Hydrogen Spillover Research Articles

Nanoscale intimacy in hierarchical catalytic structures for mediating furfural hydroconversion over Pd/CoxOy/SiAlOz

Precisely controlling nanoscale metal-acid intimacy of bifunctional catalysts is increasingly being exploited to improve the performance toward the tandem reactions. It remains a critical challenge to rationally design the spatial organization of dual-functional sites due to the lack of effective synthesis and material characterization methods at the nanoscale. Here we impose hierarchical structures into bifunctional catalysts, wherein Pd particles are controllably deposited on cobalt oxide (CoxOy) nanoglues, which themselves are dispersed on high-surface-area and acid silica-alumina (SiAlOz). The hydroconversion of furfural demonstrates that the catalytic performance is optimized by tailoring the intimacy between Pd and acid sites, that is, with an appropriate nanoscale rather than the closest intimacy. The conversion from furfural to cyclopentanone on hierarchical catalytic structures in Pd/CoxOy/SiAlOz undergoes the treble-site catalytic mechanism, comprising the dissociation of H2 on Pd, the preferential adsorption and hydrogenation of the carbonyl on CoxOy, followed by the hydrogenative ring-rearrangement of furfuryl alcohol intermediate on SiAlOz via the synergistic effect of acid sites and hydrogen spillover. Besides, the asynchronous catalysis resulting from Pd ensemble isolation from SiAlOz surface profoundly restrains the generation of tetrahydrofurfuryl alcohol by elongating the distance of hydrogen spillover, weakening the hydrogenation of the furan ring flat adsorbed on SiAlOz. Resultant Pd/CoxOy/SiAlOz-40 with an optimal Pd-acid intimacy delivers a conversion of 96% and selectivity toward cyclopentanone of 88%, outperforming most state-of-the-art noble metal catalysts. We anticipate that such a concept and synthesis strategy of hierarchical catalytic structures will extend the understanding of the metal-acid intimacy and provide a feasible approach for delicately regulating the location of functional sites in bifunctional catalysts, the results of which may enable the properties of multifunctional catalysts to be modulated to specific target processes.

Ex situ and in situ studies on structural features of Pt/Ce0.75Zr0.25O2 catalyst for water gas shift reaction

Pt/Ce1-xZrxO2 catalysts have shown high activity in water gas shift (WGS) reaction, but their structural organization has been studied insufficiently. This work represents a detailed structural study on the supported Pt species and the metal/support interface in a 5 wt% Pt/Ce0.75Zr0.25O2 catalyst in the initial state, after reductive activation, and after WGS reaction in H2-enriched reformate-simulating mixture. A wide range of methods was used: ex situ and in situ X-ray diffraction (XRD) studies, high resolution transmission electron microscopy (HRTEM), X-ray atomic pair distribution function (PDF) method, pseudo in situ X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR). The Ce0.75Zr0.25O2 mixed oxide was shown to provide a highly dispersed state of Pt species. XPS revealed that the initial catalyst contains Pt2+species. PDF analysis allowed us to propose the structure of ultrafine PtO particles and to elucidate the metal-support interaction with fixation of Pt ions on the support surface. In situ XRD, pseudo in situ XPS, and H2-TPR studies revealed the reduction of ultrafine PtO particles in H2 atmosphere at low temperatures (20–90°С) with the formation of metallic Pt0 particles and simultaneous partial reduction of the support surface due to the hydrogen spillover. Catalytic tests of the as-prepared and poisoned with chlorine 5wt% Pt/Ce0.75Zr0.25O2 catalysts in the WGS reaction showed an important role of the oxygen vacancies in the oxide support as active sites. These findings contribute to the understanding catalytic performance of Pt/Ce1-xZrxO2 systems.

