A thermochemical study of iron aluminate-based materials: a preferred class for isothermal water splitting

Abstract

The use of hydrogen as a renewable fuel has been stymied by our inability to produce it cleanly and economically. The conventional solar thermochemical approach considers a two-step redox cycle...

Na-β-Al2O3 stabilized Fe2O3 oxygen carriers for chemical looping water splitting: correlating structure with redox stability

“…10,22,26,35 Hydrogen production using iron aluminate-based materials has been proposed for solar driven thermochemical cycles that cycles between spinel iron based solid solutions through an oxygen vacancy mediated mechanism; however, this is limited to high steam-to-hydrogen ratios and the H 2 capacity does not exceed 0.5 mmol H 2 per g FeAl 2 O 4 . [36][37][38] Approaches to prevent the formation of FeAl 2 O 4 during redox operation have included the addition of alkali or alkali earth metal oxides to the oxygen carrier, yet the mechanisms behind the mitigation of FeAl 2 O 4 formation remains elusive. 23,34,39 In particular, the effect of the addition of sodium on the redox performance of Fe during redox cycling leading to the formation of free Al 2 O 3 that subsequently reacts with FeO x to form FeAl 2 O 4 .…”

“…10,22,26,35 Hydrogen production using iron aluminate-based materials has been proposed for solar driven thermochemical cycles that cycles between spinel iron based solid solutions through an oxygen vacancy mediated mechanism; however, this is limited to high steam-to-hydrogen ratios and the H 2 capacity does not exceed 0.5 mmol H 2 per g FeAl 2 O 4 . 36–38…”

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

“…However, keeping the partial pressure of water high and the partial pressure of oxygen low could be a challenge. The theoretical efficiency of the pressure swing operation is also lower compared to traditional temperature swing operations, as the reactions are not operated at their most favorable temperatures [60,61]. Another challenge induced by isothermal redox cycling is that excess steam needs to be added in order to regenerate the redox material [46,62,63].…”

Recent advances in Ru-based electrocatalysts for oxygen evolution reaction

“…3–5 One very promising approach to circumvent these drawbacks is to transform the energy derived from these sources into storable and transportable fuels such as H 2 . 6–8 Hydrogen gas produced by the hydrogen evolution reaction (HER) occurring at the cathode in electrolytic water splitting, can be stored and ultimately reacted with oxygen using fuel cell technology to generate clean, carbon free energy. 9–11 However, a bottleneck exists in the H 2 production process as a consequence of the sluggishness of the simultaneous anodic oxygen evolution reaction (OER), which occurs via a four electron–proton coupled pathway that requires high energy to overcome a kinetic barrier.…”