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  1. Abstract To achieve environmentally benign energy conversion with the carbon neutrality target via electrochemical reactions, the innovation of electrocatalysts plays a vital role in the enablement of renewable resources. Nowadays, Pt-based nanocrystals (NCs) have been identified as one class of the most promising candidates to efficiently catalyze both the half-reactions in hydrogen- and hydrocarbon-based fuel cells. Here, we thoroughly discuss the key achievement in developing shape-controlled Pt and Pt-based NCs, and their electrochemical applications in fuel cells. We begin with a mechanistic discussion on how the morphology can be precisely controlled in a colloidal system, followed by highlighting the advanced development of shape-controlled Pt, Pt-alloy, Pt-based core@shell NCs, Pt-based nanocages, and Pt-based intermetallic compounds. We then select some case studies on models of typical reactions (oxygen reduction reaction at the cathode and small molecular oxidation reaction at the anode) that are enhanced by the shape-controlled Pt-based nanocatalysts. Finally, we provide an outlook on the potential challenges of shape-controlled nanocatalysts and envision their perspective with suggestions. "Image missing" 
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    Free, publicly-accessible full text available December 1, 2024
  2. Free, publicly-accessible full text available August 11, 2024
  3. Abstract Among the multi-metallic nanocatalysts, Pt-based alloy nanocrystals (NCs) have demonstrated promising performance in fuel cells and water electrolyzers. Herein, we demonstrate a facile colloidal synthesis of monodisperse trimetallic Pt–Fe–Ni alloy NCs through a co-reduction of metal precursors. The as-synthesized ternary NCs exhibit superior mass and specific activities toward oxygen reduction reaction (ORR), which are ∼2.8 and 5.6 times as high as those of the benchmark Pt/C catalyst, respectively. The ORR activity of the carbon-supported Pt–Fe–Ni nanocatalyst is persistently retained after the durability test. Owing to the incorporation of Fe and Ni atoms into the Pt lattice, the as-prepared trimetallic Pt-alloy electrocatalyst also manifestly enhances the electrochemical activity and durability toward the oxygen evolution reaction with a reduced overpotential when compared with that of the benchmark Pt/C (△ η = 0.20 V, at 10 mA cm −2 ). This synthetic strategy paves the way for improving the reactivity for a broad range of electrocatalytic applications. 
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  4. This study demonstrates an atomic composition manipulation on Pt–Ni nano-octahedra to enhance their electrocatalytic performance. By selectively extracting Ni atoms from the {111} facets of the Pt–Ni nano-octahedra using gaseous carbon monoxide at an elevated temperature, a Pt-rich shell is formed, resulting in an ∼2 atomic layer Pt-skin. The surface-engineered octahedral nanocatalyst exhibits a significant enhancement in both mass activity (∼1.8-fold) and specific activity (∼2.2-fold) toward the oxygen reduction reaction compared with its unmodified counterpart. After 20,000 potential cycles of durability tests, the surface-etched Pt–Ni nano-octahedral sample shows a mass activity of 1.50 A/mgPt, exceeding the initial mass activity of the unetched counterpart (1.40 A/mgPt) and outperforming the benchmark Pt/C (0.18 A/mgPt) by a factor of 8. DFT calculations predict this improvement with the Pt surface layers and support these experimental observations. This surface-engineering protocol provides a promising strategy for developing novel electrocatalysts with improved catalytic features. 
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    Free, publicly-accessible full text available April 11, 2024
  5. Despite the well-known tendency for many alloys to undergo ordering transformations, the microscopic mechanism of ordering and its dependence on alloy composition remains largely unknown. Using the example of Pt 85 Fe 15 and Pt 65 Fe 35 alloy nanoparticles (NPs), herein we demonstrate the composition-dependent ordering processes on the single-particle level, where the nanoscale size effect allows for close interplay between surface and bulk in controlling the phase evolution. Using in situ electron microscopy observations, we show that the ordering transformation in Pt 85 Fe 15 NPs during vacuum annealing occurs via the surface nucleation and growth of L1 2 -ordered Pt 3 Fe domains that propagate into the bulk, followed by the self-sacrifice transformation of the surface region of the L1 2 Pt 3 Fe into a Pt skin. By contrast, the ordering in Pt 65 Fe 35 NPs proceeds via an interface mechanism by which the rapid formation of an L1 0 PtFe skin occurs on the NPs and the transformation boundary moves inward along with outward Pt diffusion. Although both the “nucleation and growth” and the “interface” mechanisms result in a core–shell configuration with a thin Pt-rich skin, Pt 85 Fe 15 NPs have an L1 2 Pt 3 Fe core, whereas Pt 65 Fe 35 NPs are composed of an L1 0 PtFe core. Using atomistic modeling, we identify the composition-dependent vacancy-assisted counterdiffusion of Pt and Fe atoms between the surface and core regions in controlling the ordering transformation pathway. This vacancy-assisted diffusion is further demonstrated by oxygen annealing, for which the selective oxidation of Fe results in a large number of Fe vacancies and thereby greatly accelerates the transformation kinetics. 
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