A combined UHV-STM-flow cell set-up for electrochemical/electrocatalytic studies of structurally well-defined UHV prepared model electrodes

Abstract

We describe the construction and discuss the performance of a novel combined ultrahigh vacuum (UHV)-electrochemistry set-up, allowing the controlled preparation and structural characterization of complex nanostructured electrode surfaces by high resolution scanning tunnelling microscopy (STM) under UHV conditions on the one hand and, after electrode transfer under clean conditions, electrochemical measurements under continuous, controlled electrolyte mass transport conditions on the other. Electrochemical measurements can be coupled with online product detection, either using an additional collector electrode or by differential electrochemical mass spectrometry (DEMS). The potential of the set-up will be illustrated in two electrocatalytic reactions on complex, but structurally well-defined bimetallic electrode surfaces, O reduction on PtAg/Pt(111) monolayer surface alloys and bulk CO oxidation on Pt monolayer island modified Ru(0001) electrodes. We will particularly demonstrate the importance of structural characterization after the electrochemical measurements for identifying structural modifications induced by the electrochemical environment and thus avoiding misleading conclusions about the structure-activity relationships.

Polycrystalline and Single‐Crystal Cu Electrodes: Influence of Experimental Conditions on the Electrochemical Properties in Alkaline Media

“…Upon continuous potential cycling (increasing time) the sizes of the peaks decrease further, indicated by the CVs of the first potential cycle compared to the CVs obtained after 10 and 50 potential cycles, respectively. The first assumption is that the surface is poisoned by impurities from the flowing electrolyte . This causes a decrease of the current density in the voltammetric features, due to irreversible blocking of impurities on certain sites.…”

“…In the section on experimental condition influence, we show that with electrolyte flow, a reduction current is measured at potentials <0.3 V, which we attribute to the presence of residual O 2 in the electrolyte. The O 2 likely originates from diffusion through the connectors at the inlets of the flow cell, located between the electrolyte supply bottle and the actual cell . In principle, complete removal of the oxygen can be achieved by flushing the connectors with inert gases such as Ar or N 2 , as shown elsewhere .…”

“…Upon continuous potentialc ycling (increasing time) the sizes of the peaks decreasef urther,i ndicated by the CVs of the first potential cycle compared to the CVs obtained after 10 and 50 potential cycles, respectively.T he first assumption is that the surface is poisoned by impurities from the flowing electrolyte. [36] This causesad ecrease of the current density in the voltammetric features,due to irreversible blockingofimpurities on certain sites. This effect should in principle be more pronounced during electrolyte flow,w here ac ontinuous supply of impurities is supplied by the electrolyte from the supply bottle, for example, dissolved Si from KOH etching of the glass ware [26b, 37] and other carbonaceouss pecieso riginating from the PFAt ubing connecting the supply bottle and the flow cell.…”

“…The flow cell set-up closely resembles the design reported in an earlier study;h owever,i th as been slightly modified to hold ad if-ferent type of UHV sample holder. [36] The potential was controlled with aB ioLogic SP-300 potentiostat. The flow cell can be operated either with electrolyte flow or with stagnant electrolyte.…”

“…The O 2 likely originates from diffusion through the connectors at the inlets of the flow cell, located between the electrolyte supply bottle and the actual cell. [36] In principle, complete removal of the oxygen can be achieved by flushing the connectors with inert gases such as Ar or N 2 ,a ss hown elsewhere. [36] In the current configuration this was, however,t echnically not possible.…”