Hydrogen Spillover Effect in Electrocatalysis:Delving into the Mysteries of the Atomic Migration

Hydrogen spillover effect has recently garnered a lot of attention in the field of electrocatalytic hydrogen evolution reactions.A new avenue for understanding the dynamic behavior of atomic migration in which hydrogen atoms moving on a catalyst surface was opened up by the setup of the word"hydrogen spillover."However,there is currently a dearth of thorough knowledge regarding the hydrogen spillover effect.Currently,the advancement of sophisticated characterization procedures offers progressively useful information to enhance our grasp of the hydrogen spillover effect.The understanding of material fabrication for hydrogen spillover effect has erupted.Considering these factors,we made an effort to review most of the articles published on the hydrogen spillover effect and carefully analyzed the aspect of material fabrication.All of our attention has been directed toward the molecular pathway that leads to improve hydrogen evolution reactions performance.In addition,we have attempted to elucidate the spillover paths through the utilization of DFT calculations.Furthermore,we provide some preliminary research suggestions and highlight the opportunities and obstacles that are still to be confronted in this study area.

Effect of metal catalyst on the mechanism of hydrogen spillover in three-dimensional covalent-organic frameworks

Hydrogen spillover mechanism of metal-supported covalent-organic frameworks COF-105 is investigated by means of the density functional theory, and the effects of metal catalysts M_4（Pt_4, Pd_4, and Ni_4） on the whole spillover process are systematically analyzed. These three metal catalysts exhibit several similar phenomena：（i） they prefer to deposit on the tetra（_4-dihydroxyborylphenyl） silane（TBPS） cluster with surface-contacted configuration;（ii） only the H atoms at the bridge site can migrate to 2,3,6,7,10,11-hexahydroxy triphenylene（HHTP） and TBPS surfaces, and the migration process is an endothermic reaction and not stable;（iii） the introduction of M_4 catalyst can greatly reduce the diffusion energy barrier of H atoms, which makes it easier for the H atoms to diffuse on the substrate surface. Differently, all of the H2 molecules spontaneously dissociate into H atoms onto Pt_4 and Pd_4clusters. However, the adsorbed H2 molecules on Ni_4 cluster show two types of adsorption states： one activated state with stretched H–H bond length of 0.88 ？A via the Kubas interaction and five dissociated states with separated hydrogen atoms. Among all the M_4 catalysts, the orders of the binding energy of M_4 deposited on the substrate and average chemisorption energy per H2 molecule are Pt_4〉Ni_4〉Pd_4. On the contrary, the orders of the migration and diffusion barriers of H atoms are Pt_4

Magic of hydrogen spillover: Understanding and application

The hydrogen spillover effect(HSPE)plays an important role in heterogeneous catalysis and hydrogen storage as an interfacial phenomenon,which facilitates the improvement of hydrogen storage properties of porous nanomaterials and indirectly or directly affects the reaction performance of multiphase catalytic reactions.The setting-up of the word“hydrogen spillover”opened up a new area to gain insight into the dynamic behavior of migrating hydrogen atoms on a catalyst surface.However,a comprehensive understanding of the HSPE is still lacking.Today,the development of advanced characterization techniques provides increasingly valuable information to further our understanding of the HSPE.Based on these considerations,in this review,we hope to provide some answers to the question“What is hydrogen spillover and how do we recognize it?”.To do this,we will rely on advanced characterization techniques as well as experimental and theoretical studies.Then,we discuss in detail the influences of the HSPE on hydrogen storage performance and the important catalytic effects of the HSPE in catalysis.These effects will be reviewed by looking through the catalytic results obtained in many reactions in thermal catalysis,electrocatalysis,and photocatalysis.Furthermore,based on the application potential of hydrogen spillover,we present some preliminary research proposals and discuss the opportunities and challenges that remain to be faced in this research area.

