Hydrogen Spillover Process Research Articles

Fischer-Tropsch synthesis: Platinum promoted Co@HCS catalysts

Hollow carbon sphere (HCS) nanoreactors were used as a catalyst support for Co, with Pt as a promoter. The hollow morphology of the HCSs nanoreactor was exploited to study the influence of the Pt promoter nanoparticle location relative to that of the Co3O4 (Co 10 wt%) nanoparticles (dCo = 3.5 – 12.5). Furthermore, the effect of Pt on the reduction behaviour and activity of the Co FTS catalyst was evaluated. The synthesis and use of Pt nanoparticles supported on/in Co@HCS FT catalysts to give CoPt@HCS and Pt/(Co@HCS) catalysts are reported. Electron microscopy, ex situ PXRD, BET, and TPR studies revealed that the prepared catalysts were successfully synthesized with well dispersed Co nanoparticles. It was observed that the proximity between the Co and Pt influenced the Co hcp/fcc ratios. A secondary hydrogen spillover effect was invoked to account for the reduction of Co3O4 on 1Pt/(10Co@HCS) at 335 °C. The complete reduction of Co3O4 to Co metal on 10Co1Pt@HCS at 350 °C was attributed to a primary hydrogen spillover effect. Following catalyst activation at 350 °C, the primary spillover process resulted in a catalyst exhibiting higher Fischer–Tropsch activity (approximately 2×) compared to both the unpromoted catalyst and catalysts where Pt and Co were separated by the HCS. This enhanced activity was partially attributed to the Co phases formed on the carbon support during reduction and the degree of catalyst reduction, which depended on the type of hydrogen spillover process. A comparison of the reduction ability of Os, Ru and Pt on the reduction of Co supported on/in HCSs and the impact of the promoter on Co hcp/fcc ratios is reported.

Bridging Nickel-MOF and Copper Single Atoms/Clusters with H-Substituted Graphdiyne for the Tandem Catalysis of Nitrate to Ammonia.

Interfacial engineering of synergistic catalysts is one of the keys to achieving multiple proton-coupled electron transfer processes in nitrate-to-ammonia conversion. Herein, by joining ultrathin nickel-based metal-organic framework (denoted Ni-MOF) nanosheets with few-layered hydrogen-substituted graphdiyne-supported copper single atoms and clusters (denoted HsGDY@Cu), a tandem catalyst of Ni-MOFs@HsGDY@Cu with dual-active interfaces was developed for the concerted catalysis of nitrate-to-ammonia. In such a system, the sandwiched HsGDY layer could serve as a bridge to connect the coordinated unsaturated Ni2+ sites with Cu single atoms/clusters in a limited range of 0 to 3.6 nm. From Ni2+ to Cu, via the hydrogen spillover process, the hydrogen radicals (H⋅) generated at the unsaturated Ni2+ sites could migrate across HsGDY to the Cu sites to participate in the transformation of *HNO3 to NH3. From Cu to Ni2+, bypassing the higher reaction energy for *HNO3 formation on the Ni2+ sites, the NO2 - detached from the Cu sites could diffuse onto the unsaturated Ni2+ sites to form NH3 as well. The combined results make this hybrid a tandem catalyst with dual active sites for the catalysis of nitrate-to-ammonia conversion with improved Faradaic efficiency at lower overpotentials.

Bridging Nickel‐MOF and Copper Single Atoms/Clusters with H‐Substituted Graphdiyne for the Tandem Catalysis of Nitrate to Ammonia

AbstractInterfacial engineering of synergistic catalysts is one of the keys to achieving multiple proton‐coupled electron transfer processes in nitrate‐to‐ammonia conversion. Herein, by joining ultrathin nickel‐based metal–organic framework (denoted Ni‐MOF) nanosheets with few‐layered hydrogen‐substituted graphdiyne‐supported copper single atoms and clusters (denoted HsGDY@Cu), a tandem catalyst of Ni‐MOFs@HsGDY@Cu with dual‐active interfaces was developed for the concerted catalysis of nitrate‐to‐ammonia. In such a system, the sandwiched HsGDY layer could serve as a bridge to connect the coordinated unsaturated Ni2+ sites with Cu single atoms/clusters in a limited range of 0 to 3.6 nm. From Ni2+ to Cu, via the hydrogen spillover process, the hydrogen radicals (H⋅) generated at the unsaturated Ni2+ sites could migrate across HsGDY to the Cu sites to participate in the transformation of *HNO3 to NH3. From Cu to Ni2+, bypassing the higher reaction energy for *HNO3 formation on the Ni2+ sites, the NO2− detached from the Cu sites could diffuse onto the unsaturated Ni2+ sites to form NH3 as well. The combined results make this hybrid a tandem catalyst with dual active sites for the catalysis of nitrate‐to‐ammonia conversion with improved Faradaic efficiency at lower overpotentials.