Theoretical study of CO2 hydrogenation to methanol on modified Au/In2O3 catalysts: Effects of hydrogen spillover and activation energy prediction for hydrogen transfer

With the increasing attention in environmental issues caused by CO2 emissions, methanol conversion by CO2 hydrogenation is an effective strategy to solve this existing energy dilemma. The rationale behind hydrogen spillover on methanol synthesis is unraveled via density functional theory (DFT) calculations in this work, furthermore, the activation energy of hydrogen transfer process as affected by spillover is also summarized in a general paradigm for facilitating the understanding of hydrogenation characteristics. The results demonstrate that the spillover strategy significantly facilitates the hydrogenation reaction by supplying available hydrogen adatoms. This effect is particularly pronounced during the stage when OH is formed directly at the substrate site and combines with H to produce H2O, leading to a substantial reduction in activation energy from the initial 3.74 eV to 0.78 eV. In addition, a comprehensive predictive model for the kinetic characteristics of hydrogen spillover process is established based on the machine learning algorithm and SISSO guidance. By employing the combined approach of SISSO and neural network, we have achieved a stable prediction performance for activation energy with R2 = 0.99 and RMSE = 0.07 eV. The variable of ChgFSAu is identified as the most representative factor in describing the activation energy, demonstrating a correlation coefficient of -0.60. The extended multidimensional expression of DistAu further highlights its close connection to activation energy, achieving an RMSE value of 0.41 eV. To sum up, this work elucidates the possible thoughts of catalyst design with spillover effect and gives reference for the description screening towards the chemical reactions similar to hydrogen spillover.

Pt/Fe-TiO2-Catalyzed Selective Carbonyl Hydrogenation: Fe-Promoted Hydrogen Spillover

Pt/Fe-TiO₂-Catalyzed Selective Carbonyl Hydrogenation: Fe-Promoted Hydrogen Spillover

Promoting Catalytic Performance Involving Hydrogen Spillover by Ion Exchange of Pt@A Catalysts to Regulate Reactant Adsorption.

Zeolite-encapsulated metal nanoparticle systems have exhibited interesting catalytic performances via the hydrogen spillover process, yet how to further utilize the function of zeolite supports to promote catalytic properties in such a process is still challenging and has rarely been investigated. Herein, to address this issue, the strategy to strengthen the adsorption energy of reactant onto the zeolite surface via a simple ion exchange method has been implemented. Ion-exchanged linde type A (LTA) zeolite-encapsulated platinum nanoclusters (Pt@NaA, Pt@HA, Pt@KA, and Pt@CaA) were prepared to study the influence of ion exchange on the catalytic performance in the model reaction of hydrogenation of acetophenone to 1-phenylethanol. The reaction results showed that the Pt@CaA catalyst exhibited the best catalytic activity in the series of encapsulated catalysts, and the selectivity of 1-phenylethanol approached 100%. As revealed by density functional theory (DFT) calculations and acetophenone temperature-programmed desorption (acetophenone-TPD) experiments, in comparison with introduced cations of Na+, H+, and K+, ion-exchanged Ca2+ on the zeolite maximumly enhanced the adsorption of carbonyl groups in acetophenone, playing a critical role in achieving the highest activity and excellent catalytic selectivity among the Pt@A catalysts.

Hydrogenation of phenol by defective ZSM-5 supporting Ni catalyst to produce cyclohexanol

Cyclohexanol is an essential intermediate in the chemical industry, which can be produced from hydrogenation of phenol. In this work, a defective ZSM-5 zeolite supporting Ni catalyst (Ni/D-ZSM) is prepared by sequenced nitric acid treatment, impregnation, and reduction. In conversion of phenol, the highly dispersed Ni with strong interaction with the defective Si-OH delivers relative higher adsorption and spillover of active hydrogen, thus promoting the hydrogenation of phenol. Moreover, owing to the unique coordination environment of Ni in defective ZSM-5 zeolite with moderate acid properties, the desorption of intermediate cyclohexanol is promoted. The turnover frequency (TOF) calculated based on the yield of cyclohexanol and amount of metal reveals that, the Ni/D-ZSM sample by 48 h acid treatment (Ni/D-ZSM-48) delivers TOF values up to 17.73 × 10-3·s−1. The designed Ni/D-ZSM-48 catalyst with relative low Ni loading of ∼ 5 wt% delivers equivalent (slightly higher) production rates of cyclohexanol with the ever-reported noble-metal samples (Rh, Ru etc.) and significantly higher than the transition-metal based catalysts.

Hydrogen Spillover Phenomenon at the Interface of Metal-Supported Electrocatalysts for Hydrogen Evolution.

