Liquid Organic Hydrogen Carriers Research Articles

Thermodynamics of reversible hydrogen storage: Does alkoxy-substitution of naphthalene yield functional advantages for LOHC systems?

The reversible hydrogenation/dehydrogenation of aromatic molecules, known as liquid organic hydrogen carriers (LOHCs), is considered an attractive option for the safe storage and release of elemental hydrogen. The LOHC systems based on the alkoxy-naphthalene/alkoxy-decalin studied in this work can become potentially attractive from the point of view of the thermodynamic conditions of the reversible hydrogenation/dehydrogenation processes. This work reports the results of a complex experimental investigation of the thermochemical properties of the reactants of the LOHC systems. The enthalpies of formation were measured using high-precision combustion calorimetry, the enthalpies of vaporization and sublimation were derived from the vapor pressure–temperature dependencies measured using the transpiration method, and the melting temperatures and enthalpies of fusion were measured using the differential scanning calorimetry method. The liquid-phase enthalpies of formation of methoxy- and ethoxy-substituted naphthalenes and methoxy- and ethoxy-substituted decalins were derived and used for the thermodynamic analysis of hydrogenation/dehydrogenation reactions and transferhydrogenation reactions.

Multi-criteria decision framework for catalyst selection: Production of formic acid as a circular liquid organic hydrogen carrier in the hydrogen economy

This study aims to use the multi-criteria decision analysis (MCDA) for the selection of suitable catalysts for the production of formic acid (FA), which serves as a circular liquid H2 carrier for the H2-carbon cycle. TOPSIS, VIKOR, ARAS, COPRAS, and PROMETHEE analytical decision-making methods were used to establish priority rankings for each method. With the exception of the top two ranks, the rankings differed across the methods. Therefore, we proposed an alternative ranking for the catalyst selection in the FA production, where all the methods’ results were given equal priority. By aggregating the outcomes from the decision methods and sorting them in ascending order, a final prioritized ranking was established. Our results showed that the proposed MCDA method was effective in identifying the most suitable catalyst for the FA production as a circular LOHC in the H2-carbon cycle. The model determined that Pd nanoparticle-based activated carbon-supported catalyst exhibited high activity, selectivity, and stability, while also being cost-effective. The findings of this study might contribute to the development of more efficient H2 storage systems based on FA.

Benzyl-methylbenzyl-benzene: Improving hydrogen storage and release performance of dibenzyltoluene based liquid organic hydrogen carrier

Liquid organic hydrogen carrier (LOHC) technology enables the safe, easy, and cost-effective storage and transportation of large quantities of hydrogen using inexpensive and mass-produced compounds. The LOHC materials play a crucial role in hydrogen storage capacity, reaction kinetics, reaction temperature, and reversibility. However, the development and optimization of LOHC materials is limited due to using of mass-produced materials for bulk hydrogen logistics. Herein, we propose a molecular engineering approach to overcome the limitations of commercial dibenzyltoluene (DBT)-based LOHC systems, considered one of the most promising LOHC materials based on the heat transfer oil, Marlotherm SH (MSH), owing to its superior physical properties (wide liquid range, and non-flammable properties), low price, and low toxicity. We devised a new chemical structure, benzyl-methylbenzyl-benzene (BMB), with highly improved dehydrogenation/hydrogenation performance achieved by rearranging the methyl group of DBT to overcome the limitations of slow reaction kinetics in terms of its chemical structure. The BMB exhibits a 150 % faster hydrogenation than MSH at 150 °C, and it releases 170 % more hydrogen compared to DBT at 270 °C. In addition, we analyzed the dehydrogenation/hydrogenation pathways according to the structures of DBT and BMB. Furthermore, we found that BMB (27 %) is inevitably generated in the MSH synthesis process alongside DBT (73 %). Based on this, we propose a streamlined and sustainable engineered method for improved MSH material manufacturing with a high BMB ratio (∼70 %). The scientific findings provide a fundamental understanding of DBT-based LOHC systems and new insights into the design of novel LOHC candidates.