Achieving Negatively Charged Pt Single Atoms on Amorphous Ni(OH)_(2)Nanosheets with Promoted Hydrogen Absorption in Hydrogen Evolution

Single-atom(SA)catalysts with nearly 100%atom utilization have been widely employed in electrolysis for decades,due to the outperforming catalytic activity and selectivity.However,most of the reported SA catalysts are fixed through the strong bonding between the dispersed single metallic atoms with nonmetallic atoms of the substrates,which greatly limits the controllable regulation of electrocatalytic activity of SA catalysts.In this work,Pt-Ni bonded Pt SA catalyst with adjustable electronic states was successfully constructed through a controllable electrochemical reduction on the coordination unsaturated amorphous Ni(OH)_(2)nanosheet arrays.Based on the X-ray absorption fine structure analysis and first-principles calculations,Pt SA was bonded with Ni sites of amorphous Ni(OH)_(2),rather than conventional O sites,resulting in negatively charged Pt^(δ-).In situ Raman spectroscopy revealed that the changed configuration and electronic states greatly enhanced absorbability for activated hydrogen atoms,which were the essential intermediate for alkaline hydrogen evolution reaction.The hydrogen spillover process was revealed from amorphous Ni(OH)_(2)that effectively cleave the H-O-H bond of H_(2)O and produce H atom to the Pt SA sites,leading to a low overpotential of 48 mV in alkaline electrolyte at-1000 mA cm^(-2)mg^(-1)_(Pt),evidently better than commercial Pt/C catalysts.This work provided new strategy for the control-lable modulation of the local structure of SA catalysts and the systematic regulation of the electronic states.

Role of Ni species in ZnO supported on Silicalite-1 for efficient propane dehydrogenation

Propane dehydrogenation(PDH)is one of the most effective technologies to produce propene.Non-noble zinc-based catalysts have paid increasing attention because of low cost and nontoxic,compared with industrial Pt and Cr-based catalysts.However,they often suffer from limited catalytic activity and poor stability.Here,we introduced moderate Ni into ZnO supported Silicalite-1 zeolite to increase catalytic activity and stability simultaneously.Zn^(2+) was the definite active site and NiZn alloy facilitated the sluggish H recombination into H_(2)via reverse spillover.Furthermore,the introduction of Ni increased Lewis acid strength caused by electron transfer from ZnO to NiZn alloy,contributing to improved stability.For resulted 0.5 NiZn/S-1,propene formation rate was 0.18 mol C_(3)H_(6)·(g Zn)^(-1)·h^(-1) at 550℃,which was above 1.5 times higher than that over Zn/S-1 without Ni.Under stability test,the deactivation of0.5 NiZn/S-1 was 0.019 h^(-1),which was only 1/10 of that over Zn/S-1.

Theoretical study of molecular hydrogen and spiltover hydrogen storage on two-dimensional covalent-organic frameworks

Molecular hydrogen and spiltover hydrogen storages on five two-dimensional （2D） covalent-organic frameworks （COFs） （PPy-COF, TP-COF, BTP-COF, COF-18 A, and HHTP-DPB COF） are investigated using the grand canonical Monte Carlo （GCMC） simulations and the density functional theory （DFT）, respectively. The GCMC simulated results show that HHTP-DPB COF has the best performance for hydrogen storage, followed by BTP-COF, TP-COF, COF-18 A, and PPy-COE However, their adsorption amounts at room temperature are all too low to meet the uptake target set by US Department of Energy （US-DOE） and enable practical applications. The effects of pore size, surface area, and isosteric heat of hydrogen on adsorption amount are considered, which indicate that these three factors are all the important factors for determining the H2 adsorption amount. The chemisorptions of spiltover hydrogen atoms on these five COFs represented by the cluster models are investigated using the DFT method. The saturation cluster models are constructed by considering all possible adsorption sites for these cluster models. The average binding energy of a hydrogen atom and the saturation hydrogen storage density are calculated. The large average binding energy indicates that the spillover process may pro- ceed smoothly and reversibly. The saturation hydrogen storage density is much larger than the physisorption uptake of H2 molecules at 298 K and 100 bar （1 bar = 105 Pa）, and is close to or exceeds the 2010 US-DOE target of 6 wt% for hydrogen storage. This suggests that the hydrogen storage capacities of these COFs by spillover may be significantly enhanced. Thus 2D COFs studied in this paper are suitable hydrogen storage media by spillover.

