High-performance and low-cost oxygen reduction reaction (ORR) electrocatalysts are essential for the next generation of energy conversion devices, such as zinc-air batteries and fuel cells. While platinum (Pt)-based materials remain the commercial standard, their widespread adoption is hindered by high costs and poor long-term durability.
In a study published in the journal ENGINEERING Energy, a joint research team from the China University of Petroleum (East China) and Tsinghua University has introduced a novel "steric hindrance" strategy to develop advanced single-atom catalysts (SACs) that outperform traditional platinum benchmarks.
The Challenge: Preventing Atomic Agglomeration Single-atom catalysts, which feature isolated metal atoms anchored on a support, offer the highest possible atom utilization efficiency. However, the synthesis of these materials often requires high-temperature pyrolysis, which can cause metal atoms to migrate and clump together—a process known as agglomeration. This reduces the number of active catalytic sites and degrades the overall performance.
The Innovation: The Steric Hindrance Effect To solve this, the research team utilized metalloporphyrins substituted with bulky tert-butylphenyl groups as precursors. These "bulky" groups act as spatial shields around the metal centers.
"The introduction of tert-butylphenyl groups provides a significant steric hindrance effect," the research team explains. "These groups act like physical barriers that prevent iron (Fe) atoms from moving and aggregating during the high-temperature treatment at 800 °C. This ensures that the iron remains in its most active, single-atom form (Fe-N₄ sites) even under extreme thermal conditions."
Superior Performance and Stability The resulting catalyst, designated as t-Fe-800/CB, demonstrated exceptional efficiency in the Oxygen Reduction Reaction (ORR). Electrochemical testing revealed several key breakthroughs:

• High Catalytic Activity: An onset potential of 0.99 V and a half-wave potential (E₁/₂) of 0.89 V (vs. RHE) in alkaline media, significantly surpassing commercial Pt/C catalysts (E₁/₂ = 0.86 V).
• Enhanced Structural Support: A remarkably high specific surface area of 1344.13 m²/g, which facilitates faster mass transfer and more efficient oxygen diffusion.
• Practical Durability: When integrated into both flexible and aqueous Zn-air batteries, the catalyst delivered stable performance and high power density, proving its immense potential for portable and wearable electronics.

Future Impact This molecular engineering approach provides a versatile and scalable toolkit for designing a wide range of advanced electrocatalysts. "By manipulating the steric environment of molecular precursors, we can precisely tune the active sites for better efficiency in various energy systems," the researchers noted. "This strategy opens new avenues for creating low-cost, high-efficiency materials for a sustainable energy future."
DOI: 10.1007/s11708-026-1059-z