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.

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.

The critical role of Ru-like hydrogen adsorption of carbon dots in a carbon-confined Ru system for boosted HER activity

Ru/NCDs with ruthenium (Ru) nanoparticles loaded on N-doped carbon dots were constructed. The confinement effect and Ru-like hydrogen adsorption capacity of NCDs effectively facilitate the hydrogen spillover process and boost the HER activity.

Selective hydrogenation of furfural to furfuryl alcohol through hydrogenation spillover over amorphized HA zeolite encapsulated platinum clusters

Design of heterogeneous catalyst to achieve efficient conversion of biomass to high added-value chemicals is still very attractive. Herein, taking industrially important selective hydrogenation of furfural to furfuryl alcohol as an example, the designed amorphized HA zeolite encapsulation of platinum clusters (denoted as Pt@HA) exhibited excellent catalytic selectivity at totally conversion of the reactant furfural, along with good reusability and poison resistance ability. The selected amorphized HA zeolite with very small pore size constrained the reactant furfural to be reacted through hydrogen spillover process at zeolite surface, instead of to be adsorbed and activated onto Pt surface. Resulting from the stronger interaction between nucleophilic oxygen atom of aldehyde group and acid site at HA zeolite surface than that of furan ring group, furfural preferred to adsorb onto Pt@HA surface with the end of aldehyde group rather than the end of furan ring group, thus facilitating the spilled H atom to react with aldehyde group to give desired furfuryl alcohol product exclusively.

The Superaerophobic N-Doped Carbon Nanocage with Hydrogen Spillover Effort for Enhanced Hydrogen Evolution.

Under the high current density, the excessive strong adsorption of H* intermediates and H2 accumulation the catalysts are the major obstacle to the industrial application of hydrogen evolation reaction (HER) catalysts. Herein, through experimental exploration, it is found that the superaerophobic Nitrogen (N)-doped carbon material can promote the rapid release of H2 and provide H* desorption site for the hydrogen spillover process, which makes it have great potential as the catalysts support for hydrogen spillover. Based on this discovery, this work develops the hydrogen spillover catalyst with electron-rich Pt sites loaded on N-doped carbon nanocage (N-CNC) with adjustable work function. Through a series of comprehensive electrochemical tests, the existence of hydrogen spillover effort has been proved. Moreover, the in situ tests showed that pyrrolic-N can activate adjacent carbon sites as the desorption sites for hydrogen spillover. The Pt@N-1-CNC with the minimum work function difference (ΔΦ) between Pt NPs and support shows superior hydrogen evolution performance, only needs overpotential of 12.2mV to reach current density of 10mA cm-2 , outstanding turnover frequency (TOF) (44.7 s-1 @100mV) and superior durability under the 360h durability tests at current density of 50mA cm-2 .

Enhanced Catalytic Selectivity in Hydrogenation of Substituted Nitroarenes through Hydrogen Spillover over Sodalite Zeolite Encapsulated Platinum Clusters

AbstractHerein, we reported that the platinum (Pt) clusters encapsulated into sodalite (SOD) zeolite as catalyst exhibited 100 % selectivity at 100 % conversion in the selective hydrogenation of p‐chloronitrobenzene to p‐chloroaniline via hydrogen spillover. The direct interaction between p‐chloronitrobenzene and encapsulated Pt was prevented by the shape selectivity of SOD zeolite, reactants were thereby adsorbed onto zeolite outer surface to facilitate the hydrogenation proceeding by hydrogen spillover process. The further kinetic study and DFT calculation showed the excellent catalytic selectivity was ascribed to the much faster rate of hydrogenation of adsorbed nitro group than that of adsorbed C−Cl group.

