Thermal treatment is a general and efficient way to synthesize intermetallic catalysts and may involve complicated physical processes. So far, the mechanisms leading to the size and composition heterogeneity, as well as the phase segregation behavior in Pt-Co nanoparticles (NPs) are still not well understood. Via in-situ environmental transmission electron microscopy, the formation dynamics and segregation behaviors of Pt-Co alloyed NPs during the thermal treatment were investigated. It is found that Pt-Co NPs on zeolitic imidazolate frameworks-67-derived nanocarbon (NC) are formed consecutively through both particle migration coalescence and the Ostwald ripening process. The existence of Pt NPs is found to affect the movement of Co NPs during their migration. With the help of theoretical calculations, the correlations between the composition and migration of the Pt and Co during the ripening process were uncovered. These complex alloying processes are revealed as key factors leading to the heterogeneity of the synthesized Pt-Co alloyed NPs. Under oxidation environment, the Pt-Co NPs become surface faceted gradually, which can be attributed to the oxygen facilitated relatively higher segregation rate of Co from the (111) surface. This work advances the fundamental understanding of design, synthesis, and durability of the Pt-based nanocatalysts.

Highly efficient and stable oxygen reduction reaction (ORR) electrocatalysts are remarkably important but challenging for advancing the large-scale commercialization of practical proton exchange membrane fuel cells (PEMFCs). In this work, we report that the introduction of interstitial hydrogen atoms into PtPd nanotubes can significantly promote ORR performance without scarifying the durability. The enhanced mass activity was 8.8 times higher than that of commercial Pt/C. The accelerated durability test showed negligible activity attenuation after 30,000 cycles. Additionally, H₂/O₂ fuel cell tests further verified the excellent activity of PtPd-H nanotubes with a maximum power density of 1.32 W·cm⁻², superior to that of commercial Pt/C (1.16 W·cm⁻²). Density functional theory calculations demonstrated the incorporation of hydrogen atoms gives rise to the broadening of Pt d-band and the downshift of d-band center, which consequently leads to the weaker intermediates binding and enhanced ORR activity.

Here, we report a Pd/PdO_x sensing material that achieves 1-s detection of 4% H₂ gas (i.e., the lower explosive limit concentration for H₂) at room temperature in air. The Pd/PdO_x material is a network of interconnected nanoscopic domains of Pd, PdO, and PdO₂. Upon exposure to 4% H₂, PdO and PdO₂ in the Pd/PdO_x are immediately reduced to metallic Pd, generating over a > 90% drop in electrical resistance. The mechanistic study reveals that the Pd/PdO₂ interface in Pd/PdO_x is responsible for the ultrafast PdO_x reduction. Metallic Pd at the Pd/PdO₂ interface enables fast H₂ dissociation to adsorbed H atoms, significantly lowering the PdO₂ reduction barrier. In addition, control experiments suggest that the interconnectivity of Pd, PdO, and PdO₂ in our Pd/PdO_x sensing material further facilitates the reduction of PdO, which would otherwise not occur. The 1-s response time of Pd/PdO_x under ambient conditions makes it an excellent alarm for the timely detection of hydrogen gas leaks.