Composition Tuning of Ru-Based Phosphide for Enhanced Propane Selective Dehydrogenation

Facile Hydrogenolysis of Sugars to 1,2-Glycols by Ru@PPh3/OPPh3 Confined Large-Pore Mesoporous Silica

Tandem hydrogenation vis-à-vis hydrogenolysis of xylose to 1,2-glycols remains a major challenge. Although one-pot conversion of xylose to 1,2-glycols requires stringent conditions, a sustainable approach would be quite noteworthy. We have developed a microwave route for the one-pot conversion of pentose (C5) and hexose (C6) sugars into glycol and hexitol, without pressurized hydrogen reactors. A pronounced hydrogenolysis of sugars to glycols is observed by Ru single atom (SA) on triphenylphosphine/phosphine oxide-modified silica (Ru@SiP), in contrast to Ru SA on pristine (Ru@SiC) and 3-aminopropyl-modified silica (Ru@SiN). A promising "ligand effect" was observed through phosphine modification of silica that presents a 70% overall yield of all reduced sugars (xylitol + glycols) from a 99% conversion of xylose with Ru@SiP. A theoretical study by DFT depicts an electronic effect on Ru-SA by triphenylphosphine that promotes the catalytic hydrogenolysis of sugars under mild conditions. Hence, this research represents an important step for glycols from biomass-derived sources.

Hydroxyapatite-Derived Heterogeneous Ru-Ru2 P Electrocatalyst and Environmentally-Friendly Membrane Electrode toward Efficient Alkaline Electrolyzer

Alkaline membrane water electrolysis is a promising production technology, and advanced electrocatalyst and membrane electrode design have always been the core technology. Herein, an ion-exchange method and an environmentally friendly in situ green phosphating strategy are successively employed to fabricate Ru-Ru₂ P heterogeneous nanoparticles by using hydroxyapatite (HAP) as a phosphorus source, which is an exceptionally active electrocatalyst for hydrogen evolution reaction (HER). Density functional theory calculation results reveal that strong electronic redistribution occurs at the heterointerface of Ru-Ru₂ P, which modulates the electronic structure to achieve an optimized hydrogen adsorption strength. The obtained Ru-Ru₂ P possesses excellent HER performance (24 mV at 10 mA cm^-2 ) and robust stability (1000 mA cm^-2 for 120 h) in alkaline media. Furthermore, an environmentally friendly membrane electrode with a sandwich structure is assembled by HAP nanowires as an alkaline membrane, Ru-Ru₂ P as a cathodic catalyst, and NiFe-LDH as an anodic catalyst, respectively. The voltage of (-) Ru-Ru₂ P || NiFe-LDH/CNTs (+) (1.53 V at 10 mA cm^-2 ) is lower than that of (-) 20 wt% Pt/C || RuO₂ (+) (1.60 V at 10 mA cm^-2 ) for overall water splitting. Overall, the studies not only design an efficient catalyst but also provide a new route to achieve a high-stability electrolyzer for industrial H₂ production.

Transition Metal Phosphide Nanoarchitectonics for Versatile Organic Catalysis

Transition metal phosphides (TMP) posses unique physiochemical, geometrical, and electronic properties, which can be exploited for different catalytic applications, such as photocatalysis, electrocatalysis, organic catalysis, etc. Among others, the use of TMP for organic catalysis is less explored and still facing many complex challenges, which necessitate the development of sustainable catalytic reaction protocols demonstrating high selectivity and yield of the desired molecules of high significance. In this regard, the controlled synthesis of TMP-based catalysts and thorough investigations of underlying reaction mechanisms can provide deeper insights toward practical achievement of desired applications. This review aims at providing a comprehensive analysis on the recent advancements in the synthetic strategies for the tailored and tunable engineering of structural, geometrical, and electronic properties of TMP. In addition, their unprecedented catalytic potential toward different organic transformation reactions is succinctly summarized and critically analyzed. Finally, a rational perspective on future opportunities and challenges in the emerging field of organic catalysis is provided. On the account of the recent achievements accomplished in organic synthesis using TMP, it is highly anticipated that the use of TMP combined with advanced innovative technologies and methodologies can pave the way toward large scale realization of organic catalysis.

