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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]

[Display omitted] • Manipulating metal-support interactions in Ni/CZA catalysts were investigated. • 20Ni/40CZA contained highly dispersed Ni nanoparticles and abundant oxygen vacancies. • 20Ni/40CZA exhibited the highest H 2 production rate and the lowest coke formation. • Coke precursor gasification was promoted by the efficient delivery of active oxygen. Understanding coke formation routes over Ni-based catalysts is essential in determining the catalytic performance in ethanol steam reforming. In this study, we focused on optimizing the active sites distribution via the metal-support interactions and understanding the coke precursor gasification in Ni/Ce x Zr 1-x O 2 –Al 2 O 3 (CZA) catalysts for ethanol steam reforming. We found that the optimized active sites distribution could minimize coke formation by enabling efficient gasification of a coke precursor on Ni. In the 20Ni/40CZA catalyst, the crystalline CZ exhibited a strong interaction with Ni, maintaining a uniform distribution of highly dispersed Ni nanoparticles and creating abundant oxygen vacancies on CZ, even at 20 wt% of Ni loading. Consequently, the resistance to coking over 20Ni/40CZA was significantly enhanced due to the efficient delivery of active oxygen atoms from steam on the abundant oxygen vacancies to the coke precursor on the Ni surface, resulting in fast gasification of the coke precursor. [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]

[Display omitted] • Macroporous Ni/Al 2 O 3 catalysts are employed for dry reforming of methane (DRM). • Geometrical effect of the macroporous Al 2 O 3 structure promotes NiAl 2 O 4 formation. • Ni exsolution from NiAl 2 O 4 in H 2 reduction results in highly dispersed Ni nanocluster. • The macroporous Ni/Al 2 O 3 catalysts significantly enhance their catalytic performance in DRM. • Coke formation is strongly inhibited over macroporous Ni/Al 2 O 3 catalysts in DRM. This study aimed to investigate the geometrical effect of macroporosity on the performance of Ni-based catalysts in the dry reforming of methane (DRM). For this, macroporous Ni/Al 2 O 3 catalysts with different Ni contents were synthesized. Characterization experiments on the macroporous Ni/Al 2 O 3 catalysts revealed that the macroporous Al 2 O 3 structure enhanced NiAl 2 O 4 formation by facilitating efficient interactions between the Ni species and accessible Al 2 O 3 sites on the macroporous wall surface during calcination. In a subsequent reduction step, Ni exsolution from the NiAl 2 O 4 structure generated highly dispersed Ni nanoclusters over the macroporous Al 2 O 3. Conversely, non-macroporous Ni/Al 2 O 3 catalysts presented substantial amounts of large isolated Ni nanoparticles at an Ni content of 20 wt%, owing to limited NiAl 2 O 4 formation caused by the lack of accessible Al 2 O 3 sites. The highly dispersed Ni nanoclusters surrounded by oxygen vacancies on the macroporous Ni/Al 2 O 3 catalysts significantly enhanced their catalytic performance in the DRM, evidenced by their high CO 2 and CH 4 conversions and strong resistance to coking. Moreover, the superior coke resistance ability of the macroporous Ni/Al 2 O 3 catalysts was attributed to the gasification of the coke precursor on Ni nanoclusters surrounded by oxygen vacancies during the DRM. [ABSTRACT FROM AUTHOR]