Synthesis and Crystal-Phase Engineering of Mesoporous Palladium–Boron Alloy Nanoparticles

Abstract

Rational design and synthesis of noble metal nanomaterials with desired crystal phases (atomic level) and controllable structures/morphologies (mesoscopic level) are paramount for modulating their physiochemical properties. However, it is challenging to simultaneously explore atomic crystal-phase structures and ordered mesoscopic morphologies. Here, we report a simple synergistic templating strategy for the preparation of palladium–boron (Pd–B) nanoparticles with precisely controllable crystal-phases and highly ordered mesostructures. The engineering of crystal-phase structures at atomic levels is achieved by interstitially inserting metallic B atoms into face-centered cubic mesoporous Pd ( fcc -mesoPd) confined in a mesoporous silica template. With the gradual insertion of B atoms, fcc- mesoPd is transformed into fcc -mesoPd 5 B, hcp -mesoPd 2 B with randomly distributed B atoms ( hcp -mesoPd 2 B-r), and hcp -mesoPd 2 B with an atomically ordered B sequence ( hcp -mesoPd 2 B-o) while preserving well-defined mesostructures. This synergistic templating strategy can be extended to engineer crystal-phase structures with various mesostructures/morphologies, including nanoparticles, nanobundles, and nanorods. Moreover, we investigate the crystal-phase-dependent catalytic performance toward the reduction reaction of p -nitrophenol and find that hcp -mesoPd 2 B-o displays much better catalytic activity. This work thus paves a new way for the synthesis of hcp -Pd 2 B nanomaterials with mesoscopically ordered structure/morphology and offers new insights of fcc -to- hcp evolution mechanisms which could be applied on other noble metal-based nanomaterials for various targeted applications.

Precise Synthesis of Hollow Mesoporous Palladium–Sulfur Alloy Nanoparticles for Selective Catalytic Hydrogenation

“…Typically, mesoPd/KIT-6 hybrids, in which highly uniform mesoPd with an average nanoparticle size of 176 nm is solidly confined in KIT-6 (Figure S4), were first synthesized with a classic nanocasting method. 21,48,49 Then, the KEST process was conducted by physically mixed mesoPd/KIT-6 and sulfur powder with a weight ratio of 1:1 and directly heat-treated at 150 o C under N 2 atmosphere for 10 h. No solvent or extra reactants are needed in this step. After that, binary h-mesoPdS alloy nanoparticles were collected by washing with H 2 O/ethanol and HF to remove unreacted S and KIT-6 template (see Materials and Methods in Supporting Information (SI) for more details).…”

Mesoporosity‐Enabled Selectivity of Mesoporous Palladium‐Based Nanocrystals Catalysts in Semihydrogenation of Alkynes

“…The meso ‐Pd nanobundles were synthesized by a traditional nanocasting method with SBA‐15 as the hard template and Na 2 PdCl 4 as the Pd source, [8] while the meso ‐PdP alloy nanobundles were prepared by a concurrent template strategy with meso ‐Pd/SBA‐15 as the template and NaH 2 PO 2 as the P source (Figure S1, see Supporting Information for synthetic details). Here we mostly focused on the characterization of meso ‐PdP alloy nanobundles, since they were inherited from meso ‐Pd nanobundles (completely same mesostructure but different composition) and exhibited a better catalytic performance (see below).…”

Emerging interstitial/substitutional modification of Pd-based nanomaterials with nonmetallic elements for electrocatalytic applications

“…Meanwhile, the crystal phase can be controlled by the reaction temperature and time. Recently, Liu and co-workers also found that fcc mesoporous Pd (fcc-mesoPd) confined in a mesoporous silica template and dispersed in a THF solution of DMAB could respectively transform into fcc-mesoPd 5 B after heating at 100 °C for 4.5 h, hcp-mesoPd 2 B-r containing randomly distributed B atoms after heating at 140 °C for 5 h, and hcp-mesoPd 2 B-o containing an atomically ordered B sequence after heating at 160 °C for 5 h. 68 Apparently, the BOC-based synthesis method is effective to synthesize PdB x nanomaterials with a designed morphology and higher B contents. However, the high cost, instability and safety issues of BOCs cannot be ignored in modern catalysis synthesis processes.…”