Publication: Metal organic framework (MOF) based electrocatalytic hydrogen production
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2023-2024
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ÖzetGünümüzde enerji kaynağı olarak kullanılan fosil yakıtların kullanılması ile atmosfere salınan karbondioksit ve diğer sera gazları küresel ısınmaya sebep olmaktadır. Bu nedenle, Hidrojen üretimi ve yakıt olarak kullanımı gibi yenilenebilir ve sürdürülebilir enerji üretim teknolojileri üzerine yeni araştırma alanlarının geliştirilmesi önemli hale gelmiştir. Hidrojen üretimi için suyun elektrolizi teknolojisinin kullanılması, dünya üzerinde temiz ve enerji verimliliği yüksek bir yakıt kaynağı sunan umut verici bir yöntemdir. Bununla birlikte, bu inanılmaz teknolojinin kullanılmasının önündeki en büyük engel, katodik ve anodik reaksiyonları daha verimli şekilde gerçekleştirmek için, yüksek verimli, ucuz ve toprakta bol miktarda bulunan alternatif elektrokatalizörlerin geliştirilmesine olan ihtiyaçtır. Elektrolizörlerde kullanılabilecek yüksek verimli ve ucuz elektrokatalizör geliştirmek için bu çalışmada, geçiş metallerine dayalı metal-organik çerçeveler (MOF'lar), elektrokimyasal hücrelerde hidrojen evrim reaksiyonlarını HER kolaylaştırmak için umut verici bir elektrokatalizör olarak araştırılmıştır. MOF temelli malzemeler ultra yüksek gözeneklilikleri, muazzam iç yüzey alanları ve olağanüstü derecede değişkenliklerinden ve harici fonksiyonel malzemeleri barındırabilme yeteneklerinden kaynaklanan benzersiz özellikleri nedeniyle elektrokatalizör olarak tercih edilmiştir. MOF temelli nanomalzemelerin farklı türleri, solvotermal bir yöntem kullanılarak monometalik MOF'lar olarak kobalt bazlı MOF ve demir bazlı MOF dahil olmak üzere sentezlenmiştir. Daha sonra Co-Fe-MOF, birlikte çöktürme ve solvotermal yöntemlerin birleştirilmesi ile bimetalik MOF olarak sentezlenmiş, ve daha sonrasında kalsinasyon işlemi ile yapılara harici Co ve Fe metallerinin yüklenmesi ile elektrokatalitik aktivitesi yüksek olabilecek yeni yapılar sentezlenmiştir. Çözücü tipi, ısıtma sıcaklığı, süresi ve metal ile ligand arasındaki oran gibi elektrokatalitik etkinlik üzerindeki çeşitli parametrelerin sonuçlarının optimizasyon sonuçları bu tez çalışmasında ele alınmıştır.Hazırlanan elektro katalizörlerin FTIR yapısal karakterizasyon tekniği uygulanmış ve MOF oluşumlarına bağlı olarak değişen yapısal titreşimi ortaya çıkarmıştır. Ayrıca XRD analizleri gerçekleştirilmiş ve keskin ve yoğun kırınım pikleri ile MOF kristal oluşumunu doğrulamıştır. Gerçekleştirilen elektrokatalitik HER çalışmaları gerçekleştirilmiştir. Co-MOF yapılarının 10 mA/cm2 akım yoğunluğunda η10= 50 mV gibi oldukça düşük bir aşırı gerilim elde edilmiştir. Co-MOF elektrokatalizörü tarafından sağlanan yüksek kinetik reaksiyona işaret eden Tafel eğim değeri 38.57 mV dec-1 ve yük transfer direnci RCT (Ω) 17 ohm olarak bulunmuştur. Elde edilen bu performansların aynı çalışma ortamında 59 ohm RCT (Ω) ile yaklaşık 38.57 mV dec-1 Tafel eğimi ile yaklaşık 42 mV aşırı potansiyele sahip olan ticari Pt/C katalizörüne yaklaşılmıştır. Benzer şekilde hazırlanan Fe-MOF elektro katalizörü ile de, yük transferi direnci RCT (Ω) olarak 2.569 ohm, aşırı gerilim olarak η10= 46 mV ve Tafel eğimi olarakta 46.71 mV dec-1 gibi daha yüksek performans değerlerine ulaşılmıştır. Benzer şekilde Co-Fe-MOF(C)@Fe-Co(A) yapısı ile η10= 57 mV ve Tafel eğimi yaklaşık 37.01 mV dec-1 ve yük transferinin direnci RCT (Ω) olaraktan 18.25 ohm performans verileri elde edilmiştir. Sonuç olarak, sentezlenen MOF'ların yüksek verimde ve kararlılıkta HER prosesinde elektrokatalizör olarak kullanılabilecekleri ortaya konulmuştur. Bu bilimsel çalışmanın önemi, iki farklı işlem çalışmasıyla yüksek verimli bir elektro katalizör olarak geçiş metali bazlı MOF'un başarılı bir şekilde sentezlenebildiğini göstermektedir. Elde edilen Co-MOF ve Fe-MOF yapıları ile herhangi bir ek kimyasal işlem olmaksızın Pt katalizörüne benzer suyun elektrolizinde katot olarak kullanılabilecek performans değerlerine ulaşılmıştır. Bu tez çalışması ile, daha kapsamlı hidrojen üretim sistemlerinin geliştirilmesinin önündeki en büyük engellerden biri olan (pahalı ve nadir olmaları) platin katalizörleri ile rekabet edebilecek MOF temelli ucuz elektrokatalizörlerin elde edilmesi sağlanmıştır.
