Highly Efficient Hydrogen Production from Dehydrogenation Reaction of Nitrogen Heterocycles via Pd⁰–Pd^δ+ Synergistic Catalysis

Abstract

Hydrogen shows great potential as a clean energy source, but its safe and efficient storage/transportation is a crucial issue for the development of hydrogen economy; therefore, the use of liquid organic hydrogen carriers for reversible hydrogen storage has attracted considerable attention. Herein, we report palladium catalysts supported on a series of rod-like Al 2 O 3 with different crystal phases (amorphous, γ, δ, and α), which are employed in hydrogen production from dehydrogenation reaction of dodecahydro-N-ethylcarbazole (12H-NECZ). The optimized 3Pd/Al 2 O 3 -γ catalyst, which is featured by a high distribution of Pd nanoparticles (∼3 nm) on the Al 2 O 3 -γ support with unique Pd 0 −Pd δ+ interfacial sites, exhibits good catalytic performance with a complete conversion of 12H-NECZ, a hydrogen selectivity of 99% within 2.0 h. The turnover frequency value reaches up to 281.2 min −1 , and H 2 production rate attains 0.66 mol H2 g Pd −1 min −1 at 180 °C, which are preponderant to the state-of-the-art catalysts. An in-depth investigation based on in situ characterizations (Fourier transform infrared and temperature-programmed surface reaction with mass spectrometry pulse measurements), kinetic studies, H/D isotope exchange, and density functional theory calculations demonstrates that Pd 0 −Pd δ+ synergistic catalysis plays a crucial role in the C−H bond cleavage of 4H-NECZ (the rate-determining step): the surface Pd 0 site facilitates the activation adsorption of 4H-NECZ, which reduces the reaction energy barrier of C−H bond rupture, while the interface Pd δ+ site boosts the desorption of final products (H 2 and NECZ). The high performance dehydrogenation catalyst developed in this work shows potential applications in chemical hydrogen storage.

Facile Synthesis of Multifunctional Ni(OH)2‐Supported Core‐Shell Ni@Pd Nanocomposites for the Electro‐Oxidation of Small Organic Molecules

“…What's more, different Pd 3d spectra are observed in the as‐prepared series of Pd‐based NCs. In details, the percent of Pd δ+ in Ni(OH) 2 /Ni 16 @Pd NCs (15.7 %) is smaller than that of Ni(OH) 2 /Ni 8 @Pd NCs (22.5 %) and Ni(OH) 2 /Ni 32 @Pd NCs (41.1 %) (Figure S6 and Table S2), which indicates the strong electronic effect and the formation of more Pd 0 in CS Ni 16 @Pd NPs [13c,d] …”

High-Rate and Selective C2H6-to-C2H4 Photodehydrogenation Enabled by Partially Oxidized Pdδ+ Species Anchored on ZnO Nanosheets under Mild Conditions

“…The high-resolution TEM (HRTEM) image in Figure B,C clearly showed the lattice plane spacings of 0.288 nm with a dihedral angle of 60°, which were indexed to the (100) and (010) planes of hexagonal wurtzite ZnO . Meanwhile, the nanoparticles displayed an interplanar spacing of 0.230 nm, corresponding to the (111) planes of cubic Pd. − Additionally, the powder X-ray diffraction (XRD) patterns in Figure S3 could be well indexed to hexagonal ZnO (JCPDS no. 36-1451) and cubic Pd (JCPDS no.…”

Facilitating the dry reforming of methane with interfacial synergistic catalysis in an Ir@CeO2−x catalyst

“…8 , the (110) facet is predominantly exposed accompanied with minor (111) facet, consistent with the previous reports 41 , 42 . As a control sample, 0.6% Ir/Al 2 O 3 displays a larger particle size (~1.3 nm) and a lower dispersion (~65%) relative to 0.6% Ir/CeO 2− x , along with lattice spacings of ~0.19 and ~0.23 nm ascribed to (400) and (311) planes of Al 2 O 3 43 . In addition, the aberration-correction high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) was conducted to explore detailed structure of Ir/CeO 2− x .…”