Copper (Cu) represents a highly interesting material for both electrolyzer and fuel cell applications, due to its ability to efficiently reduce CO₂ to hydrocarbons and H₂O to H₂, as well as to oxidize CO to CO₂ at considerably low overpotentials. Model studies of single-crystal Cu(111) electrodes were performed to correlate the interface and surface structure of Cu(111) with its electrocatalytic performance, which can help to rationalize the complex interplay between the morphology, structure and chemistry of both the electrode and electrolyte side of copper's electrochemical interface.

CO is a key intermediate in the electro-oxidation of energy carrying fuels and known to act as a catalyst poison. Cu(111) electrodes can efficiently electro-oxidize CO in alkaline media, where strong surface structural changes are observed under realistic reaction conditions with electrochemical scanning tunneling microscopy (EC-STM). Supported by first-principles microkinetic modelling, we have shown that the concomitant presence of high-energy undercoordinated Cu structures at the surface is a prerequisite for the high activity. In water electrolyzers, it is possible to produce H₂ in the course of the hydrogen evolution reaction (HER), which was studied with Ni(OH)₂ and Co(OH)₂modified Cu(111) electrodes in alkaline media. Strong morphological changes upon adatom modification lead to a significant HER rate enhancement. Intriguingly, this is induced through a decrease of the electric field strength negative of the potential of zero charge. This implies an easier reorganization of the interfacial water molecules facilitating charge transfer through the double layer, and thus enhancing the efficiency of electrocatalytic reactions.

Fransicso Sarabia

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