Ru-Ni Alloy Nanoparticles Loaded on N-Doped Amphiphilic Mesoporous Hollow Carbon@silica Spheres as Catalyst for the Hydrogenation of α-Pinene to cis-Pinane

N-doped mesoporous carbon spheres (NHMC@mSiO₂ ) encapsulated in silica shells were prepared by emulsion polymerization and domain-limited carbonization using ethylenediamine as the nitrogen source, and Ru-Ni alloy catalysts were prepared for the hydrogenation of α-pinene in the aqueous phase. The internal cavities of this nanomaterial are lipophilic, enhancing mass transfer and enrichment of the reactants, and the hydrophilic silica shell enhances the dispersion of the catalyst in water. N-doping allows more catalytically active metal particles to be anchored to the amphiphilic carrier, enhancing its catalytic activity and stability. In addition, a synergistic effect between Ru and Ni significantly enhances the catalytic activity. The factors influencing the hydrogenation of α-pinene were investigated, and the optimum reaction conditions were determined to be as follows: 100 °C, 1.0 MPa H₂ , 3 h. The high stability and recyclability of the Ru-Ni alloy catalyst were demonstrated through cycling experiments.

Ordered Hierarchical Porous Structure of PtSn/3DOMM-Al2O3 Catalyst for Promoting Propane Non-Oxidative Dehydrogenation

Herein, the hierarchical porous catalyst of 3-dimensional ordered macro-mesoporous (3DOMM) Al₂O₃ supported active PtSn nanoparticles (NPs) was prepared by the combined synthesized path of evaporation-induced self-assembly with colloid crystal template (EISA-CCT) methods. The hierarchical macro-mesoporous composite structure can markedly increase the specific surface area, accommodate the diffusion of propene, and decrease the number of surface acid sites. In addition, the special surface property and pore structure of 3DOMM-Al₂O₃ can modify the interaction between metals and substrates, as well as stabilize the metal nanoparticle, which promotes the formation of a highly active and stable PtSn phase. The PtSn/3DOMM-Al₂O₃ catalyst exhibits higher productivity and stability than PtSn/Al₂O₃ catalysts with macropore and mesopore structures. The PtSn/3DOMM-Al₂O₃ catalyst displays the best catalytic performance with propylene selectivity over 95% at a propane conversion of 33.9%. The study of the ordered hierarchical porous structure of PtSn/3DOMM-Al₂O₃ catalysts can contribute to obtaining improved catalysts in industrial processes.

The Role of Discrepant Reactive Intermediates on Ru-Ru2 P Heterostructure for pH-Universal Hydrogen Oxidation Reaction

Developing highly efficient electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cell (AEMFC). However, the kinetics of HOR in alkaline media is complicated, resulting in orders of magnitude slower than that in acid, even for the state-of-the-art Pt/C. Here, we find that Ru-Ru₂ P/C heterostructure shows HOR performance with a non-monotonous variation in a whole pH region. Unexpectedly, an inflection point located at pH≈7 is observed, showing an anomalous behavior that HOR activity under alkaline media surpasses acidic media. Combining experimental results and theoretical calculations, we propose the roles of discrepant reactive intermediates for pH-universal HOR, while H* and H₂ O* adsorption strengths are responsible for acidic HOR, and OH* adsorption strength is essential for alkaline HOR. This work not only sheds light on fundamentally understanding the mechanism of HOR but also provides new designing principles for pH-targeted electrocatalysts.

Controlled synthesis of Ru-single-atoms on ordered mesoporous phosphine polymers for microwave-assisted conversion of biomass-derived sugars to artificial sweeteners

Atomically dispersed metal-single-atoms have become a frontier in solid catalysis due to their characteristic electronic properties. However, for biomass conversion, employing metal-single-atoms as catalysts is rather challenging since they suffer from poor selectivity and yield due to inadequate metal-support interactions. We show here that Ru/triphenylphosphine (PPh)-based ordered mesoporous polymers afford high yields of reduced sugars, xylitol (yield ∼95%) and sorbitol (yield ∼65%) in a microwave reactor with formic acid as the only hydrogen donor. We have established a unique relationship within Ru/triphenylphosphine that shows an important ligand effect, in contrast to, Ru/triphenylamine and Ru/catechol. The tailored electronic properties in Ru/phosphine were thoroughly examined by using state-of-the-art experimental techniques viz. EXAFS, XANES, XPS, DRIFTS and HAADF-STEM. The resulting phosphine-modified catalysts show a promotion in activity and selectivity towards less vulnerable aldehydes for hydrogenation, further confirmed by DFT calculations. This finding reveals a new protocol to tailor the activity of metal-single-atoms utilizing functional porous polymers as nanoreactors.

