(Invited) Nitrogen-Doped High-Entropy Alloy as Efficient and Stable Electrocatalyst

Abstract

The development of Pt-based catalysts for use in fuel cells that meet performance targets of high activity, maximized stability, and low cost remains a huge challenge. The high-entropy alloy (HEA) is one of the most promising candidates for electrocatalysts, owing to their unique properties involving the high entropy effect, lattice distortion effect, sluggish diffusion effect, and “cocktail” effect.1 Alternatively, nitrogen (N)-doping effects have been well documented and demonstrated in our previous studies, which further fine-tune the adsorption energetics of intermediates and improve the corrosion resistance by the pinning effect of metal-nitrogen bonds.2-3 Combining the HEA and N-doping strategies, the tailored lattice and interstice atomic sites lead to the formation of chemically stable multiple metal-nitrogen (M-N) bonds and the generation of the possible synergistic effect on promoting ORR performance. Herein, we report a N-doped high-entropy alloy (HEA) electrocatalyst that consists of a Pt-rich shell and a N-doped PtCoFeNiCu core on a carbon support (denoted as N-Pt/HEA/C). The N-Pt/HEA/C catalyst showed high mass activity of 1.34 A mgPt -1 at 0.9 V for the oxygen reduction reaction (ORR), which substantially outperformed commercial Pt/C and most of the other binary/ternary Pt-based catalysts. The N-Pt/HEA/C catalyst also demonstrated excellent stability in both rotating disk electrode (RDE) and membrane electrode assembly (MEA) testing. Using operando X-ray absorption spectroscopy (XAS) measurements and theoretical calculations, we revealed that the enhanced ORR activity of N-Pt/HEA/C originated from the optimized adsorption energy of intermediates, consequent of the tailored electronic structure formed upon the N-doping. Furthermore, we showed that the multiple metal-nitrogen bonds formed synergistically improved the corrosion resistance of the 3d transition metals and enhanced the ORR durability.References Yao, Y.; Dong, Q.; Brozena, A.; Luo, J.; Miao, J.; Chi, M.; Wang, C.; Kevrekidis, I. G.; Ren, Z. J.; Greeley, J.; Wang, G.; Anapolsky, A.; Hu, L., High-entropy nanoparticles: Synthesis-structure-property relationships and data-driven discovery. Science 2022, 376 (6589), eabn3103.Zhao, X.; Xi, C.; Zhang, R.; Song, L.; Wang, C.; Spendelow, J. S.; Frenkel, A. I.; Yang, J.; Xin, H. L.; Sasaki, K., High-Performance Nitrogen-Doped Intermetallic PtNi Catalyst for the Oxygen Reduction Reaction. ACS Catalysis 2020, 10 (18), 10637-10645.Zhao, X.; Cheng, H.; Song, L.; Han, L.; Zhang, R.; Kwon, G.; Ma, L.; Ehrlich, S. N.; Frenkel, A. I.; Yang, J.; Sasaki, K.; Xin, H. L., Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reaction. ACS Catalysis 2020, 11 (1), 184-192.