Experimental and theoretical investigations into the activity and mechanism of the water–gas shift reaction catalyzed by Au nanoparticles supported on Zn–Al/Cr/Fe layered double hydroxides

Water–gas shift reaction (WGSR) is an industrialized reaction with numerous applications concerning CO removal and H₂ generation. Since this process is widely used and occurs at elevated temperatures, the development of high efficiency and stable catalysts for WGSR and investigating their catalytic mechanism is a hot topic. In this paper, we demonstrate Au nanoparticles supported on different layered double hydroxides (LDHs) as highly efficient and stable catalysts for WGSR. The incorporation of Au nanoparticles significantly decreases the activation energy and enhances the catalytic activity of LDHs for WGSR, with Au/ZnCr–LDHs exhibiting the best catalytic performance including: 79.4% CO conversion, 102.1 μmol g_cat⁻¹ s⁻¹ of reaction rate, 1.01 s⁻¹ TOF values and 41.7 kJ mol⁻¹ of activation energy. TPR experiments suggest that the addition of Au alters the redox cycle on the surface of the catalyst, a key intermediary step involved in the catalytic process. In situ DRIFTS shows that the production of CO₂ during WGSR involves the reaction between CO and adsorbed O, which comes from the dissociation of OH species and not the decomposition of formates. DFT calculations indicate that Au–based catalysts can effectively lower the energy barrier of the kinetically relevant step of H₂O dissociation, which is the most probable reason for the enhancement of activity. The calculated activation barriers coincide with the experimentally measured values with the order of Au/ZnCr–LDHs<Au/ZnFe–LDHs<Au/ZnAl–LDHs<LDHs. Particularly, redox mechanism B has the lowest activation barriers which is the most potential reaction pathway and perfectly supports the in–situ DRIFTS results.     

Hydrogen evolution reaction on in-plane platinum and palladium dichalcogenides via single-atom doping

Searching for the catalysts with excellent catalytic activity and high chemical stability is the key to achieve large-scale production of hydrogen (H₂) through hydrogen evolution reaction (HER). Two-dimensional (2D) platinum and palladium dichalcogenides with extraordinary electrical properties have emerged as the potential candidate for HER catalysts. Here, chemical stability, HER electrocatalytic activity, and the origin of improved HER performance of Pt/Pd-based dichalcogenides with single-atom doping (B, C, N, P, Au, Ag, Cu, Co, Fe, Ni, Zn) and vacancies are explored by first-principles calculations. The calculated defect formation energy reveals that most defective structures are thermodynamically stable. Hydrogen evolution performance on basal plane is obviously improved by single-atoms doping and vacancies. Particularly, Zn-doped and Te vacancy PtTe₂ have a ΔG_H value close to zero. Moreover, defect engineering displays a different performance on HER catalytic activity in sulfur group elements, in order of S < Te < Se in Pd-based chalcogenides, and S < Se < Te in Pt-based chalcogenides. The origin of improved hydrogen evolution performance is revealed by electronic structure and charge transfer. Our findings of the highly activating defective systems provide a theoretical basis for HER applications of platinum and palladium dichalcogenides.     

Improved catalytic stability of Pt/TiO2 catalysts for methylcyclohexane dehydrogenation via selenium addition

To improve the catalytic activity of Pt catalysts for methylcyclohexane (MCH) dehydrogenation, which is utilized for hydrogen transportation, the effects of the addition of Se on the performance of Pt/TiO₂ catalysts were investigated. In Se/Pt/TiO₂ catalysts, even a small amount of Se addition (Se/Pt = 0.01) improved the catalyst stability. Se was highly dispersed on the Pt/TiO₂ surface, without volatilizing in a reducing atmosphere at temperatures below 450 °C, and did not form an alloy with Pt. The analysis of adsorption-desorption characteristics revealed that the addition of Se promoted the desorption of products, including the main product, toluene. Moreover, an electron donation effect from Se to Pt was observed by FT-IR measurement after the reduction. The desorption characteristic caused by the electron donation effect suppressed the deterioration of the catalyst and allowed stable catalytic activity toward the MCH dehydrogenation reaction.     

