Nanoparticulate Ru on TiO2 exposed the {1 0 0} facets: Support facet effect on selective hydrogenation of benzene to cyclohexene

Hydrogen Spillover-Enhanced Heterogeneously Catalyzed Hydrodeoxygenation for Biomass Upgrading

Hydrodeoxygenation (HDO) is regarded as a promising technology for biomass upgrading to obtain sustainable and competitive chemicals and fuels. In fact, biomass HDO over heterogeneous solid catalysts is often accompanied by the phenomenon of hydrogen spillover, which further affects the catalytic performance. Thus, it is necessary to gain in-depth understand the promoting effect of hydrogen spillover in the biomass HDO process to obtain desired conversion and selectivity. This Review summarized the extensive research on hydrogen spillover in biomass refining and discussed in detail the regulation mechanism of hydrogen spillover in biomass HDO process, mainly by regulating different active center sites on catalyst supports, such as metal sites, acid sites, surface functional groups, and defective sites, which exhibit independent and synergistic characteristics promoting catalyst activity, selectivity, and stability. Finally, the prospective of hydrogen spillover in biomass HDO applications was critically evaluated, and the key technical challenges in developing "hydrogen-free" HDO and upgrading biofuels were highlighted. The presentation of hydrogen spillover-enhanced catalytic biomass HDO in this Review will hopefully provide insight and guidance for further development of efficient catalysts and preparation of high-value chemicals in the future.

Engineering the geometric and electronic structure of Ru via Ru–TiO2 interaction for enhanced selective hydrogenation

Ru/TiO2-Vo-250H with the structure of TiO2-Vo-partially encapsulated Ru nanoparticles, balances the active sites for H2 dissociation and the adsorption sites for 6-chloroquinoline, achieving the selective hydrogenation even at room temperature.

Effect of ZnSO4, MnSO4 and FeSO4 on the Partial Hydrogenation of Benzene over Nano Ru-Based Catalysts

Nano Ru-based catalysts, including monometallic Ru and Ru-Zn nanoparticles, were synthesized via a precipitation method. The prepared catalysts were evaluated on partial hydrogenation of benzene towards cyclohexene generation, during which the effect of reaction modifiers, i.e., ZnSO₄, MnSO₄, and FeSO₄, was investigated. The fresh and the spent catalysts were thoroughly characterized by XRD, TEM, SEM, XPS, XRF, and DFT studies. It was found that Zn²⁺ or Fe²⁺ could be adsorbed on the surface of a monometallic Ru catalyst, where a stabilized complex could be formed between the cations and the cyclohexene. This led to an enhancement of catalytic selectivity towards cyclohexene. Furthermore, electron transfer was observed from Zn²⁺ or Fe²⁺ to Ru, hindering the catalytic activity towards benzene hydrogenation. In comparison, very few Mn²⁺ cations were adsorbed on the Ru surface, for which no cyclohexene could be detected. On the other hand, for Ru-Zn catalyst, Zn existed as rodlike ZnO. The added ZnSO4 and FeSO₄ could react with ZnO to generate (Zn(OH)₂)₅(ZnSO₄)(H₂O) and basic Fe sulfate, respectively. This further benefited the adsorption of Zn²⁺ or Fe²⁺, leading to the decrease of catalytic activity towards benzene conversion and the increase of selectivity towards cyclohexene synthesis. When 0.57 mol·L⁻¹ of ZnSO₄ was applied, the highest cyclohexene yield of 62.6% was achieved. When MnSO₄ was used as a reaction modifier, H₂SO₄ could be generated in the slurry via its hydrolysis, which reacted with ZnO to form ZnSO₄. The selectivity towards cyclohexene formation was then improved by the adsorbed Zn²⁺.

Mechanistic insights into the contribution of Lewis acidity to brominated VOCs combustion over titanium oxide supported Ru catalyst

CH₃Br catalytic oxidation as the probe reaction was investigated over Ru supported on TiO₂ with different crystalline phases. 1% Ru/anatase TiO₂ (a-TiO₂) exhibited superior stability at 240 °C after a 180 h time-on-stream run. And there was an induced activation for 1% Ru/a-TiO₂ during the initial 60 h reaction. Then the activity sustained stable. To elucidate the intrinsic mechanism, a series of characterizations were performed such as XRD, CO-Pulse, H₂-TPR, XPS and NH₃-TPD etc. Results showed that the Ru particle size increased and the Ru⁰ content decreased as the reaction proceeded, which were not conductive to the reaction. It was assumed that the catalytic activity was strongly dependent on other factors. In combination with NH₃-TPD and Py-FTIR measurements, it was confirmed that the enhanced activity and stability was strongly associated with the surface acidity, especially moderate strong Lewis acid (L acid). The increase of the acid amount and acidity strength was led by the generation and adsorption of HBr, Br₂ and RuO_xBr_y during the reaction, among which HBr and Br₂ was easier to desorb at 250 °C. While moderate strong L acid was sourced from the formation of RuO_xBr_y. The addition of transition metal (Ce, Co, Mn, Nb and Ni) further validated that the moderate strong L acid played a decisive role in the CH₃Br catalytic oxidation.

Highly dispersed copper cobalt oxide nanoclusters decorated carbon nitride with efficient heterogeneous interfaces for enhanced H2 evolution

Photocatalytic reaction refers to a sophisticated heterogeneous catalyzing process. Exploring the interfacial reaction of catalysts will provide insights into efficient artificial photosynthetic system and promote its design. In this study, highly dispersed bimetallic CuCo₂O₄ nanoclusters decorated g-C₃N₄ heterojunction photocatalyst was produced by in-situ deposition of 0D CuCo₂O₄ spinel on the 2D g-C₃N₄ surface. Compared with CuO or Co₃O₄ modified g-C₃N₄, the optimal composite exhibits a significantly higher H₂ evolution rate of 4187.6 μmol∙g_cat^-1∙h^-1 with an apparent quantum yield (AQY) of 4.57% under the irradiation of monochromatic light (400 ± 7.5 nm) in the absence of noble metal. As suggested from the results of the photoelectrochemistry characterizations and NH₃-temperature programmed desorption (NH₃-TPD) analysis, CuCo₂O₄/g-C₃N₄ exhibited faster HER kinetics and considerable surface acidity sites, and it facilitated triethanolamine (TEOA) chemisorption and H₂ evolution, further highlighting the merits of such mixed-metal compounds. Moreover, the transfer pathway of charge carriers between CuCo₂O₄ and g-C₃N₄ heterogeneous interface was demonstrated by photo-degradation of RhB and selective photo-deposition Pt nanoparticles.

Facet engineering in metal organic frameworks to improve their electrochemical activity for water oxidation

We present a facile and low-cost method to shape ZIF into 2D nanosheets with exposed (002) facets and discover that they exhibit excellent activity for oxygen evolution reaction.