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This work investigates selective Ni locations over Ni/CeZrO x –Al 2 O 3 catalysts at different Ni loading contents and their influences on reaction pathways in ethanol steam reforming (ESR). Depending on the Ni loading contents, the added Ni selectively interacts with CeZrO x –Al 2 O 3 , resulting in the stepwise locations of Ni over CeZrO x –Al 2 O 3. This behavior induces a remarkable difference in hydrogen production and coke formation in ESR. The selective interaction between Ni and CeZrO x for 10-wt.% Ni generates more oxygen vacancies in the CeZrO x lattice. The Ni sites near the oxygen vacancies enhance reforming via steam activation, resulting in the highest hydrogen production rate of 1863.0 μmol/g cat ·min. In contrast, for 15 and 20-wt.% Ni, excessive Ni is additionally deposited on Al 2 O 3 after the saturation of Ni–CeZrO x interactions. These Ni sites on Al 2 O 3 accelerate coking from the ethylene produced on the acidic sites, resulting in a high coke amount of 19.1 mg c /g cat·h (20Ni/CZ-Al). [Display omitted] • Ni/CeZrO x –Al 2 O 3 for ethanol steam reforming are prepared at different Ni contents. • Depending on the Ni amounts, Ni selectively interacts with the CeZrO x –Al 2 O 3 support. • Stepwise Ni locations over CeZrO x –Al 2 O 3 remarkably affect the ESR reaction pathways. • Ni sites near the oxygen vacancies on CeZrO x enhance reforming via steam activation. • Ni sites on Al 2 O 3 accelerate coking from the ethylene produced on the acidic sites. [ABSTRACT FROM AUTHOR]

In this study, we investigated the metal–support interactions over Ni/CeO 2 –ZrO 2 (Ni/CZ) catalysts for ethanol steam reforming. Different Ni contents (5, 10, and 15 wt%) were loaded onto the CZ support using two catalyst preparation methods, namely one-pot, and successive impregnation methods. Using the one-pot method, the Ni species over the Ni/CZ catalysts strongly interacted with the CZ support, resulting in smaller Ni nanoparticles with abundant oxygen vacancies. In contrast, the successive impregnation method mainly generated an isolated Ni phase at a high Ni content, resulting in large Ni clusters with limited oxygen vacancies. The poor Ni dispersion over the Ni/CZ catalysts prepared by the successive impregnation method induced low ethanol conversions and hydrogen production rates. In addition, the large Ni clusters over the Ni/CZ catalysts prepared by the successive impregnation method achieved a fast-coking behavior, thereby increasing the coke amount. Further, coke gasification was demonstrated to dominate the Ni surface with the Ni/CZ catalysts prepared by the one-pot method because of the high Ni dispersion and abundant oxygen vacancies. [Display omitted] • Ni/CeO 2 -ZrO 2 catalysts for ethanol steam reforming are prepared at different methods. • The one-pot method induces the strong Ni-CZ interaction over Ni/CZ catalysts. • Ni/CZ prepared by the one-pot method contains abundant oxygen species and Ni sites. • Ni/CZ prepared by the one-pot method enhances the H 2 production rate at 550 ℃. • Mild coking on the one-pot Ni/CZ catalysts is due to efficient coke gasification. [ABSTRACT FROM AUTHOR]