Developing carbon tolerant Ni/ScCeSZ cells via aqueous tape casting for direct biogas fed solid oxide fuel cells (SOFC)

Arifin, Nor Anisa (2019). Developing carbon tolerant Ni/ScCeSZ cells via aqueous tape casting for direct biogas fed solid oxide fuel cells (SOFC). University of Birmingham. Ph.D.

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Abstract

Solid Oxide Fuel cell (SOFC) is a promising solution to energy independence, greener energy, with high electrical efficiency and theoretically compatible to operate with gaseous carbonaceous fuel. The problem arises when the benchmark materials (Ni/YSZ) performance drop with operation with carbon fuels. Hence, this thesis aims to develop SOFC cell with alternative materials that have high electrochemical performance with dry carbon fuels for intermediate temperature SOFC.

This thesis demonstrates the successful manufacturing of the anode supported cells of Ni/YSZ, Ni/ScCeSZ and Sn-Ni/ScCeSZ via reverse aqueous tape casting method. With this method, SOFC half cells with dense thin electrolyte and porous thick anode produced using multi-layered tape casting and single co-sintering stage. Ni/ScCeSZ was chosen as the base anode substrate material due to the 10ScCeSZ’s high conductivity property and better ability to tolerate carbon-based fuels. Despite the long history of Ni/ScCeSZ cell, this thesis shows the first work that compare Ni/YSZ and Ni/ScCeSZ cells for IT-SOFC with hydrogen and dry carbon fuels. Tin (Sn) introduced as dopant in the final stage to further enhanced the performance in dry carbon operation. for Sn-Ni/ScCeSZ cell. To author’s knowledge, this thesis reported the first work on the electrochemical performance in dry biogas.

Comparative study of the electrochemical performance in hydrogen and dry biogas reveals that the maximum power density of Ni/YSZ cell instantly dropped by an average of 80.6% when switched from hydrogen to biogas, 0.37 W/cm\(^2\) to 0.05W/cm\(^2\), respectively. Ni/ScCeSZ showed better performance in both fuels, with maximum power densities of 0.42 W/cm\(^2\) in hydrogen and 0.28 W/cm\(^2\) biogas (37.5 % drop). Ni/YSZ and Ni/ScCeSZ show significant differences in the ASR value in biogas operation with values of 2.52 Ω.cm\(^2\) and 0.72 Ω.cm\(^2\) respectively. With Sn-Ni/ScCeSZ, the OCV increased with the fuel swap from 0.99 V to 1.04 V and the performance in biogas lowered only by an average of 8.3% with a maximum power density of 0.314 W/cm\(^2\) in biogas.

Contradict to the literature, this thesis provides a new insight to the cause of performances drop with the fuel switch which was mainly affected by the reforming ability of Ni/ScCeSZ and Ni/YSZ anode. Small amount of amorphous carbon deposited on the Ni/YSZ anode while higher amount of graphitic carbon found on the Ni/ScCeSZ and Sn-NiScCeSZ anodes. Sn increased the catalytic activity reforming and methane cracking accompanied by increase amount of graphitic carbon on the anode.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):