Micro-tubular and micro-monolithic solid oxide fuel cells for energy and environment

Abstract

Micro-tubular solid oxide fuel cells (MT-SOFCs) have interesting features and presents several advantages and competitiveness such as better thermal shock resistance, higher power density and portable characteristics. Further enhancement in terms of cell performance remains as a challenge to be competitive with the planar design made from similar cell materials. In this work, improvement of the anode micro-structure prepared via a phase-inversion assisted process has been studied by employing common SOFC materials including nickel-yttria stabilised zirconia (Ni-YSZ). A new anode design with longer micro-channels and larger pore entrance made using solvent-based bore fluid gave better electrochemical performance compared to the conventional single-channel anode design. Such new design, when utilising YSZ material could be made into a suitable electrolyte scaffold for incorporating anode materials, copper-ceria (Cu-CeO2). MT-SOFC with Cu-based anode was tested for direct methane (CH4) utilisation. Notwithstanding the great potential of MT-SOFC, problems such as low mechanical robustness of the small micro-tube must be addressed. A multi-channel design has been proposed whereby NiO-YSZ anode substrate with various number of channels have been prepared and developed into complete single micro-monolithic cells. Their properties were compared and eventually tested for electrochemical performances. Micro-monolithic design has a better mechanical property, up to 4-8 times compared to the single-channel counterpart. Electrochemical test showed that 7-channel cell achieved about 120 % increment in terms of power density than the conventional single-channel design. The flexibility in the operation of solid oxide electrochemical reactors allows the use of such devices as a fuel cell and electrolyser. Such unique characteristics have been investigated for fuel cell operation with hydrogen (H2) and carbon dioxide (CO2) electrolysis using a novel 6-channel micro-monolithic cell in which excellent performances have been demonstrated.