Identification of active sites for hydrogenation over Ru/SBA-15 using in situ Fourier-transform infrared spectroscopy

The active sites for hydrogenation over Ru/SBA‐15catalysts were identified using in situ Fourier‐transform infrared spectroscopy.The amount of active sites was proportional to the interfacial circumference of the Ru particles.In contrast,the rate of hydrogen spillover from Ru to the support was inversely proportional to the size of the Ru metal particles.Consequently,a catalyst with small Ru metal particles has a high rate of hydrogen spillover but a low density of active sites,whereas one with large Ru particles has a low rate of hydrogen spillover but a high density of active sites.The formation of these active sites is probably an intermediate step in hydrogen spillover.

Hydrogen spillover bridged dual nano-islands triggered by built-in electric field for efficient and robust alkaline hydrogen evolution at ampere-level current density

Employing the alkaline water electrolysis system to generate hydrogen holds great prospects but still poses significant challenges,particularly for the construction of hydrogen evolution reaction(HER)catalysts operating at ampere-level current density.Herein,the unique Ru and RuP_(2)dual nano-islands are deliberately implanted on N-doped carbon substrate(denoted as Ru-RuP_(2)/NC),in which a built-in electric field(BEF)is spontaneously generated between Ru-RuP_(2)dual nano-islands driven by their work function difference.Experimental and theoretical results unveil that such constructed BEF could serve as the driving force for triggering fast hydrogen spillover process on bridged Ru-RuP_(2)dual nano-islands,which could invalidate the inhibitory effect of high hydrogen coverage at ampere-level current density,and synchronously speed up the water dissociation on Ru nano-islands and hydrogen adsorption/desorption on RuP_(2)nano-islands through hydrogen spillover process.As a result,the Ru-RuP_(2)/NC affords an ultra-low overpotential of 218 mV to achieve 1.0 A·cm^(−2)along with the superior stability over 1000 h,holding the great promising prospect in practical applications at ampere-level current density.More importantly,this work is the first to advance the scientific understanding of the relationship between the constructed BEF and hydrogen spillover process,which could be enlightening for the rational design of the cost-effective alkaline HER catalysts at ampere-level current density.

Pt single atoms in oxygen vacancies boost reverse water-gas shift reaction by enhancing hydrogen spillover

The construction of synergistic catalysis of single atom catalysts(SACs)and oxygen vacancies(OV)on supports is crucial for the enhancement of heterogeneous catalytic efficiency,yet presents considerable challenges.Herein,we have developed an amine-molecule-assisted in-situ anchoring strategy that effectively stabilizes Pt SACs on OV sites of reduced TiO_(2)(TiO_(2)–x)by controlling the interaction of amine with Pt species and TiO_(2)–x.Direct evidence indicates that Pt SACs are anchored on the OV with forming Ptδ+–OV–Ti3+sites and strong metal-support interaction,which not only prevents the sintering of Pt SACs under high-temperature reduction treatments,but also enhances the hydrogen spillover process to facilitate the formation of more OV sites.During the reverse water-gas shift(RWGS)reaction,the enhanced amount of OV sites can increase CO_(2)adsorption,while the Pt SACs can efficiently promote the activation and spillover of hydrogen.Their combined synergistic effects greatly improve its catalytic performance with a high turnover frequency(TOF)of 9289 h−1 at 330℃ and notable stability for over 200 h,surpassing those of Pt clusters and nanoparticles on TiO_(2)–x.This work provides a new avenue for the controllable synthesis of synergistic catalysts with SACs and OV,significantly advancing catalytic efficiency.

