Breaking the Intermediate Solvation Shell on Single-Atom Catalysts With a Proximal Group Perturber for Enhanced...

Area of Science:

• Electrocatalysis
• Materials Science
• Energy Conversion

Background:

• Electrocatalytic performance heavily relies on the active site's microenvironment, especially hydrogen-bonding networks.
• Tuning this network is challenging in proton-exchange membrane fuel cells (PEMFCs) due to the limited cation availability (only protons).
• Current strategies often focus on active-site optimization, neglecting the catalyst's local environment.

Purpose of the Study:

• To develop a general strategy for tuning the microenvironment of single-atom catalysts.
• To improve the electrocatalytic performance of catalysts for the oxygen reduction reaction (ORR).
• To demonstrate enhanced stability and efficiency in PEMFCs using engineered catalysts.

Main Methods:

• Introduced "immobilized molecular perturbation" by incorporating proximal P-O groups into Fe-N-C single-atom catalysts.
• Utilized spectroscopy and computational methods to confirm the engineered microenvironment's effect on ^*OH intermediates.
• Tested catalyst performance in 0.5 m H2SO4 and within a H2/O2 PEMFC setup.

Main Results:

• Engineered microenvironment selectively weakened the solvation shell of ^*OH intermediates, facilitating desorption.
• Achieved a high half-wave potential of 0.861 V in H2SO4 and a peak power density of 1024 mW cm⁻² in a PEMFC.
• Demonstrated excellent stability with 72% current retention after 253 hours at 0.65 V.

Conclusions:

• "Immobilized molecular perturbation" is an effective strategy for enhancing electrocatalysis by engineering the catalyst's second coordination sphere.
• This approach significantly boosts ORR performance and stability in PEMFCs, outperforming many non-precious metal catalysts.
• Shifts focus from active-center optimization to deliberate local microenvironment engineering for advanced electrocatalysis.