Priprava in karakterizacija kobalt-železovih plastovitih dvojnih hidroksidov

Plut, Veronika (author), Cerc Korošec, Romana (mentor)

Plastoviti dvojni hidroksidi (ang. Layered Double Hydroxides, LDH) spadajo med anionske gline in so sestavljeni iz pozitivno nabitih plasti ter anionov, ki kompenzirajo naboj. V vmesnem sloju med plastmi je prisotna tudi voda. Plasti sestavljajo dvo- in trivalentni kationi kovin v različnih množinskih razmerjih. Možno je pripraviti različne LDH, ki imajo v strukturi različne vrste kationov in anionov. Značilnost LDH je, da lahko izmenjajo anione v vmesnem sloju, čemur pravimo ionska izmenjevalna kapaciteta. Za pripravo in karakterizacijo LDH obstaja več različnih tehnik. LDH imajo različne lastnosti, npr. sorpcijske, fotokatalitske in elektrokatalitske, kar omogoča njihovo uporabo za različne namene. Namen mojega diplomskega dela je bila priprava in karakterizacija kobalt-železovih LDH z interkaliranimi kloridnimi in karbonatnimi ioni. CoFe-LDH s kloridnimi ioni smo pripravili s sintezo s soobarjanjem pri konstantnem pH, CoFe-LDH s karbonatnimi ioni pa z ionsko izmenjavo. V pripravljenih materialih je bil delež trivalentnih kationov 0,25. Vzorce smo hidrotermalno in termično obdelali. Pripravljene vzorce smo karakterizirali z rentgensko praškovno difrakcijo, infrardečo spektrometrijo, termogravimetrijo in vrstično elektronsko mikroskopijo. Ugotovili smo, da so bili nastali produkti slabo kristalinični in da so bili v vzorcu s kloridnimi ioni prisotni tudi karbonatni ioni. Analizirali smo sorpcijske in fotokatalitske lastnosti pripravljenih materialov s spremljanjem koncentracije barvila Plasmocorinth B v raztopini. Vsi pripravljeni materiali so se izkazali kot boljši sorbenti kot fotokatalizatorji, najboljši rezultati so bili pri CoFe-LDH z interkaliranimi kloridnimi ioni, ki je imel tudi relativno veliko specifično površino. Elektrokatalitske lastnosti smo analizirali s ciklično voltametrijo z rotirajočo diskasto elektrodo kot delovno elektrodo. Preverjali smo aktivnost za reakcije razvoja vodika in kisika iz vode. Za razvoj vodika se je kot boljši elektrokatalizator izkazal CoFe-LDH s kloridnimi ioni, medtem ko sta za razvoj kisika oba materiala dosegla primerljive rezultate. Pri vseh reakcijah je prišlo do relativno velike prenapetosti.

• Language: Slovenian
• Keywords: plastoviti dvojni hidroksidi, karakterizacija, sorpcija, fotokataliza, elektrokataliza
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-159055
• COBISS.SI-ID: 202666755
• Publication date in RUL: 28.06.2024

Secondary language

• Language: English
• Title: Preparation and characterization of cobalt-iron layered double hydroxides

Abstract

Layered double hydroxides (LDH) are anionic clays, consisting of positively charged layers and anions that compensate charge. Water is also present in the interlamellar space. The layers consist of divalent and trivalent metal cations with different molar ratios. It is possible to prepare different LDH with various types of cations and anions in the structure. A characteristic feature of LDH is their ability to exchange anions in the interlamellar space, known as ion exchange capacity. There are several different techniques for the preparation and characterization of LDH. LDHs have different properties, such as sorption, photocatalytic and electrocatalytic properties, which can be used for different applications. The aim of my diploma work was the preparation and characterization of cobalt-iron layered double hydroxides with intercalated chloride and carbonate ions. CoFe-LDH with chloride ions was prepared by coprecipitation synthesis at constant pH and CoFe-LDH with carbonate ions was prepared by ion-exchange. The molar ratio of trivalent cations in the prepared materials was 0,25. The samples were hydrothermally and thermally treated. The prepared samples were characterized by X-ray powder diffraction, infrared spectrometry, thermogravimetry and scanning electron microscopy. It was found that the resulting products were poorly crystalline and that carbonate ions were also present in the sample with intercalated chloride ions. The sorption and photocatalytic properties of the prepared materials were analysed by monitoring the concentration of Plasmocorinth B dye in solution. All the prepared materials proved to be better sorbents than photocatalysts. The best results were obtained for CoFe-LDH with intercalated chloride ions, which also possessed a relatively large specific surface area. The electrocatalytic properties were analysed by cyclic voltammetry with a rotating disc electrode as the working electrode. The activity for the reactions of hydrogen and oxygen evolution from water was tested. For hydrogen evolution, CoFe-LDH with chloride ions was found to be a better electrocatalyst, while for oxygen evolution both materials gave comparable results. Relatively large overpotential occurred in all reactions.

• Keywords: layered double hydroxides, characterization, sorption, photocatalysis, electrocatalysis