Synergy of compress strain and antioxidant of platinum-copper for enhanced the oxygen reduction performance

Abstract

The development of efficient and durable electrocatalysts for oxygen reduction reaction (ORR) holds a pivotal significance in the successful commercialization of proton exchange membrane fuel cells (PEMFCs) but is still challenging. Herein, we report a worm-liked PtCu nanocrystals dispersed on nitrogen-doped carbon hollow microspheres (Pt_0.38Cu_0.62/N-HCS). Benefiting from its structural and compositional advantages, the resulting Pt_0.38Cu_0.62/N-HCS catalyst delivers exceptional electrocatalytic activity for ORR, with a half-wave potential (E_1/2) of 0.837 ​V, a mass activity of 0.672 A mg_Pt^-1, and a Tafel slope of 50.66 ​mV dec^-1, surpassing that of commercial Pt/C. Moreover, the Pt_0.38Cu_0.62/N-HCS follows the desired four-electron transfer mechanism throughout the ORR process, thereby displaying a high selectivity for direct reduction of O₂ to H₂O. Remarkably, this catalyst also showcases high stability, with only a 25 ​mV drop in E_1/2 after 10,000 cycles in an acidic electrolyte. Theoretical calculations elucidate the incorporation of Cu into Pt lattice induces compressive strain, which effectively tailors the d band center of Pt active sites and strengthens the surface chemisorption of O₂ molecules on PtCu alloys. Consequently, the Pt_0.38Cu_0.62/N-HCS catalyst exhibits an improved ability to adsorb O₂ molecules on its surface, accelerating the reaction kinetics of O₂ conversion to ∗OOH. Additionally, Cu atoms, not only serving as sacrificial anode, undergo preferential oxidation during PEMFCs operation when compared to Pt, but also the stable Cu species in PtCu alloys contributes significantly to maintaining the strain effect, collectively enhancing both activity and durability. Overall, this research offers an effective and promising approach to enhance the activity and stability of Pt-based ORR electrocatalysts in PEMFCs.