Hydrogen Spillover Research Articles

Catalyzing Generation and Stabilization of Oxygen Vacancies on CeO2-x Nanorods by Pt Nanoclusters as Nanozymes for Catalytic Therapy.

Although CeO2 nanomaterials have been widely explored as nanozymes for catalytic therapy, they still suffer from relatively low activities. Herein, the catalyzing generation and stabilization of oxygen vacancies on CeO2 nanorods by Pt nanoclusters via H2 gas reduction under mild temperature (350°C) to obtain Pt/CeO2- x , which can serve as a highly efficient nanozyme for catalytic cancer therapy, is reported. The deposited Pt on CeO2 by the atomic layer deposition technique not only can serve as the catalyst to generate oxygen vacancies under mild temperature reduction through the hydrogen spillover effect, but also can stabilize the generated oxygen vacancies. Meanwhile, the oxygen vacancies also provide anchoring sites for Pt forming strong metal-support interactions and thus preventing their agglomerations. Importantly, the Pt/CeO2- x reduced at 350°C (Pt/CeO2- x -350R) exhibits excellent enzyme-mimicking catalytic activity for generation of reactive oxygen species (e.g., ·OH) as compared to other control samples, including CeO2 , Pt/CeO2 , and Pt/CeO2- x reduced at other temperatures, thus achieving excellent performance for tumor-specific catalytic therapy to efficiently eliminate cancer cells in vitro and ablate tumors in vivo. The excellent enzyme-mimicking catalytic activity of Pt/CeO2- x -350R originates from the good catalytic activities of oxygen vacancy-rich CeO2- x and Pt nanoclusters.

Water-assisted hydrogen spillover in Pt nanoparticle-based metal–organic framework composites

Hydrogen spillover is the migration of activated hydrogen atoms from a metal particle onto the surface of catalyst support, which has made significant progress in heterogeneous catalysis. The phenomenon has been well researched on oxide supports, yet its occurrence, detection method and mechanism on non-oxide supports such as metal–organic frameworks (MOFs) remain controversial. Herein, we develop a facile strategy for efficiency enhancement of hydrogen spillover on various MOFs with the aid of water molecules. By encapsulating platinum (Pt) nanoparticles in MOF-801 for activating hydrogen and hydrogenation of C=C in the MOF ligand as activated hydrogen detector, a research platform is built with Pt@MOF-801 to measure the hydrogenation region for quantifying the efficiency and spatial extent of hydrogen spillover. A water-assisted hydrogen spillover path is found with lower migration energy barrier than the traditional spillover path via ligand. The synergy of the two paths explains a significant boost of hydrogen spillover in MOF-801 from imperceptible existence to spanning at least 100-nm-diameter region. Moreover, such strategy shows universality in different MOF and covalent organic framework materials for efficiency promotion of hydrogen spillover and improvement of catalytic activity and antitoxicity, opening up new horizons for catalyst design in porous crystalline materials.

Ga2O3-Pt dual-site functionally separated catalyst for efficient hydrogenation of furfural under hydrogen spillover

The selective hydrogenation of furfural (FFL) to furfuryl alcohol (FAL) is an interest topic in the conversion of biomass. Herein, we present a Ga2O3-Pt two-component spatially isolated catalyst to achieve enhanced catalytic activity and selectivity under hydrogen spillover. Specifically, Pt and Ga2O3 active sites are confined in the micropores and mesopores of TS-1@mesoporous-silica, respectively. The Pt sites within the micropores is responsible for the activation of hydrogen while the Ga2O3 sites in mesopores acts as the active center for FFL activation. This synergistic effect of double site exhibits a significant improvement in catalytic activity and selectivity, with the turnover frequency (TOF) and FAL selectivity up to 72.2 h−1 and 96.5%, respectively. This strategy provides an idea for the understanding of synergistic nature in bicomponent catalysts under hydrogen spillover.

Unveiling the promotion effect of ethylenediamine on preparation of Ni/CeO2 catalyst for low-temperature CO2 methanation

Cost-effective CO2 conversion to value-added products remains a great challenge until present. Here, we have discovered that the ethylenediamine (EDA) assisted preparation of Ni/CeO2 catalyst remarkably promotes the CO2 methanation performance at low temperatures. The Ni/CeO2-EDA catalyst exhibits a CO2 conversion efficiency of 84% and a CH4 selectivity of 98% at 225 °C, and no visible decline of CO2 conversion is observed even after 70h of continuous reaction. The involvement of EDA is shown to effectively result in a more uniform distribution of Ni species, coupled with a reduction in particle size. In addition, the smaller particle size of Ni results in a rapid dissociative adsorption of hydrogen and H2 spillover. Accordingly, oxygen vacancies on the CeO2 surface are created and adequate H atoms are engendered for CO2 hydrogenation. Furthermore, both the formate and CO pathways occur simultaneously on the Ni/CeO2-EDA catalyst, enhancing the low-temperature methanation activity. Herein, the EDA-assisted strategy provides an effective methodology in terms of well-dispersion and highly active catalysts for low-temperature CO2 methanation.

