Hydrogen production from organic
waste by gasification and reforming
technologies offers major benefits to both the environment and climate.
The long-term stability and regeneration of the reforming catalyst
are still the biggest challenges because of carbon deposition. Here
we report a recyclable salt-supported nickel oxide NiO/NaX (X: F,
Cl, Br) catalyst for effective autothermal reforming of the oxygenated
volatile organic compound (OVOC) ethyl acetate to hydrogen. The optimal
hydrogen selectivity achieved 82.0% at 650 °C and the durability
reached 43 h. Interestingly, with the decreasing of halogen electronegativity
(F > Cl > Br) in NaX, the corresponding hydrogen selectivity
of the
catalysts decreased. Although NiO/NaX catalysts possess a very small
specific surface area and a dense microstructure, their catalytic
performance is better than that of normal Ni-based catalysts loaded
on high-specific-surface-area supports. Detailed investigations revealed
the critical roles played by halogen during the reforming reaction.
First, the strong electronegative halogen in NaX induced the formation
of hydrogen bonds with the reactants and reaction intermediates, which
may prolong the surface residence time of such species, thus ensuring
efficient hydrogen production over small-specific-surface-area catalysts
under high-temperature conditions. Second, the halogen of the support
NaX weakening the Ni–O bonds of the exposed Ni atoms in NiO/NaX
made it easier for NiO to be reduced to Ni0, thus reducing
the reaction activation energy and prompting the rapid catalytic reaction.
The strength of such metal–support interaction can be easily
modulated by varying the halogen electronegativity. This study provides
a new prospect for the design of innovative recyclable heterogeneous
catalysts with low specific surface area but high activity.