Palladium Nanoparticles Inset into the Carbon Sphere with Robust Acid Resistance for Selective Hydrogenation of Chloronitrobenzene

Enhanced nitrate reduction by metal deposited g-C3N4/rGO/TiO2 Z-schematic photocatalysts: Performance and mechanism comparison of Pd-Cu and Ag

Deposition of bimetals on Z-scheme photocatalysts has been reported to improve the nitrate nitrogen (NO3-) reduction properties. However, it is not clear whether bimetal deposition possesses advantage over single metal deposition and what is the different reaction mechanisms. In this work, the g-C3N4(Pd-Cu)/rGO/TiO2 and g-C3N4(Ag)/rGO/TiO2 composites with bimetallic Pd-Cu and single metal Ag deposited on the graphitic carbon nitride/reduced graphene oxide/titanium dioxide (g-C3N4/rGO/TiO2) Z-scheme photocatalyst were prepared, and their photocatalytic NO3- reduction properties and the mechanisms under visible light irradiation were studied. The results showed that the NO3- and total nitrogen (TN) removal efficiencies of g-C3N4(Pd-Cu)/rGO/TiO2 were 57.78% and 20.1%, respectively, 1.15 and 1.72 times higher than those of g-C3N4(Ag)/rGO/TiO2. This can be ascribed to that Pd-Cu enriched more electrons and absorbed more NO3- molecules due to the different charge densities, and the NO3- reduction process were enhanced by the staged NO3-→NO2- and NO2-→N2/NH4+ processes on Cu and Pd. The effects of reductive species were demonstrated to be photogenerated electrons > ·OH (·CO2-) > ·O2- in g-C3N4(Ag)/rGO/TiO2, while it was photogenerated electrons > ·O2- > ·OH (·CO2-) in g-C3N4(Pd-Cu)/rGO/TiO2, which may be caused by the better O2 reduction property of the latter. Finally, the cyclic experiment proved the good stability of both materials. This work provided some reference for design of metal deposited Z-scheme photocatalysts for various reduction reactions.

A well-fabricated Ru@C material derived from Ru/Zn-MOF with high activity and stability in the hydrogenation of 4-chloronitrobenzene

4-Chloroaniline (4-CAN) plays an important role in chemical and industrial production. However, it remains a challenge to avoid the hydrogenation of the C-Cl bond in the synthesis process to improve selectivity under high activity conditions. In this study, we in situ fabricated ruthenium nanoparticles (Ru NPs) containing vacancies inserted into porous carbon (Ru@C-2) as a highly efficient catalyst for the catalytic hydrogenation of 4-chloronitrobenzene (4-CNB) with remarkable conversion (99.9%), selectivity (99.9%), and stability. Experiments and theoretical calculations indicate that the appropriate Ru vacancies affect the charge distribution of the Ru@C-2 catalyst, promote the electron transfer between the Ru metal and support, and increase the active sites of the Ru metal, thus facilitating the adsorption of 4-CNB and the desorption of 4-CAN to improve the activity and stability of the catalyst. This study can provide some enlightenment for the development of new 4-CNB hydrogenation catalysts.

Pyridinic nitrogen dominated doping on Pd/carbon catalysts for enhanced hydrogenation performance

The hydrogenation of 4-carboxylbenzaldehyde over Pd catalysts is a crucial process during the production of pure terephthalic acid. Herein, ZIF-8 derived carbon materials (NC) with adjustable N types were synthesized and used as the supports of Pd catalysts. Pd supported on NC with 50.5% of pyridinic N exhibited best hydrogenation activity with a TOF value of 4.1 min-1. The microstructures of NC support and electronic structures of Pd in Pd/NC were investigated by techniques such as XRD, N2 physisorption, XPS, H2-O2 titration and TEM. The nitrogen species in CN surface not only can adjust chemical state and dispersion of Pd nanoparticles (NPs), but also promote the adsorption and activation capability of H2 molecular. Besides, the ratio of Pd0/Pd2+ and Pd dispersion were closely correlated with pyridinic nitrogen content. The improvement in hydrogenation activity and stability of Pd/CN catalyst in relative to Pd/C were ascribed to the synergistic effect of pyridinic nitrogen and active site Pd0.