Active and stable Pt-Ga2O3/Al2O3 catalyst for dehydrogenation of methylcyclohexane

Methylcyclohexane (MCH) is considered as one of the most promising liquid organic hydrogen carriers (LOHCs) in terms of hydrogen storage and delivery. However, the dehydrogenation process of MCH is relatively difficult, which requires catalyst having high activity and stability. In this work, a catalyst of Pt/Al2O3 by doping Ga2O3 was prepared and tested in the dehydrogenation of MCH, resulting in both high activity and stability. After 176 h of the reaction, the conversion of MCH is no significant decrease, and the toluene (TOL) selectivity was greater than 99%. The characterization results of the catalyst evidenced that the excellent performance of the catalyst is due to the introduction of Ga2O3, which prevents the growth of Pt species and results more positively charged Pt species. These Pt species can weaken the strength of the adsorption between Pt and dehydrogenation products, making dehydrogenation products more easily to be desorbed, which achieving high activity and stability. The catalyst shows great potential for industrial application in the future. This work provides theoretical guidance for designing highly stable dehydrogenation catalysts.

Thermally manageable and scalable reactor configurations towards efficient hydrogen release from liquid organic hydrogen carriers

In the global pursuit to minimize carbon emissions, hydrogen has emerged as a prominent alternative energy solution. This research introduces a thermally efficient, scalable, and potentially carbon–neutral system for releasing hydrogen, employing methylcyclohexane as a liquid organic hydrogen carrier (LOHC). Our heat supply mechanism utilizes benzyltoluene as a liquid–gas phase change material (PCM) to facilitate effective heat transfer from the heating units to the reactor. We have developed catalysts with high dispersion and Pt loading of Pt/γ-Al2O3 that maintain performance over extended periods, achieving a hydrogen extraction rate of 2.3 Nm3H2(g)/h (equivalent to 5 kgH2/day) in a bench-scale reactor. The bench-scale setup achieves near-equilibrium conversion at a space velocity of 2 LLOHC/(Lcat-h) and 310 °C. The PCM-enhanced system supports a scalable catalytic bed design and simplifies heat supply and startup through the use of various heating methods. We then compare catalytic dehydrogenation reactor setups using single and hybrid heat sources; the former includes an internal Joule heater, offering simplicity and reduced heat loss but depends heavily on electrical energy, while the latter combines the internal Joule heater with an external fuel combustor, facilitating rapid startup albeit with increased heat loss. Lastly, we suggest future research directions to address existing technological hurdles and to expand the application of this system in scaling up hydrogen release processes.

Ultrasonic in-situ reduction preparation of SBA-15 loaded ultrafine RuCo alloy catalysts for efficient hydrogen storage of various LOHCs

SBA-15-loaded RuCo alloy nanoparticle catalysts (RuxCoy/S15-SU) for the efficient catalysis of hydrogen storage by various liquid organic hydrogen carriers (LOHCs) were prepared via strong electrostatic adsorption (SEA)-ultrasonic in-situ reduction (UR) technology. The above prepared catalysts were subjected to a series of characterization, such as XPS, H2-TPD/TPR, N2 adsorption–desorption, ICP, CO-chemisorption, FT-IR, XRD and TEM. Ru3+ and Co2+ were evenly anchored on the surface of SBA-15 by SEA, and ultrafine RuCo alloy nanoparticles were formed by UR without any chemical reducing or stabilizing agents. The addition of Co enhanced the dispersion and antioxidant capacity of the RuCo alloy NPs with an average particle size of 2.07 nm and increased the number of catalytically active sites. The synergistic effect of ultrafine particle size and electron transfer between Co and Ru improved the catalytic performance of monobenzyltoluene (MBT) for hydrogen storage. SEA-UR technology strengthened the coordination effect between RuCo alloy NPs and Si-OH, which enhanced the catalytic stability. H2-TPD and H2-TPR indicated that the addition of Co led to more activated H2 to produce hydrogen overflow. For the hydrogenation of MBT, the produced Ru2Co1/S15-SU showed excellent catalytic performance. The hydrogen storage efficiency of MBT was 99.98 % under 110 °C and 6 MPa H2 for 26 min, and the TOF was 145 min−1, which is significantly superior to that of Ru/S15-SU catalyst and that reported in the literature. The hydrogen storage efficiency was still as high as 99.7 % after ten cycles, which was much better than that of Ru/S15-SU and commercial 5 wt% Ru/Al2O3. Ru2Co1/S15-SU is also suitable for efficiently catalyzing hydrogen storage of N-ethylcarbazole, dibenzyltoluene and acenaphthene.

