Strain-Engineered Pt Nanoparticles on N-Doped Carbon Nanotubes for Enhanced Oxygen Reduction Reaction

Developing high-performance nanocatalysts for the oxygen reduction reaction (ORR) is critical for fuel cell applications but remains challenging due to insufficient activities. Herein, we present a design of nanoscale lattice strain over Pt nanoparticles and deeply explored the relationship between the strained Pt lattices and their activities toward ORR. In comparison to the unstrained Pt(111) lattice, compressions of 8.8% and 14.6% are found for the designed Pt catalysts on carbon nanotubes (CNTs) and N-modified CNTs (N-CNTs), respectively. The more intense compression on N-CNTs arises from the strengthened Pt–N interactions and improved charge transfer, enabling faster desorption of reaction intermediates. In the case of ORR, this compressed Pt(111) lattice weakens the binding energy for the rate-determining step, specifically, the OH* binding, and leads to more desorption of the final product of H2O. Benefiting from the decreased energy barrier, the compressed Pt catalyst on N-CNT exhibits better ORR activity in the following electrochemical tests with a higher half-wave potential of 0.87 V (vs RHE) and a lower Tafel slope of 47.8 mV/dec attributed to the nanoscale structural modulation of the Pt(111) facets. Our work gives a strategy for tuning of compressed Pt-based nanocatalysts and provides an insight into the influence of carbon modification on ORR activity.