Ordered Mesoporous Intermetallic Ga-Pt Nanoparticles: Phase-Controlled Synthesis and Performance in Oxygen Reduction Electrocatalysis.

Abstract

The intermetallic phase control is a promising strategy to optimize the physicochemical properties of ordered intermetallic compounds and engineer their performance in various (electro)catalytic reactions. However, the intermetallic phase-dependent catalytic performance is still rarely reported because of the difficulty in synthesizing ordered intermetallics with precisely controlled phase structures at atomic level, especially having ordered mesoscopic structure/morphology. Here, we successfully reported a precise synthesis of two phase-pure mesoporous intermetallic gallium-platinum (meso-i-Ga-Pt) nanoparticles, including meso-i-Ga3 Pt5 with an orthorhombic space group and meso-i-Ga1 Pt1 with a non-symmorphic chiral cubic space group. The intermetallic phase control of ordered meso-i-Ga-Pt nanoparticles was realized by carefully tuning the induced Ga salts with different anions that optimized the free energies during the synthesis. The intermetallic phase-dependent catalytic performance of ordered meso-i-Ga-Pt was systematically evaluated for oxygen reduction reaction (ORR) electrocatalysis, with completely opposite catalytic performance in alkaline media. Interestingly, ordered meso-i-Ga1 Pt1 catalyst with chiral atomic arrangements disclosed unexpected high ORR activity and stability with 5.9 and 3.2 enhancement factors in mass activity compared to those of meso-i-Ga3 Pt5 and commercial Pt/C.