Synergistic structural and electronic influences of Pt bead catalysts on dehydrogenation activity for liquid organic hydrogen carriers

Alumina-supported Pt bead catalysts with uniform (PtU/θ-Al2O3) or egg-shell (PtE/θ-Al2O3) structure and their corresponding potassium-doped counterparts (K-PtU/θ-Al2O3, K-PtE/θ-Al2O3) were synthesized to elucidate the influence of structure-induced active metal distribution and promotor on the dehydrogenation of liquid organic hydrogen carriers (LOHCs). Characterizations of the catalysts confirmed that different synthetic methods led to distinct Pt distributions on the Al2O3 surface. PtE/θ-Al2O3 and K-PtE/θ-Al2O3 had an average size of 1 nm with narrow Pt distributions while PtU/θ-Al2O3 and K-PtU/θ-Al2O3 exhibited bimodal distributions in Pt particle size (<0.2 nm and <0.8 nm), which also influenced the oxidation states. Introducing the promotor (K) facilitated electron transfer into Pt, which resulted in a more metallic state. When applied to the dehydrogenation of two different LOHCs, including methylcyclohexane and perhydro-monobenzyltoluene, K-PtE/θ-Al2O3 exhibited superior catalytic activity and durability compared to other catalysts. The improved activity of K-PtE/θ-Al2O3 was primarily attributed to the combined electronic influences of the catalyst bulk structure and promotor.

Assessment of the estimation methods for the normal boiling point of liquid organic hydrogen carriers

Liquid organic hydrogen carrier (LOHC) presents a promising solution for hydrogen storage. However, its development has been impeded by the absence of normal boiling point (NBP) data for hydrogenation products, especially saturated alicyclic compounds. This gap spurs the search for a reliable and convenient estimation method to aid in the screening of new mediums and the design of chemical processes. Thanks to the intrinsic simplicity, 17 group contribution models were selected and evaluated to identify the optimal ones for different types of alicyclic compounds. The best-performing model was subsequently refined. Furthermore, two models tailored for predicting the NBP of saturated alicyclic compounds were proposed using classical approaches and artificial neural networks. The results indicate that the GCN and GM models yield lower errors in estimating the NBP of alicyclic hydrocarbons, while the GIC2 model performs better for heterocyclic compounds. The developed models are more accurate compared to the existing models. Notably, the neural-network-based model exhibits excellent performance. These models are expected to provide useful insights for large-scale screening of LOHCs for hydrogen storage.

Acceptorless ambient-temperature dehydrogenation and reversible hydrogenation of N-heterocycles over single-atom Co-N-C catalysts

Reversible hydrogen storage via Liquid organic hydrogen carriers (LOHCs) is one of the key technologies for efficient utilization of hydrogen energy. How to construct efficient dehydrogenation/hydrogenation catalysts that enable low-temperature catalysis still remains challenging. Herein, we present the design and construction of single-atom Co-N-C(x) catalysts allowing significantly improved acceptorless dehydrogenation of 1,2,3,4-tetrahydroquinoline (THQ). By varying the ligand/Co ratio, the optimal Co-N-C(1.5) can achieve 97.5% dehydrogenated product and 0.82 h−1 TOF value at ambient temperature, overperforming many reported non-noble metal even noble metal catalysts. This catalyst exhibits good recyclability and substrate versatility, enabling ambient temperature dehydrogenation of various N-heterocycles and efficient reverse hydrogenation of aromatic N-heterocycles, thus achieving the loop of reversible hydrogen storage. The active catalyst centers consist of specific Co-Nx moieties and nitrogen species within the carbon support. Controlled experiments reveal that the different performance of Co-N-C(x) is determined by density of the Co-Nx, and the rate-determining step of THQ dehydrogenation is correlated with the bond cleavages in surface-bound THQ. This work offers a promising pathway for energy-efficient and cost-effective hydrogen energy utilization under practical conditions.

Supervised Machine Learning-Based Prediction of Hydrogen Storage Classes Utilizing Dibenzyltoluene as an Organic Carrier.

