Geometrically Controlled Nanoporous PdAu Bimetallic Catalysts with Tunable Pd/Au Ratio for Direct Ethanol Fuel Cells

We report nanoporous Pd 100– x Au x ( x = 0, 25, 50, 75, 100; np-PdAu) bimetallic catalysts fabricated by electrochemically dealloying isomorphous Pd 20– y Au y Ni 80 ( y = 0, 5, 15, 20) precursors. The chemical composition of the nanoporous bimetallic catalysts can be precisely controlled by predesigning Pd/Au ratios in the ternary alloys. Dealloying at an appropriate potential for each alloy can selectively leach Ni away while the Pd and Au remain intact to form a geometrically controllable nanoporous structure. The electrocatalysis of the np-PdAu shows evident dependence on the Au/Pd atomic ratio, and the np-Pd 75 Au 25 bimetallic catalyst shows superior electrocatalytic performance toward ethanol electrooxidation in comparison with commercial Pt/C, np-Pd, and other np-PdAu alloys. Since there are no obvious geometric shape and pore size disparities among the np-PdAu samples, the dealloyed catalysts also provide an ideal system to explore the chemical origins of the excellent catalytic properties of bimetallic catalysts.