Co-self-assembly of lignin and tannin: A novel catalyst support for hydrogenation of lignin-derived aldehydes

Co-self-assembly of lignin oligomers together with other structurally similar molecules can provide composite particles with functional properties for specific applications. Herein, tannin was co-self-assembled for the first time with lignin oligomers into novel lignin–tannin particles (LxTy), induced by a dual driven force with π–π stacking interaction and hydrogen bonds. Abundant ortho-phenolic hydroxyl groups of tannin cause the efficient adsorption and partial reduction of Pd2+ ions (36.7%) by LxTy (>99%) to obtain Pd/LxTy with highly dispersed Pd nanoparticles, thereby avoiding the need for surfactants or reducing agents. Aldehyde groups of lignin-derived aldehydes could preferentially interact with phenolic hydroxyl groups on the hydrophilic shell of Pd/LxTy. Then, mitigated active hydrogen atoms on the LxTy support during the hydrogen spillover process induced a H-shift to C of −CO through a water bridge with low energy barrier and consequently selective hydrogenation to obtain lignin-derived alcohols at 30 °C.

Enhanced photocatalytic hydrogen evolution of Ru/TiO2-x via oxygen vacancy-assisted hydrogen spillover process

Hydrogen spillover effects will significantly improve the activity of photocatalytic hydrogen evolution reactions (HER), while their introduction and optimization require the construction of an excellent metal/support structure. In this study, we have synthesized Ru/TiO2-x catalysts with controlled oxygen vacancy (OVs) concentrations using a simple one-pot solvothermal method. The results show that Ru/TiO2-x3 with the optimal OVs concentration exhibits an unprecedentedly high H2 evolution rate of 13604 μmol·g−1·h−1, which was 45.7 and 2.2 times higher than that of TiO2-x (298 μmol·g−1·h−1) and Ru/TiO2 (6081 μmol·g−1·h−1). Controlled experiments, detailed characterizations, and theoretical calculations have revealed that the introduction of OVs on the carrier contributes to the hydrogen spillover effect in the metal/support system photocatalyst and that the process of hydrogen spillover in this system can be optimized by modulating the OVs concentration. This study proposes a strategy to decrease the energy barrier of hydrogen spillover and enhance photocatalytic HER activity. Moreover, it investigates the effect of OVs concentration on the hydrogen spillover effect in the photocatalytic metal/supports system.

Sub-nm RuOx Clusters on Pd Metallene for Synergistically Enhanced Nitrate Electroreduction to Ammonia.

The electrochemical nitrate reduction to ammonia reaction (NO3RR) has emerged as an appealing route for achieving both wastewater treatment and ammonia production. Herein, sub-nm RuOx clusters anchored on a Pd metallene (RuOx/Pd) are reported as a highly effective NO3RR catalyst, delivering a maximum NH3-Faradaic efficiency of 98.6% with a corresponding NH3 yield rate of 23.5 mg h-1 cm-2 and partial a current density of 296.3 mA cm-2 at -0.5 V vs RHE. Operando spectroscopic characterizations combined with theoretical computations unveil the synergy of RuOx and Pd to enhance the NO3RR energetics through a mechanism of hydrogen spillover and hydrogen-bond interactions. In detail, RuOx activates NO3- to form intermediates, while Pd dissociates H2O to generate *H, which spontaneously migrates to the RuOx/Pd interface via a hydrogen spillover process. Further hydrogen-bond interactions between spillovered *H and intermediates makes spillovered *H desorb from the RuOx/Pd interface and participate in the intermediate hydrogenation, contributing to the enhanced activity of RuOx/Pd for NO3--to-NH3 conversion.

Boosting Electrocatalytic Activity of Ru for Acidic Hydrogen Evolution through Hydrogen Spillover Strategy

Pristine Ru generally shows unsatisfying activity for the electrocatalytic hydrogen evolution reaction (HER). How to activate its HER activity through facile methodologies is very challenging. Recently, metal-supported electrocatalysts integrating metals with efficient hydrogen adsorption and supports with facile hydrogen desorption delivered a high HER performance through a metal-to-support hydrogen spillover process, where the small metal–support work function difference (ΔΦ) was identified as the criterion for the successful interfacial hydrogen spillover. Herein, we demonstrate that a hydrogen spillover strategy significantly boosts the HER activity of Ru by depositing a Ru1Fe1 alloy on CoP (Ru1Fe1/CoP) with a small ΔΦ of 0.05 eV. Experimentally, Ru1Fe1/CoP (0.7 wt % Ru loading) delivered a high Ru utilization activity of 139.8 A/mgRu and a long-term durability in acid. Mechanism investigations authenticated that the small ΔΦ guaranteed the interfacial hydrogen spillover from Ru1Fe1 with efficient hydrogen adsorption to CoP with facile hydrogen desorption and thereafter boosted the HER activity of Ru.