ConspectusHydrogen spillover, as a well-known phenomenon for thermal hydrogenation, generally involves the migration of active hydrogen on the surface of metal-supported catalysts. For thermocatalytic hydrogenation, hydrogen spillover generally takes place from metals with superiority for dissociating hydrogen molecules to supports with strong hydrogen adsorption under a H2 environment with high pressures. The former can bring high hydrogen chemical potential to largely reduce the kinetic barrier of the migration of active hydrogen species from metals to supports. At the same time, the latter can make H* migration thermodynamically spontaneous. For these reasons, hydrogen spillover is a common interfacial phenomenon occurring on metal-supported catalysts during thermocatalysis. Recently, this phenomenon has been observed for the exceptionally enhanced electrocatalytic performance for hydrogen evolution and other electrocatalytic organic synthesis. Different from hydrogen spillover for thermocatalysis under high H2 pressure, hydrogen spillover for electrocatalysis involves the migration of active hydrogen species (H*) from metals with strong hydrogen adsorption to supports with weak hydrogen adsorption, thereby suffering from a thermodynamically unfavorable process accompanied by a high kinetic barrier. Thus, the occurrence of hydrogen spillover at the electrocatalytic interface is not easy, and successful cases are rare. Understanding the underlying nature of hydrogen spillover at the electrocatalytic interface of metal-supported catalysts is critical to the rational design of advanced electrocatalysts.In this Account, we provide in-depth insights into recent advances in hydrogen spillover at the electrocatalytic interface for a significantly enhanced hydrogen evolution performance. Electron accumulation at the metal-support interface induces severe interfacial H* trapping and is recognized as the main factor in the failed hydrogen spillover. Given this, we developed two novel strategies to promote the occurrence of hydrogen spillover at the electrocatalytic interface. These strategies include (i) the introduction of ligand environments to enrich the local hydrogen coverage on metals and lower the barrier for interfacial hydrogen spillover and (ii) the minimization of work function difference between metals and supports (ΔΦ) to relieve electron accumulation and lower the kinetic barrier for hydrogen spillover. Also, we summarize the previously reported strategy of shortening the metal-support interface distance to lower the kinetic barrier for interfacial hydrogen spillover. Afterward, some criteria and methodologies are proposed to identify the hydrogen spillover phenomenon at the electrocatalytic interface. Finally, the remaining challenges and future perspectives are also discussed. Based on this Account, we aim to provide new insights into electrocatalysis, particularly the targeted control of hydrogen spillover at the electrocatalytic interface, and then to offer guidelines for the rational design of advanced electrocatalysts.

Natural Sunlight‐Driven CO2 Hydrogenation into Light Olefins at Ambient Pressure over Bifunctional Cu‐Promoted CoFe Alloy Catalyst

AbstractThe natural sunlight‐driven conversion of CO2 into valuable C2+ products is urgently being pursued at ambient pressure, yet it poses a substantial challenge. Herein, a bifunctional Cu‐promoted CoFe alloy catalyst is designed for the natural light‐driven CO2 hydrogenation into light olefins. Under a weak solar‐irradiation intensity of 0.45 kW m−2 (0.45 sun), the optimal catalyst exhibits excellent activity and selectivity, with an impressive 73.7% selectivity for C2+ hydrocarbons and an outstanding 56.5% selectivity for C2‐4 olefins, which is the best catalyst for C2+ hydrocarbons photosynthesis from natural sunlight to date. The bifunctional design of the catalyst combines the advantages of both metallic Cu and CoFe alloy components, providing a synergistic effect that enhances the CO2 hydrogenation performance. The Cu promoter plays a crucial role in enhancing the adsorption of CO2 and hydrogen spillover, while the CoFe alloy provides a stable coupling site of the C1 intermediate for promoting the C2‐4 olefins. This study provides new insights into the design of bifunctional catalysts for CO2 hydrogenation and opens up new possibilities for sustainable production of light olefins from renewable resources.

