Revealing Phase-Controlled Surface Structure in PtNi Nanocatalysts via In-situ Gas Cell Transmission Electron Microscopy

The rational design of catalysts capable of efficiently utilizing CO2 is critical for sustainable chemical processes. The Super-dry reforming of methane (Super-DRM), which couples dry reforming of methane (DRM) with the reverse water gas shift (RWGS) reactions, offers a promising route to maximize CO2 conversion. Modulating the crystal phase of nanocatalysts offers a powerful strategy to enhance catalytic performance, yet the relationship between bulk phase and catalytic behavior remains poorly understood. A significant obstacle in resolving this issue is obtaining atomic-level insights on the surface structure of phase-controlled catalyst under reaction conditions. In this study, we employ in-situ gas cell transmission electron microscopy to investigate the surface structure of faceted PtNi nanoparticles during Super-DRM at moderate temperatures (550 ℃). Atomic-resolution in-situ observations reveal that the reaction environment induces a pronounced nickel segregation and subsequent coke formation on the surface of disordered A1-PtNi nanoparticles. In contrast, the ordered L10 phase exhibits remarkable resistance to such segregation on its {111} facets. This structural rigidity effectively suppresses coke formation and lowers the kinetic barrier for CH4 activation by 27 kJ/mol compared to the disordered phase. Complemented by in-situ spectroscopy and density functional theory (DFT) calculations, our findings demonstrate that the bulk crystal ordering acts as an anchor for surface structures, governing the catalytic behaviors. This study unveils a direct atomic-level link between crystal ordering, surface reconstruction, and catalytic performance, offering valuable design principles for robust intermetallic catalysts in CO2 utilization.