Publication: Enerji dönüşüm sistemlerinde oksijen elektrokatalizi için modifiye elektrot geliştirilmesi ve çinko hava pili uygulamaları
Abstract
Yenilenebilir, temiz ve maliyeti düşük enerji ihtiyacı son yıllarda hissedilebilir şekilde artmaktadır. Bu ihtiyaca cevap vermek amacıyla, enerji dönüştüren ve depolayan elektrokimyasal sistemler (EDDS) ve bu sistemler üzerinde gerçekleştirilen araştırma çalışmaları ön plana çıkmakta ve artarak devam etmektedir. EDDS’de değişik çalışma elektrotları üzerinde gerçekleştirilen elektrokimyasal reaksiyonların önemli bir çoğunluğu irreversibil, yavaş ve zor bir şekilde gerçekleşmekte ve şarj-deşarj aşırı gerilimine sebep olmaktadır. Bu sistemlerde gerçekleşen elektrokimyasal reaksiyonlar olarak oksijen, hidrojen, hidrojen peroksit ve suyun redoks tepkimeleri sıklıkla yer almaları nedeniyle ön plana çıkmaktadır. Söz konusu tepkimeleri reversibil ve hızlı bir şekilde gerçekleştirebilmek ve bu şekilde polarizasyon nedeniyle ortaya çıkan şarj-deşarj aşırı gerilimlerini azaltmak amacıyla elektrokimyasal katalizörler kullanılmaktadır. Yakıt ve metal-hava pillerinde yarı reaksiyon olarak yer alan oksijen redoks tepkimelerinin kinetiği oldukça yavaş olduğu için oksijen elektrokatalizör geliştirilmesi bu tür sistemlerde daha da büyük bir önem kazanmaktadır. Değişik bileşikler ve yöntemler ile hazırlanan birçok kompozit malzeme modifiye elektrot hazırlamak ve bu reaksiyonları katalizlemek amacıyla denenmektedir. Yakıt pilleri ve metal hava pillerinde oksijenin indirgenmesinde katalizör olarak uzun bir süredir platin kullanılmaktadır. Fakat, platin çok kısıtlı miktarlarda bulunan ve bu nedenle de çok pahalı olan bir metaldir. Dolayısıyla, yakıt pilleri ve metal hava pilleriyle bağlantılı bilimsel çalışmalar oksijeninin katodik indirgenmesinde platine alternatif olabilecek elektrokatalizörlerin bulunması ve bu maddelerle verimli, aktif ve ucuz elektrot sistemlerinin geliştirilmesi üzerine yoğunlaşmıştır. Kimyasal ve termal olarak kararlı olan ftalosiyanin kompleksleri konjuge elektron sistemleri ve merkezlerine yerleşebilen farklı metaller ile alternatif elektrokatalizör adaylarıdır. Bu tez çalışması kapsamında ftalosiyanin temelli karbon destek malzemelerle modifiye edilmiş polimerik bağlayıcı içeren elektrokatalizörler kullanılmıştır. Katalizörlerin elektrokimyasal ve pil performans testleri gerçekleştirilmiştir.
The demand for renewable, clean, and cost-effective energy has noticeably increased in recent years. In response to this demand, research studies on electrochemical energy conversion and storage systems (EDDS) have gained prominence and are continuing to grow. A significant portion of the electrochemical reactions occurring on different working electrodes in EDDS are irreversible, slow, and difficult, leading to overvoltage during charging and discharging. Oxygen, hydrogen, hydrogen peroxide, and water redox reactions are prominent in these systems due to their frequent occurrence. Electrochemical catalysts are used to carry out these reactions in a reversible and rapid manner, aiming to reduce the overvoltage caused by polarization during charging and discharging. Since the kinetics of oxygen redox reactions, which are involved as half-reactions in fuel and metal-air cells, are quite slow, the development of oxygen electrocatalysts becomes even more crucial in such systems. Various composite materials prepared with different compounds and methods are being tried to prepare modified electrodes and catalyze these reactions. Platinum has been used as a catalyst for the reduction of oxygen in fuel cells and metal-air batteries for a long time. However, platinum is a metal that is found in very limited quantities and therefore very expensive. Consequently, scientific studies related to fuel cells and metal-air batteries have focused on finding alternative electrocatalysts to platinum for the cathodic reduction of oxygen and developing efficient, active, and inexpensive electrode systems with these materials. Phthalocyanine complexes, which are chemically and thermally stable, are alternative electrocatalyst candidates due to their conjugated electron systems and the ability to incorporate various metals at their centers. In this thesis study, electrocatalysts containing carbon support materials modified with phthalocyanine-based polymer binders have been used. Electrochemical and battery performance tests of the catalysts have been conducted.
The demand for renewable, clean, and cost-effective energy has noticeably increased in recent years. In response to this demand, research studies on electrochemical energy conversion and storage systems (EDDS) have gained prominence and are continuing to grow. A significant portion of the electrochemical reactions occurring on different working electrodes in EDDS are irreversible, slow, and difficult, leading to overvoltage during charging and discharging. Oxygen, hydrogen, hydrogen peroxide, and water redox reactions are prominent in these systems due to their frequent occurrence. Electrochemical catalysts are used to carry out these reactions in a reversible and rapid manner, aiming to reduce the overvoltage caused by polarization during charging and discharging. Since the kinetics of oxygen redox reactions, which are involved as half-reactions in fuel and metal-air cells, are quite slow, the development of oxygen electrocatalysts becomes even more crucial in such systems. Various composite materials prepared with different compounds and methods are being tried to prepare modified electrodes and catalyze these reactions. Platinum has been used as a catalyst for the reduction of oxygen in fuel cells and metal-air batteries for a long time. However, platinum is a metal that is found in very limited quantities and therefore very expensive. Consequently, scientific studies related to fuel cells and metal-air batteries have focused on finding alternative electrocatalysts to platinum for the cathodic reduction of oxygen and developing efficient, active, and inexpensive electrode systems with these materials. Phthalocyanine complexes, which are chemically and thermally stable, are alternative electrocatalyst candidates due to their conjugated electron systems and the ability to incorporate various metals at their centers. In this thesis study, electrocatalysts containing carbon support materials modified with phthalocyanine-based polymer binders have been used. Electrochemical and battery performance tests of the catalysts have been conducted.