Spray Pyrolysis Synthesis and Evaluation of Fine Bimetallic Au-Pd Particles

摘要

Spherical Au-Pd particles in the submicron range were prepared using an ultrasonic spray-pyrolysis method. HAuCl_4/H_2PdCl_6 in hydrochloric acid and Au(OH)_3/Pd(NO_3)_2 in nitric acid were used as starting solutions. At high Au/Pd ratios, particles derived from the HAuCl_4/H_2PdCl_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 H_2PdCl_6. The Au(OH)_3/Pd(NO_3)_2 solution could not be atomized continuously because of its instability. To overcome this problem, the Pd(NO_3)_2 solution was preoxidized with H_2O_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 An/ Pd ratios. Particles produced from the Au(OH)_3/Pd(NO_3)_2 solution were more uniformly alloyed than those from the HAuCl_4/H_2PdCl_6 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.