The catalyst layers for polymer-electrolyte-membrane (PEM) fuel cells were fabricated by deposition of platinum directly onto the gas diffusion layer using pulsed laser deposition (PLD). This technique reduced the number of steps required to synthesize the catalyst layers and the amount of Pt loading required. PEM fuel cells with various Pt loadings for the cathode were investigated. With a cathode Pt loading of 100 $\mathsf{\mu }$ g·cm ${}^{-2}$ , the current density of a single cell reached 1205 mA·cm ${}^{-2}$ at 0.6 V, which was close to that of a single cell using an E-TEK (trademark) Pt/C electrode with a cathode Pt loading of 400 $\mathsf{\mu }$ g·cm ${}^{-2}$ . Furthermore, for a PEM fuel cell with both electrodes prepared by PLD and a total anode and cathode Pt loading of 117 $\mathsf{\mu }$ g·cm ${}^{-2}$ , the overall Pt mass-specific power density at 0.6 V reached 7.43 kW·g ${}^{-1}$ , which was five times that of a fuel cell with E-TEK Pt/C electrodes. The high mass-specific power density was due to that a very thin nanoporous Pt layer was deposited directly onto the gas diffusion layer, which made good contact with the Nafion membrane and thus resulted in a low-resistance membrane electrode assembly.

In this study, a simple two step method is employed to sequentially synthesize bimetallic core/shell nanoparticles (NPs). In the first step, pure mono Au and Ag NPs are prepared via 1064 nm pulsed laser ablations in liquid. In the second step, the Au/Ag substrate immersed in the Au/Ag colloidal solution is exposed to the nanosecond laser at 1064 nm wavelength using various laser energies and ablation periods. The crystalline phase and morphology of the bimetallic core/shell NPs (Au/Ag, Ag/Au) are examined by x-ray diffraction and scanning electron microscopy, respectively. The results showed that highly crystalline, well-dispersed spherical monometallic and bimetallic core/shell NPs can be synthesized via pulse laser ablation in liquid. The average diameter of Au, Ag, Au/Ag, and Ag/Au NPs is 34, 40, 58, and 43 nm, respectively. With increasing laser energy, the plasmonic absorption peak of Au NPs redshifts and that of Ag NPs blueshifts. For core/shell, two plasmonic peaks were observed, each of which shifted with increasing ablation time for shell material. Organic dyes with concentrations of 10−5M of methylene-blue with NaBH4 of 0.05M and methylene-orange with NaBH4 of 0.1M are used to examine the catalytic performance of the NPs. The core/shell NPs performed better than monometallic NPs. In particular, the catalytic degradation efficiency of Au/Ag and Ag/Au NPs is approximately 90% in significantly less time than monometallic Au and Ag NPs.