加氢脱氯在环境污染控制中的应用:负载及非负载型钯和镍催化剂性能的比较(英文)

Catalytic hydrodechlorination(HDC)is an innovative means of transforming chlorinated waste streams into a recyclable product. In this study,the gas phase HDC of chlorobenzene(CB)has been studied over bulk Pd and Ni and((8±1)wt%)Pd and Ni supported on activated carbon(AC),graphite,graphitic nanofibers(GNF),Al2O3,and SiO2.Catalyst activation was examined by temperature-programmed reduction(TPR)analysis and the activated catalysts characterized in terms of BET area,transmission electron microscopy,scanning electron microscopy,H2 chemisorption/temperature-programmed desorption,and X-ray diffraction measurements.Metal surface area(1-19 m 2 /g), TPR,and H2 uptake/release exhibited a dependence on both metal and support.The Pd system delivered specific HDC rates that were up to three orders of magnitude greater than that recorded for the Ni catalysts,a result that we link to the higher H2 diffusivity in Pd.HDC was 100%selective over Ni while Pd also produced cyclohexane(selectivity<4%)as a result of a combined HDC/hydrogenation.Bulk Pd outperformed carbon supported Pd but was less active than Pd on the oxide supports.In contrast,unsupported Ni presented no measurable activity when compared with supported Ni.The specific HDC rate was found to increase with decreasing metal surface area where spillover hydrogen served to enhance HDC performance.

Synergetic effect between sulfurized Mo/γ-Al_2O_3 and Ni/γ-Al_2O_3 catalysts in hydrodenitrogenation of quinoline

An evidence for the synergetic effect between the stacked bed of Mo/γ-Al2O3 and Ni/γ-Al2O3 in the hydrodenitrogenation （HDN） reaction of quinoline has been provided in this paper. The synergism factor decreases when the reaction temperature increases （280？340 ？C）. The synergetic effect leads to improve the hydrogenation activity for the stacked bed compared with the single Mo/γ-Al2O3 bed, which may be attributed to the generation of hydrogen spillover on the Ni/γ-Al2O3 catalyst.

Hydrogen spillover in nonreducible oxides:Mechanism and catalytic utilization

Hydrogen(H)spillover in nonreducible oxides such as zeolites and Al2O3 has been a highly controversial phenomenon in heterogeneous catalysis.Since industrial catalysts are predominantly prepared using these materials as supports,it is important to understand the mechanism and catalytic functions of H spillover on their surfaces.In the past decade,fundamental studies on zeolite-encapsulated metal catalysts have revealed that H spillover and reverse spillover can be utilized in the design of hydrogenation and dehydrogenation catalysts with improved properties.Both experimental and theoretical studies have indicated that H spillover can occur in nonreducible oxides when they possess substantial acid sites that aid the surface migration of active H.In the present review,we will discuss the possible mechanisms of H spillover in nonreducible oxides and the unique opportunities of using this phenomenon for the design of advanced hydroprocessing catalysts.

Atomically Dispersed Pt and NiO Clusters Synergistically Enhanced C–O Bond Hydrogenolysis

C–Obond activation is a highly efficient,fundamental strategy in the depolymerization and hydrodeoxygenation of chemicals with oxygen-containing functional groups such as oil,coal,and biomass.Developing efficient catalysts for C–Oactivation with ultralow-loading noble and non-noble metals is highly desirable for the improvement of metal atomic utilization.Herein,bimetallic catalysts with atomically dispersed Pt and NiO clusters on different supports were fabricated,and the prepared Pt^(δ+)-NiO/Nb_(2)O_(5)and Pt^(δ+)-NiO/TiO_(2)showed outstanding activity for the hydrogenolysis of benzyl phenyl ether with>99%yield of phenol and toluene due to the excellent cooperation of atomically dispersed Pt and NiO clusters.The synergy mechanism between Pt and Ni and their respective roles in the bimetallic catalyst for C–O hydrogenolysis were clearly clarified.These findings deepen our understanding of the synergy of the two active components and are expected to provide new design concepts for the development of multicomponents catalysts.