Dibenzyltoluene (H0-DBT), a Liquid Organic Hydrogen Carrier (LOHC), presents an attractive solution for hydrogen storage due to its enhanced safety and ability to store hydrogen in a concentrated liquid form. The utilization of machine learning proves essential for accurately predicting hydrogen storage classes in H0-DBT across diverse experimental conditions. This study focuses on the classification of hydrogen storage data into three classes, low-class, medium-class and high-class, based on the hydrogen storage capacity values. We introduce Hydrogen Storage Prediction with the Support Vector Machine (HSP-SVM) model to predict the hydrogen storage classes accurately. The performance of the proposed HSP-SVM model was investigated using various techniques, which included 5-Fold Cross Validation (5-FCV), Resubstitution Validation (RV), and Holdout Validation (HV). The accuracy of the HV approach for the low, medium, and high class was 98.5%, 97%, and 98.5%, respectively. The overall accuracy of HV approach reached 97% with a miss clarification rate of 3%, whereas 5-FCV and RV possessed an overall accuracy of 93.9% with a miss clarification rate of 6.1%. The results reveal that the HV approach is optimal for predicting the hydrogen storage classes accurately.

Flow rate control in a plug-flow reactor for liquid organic hydrogen carriers dehydrogenation

Liquid organic hydrogen carriers can store hydrogen for later release through dehydrogenation reactions. The kinetic rate depends on the temperature, pressure, and hydrogen concentration itself, so it varies throughout the discharge. As such, control systems are needed to meet the end-user power demand. An innovative plug flow reactor coupled with two vessels is introduced and accurately sized. Multiple strategies are implemented in a Matlab/Simulink model to test the efficacy of control methods based on pressure, temperature, and mass flow rate. The results obtained with the simulations highlight a dramatic drop in performance (utilisation factor lower than 80%) associated with relatively high power demands (higher than 70% in the case of temperature control), whereas low demands are met with satisfactory degrees of utilisation under both pressure and temperature control. Control over the mass flow rate of external fluid leads to lackluster results and should only be chosen as an auxiliary controlled variable. Lastly, Ragone diagrams for pressure and temperature control are presented and used to identify the optimal system sizing range: effective discharge duration should be in the range 10–40h with pressure control or 5–40h with temperature control to achieve a utilisation factor of at least 80%.

Recent Advances in Reversible Liquid Organic Hydrogen Carrier Systems: From Hydrogen Carriers to Catalysts.

Liquid organic hydrogen carriers (LOHCs) have gained significant attention for large-scale hydrogen storage due to their remarkable gravimetric hydrogen storage capacity (HSC) and compatibility with existing oil and gas transportation networks for long-distance transport. However, the practical application of reversible LOHC systems has been constrained by the intrinsic thermodynamic properties of hydrogen carriers and the performances of associated catalysts in the (de)hydrogenation cycles. To overcome these challenges, thermodynamically favored carriers, high-performance catalysts, and catalytic procedures need to be developed. Here, significant advances in recent years have been summarized, primarily centered on regular LOHC systems catalyzed by homogeneous and heterogeneous catalysts, including dehydrogenative aromatization of cycloalkanes to arenes and N-heterocyclics to N-heteroarenes, as well as reverse hydrogenation processes. Furthermore, with the development of metal complexes for dehydrogenative coupling, a new family of reversible LOHC systems based on alcohols is described that can release H2 under relatively mild conditions. Finally, views on the next steps and challenges in the field of LOHC technology are provided, emphasizing new resources for low-cost hydrogen carriers, high-performance catalysts, catalytic technologies, and application scenarios.

Process Engineering Analysis of Transport Options for Green Hydrogen and Green Hydrogen Derivatives

The transition of the German economy and energy system toward CO2 neutrality requires large quantities of climate‐friendly chemical energy carriers, such as green hydrogen, to be imported. The decision on the most favorable import routes must consider its energy efficiency To respect the remaining CO2 budget to achieve the 1.5° climate target, the implementation time and therefore additional evaluation criteria must be taken into account. In this article, as a first step, the energy utilization rate () for different hydrogen import options is evaluated. Starting off from hydrogen at 25 °C and 25 bar produced in the exporting country, liquid hydrogen, ammonia, liquid methane (Green LNG), methanol, and liquid organic hydrogen carrier are considered as chemical energy carries. Liquid hydrogen is in future the most efficient import option ( = 7%) when gaseous hydrogen is supplied in the importing country. When direct utilization of the H2 derivatives is considered, the ammonia import route has the highest energy utilization rate with 77%. If point sources for CO2 are considered, direct utilization of methanol ( = 83%) and Green LNG ( = 76%) are energetically favorable import options. Additional significant criteria for a technological assessment are maturity of technologies, available capacities, infrastructures, and production processes.