Efficient photocatalytic hydrogen evolution through reverse hydrogen spillover on photoactivated copper-doped mesoporous titania spheres

Transition-metal-doped mesoporous TiO2 (M-mTiO2) spheres are highly desired for photocatalysis because of their large specific surface area and extended light absorption. Herein, a universal method is developed for the preparation of M-mTiO2 spheres and their photocatalytic mechanism is unveiled. Fe-mTiO2, Co-mTiO2, Ni-mTiO2, Cu-mTiO2 spheres are successfully prepared by the developed method. Among all M-mTiO2 samples, the Cu-mTiO2 catalyst exhibits reversible photoactivation phenomenon during photocatalysis. The photocatalytic hydrogen evolution rate on photoactivated Cu-mTiO2 can reach 3.31 mmol g−1 h−1, which is much higher than those of other M-mTiO2 and is 28.3 times of that of the mTiO2. Density functional theory (DFT) calculations reveal that the photoactivation of Cu-mTiO2 is associated with the facile formation of oxygen vacancies on Cu-mTiO2. The photoactivation induces the active site change and the light absorption increase of Cu-mTiO2. The active site change has the dominant role for the enhancement of photocatalytic performance. On the photoactivated Cu-mTiO2, the hydrogen production is through a reverse hydrogen spillover process. Our findings not only provide a universal method for the preparation of M-mTiO2 but also deepen the understanding about the photoactivation and the hydrogen production mechanism.

Water-mediated hydrogen spillover accelerates hydrogenative ring-rearrangement of furfurals to cyclic compounds

Upgrading bioderived furfurals (furfural, 5-hydroxymethylfurfural) to cyclopentanones (cyclopentanone, 3-hydroxymethylcyclopentanone) and cyclopentanols (cyclopentanol, 3-hydroxymethylcyclopentanol) is a representative bifunctional catalytic process in biomass conversion. Here, a class of Pd/NiMoO4 catalysts (Pd/NiMoO4-Cl, Pd/NiMoO4-AC) with low Pd loading (1.0 wt%) and different Pd dispersion are synthesized. The hydrogenation active sites and acidic sites of catalysts were adjusted by a water-mediated hydrogen spillover process. 56.3–85.3% yields of cyclopentanones and 65.4–85.2% yields of cyclopentanols were obtained by hydrogenative ring-rearrangement route of furfurals over Pd/NiMoO4-Cl and Pd/NiMoO4-AC, respectively. Over-hydrogenated byproducts (tetrahydrofurfuryl alcohol, 2,5-bis(hydroxymethyl)tetrahydrofuran) with a yield above 54% were generated by a full hydrogenation route over Pd/C. The difference in catalytic performance is results from alteration of the adsorption configurations of reactants and the transformation of Lewis acid sites to Brønsted acid sites by hydrogen spillover. This work presents an effective strategy for governing reaction routes and enhancing bifunctional catalysis with a hydrogen spillover mechanism.

How Nitrogen Doping Affects Hydrogen Spillover on Carbon-Supported Pd Nanoparticles: New Insights from DFT

The process of hydrogen spillover on metal nanoparticle decorated carbon surfaces has been discussed for many years due to its importance for heterogeneous catalysis and hydrogen storage. The present density functional theory (DFT) study supports recent experimental observations of the hydrogen spillover process. By use of model systems of carbon-supported palladium nanoparticles, the details of hydrogen spillover are investigated and the effects of nitrogen doping on such processes are elucidated. It is found that graphitic nitrogen atoms and water molecules significantly facilitate the hydrogen spillover reaction and serve as anchoring sites for the spillover hydrogen atoms.