Preparation and characterization of hydrophobic carbon-supported Pt3M (M = Fe,Co, Ni and Cr) bimetals for H/D isotope separation between hydrogen and water

To improve characteristics of hydrophobic catalysts for hydrogen isotope separation between hydrogen and water which is a key reaction for water detritiation and heavy water production, monodispersed Pt₃M bimetal hydrophobic catalysts were fabricated. The average diameters of Pt₃M nanoparticles ranged from 2.2 nm to 2.6 nm. The lattice parameters of Pt₃M were 3.87 Å, 3.83 Å, 3.78 Å and 3.90 Å, respectively. All compositions were well-controlled to the similar value. The addition of the metallic Fe, Ni, Cr, and Co hindered the oxidation of the metallic Pt during the preparation of Pt₃M/C catalysts. The catalytic activities for H/D isotope separation increased in the following order: Pt/C < Pt₃Ni/C ≈ Pt₃CoC < Pt₃Fe/C < Pt₃Cr/C. Catalytic performance tests demonstrated that selection of Pt₃M bimetal is a very effective approach to improve hydrophobic catalytic. Finally, the enhanced activities of Pt₃M bimetals over Pt were discussed by different mechanisms.     

Study of Ni/CeO2–ZnO catalysts in the production of H2 from acetone steam reforming

This paper reports the study of new Ni/ZnO-based catalysts for hydrogen production from substoichiometric acetone steam reforming (ASR). The effect of CeO₂ introduction is analyzed regarding the catalytic behavior and carbon deposits formation. ASR was studied at 600 °C using a steam/carbon ratio S/C = 1. Ni/xCeZnO (x = 10, 20, 30 CeO₂ wt %) catalysts showed a better performance than the bare Ni/ZnO. Ni/xCeZnO generated a lower amount and less ordered carbon deposits than Ni/ZnO. The higher the CeO₂ content in Ni/xCeZnO, the lower the amount of carbon deposits in the post-reaction catalyst. The highest H₂ production under ASR at the experimental conditions used was achieved for the Ni/xCeZnO catalysts. In-situ DRIFTS-MS experiments under ESR conditions showed different reaction pathways over Ni/20CeZnO and Ni/ZnO catalysts.     

Ni2P(O)–Fe2P(O)/CeOx as high effective bifunctional catalyst for overall water splitting

The development of cost-effective bifunctional catalysts with excellent performance and good stability is of great significance for overall water splitting. In this work, NiFe layered double hydroxides (LDHs) nanosheets are prepared on nickel foam by hydrothermal method, and then Ni₂P(O)–Fe₂P(O)/CeO_x nanosheets are in situ synthesized by electrodeposition and phosphating on NiFe LDHs. The obtained self-supporting Ni₂P(O)–Fe₂P(O)/CeO_x exhibit excellent catalytic performances in alkaline solution due to more active sites and fast electron transport. When the current density is 10 mA cm^?2, the overpotential of hydrogen evolution reaction and oxygen evolution reaction are 75 mV and 268 mV, respectively. In addition, driven by two Ni₂P(O)–Fe₂P(O)/CeO_x electrodes, the alkaline battery can reach 1.45 V at 10 mA cm^?2.     

Constructing microstructures in nickel-iron layered double hydroxide electrocatalysts by cobalt doping for efficient overall water splitting

