3D honeycomb-like PdAg Nanoframework with optimized geometric and Interface electronic structure enable efficient ethanol oxidation via dual-pathway mechanism.

The development of highly efficient and durable electrocatalysts along with investigations into the mechanism understanding for ethanol oxidation reaction (EOR) are crucial for direct ethanol fuel cells (DEFCs). Herein, a series of three-dimensional honeycomb PdAg nanoframework (HLNF) catalysts supported on nickel foam (NF) are reported, which are fabricated via magnetron sputtering combined with a dealloying process. The design aims to optimize interface electronic structure and enhance EOR performance through bimetallic synergism. Comprehensive characterizations confirm the formation of a three-dimensional porous structure featuring uniform Pd/Ag distribution and strong electronic interactions between Pd and Ag. The optimized PdAg HLNF/NF catalyst exhibits exceptional EOR performance, achieving a mass activity of 3.86 A mg, which is 1.83 times higher than that of Pd HLNF/NF, along with remarkable stability during prolonged operation. In situ Fourier transform infrared spectroscopy (FTIR) results reveal dual reaction pathways, namely the C1 pathway (complete oxidation to CO) and the C2 pathway (partial oxidation to acetate ion). Compared to Pd HLNF/NF, PdAg HLNF/NF initiates ethanol oxidation at a more negative potential of 0.2 V, with the early appearance of CO and CO spectral bands indicating faster CO formation kinetics. Moreover, PdAg HLNF/NF demonstrates enhanced CC bond cleavage capability and strong adsorption of hydroxyl (OH) signals during CO oxidation. Density functional theory (DFT) calculations reveal that Ag doping significantly upshifts the d-band center of Pd and lowers energy barriers for the key steps in both C1 and C2 reaction pathways. Overall, this effort highlights the pivotal role of three-dimensional interfacial engineering and electronic modulation in PdAg catalysts, offering a highly promising strategy for developing high-performance electrocatalysts of DEFC.