PdCoNi alloy nanoparticles decorated, nitrogen-doped carbon nanotubes for highly active and durable oxygen reduction electrocatalysis

Abstract

Alloying Pd with transition metals is an effective strategy to enhance its catalytic activity toward oxygen reduction reaction (ORR). However, these catalysts always suffer from poor durability due to metal leaching during ORR. Herein, the catalyst of PdCoNi alloy nanoparticles supported on nitrogen-doped carbon nanotubes (PdCoNi/NCNTs) is prepared via one-pot solvothermal method and subsequent calcination. Introducing Co and Ni into Pd lattice not only boosts the catalytic activity, but also promotes the stability of the catalyst. As a result, the PdCoNi/NCNTs catalyst achieves a half-wave potential of 0.907 V and a specific activity of 3.78 mA/cm2 at 0.9 V vs. RHE, with 10 mV positive shift and 17.2 times enhancement over the commercial Pt/C catalyst in alkaline solution. Meanwhile, PdCoNi/NCNTs show much improved durability, with only 5 mV shift in the half-wave potential after 10,000 cycles, remarkably superior to those of PdCo/NCNTs, PdNi/NCNTs, and Pd/NCNTs. Valence band photoemission spectral analysis and theoretical calculations indicate that the existence of Co and Ni can tune the electronic structure of Pd by compressive strain effect and coordination effect, facilitating the activation of O2 and stabilizing the alloy elements, thus delivering a desired ORR activity and stability. Meanwhile, the high stability and intrinsic catalytic activity of NCNTs is also beneficial to ORR. Furthermore, PdCoNi/NCNTs also exhibit high performance as the air cathode catalysts in lithium-air battery.