Phosphorus-Alloying as a Powerful Method for Designing Highly Active and Durable Metal Nanoparticle Catalysts for the Deoxygenation of Sulfoxides: Ligand and Ensemble Effects of Phosphorus

The modification of metal nanoparticles (NPs) by incorporating additional metals is a key technique for developing novel catalysts. However, the effects of incorporating nonmetals into metal NPs have not been widely explored, particularly in the field of organic synthesis. In this study, we demonstrate that phosphorus (P)-alloying significantly increases the activity of precious metal NPs for the deoxygenation of sulfoxides into sulfides. In particular, ruthenium phosphide NPs exhibit an excellent catalytic activity and high durability against sulfur-poisoning, outperforming conventional catalysts. Various sulfoxides, including drug intermediates, were deoxygenated to sulfides with excellent yields. Detailed investigations into the structure-activity relationship revealed that P-alloying plays a dual role: it establishes a ligand effect on the electron transfer from Ru to P, facilitating the production of active hydrogen species, and has an ensemble effect on the formation of the Ru-P bond, preventing strong coordination with sulfide products. These effects combine to increase the catalytic performance of ruthenium phosphide NPs. These results demonstrate that P-alloying is an efficient method to improve the metal NP catalysis for diverse organic synthesis.

Ethane dehydrogenation performance and high temperature stability of silica supported cobalt phosphide nanoparticles

Cobalt phosphide catalysts exhibit remarkable stability and selectivity for ethane dehydrogenation.

Construction of a Unique Structure of Ru Sites in the RuP Structure for Propane Dehydrogenation

It is an important task to develop low-cost and anticoking catalysts for the propane dehydrogenation (PDH) reaction. In this work, the P element is introduced to the Ru-based catalyst to obtain Ru sites with a unique structure and the obtained Ru_xP_y (x/y = 2:1, 1:1, 1:2) catalysts are then employed in PDH. Density functional theory (DFT) results show that the addition of P leads to the formation of separated Ru sites and the adjustment of the valance band state of Ru. The upward shift of the d-band center leads to a reduction of the reaction energy barrier for dehydrogenation of propane and an enhancement of catalytic activity. The analysis of the competition between propylene deep dehydrogenation and propylene desorption for each catalyst shows that desorption of propylene is preferred on the RuP(112) surface. Considering both catalytic activity and propylene selectivity, the RuP catalyst is potential for the propane dehydrogenation reaction. On the RuP surface, the PDH reaction proceeds by the dehydrogenation of the H atom on the methylene group (isopropyl pathway), thus restraining the deep dehydrogenation of propylene. The Ru_xP_y catalysts are also synthesized in experiments, and PDH evaluation shows that the RuP structure is a remarkable PDH catalyst with a stable structure, anticoking ability, and low cost.

Spatially isolated cobalt oxide sites derived from MOFs for direct propane dehydrogenation

The "active site isolation" strategy has been proved to be efficient for enhancing the catalytic performance in propane dehydrogenation (PDH). Herein, spatially isolated cobalt oxide sites within nitrogen-doped carbon (NC) layers supported on silicalite-1 zeolite (CoO_x@NC/S-1) were synthesized by a two-step process consisting of the pyrolysis of bimetallic Zn/Co zeolitic imidazole frameworks loaded on silicalite-1 (ZnCo-ZIF/S-1) under N₂ and the subsequent calcination in air atmosphere. This catalyst possesses exceptional catalytic performance for PDH with the propane conversion of 40% and the propene selectivity of >97%, and no apparent deactivation is observed after 10 h PDH reaction at 600 °C. With intensive characterizations and experiments, it is indicated that the real active sites of CoO_x@NC/S-1 are isolated CoO sites during the PDH process. In situ FT-IR spectroscopy shows the same intermediate product (Co-C₃H₇) during both propane dehydrogenation and propene hydrogenation, indicating that they have a reverse reaction process, and a reaction mechanism for PDH is proposed accordingly.

Subsurface-Regulated PtGa Nanoparticles Confined in Silicalite-1 for Propane Dehydrogenation

Propane dehydrogenation (PDH) is one of the most promising techniques to produce propylene. Industrial Pt-based catalysts often suffer from short-time stability under high temperature due to serious sintering and coke deposition via undesired side reactions. Detailed reaction mechanism on the surface of Pt-based nanoparticle has been well studied, while the subsurface effect remains mostly unstudied. Herein, supported PtGa nanoparticles with different surface and subsurface composition was evidenced by extended X-ray absorption fine structure (EAXFS) spectra and energy dispersive X-ray spectroscopy (EDS). Theoretical simulation demonstrated subsurface regulation would increase the electron density of surface Pt and thus weaken propylene adsorption. Propylene selectivity on the PtGa-subsurface nanoparticles was up to 98% at 600 °C while that on the Pt-subsurface nanoparticles was only 95%. Furthermore, rational designed PtGa alloy nanoparticles were encapsulated in MFI zeolite to inhibit sintering and coke deposition for enhanced catalytic stability.

Recent progress in heterogeneous metal and metal oxide catalysts for direct dehydrogenation of ethane and propane

Metal and metal oxide catalysts for non-oxidative ethane/propane dehydrogenation are outlined with respect to catalyst synthesis, structure–property relationship and catalytic mechanism.