Atomically Dispersed High-Active Site Density Copper Electrocatalyst for the Reduction of Oxygen

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Optimizing metal-nitrogen-carbon (M-N-C) catalysts for the oxygen reduction reaction (ORR) is crucial for energy applications.
• Increasing the density of active sites, specifically M-Nx, is a key strategy to boost ORR performance.

Purpose of the Study:

• To develop a single-atom catalyst, Cu-N@Cu-N-C, with an enlarged density of Cu-N4 active sites.
• To evaluate the ORR performance of the synthesized catalyst in both alkaline and acidic electrolytes.

Main Methods:

• Synthesis of Cu-N@Cu-N-C via second doping and pyrolysis (SDP) of Cu-doped zeolite imidazole frameworks.
• Characterization using N2 adsorption-desorption, ICP, XAFS, and XPS to confirm structure and composition.
• Electrochemical testing to measure half-wave potentials in alkaline and acidic media.

Main Results:

• The Cu-N@Cu-N-C catalyst exhibited significantly higher half-wave potentials (0.85 V alkaline, 0.75 V acidic) compared to the original Cu-N-C.
• SDP successfully increased Cu content (1.92 wt% vs. 0.88 wt%) and Cu-N4 site density (18.36% vs. 13.15%).
• XAFS and XPS confirmed the presence and increased proportion of Cu-N4 single-atom active centers.

Conclusions:

• The enhanced ORR performance is directly linked to the enlarged Cu-N4 active site density achieved through SDP.
• This method provides an effective route for preparing efficient and cost-effective ORR catalysts.
• The study highlights the potential of SDP for tailoring single-atom catalysts for energy conversion applications.