Abstract
Oxidized species on surfaces would significantly improve the electrocatalytic activity of Pt-based materials. Constructing three-dimensional porous structures would endow the catalysts with good stability. Here, we report a simple strategy to synthesize porous Pt–NiOx nanostructures composed of ultrasmall (about 3.0 nm) building blocks in an ethanol–water solvent. Structure and component analysis revealed that the as-prepared material consisted of interconnected Pt nanocrystals and amorphous NiOx species. The formation mechanism investigation revealed that the preformed amorphous compounds were vital for the construction of porous structure. In the ethanol oxidation reaction, Pt–NiOx/C exhibited current densities of 0.50 mA cmPt−2 at 0.45 V (vs. SCE), which were 16.7 times higher than that of a commercial Pt/C catalyst. Potentiostatic tests showed that Pt–NiOx/C had much higher current and better tolerance towards CO poisoning than the Pt/C catalyst under 0.45 V (vs. SCE). In addition, the NiOx species on the surface also outperformed an alloyed Ni component in the test. These results indicate that the Pt–NiOx porous nanomaterial is promising for use in direct ethanol fuel cells.
Highlights
Fuel cells fed with hydrogen or small organic molecules have shown great prospects in transportation and stationary power supplies, with their merits of high energy conversion efficiency, sustainable fuel sources and low harmful gas emissions.[1,2] As a common liquid fuel, ethanol can be handled, stored and transported, with a high energy density (8 kW h kgÀ1, 6.32 kW h LÀ1) and a low toxicity
According to previous studies,[4,5,6] several intrinsic reasons are responsible for these drawbacks: the cleavage of the C–C bond is necessary for CO2 generation, but this process is kinetically sluggish on pure Pt surfaces; the carbonous intermediates (CO, CHx, etc.) are generated and even a small amount of them would block the active sites of the Pt catalyst severely, which hampers the dissociative adsorption of ethanol; the adsorbed amount of oxygenated species (OH and O) is low on the pure Pt surface at a small overpotential, slowing the surface reactivation process down
Three-dimensional Pt–NiOx porous nanostructure was synthesized in ethanol–water solvent at room temperature
Summary
Fuel cells fed with hydrogen or small organic molecules have shown great prospects in transportation and stationary power supplies, with their merits of high energy conversion efficiency, sustainable fuel sources and low harmful gas emissions.[1,2] As a common liquid fuel, ethanol can be handled, stored and transported, with a high energy density (8 kW h kgÀ1, 6.32 kW h LÀ1) and a low toxicity. Nickel and its compounds have been proved to remarkably promote the catalytic activity of Pt in oxidation reactions of CO and methanol.[26,27,28,29,30] Most recently, octahedral Pt–Ni/C alloying catalyst was found to exhibit a much higher EOR current density than Pt–Ni/C and Pt/C.31 In this work, 3D Pt–NiOx porous nanostructure was constructed to evaluate the effect of NiOx species in the EOR process.
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