Structural transformations and adsorption properties of PtNi nanoalloy thin film electrocatalysts prepared by magnetron co-sputtering

Dissolution of Platinum Single Crystals in Acidic Medium

Platinum single crystal basal planes consisting of Pt(111), Pt(100), Pt(110) and reference polycrystalline platinum Pt(poly) were subjected to various potentiodynamic and potentiostatic electrochemical treatments in 0.1 M HClO4 . Using the scanning flow cell coupled to an inductively coupled plasma mass spectrometer (SFC-ICP-MS) the transient dissolution was detected on-line. Clear trends in dissolution onset potentials and quantities emerged which can be related to the differences in the crystal plane surface structure energies and coordination. Pt(111) is observed to have a higher dissolution onset potential while the generalized trend in dissolution rates and quantities was found to be Pt(110)>P(100)≈Pt(poly)>Pt(111).

Preparation of complex model electrocatalysts in ultra-high vacuum and transfer into the electrolyte for electrochemical IR spectroscopy and other techniques

Model studies at complex, yet well-defined electrodes can provide a better understanding of electrocatalytic reactions. New experimental devices are required to prepare such model electrocatalysts with atomic-level control. In this work, we discuss the design of a new setup, which enables the preparation of well-defined electrocatalysts in ultra-high vacuum (UHV) using the full portfolio of surface science techniques. The setup allows for direct transfer of samples from UHV and the immersion into the electrolyte without contact to air. As a special feature, the single crystal sample is transferred without any sample holder, which makes the system easily compatible with most electrochemical in situ methods, specifically with electrochemical infrared reflection absorption spectroscopy, but also with other characterization methods such as single-crystal cyclic voltammetry, differential electrochemical mass spectrometry, or electrochemical scanning tunneling microscopy. We demonstrate the preparation in UHV, the transfer in inert atmosphere, and the immersion into the electrolyte for a complex model catalyst that requires surface science methods for preparation. Specifically, we study Pt nanoparticles supported on well-ordered Co₃O₄(111) films which are grown on an Ir(100) single crystal. In comparison with reference experiments on Pt(111), the model catalyst shows a remarkably different adsorption and reaction behavior during CO electrooxidation in alkaline environments.

Electrifying model catalysts for understanding electrocatalytic reactions in liquid electrolytes

Electrocatalysis is at the heart of our future transition to a renewable energy system. Most energy storage and conversion technologies for renewables rely on electrocatalytic processes and, with increasing availability of cheap electrical energy from renewables, chemical production will witness electrification in the near future^1-3. However, our fundamental understanding of electrocatalysis lags behind the field of classical heterogeneous catalysis that has been the dominating chemical technology for a long time. Here, we describe a new strategy to advance fundamental studies on electrocatalytic materials. We propose to 'electrify' complex oxide-based model catalysts made by surface science methods to explore electrocatalytic reactions in liquid electrolytes. We demonstrate the feasibility of this concept by transferring an atomically defined platinum/cobalt oxide model catalyst into the electrochemical environment while preserving its atomic surface structure. Using this approach, we explore particle size effects and identify hitherto unknown metal-support interactions that stabilize oxidized platinum at the nanoparticle interface. The metal-support interactions open a new synergistic reaction pathway that involves both metallic and oxidized platinum. Our results illustrate the potential of the concept, which makes available a systematic approach to build atomically defined model electrodes for fundamental electrocatalytic studies.

Atomically-defined model catalysts in ultrahigh vacuum and in liquid electrolytes: particle size-dependent CO adsorption on Pt nanoparticles on ordered Co3O4(111) films

We have studied particle size effects on atomically-defined model catalysts both in ultrahigh vacuum (UHV) and under electrochemical (EC) conditions in liquid electrolytes.