Graphene Incororated Nanocomposite Electrode Materials for Low Temperature Solid Oxide Fuel Cell

Abstract

Graphene Incorporated Nanocomposite Electrode Materials for Low Temperature Solid Oxide Fuel Cell This PhD research work is focused on the development of graphene incorporated electrode materials that could be a best solution to achieve comparatively low operating temperature (400-600°C) with good electrical conductivity and fuel cell performance for low temperature Solid Oxide Fuel Cell (SOFC) applications. This thesis comprises of two major parts demonstrating the synthesis and characterization of composite Anodes and Cathodes. Anodes of zinc based nano-composite Al0.1Ni0.2Zn0.7 oxide (ANZ) and nano-composite Fe0.2Ni00.3Cu0.5 oxide (FNC) have been synthesized by solid state reaction method followed by incorporation of graphene and graphene oxide (GO) in varying wt.% ratios to prepare composite of ANZ-graphene (ANZ–1%G, ANZ-1.3%G, ANZ-1.5%G.) and FNC-GO anodes (FNC-1% GO and FNC-1.5 % GO) material to use for low temperature SOFC. Cathode material Li0.1Cu0.2Zn0.7 oxide (LCZ) was prepared by solid-state reaction method and perovskite cathode La0.3Sr0.7Fe0.4Ti0.6O3-δ (LSFT) was prepared by sol-gel method. Graphene incorporated cathodes LCZ–1%G, LCZ-1.5%G and graphene oxide (GO) incorporated cathodes LSFT -1% GO, LSFT -1.5% GO were developed to study for low temperature SOFCs applications. The as prepared materials were then characterized by XRD and SEM to study structural and morphological properties in detail. Thermo gravimetric analysis (TGA) was employed to observe the thermal behavior of materials while optical properties and phase transformations were investigated by UV-visible and FTIR tools, respectively. Electrical conductivity and fuel cell performance measurements have also been investigated. The XRD results of all synthesized materials revealed the crystallite size in nano scale range. SEM results confirmed the homogeneous and porous morphology which fulfill the essential requirement of electrode materials. Among anode materials, ANZ-1.3%G anode depicted OCV as 0.95 V and higher power density to be 375 mWcm-2 at 600 °C, in the presence of hydrogen as a fuel. Whereas the higher xii conductivity 43 Scm-1 and the peak power density of fuel cell as 529 mWcm-2 has been achieved for Fe0.2Ni00.3Cu0.5 incorporated with 1.5wt.% GO using H2 fuel which is enhanced value comparable to the base composite. The graphene incorporated FNC materials can be suggested as the cost-effective potential candidate as anode for LT- SOFC. DC conductivity of LCZ cathode was determined to be 3.5 Scm-1 in air atmosphere of sample containing 1.5 wt.% graphene content. The minimum value of area specific resistance (ASR) was measured 0.057 Ωcm2 was achieved for 1.5% graphene incorporated LCZ. The maximum value of open circuit voltage was recorded to be 0.95 V and peak power density has been achieved as 267.5 mWcm-2 at 580 °C with hydrogen as a fuel for the same material. Alternatively, perovskite structure of composite cathode LSFT-1.5% GO sample yielded enhanced conductivity value of 7 Scm-1 which is higher than that of LSFT-pure and LSFT-1% GO. The values of activation energies were found to be 0.132- 0.150 eV at 300-600 °C and provides good support to use the prepared material as cathode for LT-SOFC. The electrochemical performance of LSFT-1.5% fuel cell determined OCV 1.1 V and power density 362 mWcm-2 in hydrogen atmosphere at 560 °C. In view of these findings, graphene incorporated electrodes can be proposed as potential and capable choice for low temperature SOFC and hence may help to commercialize it as a cost-effective clean energy device.