Novel solid-state synthesis of surfactant- and solvent-free Pd tetrahedron nanocatalysts

Shape-controlled palladium nanocatalysts with high activity in various catalytic reactions have attracted much attention. However, the reliable synthesis of shape-controlled Pd nanocatalysts in the absence of polymeric surfactants and harmful organic solvents remains a challenging issue. This study is the first to report an automated, reproducible, and reliable solid-state synthesis of surfactant-free tetrahedral-shaped Pd nanocatalysts with high particle dispersion. By using carbon monoxide gas as a capping material for the Pd precursor during synthesis, the morphology of the Pd nanoparticles could be controlled, as revealed by computer simulations. The tetrahedral Pd nanoparticles synthesized on graphene supports exhibited higher catalytic performance for the reduction of 4-nitrophenol than those of spherical Pd nanoparticles on graphene, commercial Pd/C, and PVP stabilized Pd nanocubes on graphene due to their active edge and kink sites with high dispersion and the clean active site surface. In addition, the additional incorporation of magnetic Fe3O4 nanoparticles into the tetrahedral Pd nanoparticle-supported nanocatalysts facilitated the separation of the catalysts by magnetism, making reuse convenient. Tetrahedral Pd nanocatalysts prepared by automated, reproducible, and reliable solid-state synthesis exhibit excellent catalytic performance for 4-nitrophenol reduction.