ارزيابي خواص فوتوالكتروشيميايي نانولوله هاي اكسيد تيتانيوم سياه با نواقص ساختاري كنترل شده براي بهبود عملكرد تفكيك آب در محدوده نور مرئي

In recent decades, the excessive use of fossil fuels has not only depleted energy resources but has also caused severe environmental pollution, increased greenhouse gas emissions, an‎d accelerated global climate change an‎d global warming. This negative cycle has profoundly affected nearly all aspects of human life. Photoelectrochemical (PEC) hydrogen generation via water splitting offers a promising route to addressing future energy an‎d environmental challenges. Among photocatalysts, titanium dioxide (TiO2) has received considerable attention owing to its unique properties, such as good chemical stability an‎d suitable ban‎d-edge positions for PEC water splitting. However, its wide ban‎d gap, poor visible-light absorption, an‎d rapid recombination of photogenerated charge carriers significantly limit its photocatalytic efficiency. To enhance PEC water splitting performance an‎d increase visible-light absorption, the synthesis of Black TiO2, achieved through the introduction of oxygen vacancies (OV) an‎d Ti3+ self-doping, has emerged as a promising strategy. FESEM investigations showed that both reduction processes preserved the morphology of the TiO2 nanotubes. XRD an‎d Raman results indicated the stability of the anatase phase with a slight decrease in peak intensities, peak shifts, an‎d an increase in lattice defects. UV-Vis-DRS results showed a narrowing of the energy ban‎d gap from 3.2 eV (A) to 2.8 eV (Ar-E), leading to increased visible light absorption. XPS results confirmed a higher percentage of oxygen vacancies an‎d Ti3+ in the Ar-E sample (48%) compared to the A-E sample (24%) an‎d the Ar sample (17%), an‎d the synergistic effect of defects in the Ar-E sample. Contact angle measurements of the samples showed that the reduction process increased the hydro‎philicity of the Black-TiO2 nanotubes. Mott-Schottky results showed that the charge carrier density increased in the Black-TiO2 samples, an‎d in the Ar-E photoanode, it was approximately 1300 times higher than the initial TiO2 sample (A). The photocurrent density of the modified Black-TiO2 was 311 µA.cm-2 at a voltage of 1.23 VRHE, 2.8 times higher than the initial titanium oxide. The charge injection efficiency (ηinj) an‎d bulk charge separation efficiency (ηsep) reached 75.5% an‎d 23.2% in the Ar-E sample at a voltage of 1.23 VRHE, respectively. The Tafel slope in the Ar-E sample decreased to 171 mV dec-1, indicating faster OER reaction kinetics. The chronoamperometry test showed a stability of 96.9% in the Ar-E sample in 1 hour. The electrochemically active surface area in the Ar-E sample was 6.9 times greater than the A sample. OCP analysis showed photovoltages up to 155 mV an‎d a shorter charge carrier lifetime (0.67 s) in Ar-E, indicating improved charge separation. EIS results showed a decrease in charge transfer resistance (Rct), an increase in charge transfer kinetics (kct), an‎d a decrease in hole lifetime in the Ar-E sample. These findings emphasize the synergistic effect of the two-step reduction in the production of Black-TiO2, with increased visible light absorption an‎d light-induced charge separation efficiency, thereby improving the efficiency of PEC water splitting.

علي اشرفي

مهران نحوي , نعيمه ناصري

كيوان رئيسي , عباس بهرامي , بهروز شايق بروجني