Highly active and durable platinum group metal-free catalysts for the oxygen reduction reaction, such as Fe–N–C materials, are needed to lower the cost of proton-exchange membrane fuel cells. However, their durability is impaired by the attack of oxidizing radicals such as ·OH and HO2· that form from incomplete reduction of O2 via H2O2. Here we demonstrate that Ta–TiOx nanoparticle additives protect Fe–N–C catalysts from such degradation via radical scavenging. The 5 nm Ta–TiOx nanoparticles were uniformly synthesized on a Ketjenblack substrate using a high-temperature pulse technique, forming the rutile TaO2 phase. We found that Ta–TiOx nanoparticles suppressed the H2O2 yield by 51% at 0.7 V in an aqueous rotating ring disk electrode test. After an accelerated durability test, a fuel cell prepared with the scavengers showed a current density decay of 3% at 0.9 ViR-free (internal resistance-compensated voltage); a fuel cell without scavengers showed 33% decay. Thus, addition of Ta–TiOx provides an active defence strategy to improve the durability of oxygen reduction reaction catalysts.
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L.H., Y.S., X.X. and H.X. acknowledge support from the US Department of Energy, Office of Energy Efficiency and Renewable Energy and Hydrogen and Fuel Cell Technologies Office through the Electrocatalysis consortium (ElectroCat) and from DOE programme managers D. Papageorgopoulos, S. Thompson, D. Peterson and G. Kleen. R.S.-Y. acknowledges financial support from National Science Foundation DMR-1809439. D.J. acknowledges support from the National Science Foundation CHE-2102191. G.H. acknowledges the financial support from the Queens College, City University of New York. The authors acknowledge the support of the Maryland Nanocenter, its Surface Analysis Center and AIMLab. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the US government or any agency thereof. Neither the US government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.
The authors declare no competing interests.
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Xie, H., Xie, X., Hu, G. et al. Ta–TiOx nanoparticles as radical scavengers to improve the durability of Fe–N–C oxygen reduction catalysts. Nat Energy 7, 281–289 (2022). https://doi.org/10.1038/s41560-022-00988-w