EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The development and design of bimetallic electrodes by deposition of foreign adatoms on a host metal is one key tactic to tune their activity and selectivity for various electrocatalytic reactions. Here, irreversible adsorption$^{1}$ of Ni$^{2+}$ ions was used to prepare Ni(OH)$_{2}$ modified Cu(111) electrodes with different adatom coverages and to study their effect on the hydrogen evolution reaction (HER) and CO reduction in alkaline media. To investigate the structure-activity relation, electrochemical scanning tunneling microscopy (EC-STM) was performed and shows strong morphological changes upon adatom modification consistent with preferential adsorption of Ni(OH)$_{2}$ on the step edges. The presence of Ni(OH)$_{2}$ on Cu(111) not only leads to a significant enhancement in the rate of the HER, similar to what has been demonstrated for Ni(OH)$_{2}$/Pt(111) electrodes$^{2}$, but also changes the selectivity of the CO reduction reaction. Intriguingly, laser induced temperature jump experiments reveal that the modification of Cu(111) with Ni(OH)$_{2}$ influences the charge distribution at the solid/liquid interface by 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.

References
[1] J.M. Feliu, J.M. Orts (1991) Irreversible Adsorption of Metal Atoms in Electrocatalysis. In: Brongersma H.H., van Santen R.A. (eds) Fundamental Aspects of Heterogeneous Catalysis Studied by Particle Beams. NATO ASI Series, vol 265. Springer, Boston, MA.
[2] F. J. Sarabia, P. Sebastián-Pascual, M. T. M. Koper, V. Climent, J. M. Feliu, ACS Appl. Mater. Interfaces 2019, 11, 1, 613–623.