Metal-doped carbon nanocones as highly efficient catalysts for hydrogen storage: Nuclear quantum effect on hydrogen spillover mechanism

Abstract We investigated H-spillover mechanisms on Pt atoms decorating defective carbon nanocones (Pt/dCNC) using the multicomponent B3LYP (MC_B3LYP) method, which can take account of the nuclear quantum effect (NQE) of light nuclei. MC_B3LYP shows reduced relative energies for all stationary-point structures and lower energy barriers to H-spillover reactions. Interestingly, MC_B3LYP calculations reveal that the activation energy for H2 dissociation completely vanishes indicating that H2 molecules dissociate readily on Pt/dCNC. Our crucial finding is that the different metal (Pt and Pd) on dCNC surface has affected the thermodynamic favorability of the hydrogen dissociation process, on Pt/dCNC is facile and highly exothermic, while on Pd/dCNC is dramatically endothermic. Furthermore, comparison of combined dissociation-spillover mechanism on Pt decorated on carbon nanocone (Pt/dCNC) and Pt decorated on graphene (Pt/dG) catalysts have been focused to explain the curvature effect which can facilitate the hydrogen spillover process and provide a highly exothermic reaction, which is more thermodynamically favorable than that of a metal-graphene surface. Our new understanding of this reaction mechanism and the influence of NQEs on electronic properties will be useful for the future development of the spillover mechanism as well as the synthesis of high-performance Pt/dCNC for H2 energy applications.

Ni–La2O3 cermet hydrogen electrode originating from the in-situ decomposition of the La2NiO4+δ oxide for quasi-symmetrical solid oxide fuel cells

Ni–La2O3 cermet hydrogen electrode having almost no ionic conductivity still exhibits excellent electrochemical performance owing to the hydrogen spillover process from high hydrogen adsorption capability on the La2O3 surface. In this work, we develop Ni–La2O3 cermet hydrogen electrode originating from the in-situ decomposition of the La2NiO4+δ(LNO) oxide, and then perform the electrochemical properties for quasi-symmetrical solid oxide fuel cells (Q-SSOFCs), which own YSZ electrolyte support wrapped GDC barrier layer. The area specific resistance (ASR) of LNO air electrode increases from 2.09 to 7.41 Ω cm2, with the temperature of decreasing from 800 to 600 °C. The electrochemical performances of Q-SSOFCs with Ni–La2O3 cermet hydrogen electrode and LNO air electrode are characterized, and the values of the peak power density and the electrode polarization resistance (Rp) of the symmetrical electrodes measured at 800 °C are 245.18 mW cm−2 and 0.61 Ω cm2. These results indicate that the hydrogen spillover process of Ni–La2O3 cermet hydrogen electrode can greatly promote the hydrogen oxidation reaction.

Pd-Ni doped sulfated zirconia: Study of hydrogen spillover and isomerization of N-hexane

A palladium-nickel doped sulfated zirconia was prepared, and hydrogen spillover and bimetallic synergic effect were confirmed using this model catalyst. Isomerization of n-hexane indicated that palladium and nickel could enhance both the conversion rates and selectivity. The XRD and BET results showed that nickel had a strongly influence on the crystal form and catalyst structure. TG-DSC analysis showed the loaded nickel could decrease the sulfates concentrations. Therefore, the total acidity, especially the strong Brønsted acid sites decreased in the presence of nickel, as analyzed by pyridine IR spectroscopy. H2 TPR analysis indicated both the nickel and palladium could improve the reducibility of sulfated zirconia. And combined with XPS results, the nickel oxide was found easier to reduce in the presence of palladium, and higher reduction temperature could lead to the formation of NiAl2O4. Finally, the mechanisms of hydrogen spillover and reaction process were deduced.

Zeolite supported palladium nanoparticle characterization for fuel cell application

Palladium (Pd) has been widely used as a type of hydrogen storage material and has attracted much attention for fuel cell applications, due to its high solubility and mobility of hydrogen in Pd. In this study, Pd nanoparticles made by 1.5 wt% Pd loading on Y-zeolite under pre-treatment was employed to investigate their electrochemical activities using cyclic voltammetry (CV), and detailed local structural characterization of Pd cluster was probed by the extended X-ray absorption fine structure. Pd nanoparticle sizes were predicted at 0.81 nm–1.2 nm and the CV measurement has demonstrated that Pd zeolite catalyst has exhibited a similar tendency to those 40% Pd on XC-72R carbon. The hydrogen spillover process and surface conductance pathways contribute to the electrochemical behavior on Pd surface. In electrochemical environment, hydrogen is able to form hydride phase on Pd surface by either direct hydrogen adsorption or migrating to the centre of Pd.