Solar-Driven Thermochemical Water-Splitting by Cerium Oxide: Determination of Operational Conditions in a Directly Irradiated Fixed Bed Reactor

Abstract

Concentrated solar energy can be transformed into electricity, heat or even solar fuels, such as hydrogen, via thermochemical routes with high exergetic efficiency. In this work, a specific methodology and experimental setup are described, developed to assess the production of hydrogen by water splitting making use of commercial cerium oxide, ceria (CeO2), in a solarized reactor. A fixed bed reactor, directly irradiated by a 7 kWe high flux solar simulator (HFSS) was used. Released H2 and sample temperature levels were continuously monitored. Three tests were carried out consisting of three consecutive redox cycles each, with irradiances in the range of 1017–2034 kWm−2. It was necessary to achieve a compromise between sample temperatures (higher temperatures lead to higher reduction rates) and sample stability, since absorbed radiation can degrade a sample at lower temperature (1280–1480 °C) than in a conventional infrared oven (T > 2000 °C). Irradiating the surface of the sample with an irradiance of 2034 kWm−2 (270 W of total radiation power) during 9.5 min eventually degraded the sample, resulting in a conversion into stoichiometrically reduced oxide (Ce2O3) of 11%. A similar conversion was achieved (9.7%) after 2 min of irradiation at 270 W (100% of radiation), but without irreversibly damaging the sample.

Calcite–Fluid Interfacial Tension: H2 and CO2 Geological Storage in Carbonates

“…The large-scale hydrogen economy might one day attain great value throughout the world, which can provide a solution for mitigating human-caused emissions of greenhouse gases and meeting the increased worldwide energy need. − Hydrogen is produced via different methods such as electrolysis, methane bi-reforming, biomass gasification, and solar thermochemistry. − However, its storage at the surface is very complex due to its volatility and compressibility. An effective solution to this issue can be underground hydrogen storage (UHS), where hydrogen is injected into a geostorage site [e.g., depleted hydrocarbon reservoirs, coal seams, and deep saline aquifers − ] and withdrawn again when the need arises.…”

A perspective on three sustainable hydrogen production technologies with a focus on technology readiness level, cost of production and life cycle environmental impacts

“…Disproportionation reaction at temperatures above 600 °C: SnO SnO 2 + Sn. ZnO/Zn 2300K [ 98 ] 53.2% [ 98 ] – 1.Volatile cycle with higher reduction temperature requirement than SnO 2 /SnO. 1.…”

A Comprehensive Review on Two-Step Thermochemical Water Splitting for Hydrogen Production in a Redox Cycle

“…These two technologies are well-developed and their schematics are shown in Figure 1 [38]. Although these high temperatures are required to reach high hydrogen production rates, a major drawback is that the solar radiation can damage the samples, for example through degradation [43]. [44].…”