Tandem Electrocatalytic Alkyne Semihydrogenation over Bicomponent Catalysts through Hydrogen Spillover

AbstractElectrocatalytic alkyne semihydrogenation under mild conditions is a more attractive approach for alkene production than industrial routes but suffers from either low production efficiency or high energy consumption. Here, we describe a tandem catalytic concept that overcomes these challenges. Component (i), which can trap hydrogen effectively, is partnered with component (ii), which can readily release hydrogen for hydrogenation, to enable efficient generation of active hydrogen on component (i) at low overpotentials and timely (i)‐to‐(ii) hydrogen spillover and facile desorptive hydrogenation on component (ii). We examine this concept over bicomponent palladium‐copper catalysts for the production of representative 2‐methyl‐3‐butene‐2‐ol (MBE) from 2‐methyl‐3‐butyne‐2‐ol (MBY) and achieve a record high MBE production rate of 1.44 mmol h−1 cm−2 and a Faraday efficiency of ~88.8 % at a low energy consumption of 1.26 kWh kgMBE−1. With these catalysts, we further achieve 60 h continuous production of MBE with record high profit space.

Tandem Electrocatalytic Alkyne Semihydrogenation over Bicomponent Catalysts through Hydrogen Spillover.

Electrocatalytic alkyne semihydrogenation under mild conditions is a more attractive approach for alkene production than industrial routes but suffers from either low production efficiency or high energy consumption. Here, we describe a tandem catalytic concept that overcomes these challenges. Component (i), which can trap hydrogen effectively, is partnered with component (ii), which can readily release hydrogen for hydrogenation, to enable efficient generation of active hydrogen on component (i) at low overpotentials and timely (i)-to-(ii) hydrogen spillover and facile desorptive hydrogenation on component (ii). We examine this concept over bicomponent palladium-copper catalysts for the production of representative 2-methyl-3-butene-2-ol (MBE) from 2-methyl-3-butyne-2-ol (MBY) and achieve a record high MBE production rate of 1.44 mmol h-1 cm-2 and a Faraday efficiency of ~88.8 % at a low energy consumption of 1.26 kWh kgMBE -1. With these catalysts, we further achieve 60 h continuous production of MBE with record high profit space.

Oxygen-Vacancy-Induced Built-In Electric Field across MoCo Dual-Atomic Site Catalyst for Promoting Hydrogen Spillover in Hydrocracking and Hydrodesulfurization

Oxygen-Vacancy-Induced Built-In Electric Field across MoCo Dual-Atomic Site Catalyst for Promoting Hydrogen Spillover in Hydrocracking and Hydrodesulfurization

Substantial Impact of Built-in Electric Field and Electrode Potential on the Alkaline Hydrogen Evolution Reaction of Ru-CoP Urchin Arrays.

Although great efforts on the delicate construction of a built-in electric field (BIEF) to modify the electronic properties of active sites have been conducted, the substantial impact of BIEF coupled with electrode potential on the electrochemical reactions has not been clearly investigated. Herein, we designed an alkaline hydrogen evolution reaction (HER) catalyst composed of heterogeneous Ru-CoP urchin arrays on carbon cloth (Ru-CoP/CC) with a strong BIEF with the guidance of density functional theory (DFT) calculations. Impressively, despite its unsatisfactory activity at 10 mA cm-2 (overpotential of 44 mV), Ru-CoP/CC exhibited better activity (357 mV) than the benchmark Pt/C catalyst (505 mV) at 1 A cm-2 . Experimental and theoretical studies revealed that strong hydrogen adsorption on the interfacial Ru atoms created a high energy barrier for hydrogen desorption and spillover, resulting in unsatisfactory activity at low current densities. However, as the electrode potential became more negative (i.e., the current density increased), the barrier for hydrogen spillover from the interfacial Ru to the Co site, which had near-zero hydrogen adsorption energy, significantly decreased, thus greatly accelerating the whole alkaline HER process. This explains why the activity of Ru-CoP is relatively susceptible to the electrode potential compared to Pt/C.

