Scalable and Controllable Synthesis of Pt-Ni Bunched-Nanocages Aerogels as Efficient Electrocatalysts for Oxygen Reduction Reaction

Developing efficient and stable Pt-based oxygen reduction reaction (ORR) electrocatalysts via both economical and controllable routes is critical for the
practical application of electrochemical energy devices. Herein, a scalable, controllable, and general ambient-O₂-involved aqueous-solution cultivating strategy to prepare Pt_xM_y (M = Ni, Fe, Co) bunched-nanocages aerogels (BNCs AG) is demonstrated, based on a newly established high-M-to-Pt-precursor-ratio-and-B-incorporation-facilitated M-rich core and Pt-rich shell hydrogel formation process. The Pt₈₃Ni₁₇ BNCs AG shows prominent ORR performance with a mass activity (MA) of 1.95 A mg_Pt ⁻¹ and specific activity of 3.55 mA cm⁻², which are 8.9-times and 9.6-times that of Pt supported on carbon (Pt/C), respectively. Particularly,
the Pt₈₃Ni₁₇ BNCs AG displays greatly enhanced durability (MA 82.6% retention) compared to Pt/C (MA 31.8% retention) after a 20 000-cycles accelerated durability test. Systematic studies including density functional theory calculations uncover that the excellent activity is closely related to the optimized ligand and strain effects with the optimized Ni content in this aerogel; the outstanding durability is endowed by the lowered-down Ni leaching with the optimized Pt/Ni ratio and the inhibited sintering due to its appropriate porosity. This work provides new perspectives on the development of electrocatalysts with both high performance and low cost.