Unravelling the reaction mechanism for H2 production via formic acid decomposition over Pd: Coverage-Dependent microkinetic modeling

As a key liquid organic hydrogen carrier, investigating the decomposition of formic acid (HCOOH) on the Pd (111) transition metal surface is imperative for harnessing hydrogen energy. Despite a multitude of studies, the major mechanisms and key intermediates involved in the dehydrogenation process of formic acid remain a great topic of debate due to ambiguous adsorbate interactions. In this research, we develop an advanced microkinetic model based on first-principles calculations, accounting for adsorbate–adsorbate interactions. Our study unveils a comprehensive mechanism for the Pd (111) surface, highlighting the significance of coverage effects in formic acid dehydrogenation. Our findings unequivocally demonstrate that H coverage on the Pd (111) surface renders formic acid more susceptible to decompose into H2 and CO2 through COOH intermediates. Consistent with experimental results, the selectivity of H2 in the decomposition of formic acid on the Pd (111) surface approaches 100 %. Considering the influence of H coverage, our kinetic analysis aligns perfectly with experimental values at a temperature of 373 K.

Toward High-Energy-Density Fuels for Direct Liquid Organic Hydrogen Carrier Fuel Cells: Electrooxidation of 1-Cyclohexylethanol.

Electrochemically active liquid organic hydrogen carriers (EC-LOHCs) can be used directly in fuel cells; so far, however, they have rather low hydrogen storage capacities. In this work, we study the electrooxidation of a potential EC-LOHC with increased energy density, 1-cyclohexylethanol, which consists of two storage functionalities (a secondary alcohol and a cyclohexyl group). We investigated the product spectrum on low-index Pt single-crystal surfaces in an acidic environment by combining cyclic voltammetry, chronoamperometry, and in situ infrared spectroscopy, supported by density functional theory. We show that the electrooxidation of 1-cyclohexylethanol is a highly structure-sensitive reaction with activities Pt(111) ≫ Pt(100) > Pt(110). Most importantly, we demonstrate that 1-cyclohexylethanol can be directly converted to acetophenone, which desorbs from the electrode surface. However, decomposition products are formed, which lead to poisoning. If the latter side reactions could be suppressed, the electrooxidation of 1-cyclohexylethanol would enable the development of EC-LOHCs with greatly increased hydrogen storage capacities.

Thermodynamics of Reversible Hydrogen Storage: Are Methoxy‐Substituted Aromatics better through Oxygen Functionality?

AbstractAn attractive option for the storage of hydrogen is the reversible hydrogenation of an aromatic substance, a so‐called liquid organic hydrogen carrier. For hydrogen release, it is desirable to find substances with low enthalpies of reaction for dehydrogenation. It has been demonstrated that substitution, e.g., with methyl groups, on the ring can have a positive effect in this regard. In this study, thermochemical properties of methoxy‐substituted pyridines and quinolines and their respective hydrogenated counterparts have been analyzed from a thermodynamic point of view. Combustion calorimetry has been utilized to measure the enthalpy of formation and the transpiration method for determining the vapor pressure. Additionally, high‐level quantum‐chemical approaches have been applied to obtain caloric data in the gas phase, which provide a basis for comparison and evaluation of the experimental data. The results reveal two main effects of methoxy substitution. First, oxygenated substituents like methoxy groups have stronger effect on the Gibbs energy of reaction and thus the temperature needed thermodynamically for hydrogen release than methyl groups. Second, the effect is highly depending on the position of the substitution on the ring. Particularly methoxy groups close to a N heteroatom can have a significant positive effect, which might enable hydrogen release at equilibrium temperatures more than 50 K lower than for their unsubstituted analogue.

