Elsevier

Electrochemistry Communications

Volume 23, September 2012, Pages 33-36
Electrochemistry Communications

A cell for the controllable thermal treatment and electrochemical characterisation of single crystal alloy electrodes

https://doi.org/10.1016/j.elecom.2012.06.030Get rights and content

Abstract

A new electrochemical cell is described which provides the opportunity to perform electrochemical experiments and apply a controllable thermal treatment without exposing the sample to the laboratory atmosphere. We report typical model experiments with Pt(111) single crystal electrodes which can be performed in this cell. These include preparation and basic voltammetric characterisation of Cu/Pt(111) near-surface and surface alloys where monolayer amounts of Cu are located in the 1st and 2nd layers, respectively. The cell can also be useful for “electrochemical atomic layer epitaxy” to assemble multilayers using repetitive underpotential deposition.

Graphical abstract

Highlights

► A cell for controllable thermal treatment and electrochemical characterization. ► Annealing and characterisation without exposing samples into the laboratory atmosphere. ► Typical model experiments with Pt(111) single crystal electrodes and sub-surface alloys.

Introduction

The well-established experimental protocol for pretreating metal single crystals involves annealing the crystals before electrochemical characterisation [1], [2]. A heat treatment is necessary to prepare reproducibly well-ordered and clean surfaces [3]. Flame annealing and resistive or inductive heating followed by cooling in a reducing atmosphere are the most common techniques to prepare the single crystal surfaces of Pt, Au, Pd and other noble metals for electrochemical applications [4], [5].

Although the above-mentioned protocol has been used successfully for decades in single crystal electrochemistry, the preparation and characterisation of single crystalline surfaces could be improved even further. The majority of procedures reported in literature assume that single crystals should be transferred into the measurement electrochemical cell through the laboratory atmosphere [1], [2], [3], [4], [5], [6]. Normally, it is done under the protection of the surface by droplets of ultra clean water. However, it would be preferable to avoid this step, and anneal and perform electrochemical measurements in the same cell. This would improve reproducibility and minimise adventitious contamination from the laboratory atmosphere.

Vacuum-based surface science studies have demonstrated that by depositing different metals atop the single crystals and annealing them in the presence of reactive gases, the crystal surfaces can be efficiently tailored. Such thermal treatments are common, for example, to prepare surface alloys (SA) and near-surface alloys (NSA) [7], [8], [9]. However, using the flame annealing technique it is not possible to accurately control temperature over a wide range. This problem can be solved by using the inductive heating (IH) [10] or resistive heating [11] in the same cell. However, to the best of our knowledge, there are no reports describing the IH-temperature control and corresponding cell designs for combined high-temperature preparation, modification and electrochemical characterisation of single crystal surfaces.

In this communication, we describe a new cell, which provides an opportunity to combine electrochemical surface modification, characterisation and controllable thermal treatment. All operations can be performed without exposing the sample into the laboratory atmosphere. We report typical model experiments with Pt(111) single crystal electrodes, including the preparation and basic voltammetric characterisation of Cu/Pt(111) SA and NSA.

Section snippets

Cell design

A schematic drawing of the cell is shown in Fig. 1. It consists of compartments made of either Pyrex™ or quartz glass, an IH, a reference electrode (RE), a counter electrode (CE) and a single crystal working electrode (WE) in a standard hanging meniscus configuration.

The position of the single crystal can be adjusted vertically using a movable shaft; so the crystal can be lifted up and annealed by the inductive heater and always kept in a controllable atmosphere. The shaft provides electrical

Experimental

Before each experiment, the glassware was cleaned in a “piranha” solution consisting of a mixture of 96% H2SO4 and 30% H2O2 (3:1) for 24 h, followed by multiple heating/rinsing with Millipore© water to remove sulphates.

All model experiments described in this manuscript were performed using several Pt(111) single crystals: (a) a small bead-type Pt(111) crystal (oriented to < 0.05°) obtained from Prof. Juan Feliu (University of Alicante, Spain) prepared according to [2], and (b) with diameters of 5 

Results and discussion

In the following, we present examples of typical experiments which can be performed using the proposed cell. Fig. 3 compares typical Pt(111)-voltammograms for the crystals annealed using conventional flame annealing of bead-type single crystal (Fig. 3A) and the 5 mm crystal annealed using the method developed in this work (Fig. 3B). Three different regions are distinguishable in the voltammograms shown in Fig. 3. These are associated with hydrogen UPD (between 0.07 V and 0.4 V), the adsorption of

Acknowledgements

We thank Professor J. Feliu from the University of Alicante (Spain) for providing high-quality Pt(111) single crystal. The Center for Individual Nanoparticle Functionality is supported by the Danish National Research Foundation. A.S.B. acknowledges financial support from the European Union and the MWIFT-NRW (Hightech.NRW competition). I.E.L.S. is funded by the Energinet.dk, for the CATBOOSTER project, through the ForskEL R&D programme.

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