Single-Atom Bi Embedded in the Surface Lattice of Pd Nanoparticles: Enhancing Catalytic Activity and Stability for Formic Acid Dehydrogenation

Abstract

In recent years, palladium-based catalysts have attracted considerable attention due to their superior catalytic performance in formic acid dehydrogenation (FAD), and enhancing catalytic activity via elemental doping has emerged as a prominent research focus. However, their activity and stability remain major obstacles for practical applications. In this work, we successfully incorporated Bi into the surface lattice of Pd nanoparticles in the form of single atoms via low-temperature reduction and an optimized Bi-doping procedure. The as-formed Bi1@Pd single-atom nanoparticles were loaded on ordered mesoporous carbon CMK-3, achieving a remarkable enhancement in both catalytic activity and stability. The Bi1@Pd/CMK-3 with the optimal atomic ratio doubled the Pd mass activity of Pd/CMK-3 in terms of hydrogen production rate, and its global turnover frequency reached 19762 h−1 at 323 K in a mixed solution of formic acid and sodium formate, which is among the best-performing Pd/C catalysts with high Pd loadings reported. Spectroscopic investigations and density functional theory calculations reveal that electron transfer occurs between single-atom Bi and neighboring Pd atoms. Such electronic modulation systematically lowers the energy barrier of the HCOOH decomposition reaction. Temperature-programmed desorption/oxidation techniques of NH3 and H2 indicated that Bi doping appropriately increased the Lewis acid sites of the catalyst and the high-temperature stability of Pd nanoparticles. During a continuous FAD reaction at 353 K, the activity of Bi1@Pd/CMK-3 only decreased by 3% over 300 h, and its stability was significantly improved compared with the Bi-free catalyst, creating possibilities for its commercial application.