Cu(111) single crystal electrodes: Modifying interfacial properties to tailor electrocatalysis

Andrea Auer,Francisco J Sarabia,Christoph Griesser,Víctor Climent,Juan M Feliu,Julia Kunze-Liebhäuser

doi:10.1016/j.electacta.2021.139222

Andrea Auer, Francisco J Sarabia + Show 4 more

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https://doi.org/10.1016/j.electacta.2021.139222

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Abstract

Tailoring electrocatalyst materials to the specific requirements of a certain reaction and to optimize activity or enhance selectivity is a key tactic for the development of low-temperature fuel and electrolyzer cells for clean energy production. Here, we demonstrate the modification of Cu(111) electrodes with different sub-monolayer coverages of foreign metals (Cd) and metal hydroxides (Co(OH)2 and Ni(OH)2) for application in the hydrogen evolution reaction (HER) in alkaline media. In situ electrochemical scanning tunneling microscopy (EC-STM) reveals that these modifications have a significant influence on the morphology and structure of the Cu(111) surface with its characteristics depending on both the nature and the amount of the adsorbed metal(hydroxide). Ni(OH)2 and Co(OH)2 on Cu(111) lead to a significant enhancement of the electrocatalytic activity towards the HER in alkaline electrolyte, whereas a decrease in activity is found for Cd modified Cu(111). These trends can be rationalized by considering the strength of the interfacial electric field and its influence on the specific interactions of the electrode with the water ad-layer close to the surface, as determined by laser-induced temperature jump measurements. This comparative study therefore provides valuable information on the structure-activity relation as well as insights on the interfacial characteristics of different bimetallic Cu electrocatalysts.

Highlights

The rational design of active and selective electrocatalysts has been a central theme study in electrochemistry in the past decades
The morphological/structural effects of the modification have to be thoroughly examined in the case of Cu(111) electrodes, before an understanding of the observed activity trends is possible
We find that the structural and the related chemical changes of the electrode surfaces are intimately related to the electric field at the solid/liquid interface and to the activity towards the hydrogen evolution reaction (HER)

Summary

Introduction

The rational design of active and selective electrocatalysts has been a central theme study in electrochemistry in the past decades. Irreversible adsorption, on the other hand, occurs when, by putting a solution of a certain metallic salt in contact with an electrode at open circuit potentials, a stable adatom layer forms and remains adsorbed on the substrate in a wide potential range after transfer to a solution without the corresponding ion [4,5] In this case, the adatom coverage can be varied depending on the solution concentration or the immersion time, independently of the applied potential. HER in alkaline media, was demonstrated for Pt(111) with different amounts of Ni(OH)2 [12,13] For this system, the so-called laserinduced temperature jump method revealed a significant decrease in the electric field strength and a lowering of the energy barrier associated with the reorganization of the interfacial water network with increasing amounts of Ni(OH) on the surface [12,13]. Our study sheds light on the interfacial properties of bimetallic Cu electrocatalysts and provides evidence, that the rate of the alkaline HER is strongly affected by the facilitation of the interfacial water reorganization during charge transfer

Experimental

Results and Discussion

Conclusion