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Interfacial Water Structure as a Descriptor for Its Electro-Reduction on Ni(OH)₂-Modified Cu(111).

ABSTRACT: The hydrogen evolution reaction (HER) has been crucial for the development of fundamental knowledge on electrocatalysis and electrochemistry, in general. In alkaline media, many key questions concerning pH-dependent structure-activity relations and the underlying activity descriptors remain unclear. While the presence of Ni(OH)₂ deposited on Pt(111) has been shown to highly improve the rate of the HER through the electrode's bifunctionality, no studies exist on how low coverages of Ni(OH)₂ influence the electrocatalytic behavior of Cu surfaces, which is a low-cost alternative to Pt. Here, we demonstrate that Cu(111) modified with 0.1 and 0.2 monolayers (ML) of Ni(OH)₂ exhibits an unusual non-linear activity trend with increasing coverage. By combining in situ structural investigations with studies on the interfacial water orientation using electrochemical scanning tunneling microscopy and laser-induced temperature jump experiments, we find a correlation between a particular threshold of surface roughness and the decrease in the ordering of the water network at the interface. The highly disordered water ad-layer close to the onset of the HER, which is only present for 0.2 ML of Ni(OH)₂, facilitates the reorganization of the interfacial water molecules to accommodate for charge transfer, thus enhancing the rate of the reaction. These findings strongly suggest a general validity of the interfacial water reorganization as an activity descriptor for the HER in alkaline media.

SUBMITTER: Auer A

PROVIDER: S-EPMC8383263 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Interfacial Water Structure as a Descriptor for Its Electro-Reduction on Ni(OH)₂-Modified Cu(111).

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