Spray pyrolysis synthesis and evaluation of fine bimetallic Au-Pd particles

Abstract

Spherical Au-Pd particles in the submicron range were prepared using an ultrasonic spray-pyrolysis method. HAuCl4/H2PdCl 6 in hydrochloric acid and Au (OH) 3/Pd (NO3) 2 in nitric acid were used as starting solutions. At high Au/Pd ratios, particles derived from the HAuCl4/H2PdCl 6 solution had a spherical morphology. At low Au/Pd ratios, the particle morphology gradually deformed due to the influence of the thermal decomposition of H2PdCI6. The Au(OH)3/ Pd(NO3)2 solution could not be atomized continuously because of its instability. To overcome this problem, the Pd(NO 3)2 solution was preoxidized with H2O 2 before mixing with the Au(OH)3 solution. As a result, the Au/Pd mix solution was stabilized and spherical particles were obtained at various Au/ Pd ratios. Particles produced from the Au(OH)3/Pd(NO 3)2 solution were more uniformly alloyed than those from the HAuCl4/H2PdCl6 solution. This is also indicated in the thermo-gravimeter (TG) analysis, which shows Pd oxidation inside the particles, which inhibits the overall increase in mass.