image: Schematic illustration showing the construction of atomically rough surfaces (ARSs) by Au catalyzed reduction of metal ions
Credit: By YANG’s group
Researchers have developed a novel gold-catalyzed approach to engineer atomically rough surfaces (ARSs) on Au-based binary alloys, which significantly enhance the electrocatalytic performance for ethanol oxidation reaction (EOR), a crucial process in direct alcohol fuel cells. This breakthrough, published in Science Bulletin, could pave the way for more efficient and durable fuel cell technologies.
The EOR is a complex multistep reaction highly sensitive to the surface atomic structure of electrocatalysts. Platinum (Pt)/palladium (Pd)-based nanomaterials are currently the most efficient EOR electrocatalysts. However, reaction intermediates can strongly bind to their surfaces, blocking active sites and degrading performance. Strategies to address this include alloying, size/shape control, and surface engineering.
In this study, researchers from the Institute of Process Engineering (IPE), Chinese Academy of Sciences and Yanshan University hypothesized that combining ARSs with the ligand effect could improve EOR performance. They first synthesized Au-based bimetallic nanoalloys (AuM1, M1 = Pd or Ag) and then reduced another metal ion (M2 = Pd, Pt or Cu) on the Au sites of the alloy particle surfaces. This process creates ARSs and harnesses the ligand effect of adjacent Au atoms.
The researchers characterized the prepared nanoparticles using various techniques, such as transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray photoelectron spectroscopy (XPS). These analyses confirm the successful formation of uniform alloys and the deposition of additional metal atoms on the alloy surfaces, creating ARSs.
Electrochemical measurements show that the AuPd-Pt nanoparticles exhibit the highest electrocatalytic EOR performance. Their specific activity reaches 14.9 mA cm-2, and mass activity was 28.5 A mg-1, surpassing AuPd alloy counterparts, commercial Pd/C catalyst, and most recently reported Pd-based electrocatalysts. In situ Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) calculations reveal that the EOR process on Pd-Pt ARSs strongly prefers incomplete oxidation, producing acetate rather than carbon dioxide.
The enhanced performance of the AuPd-Pt nanoparticles can be attributed to several factors. The ARSs provide abundant low-coordinated atoms, which act as highly active sites with lower energy barriers for reactant activation. The ligand effect from adjacent Au atoms optimizes the electronic configuration of the active metals, weakening the adsorption of reaction intermediates and improving catalytic activity. Additionally, the incomplete oxidation pathway on Pd-Pt ARSs has faster reaction kinetics and is less affected by mass transport limitations and catalyst poisoning compared to the complete oxidation pathway.
“This research not only demonstrates a new method for constructing ARSs but also provides insights into the design of nanostructures for electrocatalysis,” said Jun YANG, an IPE professor. The findings could have far-reaching implications for the development of more efficient fuel cells and other electrochemical energy conversion devices.
However, the study has some limitations. The researchers mainly focused on demonstrating the construction of ARSs and their effect on the EOR reaction pathway, without conducting a detailed quantification of the EOR products. Future studies will incorporate advanced characterization techniques like ion chromatography (IC), high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography (GC) for a more comprehensive Faradaic efficiency analysis.
Overall, this gold-catalyzed strategy represents a significant step forward in the field of electrocatalysis, offering new possibilities for improving the performance of energy conversion technologies.