UTILIZATION OF NATURAL SILICA FROM RICE HUSK ASH TO IMPROVE ELECTRICAL CONDUCTIVITY OF SDC-BASED IT-SOFC ELECTROLYTE

Zolhafizi  Jaidi; Mohd Azham  Azmi; Hamimah  Abd Rahman; Nurul Farhana Abdul Rahman; Nor Suzyliana Ahmad; Wan Hasrulnizzam Wan Mahmood; Hadi Abdul Salaam; Ahmad Husni Mohd Shapri

Zolhafizi Jaidi Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia.
Mohd Azham Azmi Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia.
Hamimah Abd Rahman Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia.
Nurul Farhana Abdul Rahman Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia.
Nor Suzyliana Ahmad Department of Electronic Technology, Kolej Vokasional Batu Pahat, Jalan Kluang, 83000 Batu Pahat, Johor, Malaysia.
Wan Hasrulnizzam Wan Mahmood Faculty of Industrial & Manufacturing Technology & Engineering, Universiti Teknikal Malaysia Melaka, Jalan Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia.
Hadi Abdul Salaam Faculty of Mechanical and Automotive Engineering Technology, Universiti Malaysia Pahang Al-Sultan Abdullah 26600 Pekan Pahang, Malaysia.
Ahmad Husni Mohd Shapri Faculty of Electronic Engineering and Technology, Universiti Malaysia Perlis, 02600 Arau Perlis, Malaysia.

Keywords: Samarium-doped ceria (SDC), rice husk ash silica (RHASiO₂), solid oxide fuel cell (SOFC), electrochemical impedance spectroscopy (EIS), sintering aid

Abstract

Solid oxide fuel cells (SOFCs) rely on electrolytes with high ionic conductivity and thermal stability, especially for intermediate-temperature operations (500–700 °C). Yttria-stabilized zirconia (YSZ), the conventional SOFC electrolyte, requires high operating temperatures, which leads to thermal mismatch, interfacial degradation, and other performance issues. Samarium-doped ceria (SDC) is a promising alternative due to its superior ionic conductivity at lower temperatures. However, SDC still faces challenges in achieving full densification and minimal porosity without elevated sintering temperatures. This study explores the incorporation of natural silica derived from rice husk ash (RHASiO₂) as an eco-friendly sintering aid to enhance the structural and electrochemical performance of SDC electrolytes. RHASiO₂ was calcined at 700 °C and combined with commercial SDC powder in various weight percentages (0 %–3 %) using dry ball milling. The mixtures were uniaxially pressed into pellets and sintered at 1200 °C. Thermogravimetric analysis (TGA) showed that RHASiO₂ improved thermal stability by reducing weight loss during intermediate and final degradation phases. The microstructure and morphology were characterized using scanning electron microscopy (SEM), while porosity was quantified through image analysis using ImageJ software. The results revealed a decreasing trend in porosity with increasing RHASiO₂ content, reaching the lowest value of 4.58 % in the SDC3.0 sample. Electrochemical impedance spectroscopy (EIS) demonstrated enhanced conductivity and reduced grain boundary resistance for RHASiO₂-modified samples. The highest total ionic conductivity, 2.76 x 10^-2 S·cm⁻¹ at 700 °C, was achieved by SDC3.0, which also exhibited the lowest activation energy of 0.768 eV. These results confirm that RHASiO₂ effectively promotes densification and enhances the electrical conductivity of SDC electrolytes, offering a sustainable and low-cost route to improve SOFC performance.