PtRu nanofilm formation by electrochemical atomic layer deposition (E-ALD)

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Platinum-ruthenium (PtRu) alloys exhibit high CO tolerance, making them promising anode materials for proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC).
• Traditional synthesis methods may not offer precise control over alloy composition and nanostructure, crucial for optimizing electrocatalytic activity.

Purpose of the Study:

• To develop and characterize bimetallic PtRu nanofilms using the electrochemical form of atomic layer deposition (E-ALD).
• To investigate the CO electrooxidation performance of PtRu nanofilms with varying compositions and surface terminations.

Main Methods:

• PtRu nanofilms were fabricated using E-ALD, employing surface-limited redox replacement (SLRR) with lead (Pb) underpotential deposition (UPD) as a sacrificial layer.
• The E-ALD cycle involved Pb UPD followed by replacement with Pt(IV) or Ru(III) ions at open-circuit potential (OCP).
• Film composition was controlled by the number of E-ALD cycles, and characterized by CO adsorption and electrooxidation studies.

Main Results:

• PtRu nanofilms with atomic proportions of 70/30, 82/18, and 50/50 Pt/Ru were successfully synthesized.
• The 50/50 PtRu nanofilms demonstrated the lowest CO electrooxidation overpotentials and highest current densities compared to other compositions, pure Pt, and pure Ru.
• Surface termination studies indicated that the composition of the outermost atomic layer influences CO electrooxidation performance.

Conclusions:

• E-ALD is an effective technique for fabricating PtRu nanofilms with controlled composition and nanostructure.
• The 50/50 PtRu alloy composition exhibits superior electrocatalytic activity for CO oxidation, making it a highly promising anode material for fuel cells.
• Further optimization of surface termination can potentially enhance the performance of PtRu electrocatalysts.