Modeling of the Continuous Dehydrogenation of Perhydro‐Dibenzyltoluene in a Cuboid Reactor

The use of the dibenzyltoluene/perhydro‐dibenzyltoluene (H18–DBT) system as a liquid organic hydrogen carrier (LOHC) enables the safe and loss‐free storage of hydrogen. The release of hydrogen from the LOHC is a catalytic reaction and requires ≈27% of the lower heating value of the released hydrogen in the form of heat neglecting heat losses. The high heat requirement makes it necessary to design chemical conversion units that both provide good heat input and accommodate the high gas release. Up to 1200 L of hydrogen is released from 1 L of LOHC under reaction conditions. In this work, a cuboid reactor for the release of hydrogen from H18–DBT is demonstrated. In the experiments, it is shown that evaporation has a significant effect on the reaction rate and thus the amount of hydrogen releases. Therefore, a kinetic model capable of accounting for the release rate and evaporation in the reactor is developed. The model is successfully validated and shows deviations of less than 15% between measured and modeled hydrogen flow in the entire range considered. Since the model considers this important interaction between evaporation and hydrogen release for the first time, it is suitable for optimizing the reactor used.

Liquid organic hydrogen carriers: Process design and economic analysis for manufacturing N‐ethylcarbazole

AbstractThis paper revisits the economics of manufacturing N‐ethylcarbazole (NEC), a strong candidate for large‐scale liquid organic hydrogen carrier (LOHC) supply chains, because of its high H2 storage capacity (6 wt%), selective hydrogenation and dehydrogenation reactions, and favorable reaction enthalpy and reaction temperatures compared to other LOHC systems. Two different process routes for producing NEC from industrial chemicals are selected out of 10 possible options: one using aniline and the other using cyclohexanone and nitrobenzene as feedstock. The required capital and operational costs are estimated to determine a NEC break‐even cost for a capacity of 225 ktpa. NEC break‐even costs of $3.0 and $2.6 per kg LOHC are found for the routes. This is significantly less than the $40/kg cost that has generally been reported in literature for NEC, thus improving the economic viability of using NEC as LOHC. The total fixed capital costs are estimated to be $200 MM and $250 MM. Furthermore, the prices of the feedstock show the largest influence (76% and 72%) on the final NEC break‐even costs. The overall LOHC price contribution to the levelized H2 cost is estimated to be $0.77–$0.90 per kg H2 for a 60‐day roundtrip and $0.09–$0.10 per kg H2 for a 7‐day roundtrip. It is important to note that both routes rely heavily on laboratory scale data and the corresponding assumptions that stem from this limitation. Therefore, this research can serve as a guide to future experimental studies into validating the key assumptions made for this analysis.

Use of Biosourced Molecules as Liquid Organic Hydrogen Carriers (LOHC) and for Circular Storage

The use of Liquid Organic Hydrogen Carriers (LOHC) is one of the potential options to store hydrogen. Today, the vast majority of compounds used as LOHC come from the oil industry. Using biosourced LOHC would be a step forward in the development of this CO2-free solution. This article looks at LOHC candidates that can be obtained from biomass. The special case of formic acid and methanol, which do not fall within the definition of LOHC, is also considered. The synthesis of alcohols, polyols, amines, aminoalcohols and N-heterocyclic compounds from biosourced compounds is reviewed.

Ultrasound-assisted preparation of PdCo bimetallic nanoparticles loaded on beta zeolite for efficient catalytic hydrogen production from dodecahydro-N-ethylcarbazole

Research and development of high-performance catalysts is a key technology to realize hydrogen energy storage and transportation based on liquid organic hydrogen carriers. Co/beta was prepared using beta zeolite as a carrier via an electrostatic adsorption (ESA)-chemical reduction method, and it was used as the template and reducing agent to prepare bimetallic catalysts via an ultrasonic assisted galvanic replacement process (UGR). The fabricated PdCo/beta were characterized by TEM, XPS, FT-IR, XRD, H2-TPR, and H2-TPD. It was shown that the ultrafine PdCo nanoparticles (NPs) are evenly distributed on the surface of the beta zeolite. There is electron transfer between metal NPs and strong-metal-support-interaction (SMSI), which results in highly efficient catalytic dodecahydro-N-ethylcarbazole (12H-NEC) dehydrogenation performance of PdCo bimetallic catalysts. The dehydrogenation efficiency reached 100 % in 4 h at 180 °C and 95.3 % in 6 h at 160 °C. The TOF of 146.22 min−1 is 7 times that of Pd/beta. The apparent activation energy of the reaction is 66.6 kJ/mol, which is much lower than that of Pd/beta. Under the action of ultrasonic waves, the galvanic replacement reaction is accelerated, and the intermetal and metal-carrier interactions are enhanced, which improves the catalytic reaction performance.