In this dissertation, the concept of water splitting using solid oxide photoelectrochemical cells (SOPCs) at high temperature was introduced and experimentally investigated. High temperature photoelectrochemical water splitting physically broadens the selection of potential applicable semiconductor materials and enables more visible sunlight absorption. This newly conceived concept provides a unique pathway for solar hydrogen production, as compared to conventional photoelectrochemical cells (PECs) that use wide band gap semiconductors in aqueous environments. The theoretical framework of SOPC was elaborated, followed by the experimental investigation to search for appropriate high temperature materials. Selected high temperature Schottky and p-n junction diodes, which were expected to be applicable to the photocatalytic/oxygen electrodes of SOPCs, were fabricated and evaluated. Their rectifying characteristics were characterized at elevated temperatures. Among those diodes, only LSM/TiO2 demonstrated acceptable rectifying properties up to 450 °C, indicating that such configuration may be applicable to the proposed SOPC.
The further investigation was carried out on fabrication of the electrodes of SOPC and solid oxide fuel cell (SOFC) using fused deposition modeling (FDM), a technique of 3D printing. The goal was to directly print out ceramic substrates and eventually make porous electrodes. Ceramic filaments that consist of ceramic electrode materials and thermoplastics were fabricated in house. After experimenting many thermoplastics, Nylon 12 was identified as an ideal thermoplastic polymer to make composite ceramic filaments. The printouts were sintered in the furnace to burn out all the organics, leaving behind porous electrodes made of pure ceramics. The 3D printed cathodes on half SOFCs were evaluated and demonstrated comparable performance to conventional SOFCs using dip-coating method. Therefore, FDM provides a viable and low cost means to fabricate the porous electrodes of SOPC/SOFC
