Study on the reaction performance of Ce‐doped NiFe ₂ O ₄ oxygen carriers in the process of chemical looping hydrogen production

Abstract

Summary Chemical looping hydrogen production is a kind of hydrogen production technology with great potential. NiFe2O4 is one of the oxygen carriers with the best comprehensive hydrogen production performance, but the oxygen carrier still has the disadvantages of low hydrogen production and poor reaction stability. In this paper, a small amount of Ce was doped in the oxygen carrier to improve the hydrogen production efficiency. And the reaction stability of the oxygen carrier was improved by loading an inert carrier. The experimental results showed that the 6 wt% Ce‐NiFe2O4 oxygen carrier had the highest H2 yield, and the hydrogen yield per unit mass of oxygen carrier was increased from 194 to 367 mL/g. Thermodynamic simulation and characterization results showed that the doping of Ce could enhance the oxygen release capacity and hydrogen production capacity. In the cyclic experiment, due to the damage of the oxygen carrier spinel structure and the sintering of oxygen carrier particles, the reaction activity of the 6 wt% Ce‐NiFe2O4 oxygen carrier gradually reduced and the hydrogen production in the steam reactor decreased significantly after 15 cycles. After the loading of Al2O3 inert support on the 6 wt% Ce‐NiFe2O4 oxygen carrier, the hydrogen production was greatly improved and remained stable after 15 cycles. The modification of the oxygen carrier could not only increase the hydrogen production but also the economic efficiency for the reduced amount of Ce and Ni.

Synergistic effect to enhance hydrogen generation of Fe 2 O 3 /Ce 0. 8 Sm 0 . 1 Gd 0 .

“…By deconvoluting the XPS spectra, we can observe three peaks at around ~529.8, ~531.5, and ~532.9 eV. By comparing with data from the standard database, these three peaks stem from the contribution of lattice oxygen (O I ), oxygen species that are weakly adsorbed on oxygen vacancies (O II ), and absorbed oxygen and moisture (O III ) 51 . The relative content of oxygen species is summarized in Table 4.…”

“…By deconvoluting the XPS spectra, we can observe three peaks at around $529.8, $531.5, and $532.9 eV. By comparing with data from the standard database, these 51 The relative content of oxygen species is summarized in Table 4. The oxygen vacancy concentration of the oxygen carriers follows the rank of:…”

A brief review of hydrogen production technologies

“…However, thermodynamic constraints caused the reduced-state oxygen carriers to only partially restore lattice oxygen in a steam atmosphere to a ternary mixture phase of Ni, Fe3O4, and Ni(1−x)Fe(2+x)O4. To improve the stability of NiFe2O4, Gao et al [45] doped Ce into NiFe2O4 oxygen carriers to enhance hydrogen production efficiency and reaction stability. The results showed that when the addition of Ce was 6%, NiFe2O4 oxygen carriers had the highest hydrogen production rate, which was attributed to the fact that doping with Ce improved the oxygen release capability and the stability of oxygen carriers.…”