A Mild CO₂ Etching Method To Tailor the Pore Structure of Platinum-Free Oxygen Reduction Catalysts in Proton Exchange Membrane Fuel Cells

Abstract

The structural tailoring of pores is essential to highperformance Fe/N/C electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Current strategies for pore structure engineering are usually accompanied with a drastic change of the intrinsic activity-related surface, which may mask the real effects of the porous structure on ORR activity. Herein, a mild carbon dioxide (CO 2 ) etching method was used to flexibly tailor the pore structure of Fe/N/C electrocatalysts without drastic changes in their surface structure and property. In this way, via employing the Fe/N/C electrocatalysts as a model, the intrinsic impact of the pore structure on ORR activity was revealed. In addition, the CO 2 etching method developed a high-quality electrocatalyst (sample Fe/N/C−5% CO 2 ) with polarization performance exceeding that of the commercial Pt/C catalyst in the fuel cell working voltage region (>0.65 V). This work will promote the ongoing intensive studies on the rational design of the pore structures in the Fe/N/C electrocatalysts.

Synthesis of Mesoporous Fe/N/C Electrocatalyst for Improved Oxygen Reduction Reaction Activity Through CO2‐Assisted Pyrolysis

“…The 10 % CO 2 ‐treated electrocatalyst displayed the S BET of 1809 m 2 /g, which is more than twice that of the electrocatalyst (830 m 2 /g) without CO 2 treatment. The increase in the S BET is a result of the inclusion of mesopores [17] . Furthermore, the isotherms of both electrocatalysts reveal a type‐IV curve, confirming the mesoporous structures.…”

“…The increase in the S BET is a result of the inclusion of mesopores. [17] Furthermore, the isotherms of both electrocatalysts reveal a type-IV curve, confirming the mesoporous structures. The pore volume of micropores and mesopores is shown in Figure 1(b-c).…”

Impact of Pore Structure on Two‐Electron Oxygen Reduction Reaction in Nitrogen‐Doped Carbon Materials: Rotating Ring‐Disk Electrode vs. Flow Cell

“…These CO 2 ‐etched materials are marked as N/C‐ x % CO 2 , where x % is the volumetric content of CO 2 in the gas mixture from 0 % to 75 %. Since the CO 2 primarily reacts with the carbon support evenly on all surfaces, the change of surface structure and property of the resulting catalyst is minimized, [16] providing a materials platform to reveal the intrinsic impact of pores on the two‐electron ORR activity and selectivity.…”

Catalytic approaches towards highly durable proton exchange membrane fuel cells with minimized Pt use

“… 112 The performance in the high current density region could be enhanced further by enlarging the pores of Fe–N–C catalysts using mild CO 2 etching. 114 …”

“…112 The performance in the high current density region could be enhanced further by enlarging the pores of Fe-N-C catalysts using mild CO 2 etching. 114 Fe-N-C catalysts suffer from poor durability due to Fenton reactions, producing H 2 O 2 , which degrades the cell signicantly. 115 As an alternative, Wang, Litster, and Wu's groups prepared Co-N-C catalysts derived from Co-doped ZIF-8 capped with Pluronic F127 surfactants.…”