Examinando por Autor "Pérez, Alejandro"

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Hydrogen production by isothermal thermochemical cycles using La0.8Ca0.2MeO3±δ (Me = Co, Ni, Fe and Cu) perovskites
(Elsevier, 2023) Pérez, Alejandro; Orfila, María; Linares, María; Sanz, Raúl; Marugán, Javier; Molina, Raúl; Botas, Juan A.
Solar-driven thermochemical water splitting has the potential to transform concentrated solar energy into green hydrogen and other solar fuels. In this work, La0.8Ca0.2MeO3±d (Me ¼ Co, Ni, Fe and Cu) perovskites have been synthesised by a modified Pechini method and evaluated as materials for hydrogen production by two step thermochemical water splitting cycles. Performing the thermal reduction at temperatures of 1200 and 1000 C, while the oxidation is done at 800 C, allows a remarkable and stable hydrogen production after 5 consecutive cycles. However, the perovskites suffer changes in the structure after each redox cycle, with potential effects in the long-term cyclic operation. On the contrary, the isothermal thermochemical cycles at 800 C produce a stable amount of hydrogen with each consecutive cycle maintaining the perovskite structure. This hydrogen production ranges from 3.60 cm3 STP/gmaterial$cycle for the material with the lowest productivity (La0.8Ca0.2FeO3±d) to 5.02 cm3 STP/gmaterial$cycle for the one with the highest activity (La0.8Ca0.2NiO3±d). Particularly the Ni-based material shows the highest H2 productivity accompanied by very good material stability after 15 consecutive cycles, being possible to combine with current solar thermal facilities based on concentrated solar power technologies like plants with central receivers.
Reticulated porous structures of La0.8Al0.2NiO3-δ perovskite for enhanced green hydrogen production by thermochemical water splitting
(Elsevier, 2024-12) Pérez, Alejandro; Orfila, María; Díaz, Elisa; Linares, María; Sanz, Raúl; Marugán, Javier; Molina, Raúl; Botas, Juan A.
The preparation and optimisation of La0.8Al0.2NiO3-δ (LANi82) perovskite shaped as reticulated porous ceramic (RPC) structures for H2 production by thermochemical water splitting is presented for the first time. The perovskite was first synthesised in powder form following a modified Pechini method. The redox properties of the LANi82 were first tested under N2/air flow in a thermogravimetric analyser. After that, the sponge replica method for preparing RPCs was optimised in terms of slurry composition and final thermal treatment to obtain a LANi82-RPC structure with porosity and strength appropriate to enhance heat and mass transfer in further solar reactors. The optimised LANi82-RPC material showed an outstanding hydrogen production of 8.3 cm3 STP/gmaterial·cycle at isothermal conditions (800 °C). This production was increased up to 11.5 cm3 STP/gmaterial·cycle if the thermal reduction was performed at 1000 °C. Additionally, a stable activity with almost constant H2 production in consecutive cycles was obtained for the optimised LANi82-RPC in both cases. The structure of the reticulated porous materials, with open macroporosity and wide interconnected channels, enhances heat and mass transfer, leading to higher hydrogen productions of the LANi82-RPC as compared to the materials as powder form in the same experimental set-up. These facts reinforce the favourable prospects of LANi82-RPC for large-scale hydrogen production, improving the coupling to current solar thermal concentration technologies developed, such as concentrated solar power tower