Mechanistic Study and Active Sites Investigation of Hydrogen Production from Methane and H 2 O Steady-State and Transient Reactivity with Ir/GDC Catalyst.

Lachquer, Farah; Toyir, Jamil

Catalytic activity, mechanisms, and active sites were determined for methane steam reforming (MSR) over gadolinium-doped ceria (GDC) supported iridium (0.1 wt%) prepared by impregnation of GDC with iridium acetylacetonate. Isothermal steady-state rate measurements followed by micro-gas chromatography analysis were performed at 660 and 760 °C over Ir/GDC samples pretreated in N2 or H2 at 900 °C. Transient responses to CH4 or H2O step changes in isothermal conditions were carried out at 750 °C over Ir/GDC pretreated in He or H2 using online quadrupole mass spectrometry. In the proposed mechanism, Ir/GDC proceeds through a dual-type active site associating, as follows: (i) Ir metallic particles surface as active sites for the cracking of CH4 into reactive C species, and (ii) reducible (Ce4+) sites at GDC surface responsible for a redox mechanism involving Ce4+/Ce3+ sites, being reduced by reaction with reactive C into CO (or CO2) depending on the oxidation state of GDC and re-oxidized by H2O. Full reduction of reducible oxygen species is possible with CH4 after He treatment, whereas only 80% is reached in CH4 after H2 treatment.

HYDROGEN production; METALLIC surfaces; CATALYTIC activity; OXIDATION states; MASS spectrometry

Hydrogen, 2024, Vol 5, Issue 4, p882

2673-4141

Academic Journal

10.3390/hydrogen5040046