Pt-based nanoparticles have been studied extensively for electrochemical oxidation of fuels, but CO poisoning has been a main issue for the catalyst to drive fuel oxidation to completion (to CO₂). Here we present two examples to demonstrate that by controlling Pt interfaces with Au, the Pt-catalysis can be made more efficient towards C-C bond cleavage and alcohol oxidation.

Using MPtAu (M = Fe, Co) nanoparticles as an example, we have demonstrated that the presence of Au in MPtAu facilitates MPt structure transformation from chemically disordered solid solution structure to chemically ordered intermetallic structure for the formation of core/shell L10-MPt/AuPt. This thin AuPt shell promotes formic acid oxidation reaction (FAOR) and alcohol oxidation reaction (AOR) with high CO tolerance. The L10-MPt structure stabilizes M in the oxidative acid solution and significantly enhances the catalysis of the AuPt shell. For FAOR, the core/shell L10-FePt/AuPt nanoparticles have a mass activity as high as 2.8 A/mg Pt and retain 92.5% of this activity after a 13 h stability test in 0.1 M HClO4 solution. The L10-CoPt/AuPt nanoparticles are active for methanol and ethanol oxidations with mass activities at 1.49 A/mgPt and 1.55 A/mgPt respectively in 0.1 M HClO4 solution with negligible degradation in mass activities and Co/Pt/ Au composition changes after 10000 potential cycles. The AOR activity can be further enhanced by core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs. The NWs with a highest percentage (~75%) of stepped Au/Pt sites show the highest activity for ethanol electrooxidation, reaching 196.9 A/mgPt (32.5 A/mgPt+Au). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as n-propanol and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy studies suggest that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to promote C-C bond cleavage and drive the AOR more deeply towards CO₂.

Our studies provide some important evidence that low-coordinated Pt surface alloyed with Au is essential for enhancing its catalysis power toward deep oxidation of alcohols. Such surface design will be central to the understanding of future catalyst development to promote electro-oxidation reactions with high efficiency, which will be key to renewable and sustainable energy applications.

Shouheng Sun

Appearances