Hongjing Wang,Tongqing Zhou,Shan Xu,Kai Deng,Hongjie Yu,You Xu,Xiaonian Li,Ziqiang Wang,Liang Wang
The development of effective and stable cathode electrocatalysts is highly desired for fuel cells. Controlling the composition and morphology of Pd-based materials can provide a great opportunity to improve their oxygen reduction reaction (ORR) performance. Here, we report the synthesis of hexagonal close-packed (hcp) Pd2B nanosheet assemblies (Pd2B NAs) via the boronation reaction between as-synthesized Pd NAs and N,N-dimethylformamide. The hcp Pd2B NAs with uniform pore distribution can provide sufficient active sites for ORRs. The insertion of B atoms can induce the phase transition from face-centered cubic structure to hcp structure, as the most thermodynamically stable phase in the Pd-B alloy, which is beneficial for enhancing the ORR stability and toxicity resistance. Therefore, the hcp Pd2B NAs exhibit superior mass activity, specific activity and excellent stability for ORR. The present strategy of boron-intercalation-triggered crystalline transition of Pd-based nanomaterials is valuable for the design of metal–nonmetal catalysts with enhanced performance.
Furfural-based bifuran diacids/diesters, such as 2,2′-bifuran-5,5′-dicarboxylic acid (BFDCA), are important biomass-derived chemicals in the production of high-performance polymers and plasticizers. However, the synthesis of bifuran diacids/diesters lacks an efficient heterogeneous catalytic system. Here, we report that the interstitial modification of a PdNi bimetallic nanoalloy with boron atoms supported on nitrogen-doped carbon exhibited high catalytic efficiency in the conversion of halogenated furoic acids/esters to bifuran diacids/diesters via sequential oxidative addition and reductive elimination steps initiated at room temperature, affording a high yield with a Pd/Ni molar ratio of 1:1. The conversion of 5-bromo-2-furoic acid to BFDCA has a turnover frequency value of up to 672.0 h–1, 2.5 times higher than that of commercial Pd/C. The comprehensive characterization results demonstrated that boron as an interstitial atom entered into the lattice of the PdNi alloy, leading to lattice distortion and the regulation of the electronic state of Pd. Density functional theory calculations exhibited that these electronegative Pd sites were pivotal active species in the oxidation addition, where Ni facilitated the coordination of Pd and carbon–halogen bonds. The optimal catalyst showed excellent stability and recyclability in alkaline aqueous solution. This protocol provides an efficient strategy for the reductive homocoupling and sustainable production of bifuran diacids/diesters and their derivatives from biomass resources.
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