Micromorphology and phase composition manipulation of nanoporous gold with high methanol electro-oxidation catalytic activity through adding a magnetic field in the dealloying process
American Chemical Society
School of Engineering
By dealloying a rapidly solidified (RS) Al2Au alloy, nanoporous gold (np-Au) samples with a three-dimensional (3D) interpenetrating ligament-channel structure are fabricated in 0, 0.02, and 0.2 T magnetic fields. Adding magnetic field leads to intermediate AlAu phase formation, decreases the dealloying rate, and triggers the formation of fine nanocrystals and amorphous phase in the np-Au ligaments. The np-Au samples dealloyed in 0, 0.02, and 0.2 T for 24 h (DA0, DA1, and DA2) appear in maze-like, honeycomb-like, and soda cracker-like micromorphologies, respectively. The DA1 sample possesses the smallest lattice constant a0 and highest preferred orientation factor F(111) of the (111) face. The parameters like surface coverage of the redox species Γ*, charge-transfer rate constant ks, exchange current density j0, corrosion potential Ecorr, and charge transfer resistance Rct indicate that the methanol electro-oxidation activity of the three samples is in this order: DA1 > DA2 > DA0, which can be ascribed to crystallographic, thermodynamic, and defective reasons. This work supplies a new method to enhance the methanol catalytic activity of np-Au.