At the current time, with increasing global warming issue is caused mainly by increasing carbon dioxide levels and other toxic gases because of relying on fossil fuels as the main energy foundation. Thus, it became too significant to spot the light on a new research area that relies on producing energy from renewables and sustainable sources. The utilization of water electrolysis technology for hydrogen production is a promising method, offering a clean and highly energy-efficient fuel source on Earth. However, the major obstacle that hampers utilizing this incredible technology is finding alternative electrocatalysts that are highly efficient, inexpensive, and earth-abundant since Nobel metal-based catalysts are the most effective electrocatalysts to drive the cathodic and anodic reactions, but their high price and limited availability water electrolysis. In this research, metal-organic frameworks (MOFs) based on transition metals have been explored as a promising electrocatalyst for facilitating hydrogen evolution reactions (HER) in electrochemical cells, due to their unique features starting from their ultrahigh porosity, enormous internal surface area, and an extraordinary degree of variability, and their ability to host external guest. Particularly, different types of these nanomaterials have been synthesized including cobalt-based MOF, and iron-based MOF as monometallic MOFs by using a solvothermal method. then Co-Fe-MOF was synthesized as a bimetallic MOF with stirring and heating methods, additionally, the calcination process and loading of their structure with metal ions were conducted in the lab area by using a CVD device. Optimization of the outcome of diverse parameters on the electrocatalytic effectiveness such as the solvent type, heating temperature, duration, and the ratio between metal and ligand have been covered in this thesis plan.FTIR Structural characterization technique of the as-prepared electrocatalysts has been performed and revealed the structural vibration changing due to MOF formations, additionally, XRD has been conducted and confirmed MOF crystal formation through sharp and intense diffraction peaks. Remarkably, the vital evidences that prove the high HER catalytic activity have been provided through the practical measurements that were done through lab experiments appropriately with incredible achievement by utilizing Co-MOF to lower the HER overpotential to η10= 50 mV to attain a current density of 10 mA/cm2 and obtained Tafel slope value 38.57 mV.〖dec〗^(-1) that indicate to high kinetic reaction provided by new catalyst and resistance of charge transfer R_CT (Ω) to be 17.59 ohms that approaches commercial Pt/C catalyst which has about 42 mV of overpotential with Tafel slope about 34.32 mV.〖dec〗^(-1) .and resistance of charge transfer R_CT (Ω) about 2.569 ohms furthermore Fe-MOF also achieved another incredible overpotential reduction with η10= 46 mV and Tafel value 46.71 mV.〖dec〗^(-1) resistance of charge transfer R_CT (Ω) to be 3.366 ohms. Add to these research accomplishments the study of bimetallic-MOF which is Co-Fe-MOF(C)@Fe-Co(A) with η10= 57 mv and Tafel slope about 37.01 mV.〖dec〗^(-1). Resistance of charge transfer R_CT (Ω) to be 18. 