Motivated by the high performance of intermetallic compounds with their ordered structures, developing synthetic methods for preparing intermetallic compounds is highly desired. Herein, we report facile syntheses and rational design of the structurally ordered Cu-based intermetallic compounds (CuM (M = Pt, Pd, Au)). To achieve this, intermetallic nanoparticles were synthesized in solution by a butyllithium co-reduction method at 240 °C. The developed wet-chemistry syntheses of ordered intermetallic CuM nanoparticles avoided solid annealing process, and thus relatively small intermetallic nanocrystals were formed. The ordered PtCu nanocatalysts displayed enhanced chemoselectivity relative to the PtCu solid-solution alloy and individual monometallic nanocatalysts for catalytic hydrogenations of a series of substituted nitroaromatics. The DFT-based theoretical calculations for hydrogenations of halonitrobenzenes suggest that the surface geometry of ordered PtCu structures favor the hydrogenation of nitro substituent and disfavor the hydrodechlorination by-reaction, resulting in enhanced chemoselectivity.
Supported Pt catalysts suffer from low reaction selectivity (<65% at 100% conversion) in the selective catalytic oxidation of ammonia (NH3-SCO) because of their intrinsic over-oxidation tendencies. Herein, a strategy based on facilitating byproduct NOx reduction to N2 is demonstrated at CuOx/PtCu catalysts, aiming to tackle the low selectivity challenge. This PtCu alloy sample with a CuOx-rich surface displays an N2 selectivity of 95%, while its turnover frequencies are the highest among reported supported Pt-based catalysts. The enhanced reaction activities and N2 selectivities are primarily attributed to the Pt-Cuδ+ dual-site synergies at the CuOx/PtCu interface, in which dual sites exhibit distinct NH3 adsorption, activation, and dehydrogenation behaviors. The Olat assisted internal selective catalytic reduction mechanism at CuOx/PtCu with N2O22– as the central intermediates is proposed. Density functional theory calculation and temperature-programmed surface reaction measurements show that the N–O bond in N2O22– tends to break simultaneously with the assistance of Ov in CuOx followed by the easy transition from N2O22– to N2, which serve as the origin of the high selectivity.
Pengfei Guo,Zhongyan Zhang,Ru Feng,Fei Peng,Xingyu Luo,Xiaofeng Xu,Xiaoling Lang,Yaqing Cen,Meiqin Shi
The durability of platinum-group metal catalysts for oxygen reduction reaction (ORR) remains a critical determinant for the commercial viability of proton exchange membrane fuel cells (PEMFCs). Herein, we report a PtCu catalyst featured with a short-range ordered crystal structure and stabilized by a nitrogen-doped carbon shell. Notably, triphenylphosphine was strategically employed as a coordinating agent to regulate the uniformly growth of Pt and Cu complex. The N-doped carbon shell derived from zeolitic imidazolate framework-8 ( ZIF-8) served a dual protective function: (1) physically isolating PtCu nanoparticles to mitigate agglomeration during thermal annealing, and (2) electrochemically stabilizing the catalyst against dissolution under accelerated durability test. X-ray absorption fine structure (XAFS), supported by density functional theory (DFT) calculations revealed that the short-range ordered structure in the PtCu kinetically impeded both Pt leaching and Cu segregation, which is beneficial for improving catalyst stability. Durability tests demonstrates only 15 % mass activity loss after 50 K electrochemical cycles, underscoring the efficacy of Pt-Cu interface design in addressing durability challenges for PEMFC cathodes.
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