Dual‐Type Ru Atomic Sites for Efficient Alkaline Overall Water Splitting

AbstractMonotypic catalytic site for bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at low overpotential is a grand challenge in alkaline water splitting. Herein, a new strategy of dual‐type atomic site‐support interaction is reported, in which ruthenium heteroatoms are in situ implanted into both the N‐C nanosheet matrix (Ru1‐N‐C) and supported Co2P nanoparticle lattice (Ru2‐P‐Co) for boosting alkaline water splitting. It is found that the Ru1‐N‐C and Ru2‐P‐Co can give rise to a synergistic effect for boosting HER and OER catalysis. Density functional theory calculations disclose that for HER, the Ru‐functionalized Co sites in Co2P assume the task of expediting H2O adsorption‐dissociation, and the adjacent coordination unsaturated Ru1‐N‐C sites can facilitate the following H2 desorption kinetic. The study found that the hydrogen spillover mechanism contributes to an ultralow HER polarization of 69 mV at 10 mA cm−2. While for OER, due to electronegativity discrepancies, the doped Ru within Co2P triggers electronic coupling, thereby efficiently tuning Ru d‐band center. This grants its electronic characteristic preferred for modulating rate‐determining step of OER to reduce the corresponding energy barrier, leading to superior OER catalytic activity . This work offers new understandings into catalyzing different reactions with multiple intermediate adsorptions by different atomic site‐support interplays.

Hydrogen Spillover Accelerates Electrocatalytic Semi-hydrogenation of Acetylene in Membrane Electrode Assembly Reactor.

Electrocatalytic acetylene semi-hydrogenation (EASH) offers a promising and environmentally friendly pathway for the production of C2H4, a widely used petrochemical feedstock. While the economic feasibility of this route has been demonstrated in three-electrode systems, its viability in practical device remains unverified. In this study, we designed a highly efficient electrocatalyst based on a PdCu alloy system utilizing the hydrogen spillover mechanism. The catalyst achieved an operational current density of 600 mA cm-2 in a zero-gap membrane electrode assembly (MEA) reactor, with the C2H4 selectivity exceeding 85%. This data confirms the economic feasibility of EASH in real-world applications. Furthermore, through in situ Raman spectroscopy and theoretical calculations, we elucidated the catalytic mechanism involving interfacial hydrogen spillover. Our findings underscore the economic viability and potential of EASH as a greener and scalable approach for C2H4 production, thus advancing the field of electrocatalysis in sustainable chemical synthesis.

Mediating trade-off between activity and selectivity in alkynes semi-hydrogenation via a hydrophilic polar layer

As a crucial industrial process for the production of bulk and fine chemicals, semi-hydrogenation of alkynes faces the trade-off between activity and selectivity due to undesirable over-hydrogenation. By breaking the energy linear scaling relationships, we report an efficient additive-free WO3-based single-atom Pd catalytic system with a vertical size effect of hydrogen spillover. Hydrogen spillover induced hydrophilic polar layer (HPL) with limited thickness on WO3-based support exhibits unconventional size effect to Pd site, in which over-hydrogenation is greatly suppressed on Pd1 site due to the polar repulsive interaction between HPL and nonpolar C=C bonds, whereas this is invalid for Pd nanoparticles with higher altitudes. By further enhancing the HPL through Mo doping, activated Pd1/MoWO3 achieves recorded performance of 98.4% selectivity and 10200 h−1 activity for semi-hydrogenation of 2-methyl-3-butyn-2-ol, 26-fold increase in activity of Lindlar catalyst. This observed vertical size effect of hydrogen spillover offers broad potential in catalytic performance regulation.

The interaction between Pd/CeO2 crystal surface and electric field: Application to complete oxidation of methane

Pd/CeO2 with different crystal faces can significantly affect the methane oxidation process, but the catalytic behavior in electric field is not clear yet. The supported Pd/CeO2 with rod, octahedral and cubic morphologies were synthesized by hydrothermal method, and their methane oxidation efficiency in electric field was measured. The structure of Pd/CeO2 and reaction mechanism in electric field were investigated by XRD, BET, XPS, H2-TPR, TEM and in situ DRIFTs. Studies show that the synergistic effect between electric field and (111) crystal plane in octahedral CeO2 is the strongest and (110) in rod CeO2 is the main active restraint crystal plane. The Pd atoms on the surface of Pd/CeO2-oct are exposed to the most amount of Pd atoms and the main Pd nanoparticles are present. Pd species on CeO2-cube and CeO2-rod surface with relatively low activity exist mainly in the form of Pd2+ and Pd4+, whereas Pd0 and Pd2+ on the Pd/CeO2-oct surface are more favorable for CH4 oxidation in the catalytic cycle. Pd4+ is inactive for CH4 oxidation. In addition, H migration from Pd active site to the support induced by hydrogen spillover can enhance the oxidation activity of CH4 in electric field. The conversion of carbonate/hydrogencarbonate to formate is an advantageous step in the methane oxidation process, with the active sequence being octahedral (111) > cubic (100) > rod (110) faces in/without electric field.

