Structural Changes of Intermetallic Catalysts under Reaction Conditions

Abstract

Intermetallics or ordered intermetallic alloys have received more and more attention for the applications of catalysis. Under practical reaction conditions, their atomic arrangements as well as chemical compositions can undergo diverse changes, including reshaping, segregation, disordering, sintering, oxidation, and leaching. These changes directly related to their stability are of great importance for their performances. Herein, the research advances of the structure–performance correlations of intermetallic catalysts, especially on how the structural changes modify their catalytic activity, are reviewed. First, the crystal and electronic structure as well as characterization techniques are introduced. Afterward, the changes of structures under typical reaction conditions by highlighting the underlying mechanisms are discussed. Then, strategies for optimizing the structures are surveyed. Finally, the challenges and perspectives by highlighting the importance of the utilization of in situ techniques are presented.

Highly Stable Bimetal Ni–Co on Alumina-Covered Spinel Oxide Derived from High Entropy Oxide for CO2 Methanation

“…The dispersion degree of HEO-700 is between HEO-600 and HEO-800, which is also reflected in its ability to resist sintering and stabilize alloys. Thus, HEO-700S and HEO-800S maintained higher CO 2 conversions and CH 4 selectivities. ,,, …”

“…In contrast, in the reducing atmosphere, the spinel phases could be reduced to metal and Al 2 O 3 , thus resulting in a dynamic redox cycle under a coexisting atmosphere. Moreover, the metal component with high redox potential is more easily oxidized in an alloy catalyst, and the redox potential of Co is higher than that of Ni. As a result, Co is more easily oxidized than Ni, and CoO x can react with Al 2 O 3 to easily form CoAl 2 O 4 in a CO 2 atmosphere, which is one of the main reasons for the deactivation of cobalt-based catalysts.…”

Pathways towards Achieving High Current Density Water Electrolysis: from Material Perspective to System Configuration

“…After prolonged practical operations, the composition, shape, and structure of electrocatalysts may suffer from major degradation, especially under extreme redox conditions. [298,299] Hence, a delicate trade-off balance between catalytic activity and stability is crucial if HCD water electrolyzers are to be implemented on an industrial scale. The above sections mainly introduce the effects of large current density on the stability and overall performance of water electrolysis; herein, we will focus on three critical phenomena that can affect the long-term durability of electrocatalysts: (i) structural transformation or surface reconstruction; (ii) dissolution of active sites; and (iii) catalyst detachment due to mechanical stress.…”

Unveiling the nucleation and evolution of twinned intermetallic nanocrystals for CO-tolerant selective hydrogenation

“…The nucleation and growth processes of nanocrystals can be divided into classical theory and non-classical theory. 8,51–53 In the classical nucleation process, the nucleation step firstly occurs via a one-step nucleation pathway by the direct aggregation of monomers into nanocrystals, followed by the growth process based on the surface reaction and monomer diffusion to the surface. However, the classical nucleation theory was generally applicable for the wet chemical synthesis of monometallic nanocrystals.…”