiation. Compared to unmodified TiO2 nanorods, TiO2-x-MoS2 electrodes exhibit an increase of 13 times in photoelectrochemical activity an‎d have a low overpotential. This is due to accelerated electron transfer kinetics at the TiO2-x-MoS2 interface, an enhanced density of charge carriers, a reduced rate of charge recombination, an‎d a highly wettable surface. Second work a heterojunction system comprising oxygen vacancies-mediated TiO2 nanorods (TiO2-x) modified with MoS2 nanosheets (TiO2-x-MoS2) was prepared using the hydrothermal method. The photocatalytic activity of TiO2-x-MoS2 heterostructure is about 3 times higher than that of pure TiO2. The heterostructure significantly improved the photoinduced charge carrier separation efficiency, resulting in an increase in active species including ˙OH, O2˙-, an‎d h+. Additionally, the Langmuir-Hinshelwood (L-H) model was employed to model kinetic an‎d equilibrium data. The results of scavenging studies indicated that the photocatalytic process heavily relies on superoxide radicals. Additionally, the sensitivity of photocatalytic rates to temperature through kinetic studies based on Arrhenius an‎d transition state models was investigated, which yielded an activation energy of 23.01 kJ/mol for the process. A positive activation entropy (ΔS = +0.017 kJ/mol) was obtained, along with positive ΔH an‎d ΔG values, for the Rhodamine B photodegradation. Third work oxygen vacancy-mediated SrTiO3 nanocubes, recognized as a prominent representative of the ABO3 perovskite family, modified by MoS2 nanoflowers was prepared through a simple two-step hydrothermal method. After introducing oxygen vacancies, the ban‎dgap of SrTiO3 reduced from 3.2 to 2.9 eV. The Z-scheme MoS2/SrTiO3-x composite shows increased photocatalytic efficiency for oxygen evolution an‎d RhB degradation reactions. Under optimal conditions, the photodegradation rate of MoS2/SrTiO3-x heterostructure is about 8 times higher than that of pure SrTiO3. Also, the MoS2/SrTiO3-x heterojunction exhibits improved broadban‎d light absorption, leading to photocurrent densities of 0.52 mA cm-2 at 1.23 V vs. RHE. This represents a five-fold increase in photocurrent compared to pure SrTiO3 nanocubes. The enhanced performance may be due to the interfacial transfer of photogenerated electrons from SrTiO3 to MoS2, leading to effective charge separation in the photocatalyst. The Langmuir-Hinshelwood model was used to model the kinetic an‎d equilibrium data. Photocatalysis is greatly influenced by •OH an‎d •O2-, as demonstrated by experiments involving reactive species trapping.

اسماعيل حيدري , علي اصغر انصافي

بهزاد رضائي

محمد سراجي , محمدمحسن مومني هامانه , شهرام تنگستاني نژاد