Constructing a Pd-Co Interface to Tailor a d-Band Center for Highly Efficient Hydroconversion of Furfural over Cobalt Oxide-Supported Pd Catalysts.

Cobalt is an alternative catalyst for furfural hydrogenation but suffers from the strong binding of H and furan ring on the surface, resulting in low catalytic activity and chemoselectivity. Herein, by constructing a Pd-Co interface in cobalt oxide-supported Pd catalysts to tailor the d-band center of Co, the concerted effort of Pd and Co boosts the catalytic performance for the hydroconversion of furfural to cyclopentanone and cyclopentanol. The increased dispersion of Pd on acid etching Co3O4 promotes the reduction of Co3+ to Co0 by enhancing hydrogen spillover, favoring the creation of the Pd-Co interface. Both experimental and theoretical calculations demonstrate that the electron transfer from Pd to Co at the interface results in the downshift of the d-band center of Co atoms, accompanied by the destabilization of H and furan ring adsorption on the Co surface, respectively. The former improves the furfural hydrogenation with TOF on Co elevating from 0.20 to 0.62 s-1, and the latter facilitates the desorption of formed furfuryl alcohol from the Co surface for subsequently hydrogenative rearrangement of the furan ring to cyclopentanone on acid sites. The resultant Pd/Co3O4-6 catalyst delivers superior activity with a 99% furfural conversion and 85% overall selectivity toward cyclopentanone/cyclopentanol. We anticipate that such a concept of tailoring the d-band center of Co via interface engineering provides novel insight and feasible approach for the design of highly efficient catalysts for furfural hydroconversion and beyond.

Tuning work function difference of copper/cobalt oxides heterointerfaces enables efficient electrochemical nitrate reduction

Metal/metal-oxide heterointerfaces receive extensive attention in electrocatalysis on account of the strong synergy between the two components at the interface. However, the key factor governing such interfacial synergy is still unclear, making it extremely challenging to rationally design electrocatalyst with desired heterointerfaces. Here, we select metallic copper/cobalt-oxide (i.e., Cu/Co3O4) heterointerfaces as model catalysts for the nitrate reduction reaction (NO3-RR) and tuned work function difference (ΔΦ) between Cu/Co3O4 by introducing oxygen vacancies (Ov) on Co3O4. By combing experimental and theoretic results, we observe that the ΔΦ is a key factor that governs the interfacial synergy, which included the transfer of electrons from Cu to Co3O4 and the spillover of hydrogen from Co3O4 to Cu. Consequently, the Cu/Co3O4 interface with an optimized ΔΦ displayed the best NO3−RR performance, outperforming most of other reported electrocatalysts. The above findings will create new opportunities for rationally designing heterointerfaces for efficient electrocatalysis by tuning ΔΦ.

Hydrogen spillover in MoOxRh hierarchical nanosheets boosts alkaline HER catalytic activity

The low intrinsic catalytic performance and stability are the two dominant obstacles for alkaline hydrogen evolution reaction (HER) electrocatalyst. Herein, amorphous molybdenum oxide (MoOx) has been introduced to rhodium hierarchical nanosheets (MoOxRh-HNS) at atomic level efficiently reducing the barrier for hydrogen spillover from Rh to MoOx; thereby, MoOxRh-HNS exhibit superior HER activity with mass activity of 23.9 A mgnoble metal−1 at overpotential of 200 mV, which is boosted by 10.8- and 14.9-fold with relative to Rh-HNS and Pt/C in alkaline media, respectively. Meanwhile, Tafel slope is as low as 22.5 mV dec−1 for MoOxRh-HNS revealing a hydrogen-spillover-involving HER mechanism proved by the electrochemical test as well as operando electrochemical impedance spectroscopy. Density functional theory calculation indicates the adsorbed hydrogen on MoOxRh promotes the water dissociation and balances the hydrogen binding strength to a moderate level. Simultaneously, the hierarchical nanosheet structure contributes a robust HER stability at 500 mA cm−2. This work offers a new methodology to construct a high-performance alkaline HER electrocatalyst with industrial-level current density.

