Electrodeposition of dendritic Pd nanoarchitectures on n-GaN(0001): nucleation and electrocatalysis for direct formic acid fuel cells

Dendritic Pd nanoarchitectures were electrochemically deposited on single-crystal n-GaN(0001) by cyclic voltammetry and employed as anode electrocatalyst for direct formic acid fuel cells. The Pd deposition on n-GaN(0001) was found to commence at 0.2 V vs. Ag/AgCl without underpotential deposition process and follow the typical instantaneous nucleation in large overpotential region. High-resolution transmission electron microscope images revealed that numerous small branches were formed around the trunk of dendritic structures and grew along the <111> directions. The as-obtained dendritic Pd nanoarchitectures showed good catalytic performance for formic acid and the oxidation peak potential appeared at 0.45 V vs. Ag/AgCl. The maximum current density and mass activity were 19.7 mA cm−1 and 904 mA mg−1, respectively, for the dendritic Pd nanocrystals obtained by cycling the potentials from -0.25 to 1.0 V for 5 times.