Malaysian Journal of Analytical Sciences Vol 20 No 3 (2016): 633 - 641

DOI: http://dx.doi.org/10.17576/mjas-2016-2003-24

 

 

 

CONDUCTIVITY AND THERMAL STABILITY OF SOLID ACID COMPOSITES CsH₂PO₄/NaH₂PO₄/SiO₂

 

(Konduktiviti dan Kestabilan Terma Asid Pepejal Komposit CsH₂PO₄/NaH₂PO₄/SiO₂)

 

Norsyahida Mohammad¹, Abu Bakar Mohamad^{1, 2}, Abdul Amir Hassan Kadhum², Loh Kee Shyuan^1*

 

¹Fuel Cell Institute

²Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

 

*Corresponding author: ksloh@ukm.edu.my

 

 

Received: 5 February 2016; Accepted: 22 April 2016

 

 

Abstract

Solid acid composites CsH₂PO₄/NaH₂PO₄/SiO₂ with different mole ratios of CsH₂PO₄ and NaH₂PO₄ to SiO₂ were synthesized and characterized. Preliminary infrared measurements of CsH₂PO₄ and its composites indicated that hydrogen bonds breaking and formation were detected between 1710 to 2710 cm^-1, while the rotation of phosphate tetrahedral anions occurred between 900 and 1200 cm^-1.  The superprotonic transition of CsH₂PO₄/NaH₂PO₄/SiO₂ composite was identified at superprotonic temperatures between 230 and 260 °C, under atmospheric pressure. This study reveals higher conductivity values for composites with higher CsH₂PO₄ (CDP) content. Solid acid composite CDP 613 appeared as the composite with the highest conductivity that is 7.2 x 10^-3 S cm^-1 at 230 °C. Thermal stability of the solid acid composites such as temperature of dehydration, melting and decomposition were investigated. The addition of NaH₂PO₄ lowers the dehydration temperature of the solid acid composites.

 

Keywords: solid acid, conductivity, thermal analysis, caesium dihydrogen phosphate, fuel cell

 

Abstrak

Asid pepejal komposit CsH₂PO₄/NaH₂PO₄/SiO₂ dengan nisbah mol CsH₂PO₄ kepada SiO₂ dan NaH₂PO₄ kepada SiO₂ yang berbeza telah disintesis dan dicirikan dalam ujikaji ini. Pencirian awal sinar inframerah menunjukkan bahawa pemecahan dan pembentukan ikatan hidrogen dikesan antara 1710 cm^-1 dan 2710 cm^-1, manakala putaran anion tetrahedron fosfat berlaku diantara 900 cm^-1 dan 1200 cm^-1. Fasa peralihan berkonduktiviti tinggi bagi asid pepejal komposit CsH₂PO₄/NaH₂PO₄/SiO₂ telah dikenal pasti antara suhu 230 hingga 260 °C, di bawah tekanan atmosfera. Nilai kekonduksian proton adalah lebih tinggi bagi komposit yang mempunyai kandungan CsH₂PO₄ (CDP) yang lebih tinggi. Asid pepejal komposit CDP 613 telah muncul sebagai komposit dengan kekonduksian tertinggi iaitu 7.2 x 10^-3 S cm^-1 pada suhu 230 °C. Kestabilan terma asid pepejal komposit seperti suhu dehidrasi, takat lebur dan penguraian telah dikenal pasti melalui analisis termogravimetri dan kalorimeter imbasan perbezaan. Penambahan NaH₂PO₄ merendahkan suhu dehidrasi asid pepejal komposit.

 

Kata kunci: asid pepejal,  kekonduksian, analisa terma, sesium dihidrogen fosfat, sel fuel

 

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