Spectroelectrochemical Probing of the Strong Interaction between Platinum Nanoparticles and Graphitic Domains of Carbon

Abstract

This study focuses on clarifying the strong interaction existing between extended graphitic domains of ordered carbonaceous materials such as multiwalled carbon nanotubes and platinum nanoparticles. This interaction results from the heterogeneous nucleation of platinum nanoparticles onto the carbon support. The metal clusters are chemically synthesized by using the carbonyl route. Two different carbon supports are used namely, homemade multiwalled carbon nanotubes, MWCNT-m, and classical Vulcan XC-72. Physicochemical properties of these materials are described by Raman spectroscopy, Xray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The effect of the strong interaction on the electronic properties of platinum nanoparticles is electrochemically probed by means of CO stripping experiments coupled with in situ Fourier transform infrared spectroscopy (FTIR). Density functional theory (DFT) is used to evaluate changes to the electronic structure of a platinum cluster interacting with a graphite substrate and their effects on CO adsorption on the cluster. Results are correlated with structural and electronic properties of platinum nanoparticles. The stability of Pt/carbon catalysts under electrochemical potential cycling is correlated with the properties of carbon substrates.

What Can We Learn in Electrocatalysis, from Nanoparticulated Precious and/or Non-Precious Catalytic Centers Interacting with Their Support?

“…However, the surface chemistry is totally different as depicted in Figure 28c. There is a sole CO-oxidation peak on the Pt/Vulcan sample, whereas there are two peaks on the Pt/MWCNT-m sample [201]. Based on Raman, XPS and DFT calculation results one can conclude that the peak I should be related to monoxide carbon oxidation on the platinum surface interacted with the sp 2 domain of the support, and peak II attributed to oxidation on Pt site interacted with the sp 3 domain [201].…”

“…There is a sole CO-oxidation peak on the Pt/Vulcan sample, whereas there are two peaks on the Pt/MWCNT-m sample [201]. Based on Raman, XPS and DFT calculation results one can conclude that the peak I should be related to monoxide carbon oxidation on the platinum surface interacted with the sp 2 domain of the support, and peak II attributed to oxidation on Pt site interacted with the sp 3 domain [201]. The ORR stability, Figure 28d,e, in acid medium was improved on CNTs support with respect to carbon, and attributed to the interaction between Pt NPs and sp 2 domains of CNT.…”

“…The supports of this kind of composite materials are widely used for Pt or other catalytic centers [194][195][196][197][198]. The utilization of supporting materials can affect the nanoparticle (NPs) morphology, dispersion, and create a support-metal interaction (SMSI) [199][200][201][202]. These facts can favor the catalytic process, and hence, the support has a great impact on the design of composites based catalysts, aiming at improving the kinetics and stability for the electrocatalytic processes in low temperature fuel cells.…”

“…In addition to oxides, noble metals supported onto carbon-based materials showed also SMSI, as revealed by the electron transfer at Pt-C interface [201]. For non-precious metals, it is well known that Co-N chemical bonds form from cobalt-oxides supported N-doped carbon materials [205][206][207].…”

“…Taking CNT as an example, the Raman spectra show that the oxidized multi-walled CNT (ox.MWCNT) has dominant graphitic sp 2 domains, as compared to carbon (Vulcan XC-72) which shows highly disordered sp 3 domains, Figure 27b When a catalytic center, e.g., Pt, is chemically deposited onto highly graphitic carbon the interaction takes place with both sp 3 and sp 2 domains, Figure 28a,b, shows the close Pt particle size and morphology [201]. However, the surface chemistry is totally different as depicted in Figure 28c.…”