Effect of structure of Pd@Fe core–shell cubes on the enhancement of H₂ conversion in direct reaction of H₂ and O₂

Structure engineering is an integrated strategy to regulate the performance of nanoparticles for various catalytic reactions, since the nanoparticle composition, shape, and interface affect the reaction activity and selectivity. Herein, we report a simple synthesis of clear core–shell structured Pd@Fe nanocubes with different shell thicknesses, which exhibit higher H₂ conversion efficiency in direct hydrogen peroxide generation compared with ordinary Pd cubes. This result can be attributed to two main reasons: (i) the conformal growth of the Fe oxide shell consisting of loose structured Fe₃O₄ favors H₂ penetration, and (ii) the capping agent (Br⁻) on the Pd–Fe₃O₄ interface that blocks the Pd active sites is removed during the shell formation. Therefore, the Fe oxide shell of the Pd@Fe nanoparticles not only helps maintaining the morphology of the nanoparticles but also increases the number of active sites on the inner core surface, confirming the advantage of the core–shell structure.