Crystal structure and surface species of CuFe2O4 spinel catalysts in steam reforming of dimethyl ether

Copper–iron spinel (CuFe2O4) in cubic phase was prepared via a simple citrate sol–gel method, and was transformed into tetragonal phase of high crystallinity by calcining in air at 900 °C. Composites of CuFe2O4 spinel and γ-Al2O3 were investigated for catalytic production of hydrogen from dimethyl ether steam reforming (DME SR). X-ray photoelectron spectroscopy showed Cu1+-rich surface species (Cu1+/Cu0 = ca. 3/2 with negligible Cu2+) over the calcined CuFe2O4 subjected to in situ H2 reduction. The spinel-oxides with lower content of reducible Cu species possessed higher amount of Cu1+ species under the reducing atmosphere, corresponding to higher DME SR activity. Copper clusters highly dispersed in the matrix of iron oxides were reduced from the spinel structure, and the strong interaction between them should result in the high activity and durability. The degraded catalysts after DME SR were regenerated by calcining in air in the temperature range of 350–800 °C. Slow deactivation of the composites observed during DME SR at 375 °C was mainly attributable to non-graphitic carbonaceous species deposited on the catalyst surface.