Underpotential and Electroless Pb Monolayer Deposition on Ru(0001)

Abstract

The work reporting a detailed and comparative study of Pb UPD and Pb e-less ML deposition on Ru(0001) substrate is presented. The electrochemical results are analyzed through the scope of the adsorption isotherm formalism where parameters describing the thermodynamics of deposited Pb monolayer obtained by each process are compared. In addition to these results, the in situ STM and electrochemical quartz micro balance data are presented for each process identifying the mutual mechanistic similarities and differences between electroless Pb and underpotential Pb monolayer. Considerable applications of Ru metal in microelectronics and catalysis rise significance of these results for variety of future developments in these areas.

Electroless Pb Monolayer Deposition—Prelude for Further Advances in Catalyst Monolayer Synthesis via Surface Limited Redox Replacement Reaction

“…This means that the completion of the deposition process is confined within the Pb underpotential region where only two-dimensional (2D) phase of Pb deposit is thermodynamically stable . This is illustrated in Figure showing the surface morphology change during the deposition on Au(111) and Ru(0001) …”

“…19 This is illustrated in Figure 2 showing the surface morphology change during the deposition on Au(111) 10 and Ru(0001). 11 The Pb ML nucleation is visible immediately after the introduction of V 2+ ions. It is followed by 2D growth which gradually smooths out the surface by completion of the Pb ML e-less , Figure 2A Beyond the discussed examples, other common methods could be employed to study the Pb ML e-less depostion.…”

“…So far, all substrates which demonstrate the Pb ML e-less deposition also exhibit the Pb UPD phenomenon. [10][11][12]19 Therefore, in situ and ex situ methods employed in UPD studies can be also used to study the Pb ML e-less deposition. The most common one is monitoring of the open circuit potential (OCP) transients.…”

“…The solution for Pb ML e‑less deposition is shown in Table . , It can be prepared by mixing solutions containing Pb 2+ ions and V 2+ ions. This approach is suitable for in situ studies where the aliquot containing V 2+ ions is added to the solution with Pb 2+ ions while the open circuit potential (OCP) or electrochemical quartz microbalance (ECQMB) transients are recorded.…”

“…However, recent developments in the area of electroless (e-less) deposition show promising results. They demonstrate that UPD-like monolayers can be synthesized on various catalytically relevant substrates using an e-less deposition with simple experimental routine and solution chemistry. − Several reports indicate that the e-less Pb ML (Pb ML e‑less ) deposition is of particular interest. − It occurs on substrates that do exhibit the Pb UPD phenomenon, and it can be used to modify catalytically active substrates (noble metals), improving their activity for particular reactions. , The Pb ML e‑less can also replace the UPD ML in the SLRR reaction, enabling formation of the catalyst ML on substrates with nonconductive support. In this case, the full deposition cycle requires consecutive immersion of the substrate in the solution for the Pb ML e‑less deposition (first step) and then in the solution for the SLRR, that is, catalyst deposition (second step).…”