NiOx(H) locked Au clusters against CO-induced aggregation for robust water-gas shift catalysis
Despite the supported Au demonstrating superior activity in catalyzing various reactions, their stubborn and widespread deactivation issue has long remained unsolved. Therefore, the challenge in current investigations of Au-based catalysts could be divided into two aspects: uncovering the authentic molecular induction for the deactivated evolution and fabricating interfacial structures combining efficiency and stability. In this work, by incorporating NiO x (H) adjacent to small active Au 1 /Au n species, the as-formed 0.5Au-5NiO x (H)/CeO 2 catalyst simultaneously achieved high reactivity ( r = 5.23 mmol CO ·g Au −1 ·s −1 ) toward the water-gas shift (WGS) reaction and remarkable long-term stability with time-on-stream of 100 h at 250 °C, significantly surpassing the reference Au/CeO 2 counterpart as well as the other oxides-supported Au catalysts reported previously. Comprehensive in-situ characterizations and DFT calculations revealed that the CO molecules, rather than H 2 , H 2 O, or CO 2 molecules, are the dominant molecular driver for Au aggregation, correspondingly inducing the degraded catalytic efficiency. Specifically, on the one hand, the strong CO−Au coordination degraded the ejection barrier of Au atoms from Au-Au coordination; on the other hand, the −OH groups as intermediates from H 2 O dissociation, participating in the stabilization of Au species upon the surface, were dynamically consumed by CO molecules. For these regards, the adjacent Ni adatoms promote the sufficient generation of stable −OH groups for stabilizing Au atoms under WGS reaction. As a result, the corresponding Au−Au ejection and Au−O diffusion barriers of as-formed Au n −O(H)−Ni/CeO 2 combinations are significantly enlarged, which thereby boosts the structural stability in the CO-containing atmospheres.
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