Interparticle Hydrogen Spillover in Enhanced Catalytic Reactions.

Interparticle hydrogen spillover is the phenomenon of H migration over different catalyst particles, which should be a physical mixture of at least two solid catalysts. In this review, we analyze examples of enhanced catalysis based on interparticle (reverse) hydrogen spillover. Simple physical mixtures of powdered catalysts containing metal catalysts of H2 dissociation/recombination and solid catalysts with active sites for substrate activation significantly enhance catalytic reactions. These reactions include aromatic hydrogenation, CO2 methanation, and the deoxydehydration of polyols, aromatization of lower paraffins, and direct coupling of benzene and alkanes. The acceleration effect and proposed reaction pathway of each example involving interparticle (reverse) hydrogen spillover are summarized. Simple reaction systems comprising physical mixtures of at least two powdery solid catalysts should enable unique catalysis in the future with the aid of interparticle (reverse) hydrogen spillover.

Controlled construction of Co3S4@CoMoS yolk-shell sphere for efficient hydrodesulfurization promoted by hydrogen spillover effect

A yolk-shell structured Co3S4@CoMoS catalyst was prepared through Oswald ripening method and subsequently used for hydrodesulfurization (HDS) reaction. The shells, constructed from Co-promoted MoS2 nanosheets, possess abundant active sites and facilitate the adsorption of reactants through the development of pore channels. The MoS2 sheets are arranged in a staggered and convoluted manner, creating numerous defect sites. The shorter MoS2 slabs provide a wide distribution of reactive sites, ensuring efficient reactions. The Co3S4 species within the inner core acts as an auxiliary active phase, inducing the hydrogen spillover effect in the HDS system. This facilitates the transfer of active hydrogen species to the CoMoS shell, where both CoMoS and Co3S4 phases synergistically enhance the HDS reaction. The Co3S4@CoMoS catalyst achieved up to 99.2% dibenzothiophene (DBT) conversion and 94.9% 4,6-dimethyldibenzothiophene conversion at the lower dosage (30 mg). The structure-activity relationships between active phase and HDS activity were investigated via in-situ infrared spectroscopy and other characterizations as well as density functional theory calculations.

Partial carbon encapsulation synthesis of separated Ni-Ag catalyst for efficient selective hydrogenation of acetylene: Synergizing hydrogen spillover and steric hindrance

The selective hydrogenation of acetylene is a vital process to for the purification of crude ethylene in petroleum industry. Achieving high activity and selectivity simultaneously over Ni-based catalysts is still challenging. Herein, a partial encapsulation strategy is proposed by fabricating carbon-encapsulated Ag nanoparticles and un-encapsulated Ni nanoparticles on Al2O3 surface (Ni-Ag@C/Al2O3) toward the enhanced selectivity without loss of activity. In particular, the Ni-Ag@C/Al2O3 exhibits higher ethylene selectivity of 81% at the complete acetylene conversion along with excellent stability for 30-h, in sharp with the Ni/Al2O3 (6%) and Ni-Ag/Al2O3 (54%) catalyst. The enhanced selectivity is attributed to the promotion of hydrogen spillover by the carbon species on Al2O3 surface and the inhibition of oligomer formation by a steric hindrance formed by the carbon layer on the Ag surface. This study provides a new structural design avenue of bifunctional bimetallic catalyst for selective hydrogenation reaction.

Theoretical Investigation of Hydrogen Adsorption and Hydrogen Spillover on Graphene Monolayer-Supported Single Transitional Metal Atoms

Theoretical Investigation of Hydrogen Adsorption and Hydrogen Spillover on Graphene Monolayer-Supported Single Transitional Metal Atoms