Pd-modified CuO-ZnO-Al_(2)O_(3)catalysts via mixed-phases-containing precursor for methanol synthesis from CO_(2)hydrogenation under mild conditions

A series of palladium-modified(Pd-modified)CuO-ZnO-Al_(2)O_(3)(CZA)catalysts with various Pd loadings(0.3 wt%to 2.4 wt%)were prepared using the wetness impregnation method,on two CZA supports with different structures that are CZA-aged precursor composed of a mixture of zincian-malachite and hydrotalcite-like phases(CZA-zH),and CuO-ZnO-Al_(2)O_(3)metal oxide nanoparticles(CZA-MO).Enhancement on catalytic activity can be observed on both Pd-modified CZA catalysts in a temperature range of 180-240℃for methanol synthesis via CO_(2)hydrogenation.Pd/CZA-zH catalysts exhibited a more efficient and stable production of methanol at a relatively low reaction temperature of 180℃for 100 hrs of reaction.The improvement of activity is mainly ascribed to a higher surface area and abundant oxygen-containing functional groups(e.g.,-OH)of CZA-zH support,which is beneficial for better adsorption and distribution of Pd promoter.Hydrogen temperature programmed reduction and X-ray photoelectron spectroscopy results demonstrated a better interaction between Pd and Cu on Pd/CZA-zH catalysts via enhanced reducibility of CuO,and peak shift of Cu to a lower binding energy.The difference in the efficient utilization of hydrogen spillover effect of Pd promoter over two CZA supports resulted in the different performances for methanol synthesis under mild reaction co℃nditions.

Construction of pH-universal hydrogen evolution freeway in MoO_(3)-MoNi_(4)@Cu core-shell nanowires via synergetic electronic and geometric effect

Both the adsorption/dissociation of water molecules and hydrogen intermediate(H*)are the major limitations to hydrogen evolution reaction(HER).Herein,the modulation of electronic structure and geometric configuration are combined to design onedimensional electrocatalyst with outstanding HER activity in a wide pH range.The catalyst was composed of molybdenum trioxide doped molybdenum nickel alloy supported by copper nanowires(MoO_(3)-MoNi_(4)@Cu NWs).As revealed by the experimental characterizations and theoretical calculations,Cu NWs act as the electron donator to MoNi4,resulting in up shift of the d-band center in MoNi4,thus expediting H_(2)O adsorption and dissociation.Moreover,the introduction of amorphous MoO_(3) sets up a unique geometric configuration on MoNi4 for the accelerated H*transfer via hydrogen-bond and hydrogen spillover.This work provides a synergetic route for constructing HER freeway and promotes further investigations on more versatile electrocatalysis involving H_(2)O or H*.

Molybdenum-doped titanium dioxide supported low-Pt electrocatalyst for highly efficient and stable hydrogen evolution reaction

The Platinum(Pt)-based catalysts exhibit excellent catalytic performance for the hydrogen evolution reaction(HER) while suffering from poor stability due to the weak interaction between the carbon support and Pt.Herein,a molybdenum-doped titanium dioxide(Ti_(0.9)Mo_(0.1)O_(2)) supported low-Pt electrocatalyst with stronger interaction between catalyst and support is applied to tune the electrocatalytic performance of Pt.The Ti_(0.9)Mo_(0.1)O_(2) support can not only tolerate the corrosion environment in the catalytic system,but also generate strong metal-support inte raction(SMSI) between the oxide and catalyst.A facile solvothermal method is used to prepareTi_(0.9)Mo_(0.1)O_(2) as support to anchor Pt nanoparticles.The 5% Pt supported on Ti_(0.9)Mo_(0.1)O_(2) catalyst exhibits 4.4-fold mass activity(MA) at an overpotential of 50 mV and higher stability than 20% Pt/C with only 1/4 Pt loading.The SMSI between the Ti_(0.9)Mo_(0.1)O_(2) and Pt prevents the Pt aggregation to achieve excellent stability,and hydrogen spillover effect in the interface between Pt and support benefits the hydrogen production process.This work presents a novel sight for the fabrication and design of oxide supported catalysts in various catalytic system by reasonably employing support effect.