ZrO2 promoted Ru/In2O3 catalyst for selective hydrogenation of CO2 to methanol

With the strong metal-support interaction, In2O3 supported Ru catalyst has been confirmed to be active for selective hydrogenation of CO2 to methanol. Herein, we report that the addition of ZrO2 into Ru/In2O3 further improves the catalytic activity for CO2 hydrogenation to methanol. The catalyst characterization shows a formation of In2O3-ZrO2 solid solution, which is an excellent support for the highly dispersed Ru catalyst. Compared to Ru/In2O3, a significantly higher methanol selectivity is achieved over the Ru/In2O3-ZrO2 catalyst with 1 wt% Ru loading. The methanol space–time yield (STY) reaches 0.685 gMeOH h−1 gcat−1 at 300 ℃, 5 MPa, and 21000 cm3 gcat−1h−1. It has more than 20% increase compared to Ru/In2O3. The addition of ZrO2 optimizes the oxygen vacancies of In2O3, improves the CO2 adsorption and enables a more stable catalyst architecture, while the hydrogen spillover by the highly dispersed ruthenium improves the hydrogen activation ability of the catalyst. All these results in a high level of methanol yield.

Promoting effect of titanium on C―O hydrogenolysis of erythritol to 1,4-butanediol over Pt/W/Ti-SBA-15 catalysts

The C―O hydrogenolysis of erythritol was investigated using Pt/W/Ti-SBA-15 catalysts (4 wt% Pt, 1 wt% W and Si/Ti molar ratio = 50, 33, 20 and 10). Ti-incorporation enhanced the hydrogenolysis activity and the yield of 1,4-butanediol (1,4-BDO). A catalyst with Si/Ti = 20 afforded erythritol conversion of 94 mol% with 1,4-BDO yield of 32.6 mol% and total BDOs yield of 51.7 mol% at 190 °C, 50 bar H2 and 12 h. For the catalyst with no titanium (Pt/W/SBA-15), a double the time was required to achieve such yield. There observed electronic connectivity amongst Ti, Pt and W. For the catalyst with Si/Ti = 20, a greater amount of interfacial Pt-O-W(Ti) sites with Pt in + 2 oxidation state was present. The enhanced catalytic performance of these catalysts was corresponded to dispersed Pt (that facilitate hydrogen activation and spillover) and acidic interfacial Pt-O-W sites (that promote the adsorption and hydrogenolysis of erythritol to diols).

Activation of Molecules H<sub>2</sub> on Platinum and Platinovanadium Clusters: Quantum-Chemical DFT Modeling

The NEB DFT/PBE0/def2tzvp quantum-chemical method with the construction of minimum energy paths (MEP) was used to study the activation of H2 molecules by Pt4 and Pt3V clusters. It is shown that, in the case of Pt4 and Pt3V clusters, barrier-free dissociative adsorption of H2 molecules occurs on platinum centers, while molecular adsorption of hydrogen occurs on the vanadium atom in Pt3V with a slight weakening of the H–H bond, but without its breaking. The noted features of the coordination of H2 molecules are explained at the level of the MO method. It has been established that the migration of the H atom from one cluster metal center to another in the considered model clusters, as, possibly, in the phenomenon of hydrogen spillover, occurs at small activation barriers in the direction of the displacement vector corresponding to the normal vibration of the system in the transition state. In the process of hydrogen migration, a significant role of Pt–H–Pt and V–H–Pt bridging groups, which facilitate the transition of H atoms from one metal center of the cluster to another, has been revealed.

Reversed Spillover Effect Activated by Pt Atom Dimers Boosts Alkaline Hydrogen Evolution Reaction

AbstractThe hydrogen spillover effect has garnered considerable attention as a promising avenue to enhance the activity of the hydrogen evolution reaction (HER) in metal‐support compound materials. Herein, Pt atom dimers on the NiOOH support are successfully synthesized with a reversed hydrogen spillover effect, demonstrating much better alkaline HER activity than Pt single atoms and Pt clusters. Atomic and electronic structure characterizations unequivocally verify the anchoring of Pt atom dimers on NiOOH through Pt─O bonds, thus obtaining a reversed and enhanced hydrogen spillover effect. Theoretical and experimental results indicate that NiOOH exhibits pronounced water dissociation capability, while the Pt atom dimers, in comparison to Pt single atoms and Pt clusters, demonstrate superior hydrogen desorption ability. The reversed spillover with Pt atom dimers leads to remarkable HER activity in alkaline solutions, as evidenced by an ultra‐small overpotential of 13 mV at 10 mA cm−2. These findings not only provide insights into the potential use of atom dimers for HER, but also shed light on reversed spillover in designing high‐performance catalysts.

