High surface area mixed metal oxide nanoparticles for photocatalysis and fuel cell applications

This research develops three approaches to the development of advanced functional nanomaterials for sustainable energy applications. The first two focus on photocatalysis using a modified sol-gel citrate method, while the third explores nanocomposite cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). First, phase-pure, mesoporous ZnAl₂O₄ materials with very high surface area (to 344 m²/g), uniform pores, and small crystallites were achieved in a novel synthesis involving calcination under limited O₂ and in-situ carbon self-templating. These materials exhibited oxygen vacancies, reduced band gap, and extended exciton lifetime, leading to exceptional photocatalysis for degradation of Congo Red dye (>99% in <30 minutes) and doubling H₂ production rate compared to conventionally-made ZnAl₂O₄. Second, Cu was doped into this framework, creating phase-pure Zn₁₋ₓCuₓAl₂O₄ spinel nanomaterials. Oxygen vacancy concentration increased and enabled visible-light absorption, and the exciton lifetime was dramatically increased. This suppressed charge recombination, and, coupled with optimised surface properties, resulted in superior H₂ evolution and dye degradation rates. Third, undoped, Mn-doped, and Cu/Mn-doped Co₃O₄/NiO nanocomposite cathodes were developed for IT-SOFCs. Mn doping improved the microstructure and accelerated oxygen reduction kinetics. The Mn-doped composite demonstrated low polarisation resistance and excellent thermal stability, identifying it as a highly promising cathode material.