The development of Ni–Fe layered double hydroxide (NiFe LDH) catalysts for overall water splitting (OWS) is urgently required. NiFe LDHs are promising catalysts for the oxygen evolution reaction (OER). However, their hydrogen evolution reaction (HER) performance is restricted by slow kinetics. The construction of multiple types of active sites to simultaneously optimise the OER and HER performance is significant for OWS using NiFe LDHs. Hence, a Co-doped NiFe LDH electrocatalyst with dislocations and stacking faults was designed to modulate the electronic structure and generate multiple types of activity sites. The Co_0.03-NiFe_0.97 LDH catalyst only required overpotentials of 280 (50 mA cm⁻², OER) and 170 mV (10 mA cm⁻², HER). However, it reached a current density of 50 mA cm⁻² at 1.53 V during OWS. Co_0.03-NiFe_0.97 LDHs could be stabilised for 140 h at 1.52 V. Furthermore, Co_0.03-NiFe_0.97 LDHs exhibited a higher electrocatalytic activity than commercial Raney nickel and Pt/C||IrO₂ under industrial conditions. The significant specific surface area, high conductivity, and unique microstructures are the major factors contributing to the excellent OWS performance. This study suggests an efficient strategy for introducing microstructures to fabricate catalysts with high activity for application in OWS.     

Facile synthesis of copper selenide with fluffy intersected-nanosheets decorating nanotubes structure for efficient oxygen evolution reaction

Rational nanostructure design is the key point to prepare catalysts with superior catalytic performance, and tedious preparation method limits them large-scale application. Here, a Cu₂Se with fluffy intersected-nanosheets decorating nanotubes structure were prepared by a simple and rapid solution-immersion method at room temperature. The hollow hierarchical structure on a good conductor Cu foam (CF) enlarges surface available sites, enhances the conductivity of electrode materials, then endowing the catalyst with quick charge/mass transportation and favorable oxygen evolution reaction (OER) performance. In alkaline medium, our as-prepared Cu₂Se/CF electrode demonstrates high OER performance, especially for lower overpotential (200 mV at 10 mA cm⁻²) compared with the previously reported Cu-based catalysts. Moreover, the Cu₂Se catalyst could afford galvanostatic test of 10 mA cm⁻² test over 12 h and present superior OER tolerance. These results indicate that the Cu₂Se catalyst via cost efficiency and efficient solution-immersion method could be applied to large-scale efficient OER.     

Preparation of nanocrystalline metal (Cr,Al, Mn,Ce, Ni,Co and Cu) modified ferrite catalysts for the high temperature water gas shift reaction

Water gas shift reaction is an essential process of hydrogen production and carbon monoxide removal from syngas. Fe–Cr–Cu catalysts are typical industrial catalysts for high temperature water gas shift reaction but have environmental and safety concerns related to chromium content. In this work nanocrystalline metal (M)-modified ferrite catalysts (M = Cr, Al, Mn, Ce, Ni, Co and Cu) for replacement of chromium were prepared by coprecipitation method and the effects of promoters on the structural and catalytic properties of the iron based catalysts were studied. Prepared catalysts were characterized using X-ray diffraction (XRD), N₂ adsorption (BET), temperature-programmed reduction (TPR) and transmission electron microscopies (TEM) techniques. Temperature-programmed reduction measurements inferred that copper favors the active phase formation and significantly decreased the reduction temperature of hematite to magnetite. In addition, water gas shift activity results revealed that Fe–Al–Cu catalyst with Fe/Al = 10 and Fe/Cu = 5 weight ratios showed the highest catalytic activity among the prepared catalysts. Moreover, the effect of calcination temperature, GHSV and steam/gas ratio on the catalytic performance of this catalyst was investigated.     

Three-dimensional hierarchical nanoporous (Mn,Ni)-Doped Cu2S architecture towards high-efficiency overall water splitting

