Nanoporous PdCu alloy for formic acid electro-oxidation

In this work, nanoporous PdCu alloys (np-PdCu) with predetermined bimetallic ratios are fabricated by selectively dealloying PdCuAl ternary alloys in 1.0 M NaOH solution. Electron microscope and X-ray diffraction characterizations show that the nanoporous metals have three-dimensional bicontinuous ligament-pore structure with uniform ligament size. Electrochemical measurements demonstrate that np-PdCu has greatly enhanced electrocatalytic activity and structure stability towards formic acid oxidation (FAO) compared with nanoporous Pd (np-Pd). The surface specific activities of the nanoporous metals follow the order that np-Pd50Cu50 > np-Pd75Cu25 > np-Pd30Cu70 > np-Pd. The peak current density on np-Pd50Cu50 shows the highest value, which is about six times of that on np-Pd. The alloy ratio also has a significant effect on the electrocatalytic behavior of the PdCu alloy towards FAO. When the Cu content is lower than 50 at.%, the FAO is mainly through the direct pathway; when the Cu content reaches 70 at.%, the FAO through the CO pathway increases. Moreover, electrochemical stripping experiment and continuous potential scan demonstrate that np-Pd50Cu50 has a better resistance to CO poisoning and enhanced structure stability compared with other alloy samples. These results indicate the potential application of the np-Pd50Cu50 in direct formic acid fuel cell.

► Nanoporous PdCu alloys with predetermined alloy ratios are successfully fabricated by a simple dealloying process.
► The alloy ratio has a significant effect on both catalytic activity and catalytic behavior of the alloy catalyst for formic acid electro-oxidation.
► Nanoporous PdCu alloy with appropriate alloy ratio has greatly enhanced electrocatalytic activity towards formic acid oxidation and resistance to CO poisoning.