(560ct) Atom-Thick Ir-Rich Skin on Ptir Nanocube Electrocatalysts for Efficient Ethanol Oxidation

Authors: 
Chang, Q., University of California, San Diego
Kattel, S., Florida A&M University
Su, D., Brookhaven National Laboratory
Chen, J. G., Columbia University
Chen, Z., University of California San Diego
Li, X., Brookhaven National Laboratory
The direct alcohol fuel cell (DAFC) as an alternative power source for various applications has attracted great attention due to its high efficiency under ambient operating conditions. Ethanol is more favored as the fuel than methanol due to its higher energy density, lower toxicity, and larger mass-production capacity. However, the state-of-the-art Pt-based electrocatalysts possess limited active sites to break C-C bond and are easily poisoned during ethanol oxidation reaction (EOR), which leads to very low fuel utilization efficiency and hinders the commercialization of DEFCs. Here, we report colloidal preparation of PtIr core-shell nanocubes (NCs) with atom-thick Ir-rich shells to enhance EOR performance. Compared with pure Pt NCs and Pt17Ir NCs (two-atom thick Ir-rich skin), we demonstrate that (100)-exposed Pt38Ir NCs with one-atom-thick Ir-rich skin present excellent EOR activity, improved CO2 selectivity and long-term stability. The EOR current density of Pt38Ir NCs electrocatalyst is 4.5-times higher than that of Pt/C with a negatively shifted EOR onset potential of 320 mV. Also, it can deliver a CO2 current density up to 14 times higher than that of commercial Pt/C at 0.85 V. We find that the improved EOR performance can be ascribed to the favorable cleavage of the C-C bond by strongly absorbed *CxHyO/CxHy species and easily desorption of CO from the PtIr surface. This work highlights the decisive role of surface atom layers on shape-controlled electrocatalysts, and shed light on further development of effective EOR electrocatalysts.