Surface and interface engineering of FePt/C nanocatalysts for electro-catalytic methanol oxidation: enhanced activity and durability

Abstract

A methodology by coupling a microfluidic-batch process with in situ carbon-black mixing, successive annealing and de-alloying post-treatment was developed for engineering surface and interface microstructures of FePt/C nanocomposites. Ultra-small angular FePt nanocrystals rich in vertexes/terraces/steps and with Pt contents gradually increasing from the inner to the outer part can be synthesized at certain Fe/Pt atomic ratios (2/1 or 1.1/1), which can directly grow on carbon-black for enhanced nanocrystal–carbon interface interaction by introducing the in situ carbon-black mixing process. Composition and structure characterization suggests that FePt@(Fe_1−xPt_x)O_y(OH)_z/C nanocomposites with FePt alloy cores and surface Pt-doping hydroxyl iron oxide shells are formed after annealing. After controlled de-alloying of Fe in annealed nanocrystals with a Fe/Pt ratio of 2/1, the finally formed nanocatalysts exhibited excellent electrochemical catalytic performance using the methanol oxidation reaction as a model, preserving an activity of 1610 mA mg⁻¹ Pt⁻¹ (12 times the commercial Pt/C catalysts, higher than the best result (7.9 times the commercial Pt/C catalysts) just published in Science (Science, 2016, 354, 1410–1414), enhanced durability and high tolerance to CO poisoning.