Platinum-based bimetallic catalysts exhibit surface atomic rearrangement in various adsorbate environments, which significantly impacts catalysis. A molecular-level understanding of intermediate structures created during catalysis is essential for developing high-performance bimetal catalysts. We show that intermediate Pt−NiO 1−x interfacial structures drive the catalytic synergistic effect observed on Pt 3 Ni nanocrystals. Real-time microscopic observations at ambient pressure show the formation of oxygen-driven Ni oxide clusters on the surface and provide direct evidence of Pt−NiO 1−x interfacial structure formation. Spectroscopic analysis, including ambient-pressure X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy, and catalytic measurements elucidate the role of Pt−NiO 1−x interfacial structures and the catalytic reaction mechanism in CO oxidation. Our results indicate that metal-oxide interfacial intermediate structures in bimetal catalysts relate to the catalytic enhancement of the strong metal−support interaction (SMSI) effect.

Modern surface science faces two major challenges, a materials gap and a pressure gap. While studies on single crystal surface in ultrahigh vacuum have uncovered the atomic and electronic structures of the surface, the materials and environmental conditions of commercial catalysis are much more complicated, both in the structure of the materials and in the accessible pressure range of analysis instruments. Model systems and operando surface techniques have been developed to bridge these gaps. In this Review, we highlight the current trends in the development of the surface characterization techniques and methodologies in more realistic environments, with emphasis on recent research efforts at the Korea Advanced Institute of Science and Technology. We show principles and applications of the microscopic and spectroscopic surface techniques at ambient pressure that were used for the characterization of atomic structure, electronic structure, charge transport, and the mechanical properties of catalytic and energy materials. Ambient pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy allow us to observe the surface restructuring that occurs during oxidation, reduction, and catalytic processes. In addition, we introduce the ambient pressure atomic force microscopy that revealed the morphological, mechanical, and charge transport properties that occur during the catalytic and energy conversion processes. Hot electron detection enables the monitoring of catalytic reactions and electronic excitations on the surface. Overall, the information on the nature of catalytic reactions obtained with operando spectroscopic and microscopic techniques may bring breakthroughs in some of the global energy and environmental problems the world is facing.

Identifying the active sites of Cu nanoparticles that convert CO2 to multi-carbon (C2+) materials have remained elusive. It is caused by reconstructing Cu during electrochemical CO2 reduction and underestimated the...