TiO_(2) nanorods based self-supported electrode of 1T/2H MoS_(2) nanosheets decorated by Ag nano-particles for efficient hydrogen evolution reaction

Molybdenum disulfide(MoS_(2))has shown significant promise as an economic hydrogen evolution reaction(HER)catalyst for hydrogen generation,but its catalytic performance is still lower than noble metalbased catalysists.Herein,a silver nanoparticles(Ag NPs)-decorated 1T/2H phase layered MoS_(2) electrocatalyst grown on titanium dioxide nanorod arrays(Ag NPs/1T(2H)MoS_(2)/TNRs)was prepared through acid-tunable ammonium ion intercalation.Taking advantage of MoS_(2) layered structure and crystal phase controllability,as-prepared Ag NPs/1T(2H)MoS_(2)/TNRs exhibited ultrahigh HER activity.As-proposed strategy combines facile hydrogen desorption(Ag NPs)with efficient hydrogen adsorption(1T/2H MoS_(2))effectively circumventes the kinetic limitation of hydrogen desorption by 1T/2H MoS_(2).The as-prepared Ag NPs/1T(2H)MoS_(2)/TNRs electrocatalyst exhibited excellent HER activity in 0.5 mol/L H2SO4 with low overpotential(118 mV vs.reversible hydrogen electrode(RHE))and small Tafel slope(38.61 mV/dec).The overpotential exhibts no obvious attenuation after 10 h of constant current flow.First-principles calculation demonstrates that as-prepared 1T/2H MoS_(2) exhibit a large capacity to store protons.These protons can be subsequently transferred to Ag NPs,which significantly increases the hydrogen coverage on the surface of Ag NPs in HER process and thus change the rate-determining step of HER on Ag NPs from water dissociation to hydrogen recombination.This study provides a unique strategy to improve the catalytic activity and stability for MoS_(2)-based electrocatalyst.

Light doping of tungsten into copper-platinum nanoalloys for boosting their electrocatalytic performance in methanol oxidation

Coupling the bi-functional mechanism with compressive lattice strain might be an effective way to boost the electrocatalysis of platinum(Pt)-based nanoparticles for methanol oxidation reaction(MOR).This strategy weakens the chemisorption of poisoning CO-like intermediates generated during MOR on the active Pt sites by lowering their d-band center.In this context,we herein report the synthesis of ternary copper-tungsten-platinum(CuWPt)nanoalloys with light doping of W element by simply co-reducing their precursors at elevated temperature.In this ternary alloy system,the presence of only small amount of W element not only weakens the chemisorption of CO-like intermediates by lowering the Pt d-band center through compressive lattice strain,but also cleans the active Pt sites by“hydrogen spillover effect”,endowing the as-prepared CuWPt nanoalloys at an appropriate Cu/W/Pt ratio with good activity for MOR.In specific,the ternary CuWPt alloy nanoparticles at a Cu/W/Pt molar ratio of 21/4/75 show a specific activity of 2.5 mA·cm^(−2)and a mass activity of 2.11 A·mg^(−1)with a better durability,outperforming those ternary CuWPt alloy nanoparticles at other Cu/W/Pt ratios,binary CuPt alloys and commercial Pt/C catalyst as well as a large number of reported Pt-based electrocatalysts.In addition,a single direct methanol fuel cell(DMFC)assembled using ternary CuWPt nanoalloys as anodic catalysts shows a power density of 24.3 mW·cm^(−2)and an open-circle voltage of 0.6 V,also much higher than those of the single DMFC assembled from commercial Pt/C catalysts.