Sputter deposition of highly active complex solid solution electrocatalysts into an ionic liquid library: effect of...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Complex solid solution electrocatalysts, including high-entropy alloys, offer unique catalytic properties due to multi-element active sites.
• A key challenge is understanding structure-activity relationships for rational catalyst design.

Purpose of the Study:

• To synthesize and characterize chromium-manganese-iron-cobalt-nickel (Cr-Mn-Fe-Co-Ni) nanoparticles.
• To investigate their intrinsic electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline media.
• To correlate nanoparticle properties (size, crystallinity, composition) with ORR performance.

Main Methods:

• Magnetron sputtering of a high-entropy Cantor alloy target into an ionic liquid library.
• Synthesis of nanoparticles with varying sizes (1.3–2.6 nm), crystallinity (amorphous, FCC, BCC), and composition.
• Electrocatalytic testing for the oxygen reduction reaction in alkaline conditions.

Main Results:

• Synthesized Cr-Mn-Fe-Co-Ni nanoparticles exhibited a narrow size distribution but varied in size, crystallinity, and composition.
• These nanoparticles demonstrated unprecedented intrinsic electrocatalytic activity for the ORR, with some exceeding platinum's performance.
• Optimal activity was achieved with body-centered cubic (BCC) nanoparticles featuring low manganese and iron content, synthesized using the ionic liquid [Emimi][(Tf)2N].

Conclusions:

• Cr-Mn-Fe-Co-Ni complex solid solution nanoparticles represent a promising new class of electrocatalysts for the ORR.
• Tailoring nanoparticle crystallinity and composition is crucial for enhancing electrocatalytic performance.
• The study highlights the potential of high-entropy alloys for advanced catalytic applications.