Dealloying technique is an important approach to design porous structures and highly active catalysts. In this work, monolithic nanoporous (Mn,Ni)-doped Cu₂S skeletons with controllable composition and tunable porosity are synthesized via dealloying and sulfuration technique. The as-prepared S-np-Mn₇₀Cu₂₉Ni₁ electrode exhibits outstanding catalytic performance toward HER and OER in 1.0 M KOH solution, which drives high current density of 50 mA cm^?2 at the overpotentials of 136 and 317 mV respectively. The excellent catalytic performance is attributed to the unique three-dimensional interconnected bicontinuous nanoporous architecture, which not only exposes high-density catalytic active sites, but also accelerates electron/mass transfer between catalyst surface and electrolyte. Density functional theory (DFT) calculations also reveal that (Mn,Ni)-doped Cu₂S matrix can accelerate water adsorption/dissociation and optimize adsorption-desorption energetics of H intermediates, thus improving the intrinsic HER activity of nanoporous Cu₂S electrocatalysts. Meanwhile, an alkaline water electrolyzer is constructed with the S-np-Mn₇₀Cu₂₉Ni₁ electrode as anode and cathode respectively, depicting remarkable performance in water electrolysis. In the light of advantages such as adjustable composition and tunable porosity in alloying-dealloying process, it offers a new vision for tuning the porosity and catalytic activities of transition metal sulfides and other active catalysts.     

Atomic metal,N, S co-doped 3D porous nano-carbons: Highly efficient catalysts for HT-PEMFC

A new strategy for fabricating atomically dispersed heteroatom-doped nanoporous carbon materials is reported. Through the self-assembly of dopamine, triblock copolymer F127, and metal ions, different three-dimensional atomic metal-N/S doped carbon catalysts are obtained after pyrolysis. Noble metal salts with ferrous sulfate induce the bimetallic monatomic FeM (M = Pd, Pt) N, S-doped carbon catalysts. Minute amounts of Pt or Pd single atoms in the catalysts greatly improve the oxygen reduction reaction (ORR) activity both in acidic and alkaline conditions. Typically, the obtained Fe, Pt–N/S co-doped carbon (FePt-NSC) catalyst exhibits superior ORR performance with positive half-wave potentials (E_1/2) of 0.89 and 0.80 V in alkaline and acidic solutions, respectively. In addition, FePt-NSC displays dominant four electron catalytic process and excellent electrocatalytic stability. The high temperature proton exchange membrane fuel cell (HT-PEMFC) test (160 °C) illustrates that FePt-NSC reaches 0.67 V at 400 mA/cm² and achieves the peak power density of 628 mW/cm², better than most of the catalysts reported at the similar conditions. These results indicate the atomic metal-N/S doped porous carbon catalysts to be highly promising low-Pt catalysts for HT-PEMFC.     

Predicted superior hydrogen evolution activities of MoC via surface dopant

Molybdenum carbides (MoC) are regarded as promising candidates for electrocatalytic hydrogen evolution reaction (HER) as their stabilities, high conductivities. Non-metallic doping is a robust way to enhance the HER activity of MoC in experiments, yet the systematic theoretical study is still lacking. In this work, we investigate the surface doping effect on HER activity of C-terminated γ-MoC(100) by density functional theory (DFT). The thermodynamical stability and realistic catalytic surface of doped surfaces, including mono- and co-doping by three elements (N, P and S) with various doping ratios, are verified by formation energies and surface Pourbaix diagrams, respectively. According to the hydrogen adsorption ability on different coverage and the calculated exchange current densities (i₀) of the doped surfaces, the surfaces doping in range of (P% > 60% and N% > 5%), (60% < N% <85% and P% < 25%), and (60% < N% < 85% and S% < 25%), show larger i₀ (i₀ > 4 mA/cm²). Especially the N/P co-doping γ-MoC(100), their larger i₀ in greater range enables their promising excellent performance in hydrogen evolution in experiments. The improved HER activities of doped MoC(100) are ascribed to suitable hydrogen adsorption abilities tuned by suitable p_z-band centers and the charge redistribution. Our DFT simulations provide more insight and guidance for improving the HER performance of electrode catalysts using non-metallic doping effects.     

