Unveiling the formation mechanism of PbPd intermetallic phases in solvothermal synthesis using X-ray total scattering.

Pd possesses attractive catalytic properties and nano-structuring is an obvious way to enhance catalytic activity. Alloying Pd with Pb has been shown to enhance the catalytic effect of alcohol oxidation. Further optimization of the catalytic effect can be accomplished by controlling the particle size and key to this is understanding the formation mechanism. By monitoring solvothermal syntheses using X-ray total scattering, this study unveils the formation mechanism of PbPd intermetallic nanoparticles. The formation occurs through a multi-step mechanism. Initially, Pd nanoparticles are formed, followed by incorporation of Pb into the Pd-structure, thus forming PbPd intermetallic nanoparticles. By varying the reaction time and temperature, the incorporation of Pb can be controlled, thereby tailoring the phase outcome. Based on the solvothermal syntheses, autoclave syntheses were performed, resulting in the synthesis of PbPd and PbPd with a purity above 93%. The catalytic effect of these intermetallic phases towards the hydrogen evolution reaction (HER) is assessed. It is found that Pd, PbPd, and PbPd have comparable stabilities, however, the overpotential increases with increasing amounts of Pb.