2, Benet Laboratories, Armament Research, Development and Engineering Center, U.S. Army RDECOM-ARDEC, Watervliet, New York, United States
Hierarchically structured platinum-palladium alloy macrotubes with square cross-section and porous sidewalls composed of fibril textured nanoparticles were synthesized from high aspect ratio insoluble Mangus’ salt needles in a single reduction step. Salt needle templates formed from the precipitation of oppositely charged square planar ion complexes were reduced in solution and resulted in macrotubes ranging from 10’s to 100’s µm long and 100 to 200 nm wide conforming to template dimensions. Porous sidewall structures varied from spheres to fibrils with the ratio of platinum to palladium in the salt template. X-ray diffractometry indicated alloy metal content with no oxide peaks. Specific capacitance and solvent accessible surface area of macrotubes pressed into free-standing films was determined from electrochemical impedance spectroscopy. Potential for catalysis was assessed from hydrogen adsorption and desorption in 0.5 M H2SO4 using cyclic voltammetry. Salt templates offer a synthesis route to achieve a range of porous metal and metal alloy structures for catalytic, sensing, and energy applications.