Comparisons of Pt catalysts supported on active carbon,carbon molecular sieve,carbon nanotubes and graphite for HI decomposition at different temperature

A series of Pt catalysts supported on activated carbon (AC), carbon molecular sieve (CMS), carbon nanotubes (CNT) and graphite (GR) were prepared by the impregnation method. Their catalytic performances in HI decomposition were evaluated in a fixed bed reactor at temperatures ranging from 400 to 550 °C under atmospheric pressure. The different Pt catalysts before and after HI decomposition at different temperature were characterized by BET, XRD and TEM, respectively. The results of the activity evaluation indicated that the activity order of different Pt catalysts changed significantly with the variation of reaction temperature. At 400 °C, different supported Pt catalysts activities decreased in order of Pt/CMS > Pt/AC > Pt/CNT > Pt/GR. At 450 °C, the activities of different Pt catalysts followed the order of Pt/AC ≈ Pt/CNT > Pt/CMS > Pt/GR. At 500 and 550 °C, the Pt/CNT showed the optimum activity and stability during HI decomposition, which could be attributed to the high dispersion of Pt particles and the special microstructure of CNT. The XRD and TEM results illustrated that the Pt particle size or Pt dispersion in different supported Pt catalysts showed different sensitivity to the reaction temperature.     

Cu2S@NiFe layered double hydroxides nanosheets hollow nanorod arrays self-supported oxygen evolution reaction electrode for efficient anion exchange membrane water electrolyzer

Herein, we prepared highly active self-supported Cu₂S@NiFe layered double hydroxides nanosheets (LDHs) oxygen evolution reaction (OER) electrode (Cu₂S@NiFe LDHs/Cu foam) with three-dimensional (3D) multilayer hollow nanorod arrays structure, which is composed of the outer layer (two-dimensional (2D) NiFe LDHs) and the inner layer (one-dimensional (1D) Cu₂S hollow nanorod arrays). The unique structure of NiFe LDHs and Cu₂S hollow nanorod composites can expose more active sites, and simultaneously promote electrolyte penetration and gas release during the water electrolysis process. Thus, the Cu₂S@NiFe LDHs/Cu foam electrode exhibits a significant OER performance, with the overpotentials of 230 and 286 mV at 50 and 100 mA cm⁻², respectively. Anion exchange membrane water electrolyzer (AEMWE) with the prepared electrode can attain a voltage of 1.56 V at the current density of 0.50 A cm⁻², showing a good performance that is comparable to the-state-of-the-art AEMWE in 1 M KOH. In addition, the AEMWE can be run for 300 h at the current density of 0.50 A cm⁻². The high performance and good stability of AEMWE are attributed to the special structure of the OER electrode, which can prevent the agglomeration of nanosheets and thus expose more active sites at the edge of the nanosheets.     

Preparation and characterization of hollow carbon sphere supported catalysts (M@HCS [M=Pt,Ir, Ni]) for HI decomposition in the iodine–sulfur cycle for hydrogen production

Catalysts for HI decomposition are important in hydrogen production via the iodine–sulfur cycle. The catalysts should have a good activity, excellent thermal stability at 400 °C-500 °C, and corrosion resistance to HI and iodine. In this study, a series of hollow carbon sphere (HCS) supported mono-metallic catalysts M@HCS (M = Pt, Ir, Ni) were fabricated by coating the silica core with dopamine, carbonization, and sacrificial core technique. Active carbon-supported monometallic catalysts (M/C) were also prepared via the impregnation method. Catalytic activities of M@HCS and M/C during HI decomposition at 500 °C were compared. The composition, structure, specific surface area, morphology, and surface chemical states of M@HCS and M/C were characterized via inductively coupled plasma (ICP), X-ray diffraction (XRD), Brunauere-Emmette-Teller (BET) surface area, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Results showed that the catalytic performance of M@HCS was better than that of M/C probably because of the synergistic effects between the active metals and HCSs.     

