Aao Şablonlar İçerisine Nikel Biriktirme İle Yüksek Kapasiteli Hibrit Kapasitör Elektrotlarının Üretimi

Abstract

Süperkapasitörler, pillere göre daha yüksek şarj-deşarj hızına, güç yoğunluğuna ve uzun çevrim ömrüne sahip olan enerji depolama aygıtlarıdır. Dünyada devamlı artan enerji ihtiyacından dolayı enerji depolama aygıtlarının önemi artmıştır ve süperkapasitörlerin potansiyelinin arttırılabileceği öngörülerek araştırmalar süperkapasitörler üzerine yoğunlaşmıştır. Yük depolama mekanizmasına göre elektriksel çift tabaka kapasitörler (EDLC) ve psödokapasitörler olarak ikiye ayrılan süperkapasitörlerden EDLC’ler, yükü elektrostatik olarak depolarken; psödokapasitörler, yükü faradayik olarak depolarlar. EDLC’lerde kullanılan elektrotlar karbon esaslı iken, psödokapasitörlerinki iletken polimer veya metal oksit/hidroksit esaslıdır. Her iki süperkapasitör çeşidinin de kendine özgü avantajları mevcuttur. Bu avantajların tümünden faydalanmak için hem elektriksel çift tabaka kapasitör özelliği gösteren karbon esaslı elektrot hem de psödokapasitif özellik gösteren metal oksit/hidroksit elektrotlar kullanılarak hibrit kapasitörler oluşturulmuştur. Bu çalışmada öncelikle hibrit kapasitör bileşenlerinden metal oksit/hidroksit elektrotlar incelenmiş ve metal oksit/hidroksit malzemeler içerisinden en yüksek teorik kapasitansa sahip olan Ni seçilmiştir. Daha sonra ana çalışmalar; Ni esaslı yüksek kapasitansa sahip metal oksit/hidroksit elektrot üretimine yoğunlaşmıştır. Süperkapasitör amaçlı kullanılacak elektrodun elektroaktif yüzey alanının geniş olması gerektiğinden, Ni esaslı elektrodun üretiminde kendi ürettiğimiz anodik alüminyum oksit (AAO) şablonlar kullanılmıştır.

Energy storage devices have become more important in our lives. The increasing demand in high power energy storage devices has stimulated research efforts on electrochemical power sources such as fuel cells, batteries and supercapacitors. Among various energy storage devices, supercapacitors have been considered as one of the most promising candidates. Supercapacitors, also known as ultracapacitors or electrochemical capacitors. They are governed by the same fundamental equations as conventional capacitors, but utilize higher surface area electrodes and thinner dielectrics to achieve greater capacitances. This allows for energy densities greater than those of conventional capacitors and power densities greater than those of batteries. Conventional capacitors consist of two conducting electrodes separated by an insulating dielectric material. When a voltage is applied to a capacitor, opposite charges accumulate on the surfaces of each electrode. The charges are kept separate by the dielectric, thus producing an electric field that allows the capacitor to store energy. Conventional capacitors have relatively high power densities, but relatively low energy densities when compared to electrochemical batteries and to fuel cells. That is, a battery can store more total energy than a capacitor, but it cannot deliver it very quickly, which means its power density is low. Supercapacitors store energy using ion adsorption and/or fast surface redox reactions. These are called, non-Faradaic and Faradaic mechanisms, respectively and supercapacitors can be divided into three general classes: electrochemical double-layer capacitors, pseudocapacitors, and hybrid capacitors. Each class is characterized by its unique mechanism for storing charge. These are, respectively, non-Faradaic, Faradaic, and a combination of the two. Faradaic processes, such as oxidation-reduction reactions, involve the transfer of charge between electrode and electrolyte. A non-Faradaic mechanism, by contrast, does not use a chemical mechanism. Hybrid capacitors attempt to exploit the relative advantages and mitigate the relative disadvantages of EDLCs and pseudocapacitors to realize better performance characteristics. Utilizing both Faradaic and non-Faradaic processes to store charge, hybrid capacitors have achieved energy and power densities greater than EDLCs without the sacrifices in cycling stability and affordability that have limited the success of pseudocapacitors. Electrodes are one of the most important components of supercapacitors and they play a significant role in enhancing the energy density. Carbonaceous materials, transition metal oxides/hydroxides and conducting polymers are used as supercapacitor electrode materials. Various transition metal oxides (RuO2, NiO, Ni(OH)2 MnO2, Co3O4, etc.) have been proved as electrode materials for supercapacitors, and the major focus of the research has been on cost reduction, achieving higher energy densities with environmentally friendly materials. The energy density of supercapacitors is directly proportional to capacitance and surface area of electrodes. For this reason, R&D studies have focused on surface area of electrodes. In recent years, nickel oxides/hydroxides are common electrode materials in supercapacitors due to their low cost, environmentally friendliness and high electrochemical reaction activity. In the present work, we report a novel nickel electrode preparation method via DC electrodeposition of nickel nanowires by using anodic aluminium oxide (AAO) templates.