RuNi/MMO Catalysts Derived from a NiAl-NO3-LDH Precursor for CO Selective Methanation in H2-Rich Gases

CO selective methanation (CO-SMET) is a promising method for deep CO removal from H2-rich gases. In this study, a series of RuNi/MMO catalysts are prepared using the support MMO-N derived from NiAl-NO3-LDHs, which was prepared from NiAl-CO3-LDHs via an acid–alcohol ion-exchange reaction. The prepared catalysts were characterized by XRD, SEM, TEM, XPS, H2-TPR, CO-TPD, CO2-TPD, NH3-TPD, and TG. The RuNi/MMO-N catalyst demonstrated excellent CO-SMET performance, successfully reducing the CO to less than 10 ppm with a selectivity greater than 50% in a reaction temperature window ranging from 180 °C to 260 °C. Compared with similar catalysts derived from NiAl-CO3-LDHs, the exceptional CO-SMET capability of the RuNi/MMO-N catalyst is suggested to be associated with a more effective hydrogen spillover, a larger number of electron-rich Ni sites, and a higher density of acid sites on the surface of RuNi/MMO-N, which are conducive to CO adsorption and the inhibition of CO2 methanation.

Hydrogen Spillover Intensified by Pt Sites on Single-Crystalline MoO3 Interconnected Branches for Hydrogen Evolution

Hydrogen Spillover Intensified by Pt Sites on Single-Crystalline MoO₃ Interconnected Branches for Hydrogen Evolution

Effect of Hydrogen Spillover on the Ru/TiO2-Catalyzed Guaiacol Hydrodeoxygenation: Rutile vs Anatase TiO2

Effect of Hydrogen Spillover on the Ru/TiO₂-Catalyzed Guaiacol Hydrodeoxygenation: Rutile vs Anatase TiO₂

Cooperative effect of multi-active sites in WOx-modified ZrO2 supported highly dispersed Pd catalysts for promoting benzene hydroalkylation

Designing efficient metal–acid bifunctional catalysts is a challenging task to achieve the one-step benzene hydroalkylation to produce cyclohexylbenzene (CHB), which has significant importance due to the economic potential for the industrial production of phenol. In this study, a series of WOx-modified ZrO2 supported highly dispersed Pd catalysts were developed by modulating the surface acidity of ZrO2 through the introduction of WOx species. The as-constructed Pd/WOx-ZrO2 catalyst bearing a low Pd loading of 0.4 wt% and a W content of 21 wt% exhibited a superior catalytic performance, along with an unprecedentedly high productivity of CHB (144.6 mmolCHB·gcat−1·h−1), much higher than those obtained by using the state-of-the-art catalysts. It was demonstrated that highly dispersed Pd species could promote the formation of active hydrogen species and favor the hydrogen spillover on the catalyst surface that induced the generation of surface oxygen vacancies and Brønsted acidic sites originating from surface-loaded WOx. Comprehensive structural characterizations and catalytic experiments showed that the favorable metal–acid cooperation on Pd/WOx-ZrO2 catalysts and the cooperation between Lewis acid sites and Brønsted acid sites, as well as the presence of abundant defective oxygen vacancies, efficiently regulated the adsorption and activation of molecular hydrogen, benzene, and cyclohexene intermediate, leading to the improved catalytic hydroalkylation activity. These findings provide new high-performance metal–acid bifunctional catalysts with multi-active site cooperation structures for one-step hydroalkylation of benzene to CHB.

DFT study of Pd4 and Pd3P supported on modified graphene for hydrogen storage

In this study, density functional theory (DFT) calculations were utilized to investigate the feasibility of using Pd4 and Pd3P clusters for hydrogen adsorption and spillover, with a focus on their potential as hydrogen storage materials. Four different modified graphene slabs were examined and the results showed that pristine graphene (PG), phosphorus-doped pristine graphene (PPG), and phosphorus-doped single vacancy graphene (PSVG) are not suitable surfaces for decorating Pd4 and Pd3P clusters for hydrogen adsorption and spillover. Our results showed that Pd4/SVG and Pd3P/SVG materials exhibited high binding energies of −5.37 eV and −4.49 eV respectively, which indicated their potential to prevent desorption of Pd–H hydrides with H2 desorption. The stability of Pd4/SVG and Pd3P/SVG was also confirmed by molecular dynamics at a temperature of 500 K. Moreover, the decoration of Pd3P on SVG resulted in hydrogen adsorption with an average energy of 0.25 eV/H2, falling within the ideal useable range. At full saturation, the energy barrier for spillover decreased from 0.86 eV to 0.75 eV, and the system could store up to 5.74 wt% of hydrogen. Furthermore, the spillover reaction occurred rapidly at room temperature within 0.68 s. Our findings suggest that Pd3P decorated single vacancy graphene represents a promising hydrogen storage material, providing valuable insights into the development of effective hydrogen storage technologies.

