A facile solvothermal strategy is developed for the preparation of nanometer sized Pd-Cu alloy. We can control the morphology of these alloys with the use of ethylene glycol (EG) in the presence of KOH. Namely, by increasing the concentration of KOH/EG, the Pd-Cu alloys with different morphologies from near-spherical nanoparticles (NPs) to nanorods and nanowire networks have been prepared. Among all these alloys, near-spherical Pd-Cu NPs-modified electrodes exhibit the highest catalytic activity (11.7 mA/cm2) and stability toward the electrooxidation of ethanol in comparison with commercial Pd/C-modified ones (2.1 mA/cm2).
In recent years, fuel cells based on energy conversion have gathered increasing attraction due to their favorable efficiency, high specific energy density, and low environmental damage [
It has been reported that the shape, size and composition of NMs are the key factors to their catalytic activity [
In this study, we present a facile solvothermal strategy to synthesize shape-controlled bimetallic Pd-Cu alloys. Here, the EG is used as both solvent and reducing agent. To the best of our knowledge, there has been no prior work regarding the morphology-controlled synthesis of Pd-Cu alloys through tuning the concentration of KOH/EG. In order to find out the optimal alloy, the catalytic activity of Pd-Cu alloys was investigated for EOR, using commercial Pd/C catalyst as references.
To synthesize Pd-Cu alloys, 0.5 mL of 48 mM Na2PdCl4/EG and 0.1 mL of 240 mM Cu(CH3COO)2
A Hitachi H7650 transmission electron microscopy (TEM) was used to observe the nanoparticle shape and distribution. The nanoparticle structures and phase purity were conducted by powder X-ray diffraction (XRD) spectroscopy using a Japan Rigaku D/max-2500 diffractometer equipped with Cu K
The electrochemical experiments in this study were performed with a conventional three-electrode electrochemical cell on a CHI 660E electrochemical workstation (CH Instruments, Chenhua Company, Shanghai, China). A platinum foil, a saturated calomel electrode (SCE), and a glassy carbon electrode (GCE, 3 mm in diameter) were used as the counter electrode, the reference electrode, and the working electrode, respectively. Aliquots (14
Figure
(a) Schematic illustration of the synthetic pathways leading to the formation of Pd-Cu alloys with three different structures and (b) XRD patterns for the corresponding alloys.
The as-prepared electrocatalysts were characterized using TEM analysis. Figures
(a, b) Typical TEM images of Pd-Cu near-spherical NPs with different magnifications. (c) Particle size distribution analysis. (d) EDS spectrum of the corresponding NPs.
With an increase of the concentration of KOH/EG, we observed that the shape of as-prepared alloys changed from near-spherical to nanorods structures. Figures
(a, b) Typical TEM images of Pd-Cu nanorods with different magnifications. The inset in (a) is the corresponding EDS spectrum.
In order to explore the effect of KOH/EG on the morphology, we further increased the concentration of KOH/EG while keeping all other synthetic conditions unchanged. Figures
(a, b) Typical TEM images of Pd-Cu nanowire networks with different magnifications. (c) Particle size distribution analysis. (d) EDS spectrum of the corresponding alloys.
According to the above results, the morphology of the prepared Pd-Cu alloys can be remarkably changed by varying the concentration of KOH/EG [
Typical TEM images of Pd-Cu alloys with different magnifications collected under the same conditions, except the variation in the concentration of KOH/EG: (a, b) 0.1 mM and (c, d) 1 M.
Figure
CV curves of modified electrodes for commercial Pd/C, near-spherical Pd-Cu NPs, nanorods Pd-Cu alloys, and nanowire networks Pd-Cu alloys in 0.5 M KOH at a scan rate of 50 mV s−1.
(a) CV curves and (b) CA curves (at −0.25 V
To further evaluate the stability on ethanol electrooxidation of Pd-Cu alloy catalysts and commercial Pd/C catalyst, we recorded CA curves for 600 s at −0.25 V (
In this study, a simplified one-pot synthetic strategy has been developed to prepare Pd-Cu alloys with various morphologies from near-spherical to nanorods and nanowire networks structures. The use of KOH/EG with different concentration was demonstrated to play a critical role in the shape evolution of Pd-Cu alloys. Among these alloys, the near-spherical Pd-Cu catalyst shows the highest specific activity and stability toward the electrooxidation of ethanol in comparison with commercial Pd/C catalyst, mainly due to the advantages of more edge truncation, a greater number of active sites, and bimetallic synergistic effects. Having the excellent electrocatalytic activity, optimal stability, and cost effectiveness, the near-spherical Pd-Cu NPs exhibit great potential as an efficient anode catalyst for DEFCs.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by National Natural Science Foundation of China (Approval nos. 21103055 and 21473063).