31762

طراحي، ساخت و بررسي خصوصيات تركيبات كامپوزيتي و هيبريدي بر پايه گرافن به منظور كاربرد در ابرخازن ها و فوتوكاتاليست ها

دكتري تخصصي (PhD)

فيزيك- حالت جامد و ماده چگال

1398

1403/7/18

محمدرضا زماني ميميان

علي ملكي

فيزيك

با توجه به سرعت بالاي مصرف سوخت‌هاي فسيلي و افزايش آلودگي‌هاي زيست‌محيطي ناشي از آن‌ها، درخواست جهاني براي گسترش انرژي‌هاي جايگزين با كارايي بيشتر رو به افزايش است. بنابراين، نياز به يك سيستم ذخيره‌سازي انرژي كارآمدتر بيشتر احساس مي‌شود. در بخش اول، براي ارتقاء ظرفيت ابرخازن‌ها، الكترود نانوكامپوزيت‌هاي جديد گرافن اكسيد كاهش‌يافته/واناديم تتراسولفيد/كبالت تري‌اكسيد (Co₃O₄/VS₄/rGO-SDBS) با روش هيدروترمال كه نيازي به هيچ افزودني ندارد، سنتز شد. كامپوزيت Co₃O₄/VS₄/rGO-SDBS@NF ظرفيت ويژه‌اي برابر با F g⁻¹ 2620 در A g⁻¹1 نشان مي‌دهد كه به‌طور قابل توجهي نسبت به كامپوزيت VS₄/rGO-SDBS@NF با ظرفيت F g⁻¹ 284 در محلولM 6 KOH بالاتر است. علاوه بر اين، الكترود به‌دست‌آمده Co₃O₄/VS₄/rGO-SDBS@NF داراي پايداري چرخه‌اي عالي است و 97.4% از ظرفيت اوليه خود را پس از 5000 چرخه حفظ مي‌كند. سپس در مرحله ي بعدي براي افزايش عملكرد ابرخازن نامتقارن، از اين الكترود به‌عنوان قطب مثبت و پارچه كربن به‌عنوان قطب منفي استفاده گرديد. تحليل‌هاي تجربي براي بررسي تأثير مورفولوژي، ساختار، سطح ويژه و بار سطحي بر عملكرد الكتروشيميايي انجام شد. ابرخازن نامتقارن(ASC) ظرفيت ويژه‌اي برابر با F g⁻¹238.8 در A g⁻¹ 0.5 نشان مي‌دهد و پس از 8500 چرخه شارژ-دشارژ، 82.60% ظرفيت اوليه را حفظ مي‌كند كه فرآيندهاي الكتروشيميايي مؤثري را به نمايش مي‌گذارد. علاوه بر اين، دستگاه ASC چگالي انرژي برابر با Wh kg⁻¹74.6 در چگالي توان W kg⁻¹ 1500 را نشان مي‌دهد. در بخش دوم، كامپوزيت ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ سنتز شد. كامپوزيت ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ فعاليت فوتوكاتاليستي فوق‌العاده‌اي (99.86%) در تخريب رنگ رودامين در محلول آبي تحت تابش نور خورشيد نشان داد. علاوه بر اين، رفتار ابرخازني كامپوزيت ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ با استفاده از تكنيك‌هاي ولتامتري چرخه‌اي (CV) و شارژ-دشارژ گالوانواستاتيك(GCD) در الكتروليت 6M KOH آزمايش شد. عملكرد رضايت‌بخش كامپوزيت ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ عمدتاً به اثر هم‌افزايي ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ و وجود RGO در اين كامپوزيت نسبت داده مي‌شود.

1403/10/08

Design, Fabrication, and Characterization of Graphene-based Composite and Hybrid Materials for Applications in Supercapacitors and Photocatalysts

10/10/2025 12:00:00 AM

Given the rapid consumption of fossil fuels and the increasing environmental pollution resulting from their use, there is a growing global demand for the expansion of more efficient alternative energy sources. Consequently, the need for a more efficient energy storage system has become increasingly apparent. In this context, supercapacitors have garnered significant attention due to their high power density, longer cycle life, and rapid charge-discharge capabilities compared to traditional batteries and capacitors. However, the low energy density of supercapacitors limits their effectiveness. Therefore, our approach in this thesis focuses on enhancing the energy density of supercapacitors while maintaining high power density through the use of novel electrode materials. To improve the energy storage capacity of supercapacitors, we synthesized new nanocomposite electrodes consisting of reduced graphene oxide/vanadium tetrasulfide/cobalt oxide (Co₃O₄/VS₄/rGO-SDBS) via a hydrothermal method that requires no additives. The Co₃O₄/VS₄/rGO-SDBS@NF composite demonstrates a specific capacity of 2620 F g⁻¹ at a current density of 1 A g⁻¹, significantly higher than the 284 F g⁻¹ observed for the VS₄/rGO-SDBS@NF composite in a 6 M KOH solution. Furthermore, the resultant Co₃O₄/VS₄/rGO-SDBS@NF electrode exhibits excellent cycling stability, retaining 97.4% of its initial capacity after 5000 cycles. In summary, the use of a simple and accessible synthesis method, the absence of binders, a specific growth technique, and the achievement of a unique morphology with effective electrochemical performance result in significant improvements over recent studies. These findings provide a new perspective for the selection and synthesis of materials, as well as the design and construction of electrodes for supercapacitors as energy storage devices. In the subsequent phase, to enhance the performance of asymmetric supercapacitors, this electrode was employed as the positive electrode, while carbon cloth served as the negative electrode. Experimental analyses were conducted to investigate the effects of morphology, structure, specific surface area, and surface charge on electrochemical performance. The asymmetric supercapacitor (ASC) exhibits a specific capacity of 238.8 F g⁻¹ at a current density of 0.5 A g⁻¹, demonstrating capacity retention after 8500 charge-discharge cycles, indicative of effective electrochemical processes. Additionally, the ASC device shows an energy density of 74.6 Wh kg⁻¹ at a power density of 1500 W kg⁻¹. In the second part, the ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite was synthesized. Due to its fully porous graphene structure and rapid redox reactions, this composite not only exhibits supercapacitive properties but also demonstrates photocatalytic performance for the degradation of rhodamine B dye. The ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite showed remarkable photocatalytic activity (99.86%) for the degradation of rhodamine dye in aqueous solution under sunlight and mercury lamp irradiation. Moreover, the supercapacitive behavior of the ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite was investigated using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques in a 6 M KOH electrolyte. The satisfactory performance of the ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite can be primarily attributed to the synergistic effects of ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ and the presence of RGO within this composite. The results of this study will contribute to determining the most efficient and cost-effective methods for dye removal from textile industry wastewater, as well as establishing this composite as an effective material for supercapacitor applications. Overall, the goal of this thesis is to present a novel approach for the design and development of new high-performance materials for dual applications, including their use as electrode materials in supercapacitors and as active materials in photocatalytic processes.

كامپوزيت , ابرخازن , گرافن , فتوكاتاليست , هيبريد

composite , supercapacitor , Graphene , photocatalyst , hybrid

Samane Mahmoodi

Dr. Mohammad Reza Zamani