25 ohms. Consequently, the synthesized MOFs have a great effect on enhancing HER performance of the water electrolysis to produce hydrogen efficiently, displaying high intrinsic activity compared to noble metals (Pt). finally, MOF catalysts showed great stability after running the LSV polarization curve for 100 cycles. The significance of this scientific work will be represented in successfully synthesizing transition metal-based MOF as a highly efficient electrocatalyst with two distinctive case studies the first one shows the success in finding monometallic MOF catalysts with similar performance to the Pt catalyst without any additional chemical process( remarkable success through the preparation method itself), and the second case shows the significance of the calcination process parameters to enhance the catalytic activity (Co-Fe-MOF(C)@Fe-Co(A) (represent noticeable success in optimizing well the calcination process with effective parameters).This research study represents one of the most successful studies that were done and managed to report the lowest achieved overpotential at all since we managed to break off the limitation for finding available and inexpensive catalysts that are competitive with platinum catalysts that represent the major obstacles (being expensive and rare) that hamper the development of more and more sophisticated hydrogen production systems.
At the current time, with increasing global warming issue is caused mainly by increasing carbon dioxide levels and other toxic gases because of relying on fossil fuels as the main energy foundation. Thus, it became too significant to spot the light on a new research area that relies on producing energy from renewables and sustainable sources. The utilization of water electrolysis technology for hydrogen production is a promising method, offering a clean and highly energy-efficient fuel source on Earth. However, the major obstacle that hampers utilizing this incredible technology is finding alternative electrocatalysts that are highly efficient, inexpensive, and earth-abundant since Nobel metal-based catalysts are the most effective electrocatalysts to drive the cathodic and anodic reactions, but their high price and limited availability water electrolysis. In this research, metal-organic frameworks (MOFs) based on transition metals have been explored as a promising electrocatalyst for facilitating hydrogen evolution reactions (HER) in electrochemical cells, due to their unique features starting from their ultrahigh porosity, enormous internal surface area, and an extraordinary degree of variability, and their ability to host external guest. Particularly, different types of these nanomaterials have been synthesized including cobalt-based MOF, and iron-based MOF as monometallic MOFs by using a solvothermal method. then Co-Fe-MOF was synthesized as a bimetallic MOF with stirring and heating methods, additionally, the calcination process and loading of their structure with metal ions were conducted in the lab area by using a CVD device. Optimization of the outcome of diverse parameters on the electrocatalytic effectiveness such as the solvent type, heating temperature, duration, and the ratio between metal and ligand have been covered in this thesis plan.FTIR Structural characterization technique of the as-prepared electrocatalysts has been performed and revealed the structural vibration changing due to MOF formations, additionally, XRD has been conducted and confirmed MOF crystal formation through sharp and intense diffraction peaks. Remarkably, the vital evidences that prove the high HER catalytic activity have been provided through the practical measurements that were done through lab experiments appropriately with incredible achievement by utilizing Co-MOF to lower the HER overpotential to η10= 50 mV to attain a current density of 10 mA/cm2 and obtained Tafel slope value 38.57 mV.