A comprehensive investigation into the relationships between the electronic structure of a surface and its catalytic properties is crucial for advancing our understanding of the fundamental mechanisms driving catalytic activity. Platinum and Pt-based systems are widely recognized for their exceptional catalytic performance numerous applications. To elucidate the correlations between electronic configuration and catalytic behavior, we performed a systematic study by depositing gold onto platinum surfaces. The model reaction selected for this investigation was the electrooxidation of formic acid, a reaction of particular relevance due to its role in low-temperature direct formic acid fuel cells (DFAFCs).The modification of Pt surfaces with Au has been reported extensively in the literature, with numerous studies demonstrating advantageous changes in catalytic properties upon the interaction of these two metals. However, despite the considerable attention this system has garnered, the precise mechanisms underlying these enhancements remain incompletely understood. Two predominant hypotheses have been proposed to explain these phenomena: (1) the geometric effect, whereby changes in surface morphology influence catalytic behavior, and (2) the electronic effect, which posits that alterations in electronic structure, particularly at the metal-metal interface, play a main role.In our work, we sought to distinguish between these two effects by preparing samples using two distinct methodologies: electrodeposition and sputtering. The electrodeposition technique, by its nature, tends to produce layers that are more likely to exhibit pseudomorphic growth, potentially leading to stronger electronic interactions between the deposited and substrate layers. In contrast, the sputtering method is expected to result in less coherent growth, with potentially weaker interactions. By comparing the catalytic activities of these differently prepared samples, we aimed to discern which effect – geometric or electronic – predominates in the enhancement of catalytic performance.Comprehensive characterization of the electronic properties of the samples was performed using X-ray Photoelectron Spectroscopy (XPS). Specifically, we focused on analyzing the binding energies of core levels, alongside a detailed investigation of the valence band spectra, paying particular attention to the density of states near the Fermi level and the shifts in the d-band center. These parameters are critical for understanding the electronic interactions at the Au-Pt interface. Additionally, the catalytic activity was studied through cyclic voltammetry (CV), where we observed synergistic effects in the oxidation of formic acid on both types of samples.Our findings contribute to the growing body of knowledge on the interplay between electronic and geometric factors.
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Feb 1, 2025
Sepideh Bakhtshokouhi + 1
Just Published
Open Access