Adjusting active sites and metal-support interactions of ceramic-loaded Pd/P-CeO2-Al2O3 coating to optimize CO2 methanation pathways

Adjusting the active sites and metal-support interactions (MSI) of catalytic coatings on foam ceramics is a desirable strategy to improve CO2 methanation performance. By using a three-dipping and one-roasting technique, a highly active Pd/P-CeO2-Al2O3 catalyst (HA-Pd/PCA) with uniform three-dimensional mesh-like pores and daisy-like clusters was created. As PdO that was embedded in oxygen vacancies of CeO2 was reduced, oxygen vacancies were released. Pd then interacted with lattice oxygen close to the oxygen vacancies to create a strong MSI effect in the form of electron transfer. This translates to better Pd dispersion and more effective activation of the hydrogen. Moreover, the path of the hydrogen spillover that was necessary to hydrogenate the CO2 adsorbed in oxygen vacancies was shortened. In terms of the presence of acid-base sites, oxygen species, and oxygen vacancies, HA-Pd/PCA provided significant advantages. Based on this, the rate of carbonate to formate increased and the conversion pathway changed from a single bidentate formate to a dual pathway comprising bidentate formate and monodentate formate. The consumption and regeneration of hydroxyl groups were kept in balance. The outcomes demonstrated that HA-Pd/PCA had ideal stability, 100 % CH4 selectivity, and 86 % CO2 conversion.

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.

A comparative study of RuO2 and Ru reveals the role of oxygen vacancies in electrocatalytic nitrogen reduction to ammonia under ambient conditions

Nitrogen molecule reduction to ammonia requires adsorption and hydrogenation sites. In this study, the nitrogen reduction reaction (NRR) activity of RuO2 and metallic Ru catalysts was studied to explore the role of oxides and metallic dual active sites. Ruthenium oxide nanoparticles displayed an ammonia production rate of 16.5 µg h−1 cm−2 with a Faradaic efficiency (FE) of 0.26% at − 0.15 V vs. RHE in N2-saturated 0.1 M KOH which is 58% higher compared to Ru black (6.8 µg h−1 cm−2 with 0.19% FE at −0.15 Vvs.RHE). This is attributed to the formation of oxygen vacancies (Vo) on the RuO2 surface during cathodic potential polarization, which provides a facile adsorption site for N2 in addition to the Ru4+ active site while the proton supplied via hydrogen spillover from the metal hydride site to the adsorbed Vo-N2 site. This assumption was validated by detailed XPS, XRD, and N2 TPD analysis.

Efficient processing of tritiated water by using a two-stage Pd membrane reactor with Pt/TiO2 catalyst

Large amounts of tritiated water (HTO) will be produced during the operation of nuclear power plants and fusion devices, which is harmful to the environment and human due to its radioactivity and toxicity. So, the tritium concentration of tritiated water must be reduced to a very low value before discharge. Hydrogen-water isotope exchange reaction (H2 + HTO→H2O + HT) based on palladium membrane reactor has been proposed to process tritiated water. However, a comprehensive study about the influence of operation parameters on the membrane reactor performance is insufficient, which is not conducive to the design of reactor in practical application. Moreover, the commonly used Pt/Al2O3 or Ni/SiO2 catalysts are not active for tritiated water dissociation, so the catalytic activity of these catalysts is not high. In order to process tritiated water more effectively, a two-stage membrane reactor has been designed and established in this work, and Pt/TiO2 catalyst with rich oxygen vacancies is used to catalyze the hydrogen-water isotope exchange reaction for the first time. The membrane reactor performance shows an approximate linear relationship with a new combined parameter S0.5P1.5R/F2 (S is membrane area, F is water flow rate, P is vapor partial pressure, R is swamping ratio), which can be used predict the membrane performance. The isotope exchange reaction activity of Pt/TiO2 is better than that of Pt/Al2O3 due to its good ability for water dissociation and the hydrogen spillover effect. At last, a tritiated water processing experiment by using two-stage membrane reactor with Pt/TiO2 catalyst with rich oxygen vacancies has been carried out. The tritium decontamination factor reaches 40588, which is the highest experimental value so far. The results indicate that the two-stage Pd membrane reactor based on hydrogen-water isotope exchange reaction is an efficient technology for tritiated water processing.