〖dec〗^(-1) that indicate to high kinetic reaction provided by new catalyst and resistance of charge transfer R_CT (Ω) to be 17.59 ohms that approaches commercial Pt/C catalyst which has about 42 mV of overpotential with Tafel slope about 34.32 mV.〖dec〗^(-1) .and resistance of charge transfer R_CT (Ω) about 2.569 ohms furthermore Fe-MOF also achieved another incredible overpotential reduction with η10= 46 mV and Tafel value 46.71 mV.〖dec〗^(-1) resistance of charge transfer R_CT (Ω) to be 3.366 ohms. Add to these research accomplishments the study of bimetallic-MOF which is Co-Fe-MOF(C)@Fe-Co(A) with η10= 57 mv and Tafel slope about 37.01 mV.〖dec〗^(-1). Resistance of charge transfer R_CT (Ω) to be 18. 25 ohms. Consequently, the synthesized MOFs have a great effect on enhancing HER performance of the water electrolysis to produce hydrogen efficiently, displaying high intrinsic activity compared to noble metals (Pt). finally, MOF catalysts showed great stability after running the LSV polarization curve for 100 cycles. The significance of this scientific work will be represented in successfully synthesizing transition metal-based MOF as a highly efficient electrocatalyst with two distinctive case studies the first one shows the success in finding monometallic MOF catalysts with similar performance to the Pt catalyst without any additional chemical process( remarkable success through the preparation method itself), and the second case shows the significance of the calcination process parameters to enhance the catalytic activity (Co-Fe-MOF(C)@Fe-Co(A) (represent noticeable success in optimizing well the calcination process with effective parameters).This research study represents one of the most successful studies that were done and managed to report the lowest achieved overpotential at all since we managed to break off the limitation for finding available and inexpensive catalysts that are competitive with platinum catalysts that represent the major obstacles (being expensive and rare) that hamper the development of more and more sophisticated hydrogen production systems.
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(MOF)Metal-Organik Çerçeve, (Co-MOF)Kobalt Bazlı Metal-Organik Çerçeve, (Fe-MOF)Demir Bazlı Metal-Organik Çerçeve, (Co.C.MOF)Kobalt Kalsine Esaslı Metal-Organik Çerçeve, (Co.C.MOF/Fe. Co)Kobalt Kalsine Bazlı Demir ve Kobalt Yüklü Metal-Organik Çerçeve, (Co. Fe-MOF)Kobalt Ve Demir Bazlı Metal-Organik Çerçeve, (Co.Fe.C.MOF/ Fe. Co)Kobalt ve Demir Kalsine Esaslı Demir ve Kobalt Yüklü Metal-Organik, (CVD)Kimyasal Buhar Biriktirme, (DMF)Dimetilformamid, (BIM)Benzimidazol, (EIS)Elektrokimyasal Empedans Spektroskopisi, (LSV)Doğrusal Süpürme Voltammetrisi, ( HER)Hidrojen Evrimi Yarı Reaksiyonu, (GCE)Camsı Karbon Elektrot, (TEM)Transmisyon Elektron Mikroskobu, (SEM)Taramalı Elektron Mikroskobu, (XPS)X-Işını Fotoelektron Spektroskopisi, (XRD)X-Işını Kırınımı, (FT-IR) Fourier Dönüşümü Kızılötesi, (RS)Raman Spektroskopisi, (EtOH)Etanol, (TEA)Trietilamin, (TOF)Dönüş Frekansı. (MOF)Metal-Organic Framework, (Co-MOF)Cobalt-based Based Metal-Organic Framework, (Fe-MOF)Iron-Based Metal-Organic Framework, (Co.C.MOF)Cobalt Calcinated Based Metal-Organic Framework, (Co.C.MOF/Fe. Co)Cobalt Calcinated Based Metal-Organic Framework Loaded with Iron and Cobalt, (Co. Fe-MOF)Cobalt And Iron-Based Metal-Organic Framework, (Co.Fe.C.MOF/Fe. Co)Cobalt And Iron Calcinated Based Metal-Organic Loaded with Iron and Cobalt, (CVD)Chemical Vapor Deposition, (DMF)Dimethylformamide, (BIM)Benzimidazole, (EIS)Electrochemical Impedance Spectroscopy, (LSV)Linear Sweep Voltammetry, (HER)Hydrogen Evolution Half Reaction, (GCE)Glassy Carbon Electrode, (TEM)Transmission Electron Microscopy, (SEM)Scanning Electron Microscopy, (XPS)X-Ray Photoelectron Spectroscopy, (XRD)X-Ray Diffraction, (FT-IR)Fourier Transform Infrared, (RS)Raman Spectroscopy, (EtOH) Ethanol, (TEA)Triethylamine, (TOF)Turn Over Frequency.