Plasma-assisted Ni catalysts: Toward highly-efficient dry reforming of methane at low temperature

Dry reforming of methane (DRM) reaction can convert primary greenhouse gases (CH₄ and CO₂) to value-added chemicals (H₂ and CO), but generally suffers from harsh reaction conditions (>700 °C) and inevitable deactivation of catalysts. In this work, we report supported Ni catalysts based on a topotactic transformation process from the layered double hydroxides (NiZnAl?LDHs) precursors. Structural characterizations (XRD, HRTEM, CO chemisorption) verify a uniform distribution of Ni nanoparticles (～7 nm) on the mixed metal oxides support with a high dispersion (denoted as Ni/MMO). With the assistance of non-thermal plasma (NTP), the optimal sample (Ni/MMO?S2) exhibits a good catalytic conversion of CH₄ (～69%) and CO₂ (～54%) at low temperatures (30–60 °C), which is comparable with the activity of thermocatalytic process at ～650 °C without NTP. The energy efficiency of NTP-assisted catalysis process is an order of magnitude higher than that of thermocatalytic process at ～650 °C and enhances by 80% relative to NTP-alone process at low temperatures. The Ni/MMO?S2 catalyst shows satisfactory stability after 600 min stability test, with a slight decrease in conversion (within ～1%). In addition, a combined study including catalytic evaluations, operando OES, XAFS and XPS verifies that metallic Ni species acts as active center, which can promote the dissociation of CH₄ and CO₂ into highly reactive intermediate species with the assistance of NTP. This synergistic effect between plasma and Ni catalyst remarkably decreases the apparent activation energy by ～50%, accounting for the high catalytic performance at low temperatures. This work demonstrates a promising synergistic catalysis strategy between plasma and catalysts at low temperatures, which can be extended to other reactions operated under harsh conditions.     

Electrochemical hydrogen evolution reaction over Co/P doped carbon derived from triethyl phosphite-deposited 2D nanosheets of Co/Al layered double hydroxides

Hydrogen is widely considered an emissions-free alternative energy carrier for sustainable energy devices, such as fuel cells and nickel-metal hydride batteries. Recently, electrochemical hydrogen evolution reaction (HER) from water splitting has been attracted as an eco-friendly process for producing hydrogen. Herein, we report a Co/P-doped carbon material (Co/P/C) derived from cobalt-aluminum layered double hydroxide nanosheets (LDHs) for HER. The Co/P/C was synthesized using triethyl phosphite as phosphate and carbon sources by a one-step chemical vapor deposition (CVD) process. The regular arrangement of Co and Al atoms in the precursor LDHs allowed Co/P species to be highly dispersed under optimized CVD conditions. The carbon nanotube formed by the CVD process improved the catalytic activity of Co/P/C. The optimized Co/P/C exhibits a low overpotential of 240 mV at ?10 mA cm^?2 for HER, comparable to the commercial Pt/C catalyst. This work provides a new direction for developing transition-metal and hetero-atom co-doped carbon materials with high catalytic activity for HER.     

Accelerated oxygen evolution kinetics on NiFeAl-layered double hydroxide electrocatalysts with defect sites prepared by electrodeposition

NiFe layered double hydroxides (LDHs) is considered to be one of the LDHs electrocatalyst materials with the best electrocatalytic oxygen evolution properties. However, its poor conductivity and inherently poor electrocatalytic activity are considered to be the limiting factors inhibiting the electrocatalytic properties for oxygen evolution reaction (OER). The amorphous NiFeAl-LDHs electrocatalysts were prepared by electrodeposition with nickel foam as the support, and the D-NiFeAl-LDHs electrocatalyst with defect sites was then obtained by alkali etching. The mechanism of catalysts with defect sites in OER was analyzed. The ingenious defects can selectively accelerate the adsorption of OH⁻, thus enhancing the electrochemical activity. The D-NiFeAl-LDHs electrocatalyst had higher OER electrocatalytic activity than NiFe-LDHs electrocatalyst: its accelerated OER kinetics were mainly due to the introduction of iron and nickel defects in NiFeAl-LDHs nanosheets, which effectively adjusted the surface electronic structure and improved OER electrocatalytic performance. There was only a low overpotential of 262 mV with the current density of 10 mA cm⁻², and the Tafel slope was as low as 41.67 mV dec⁻¹. The OER electrocatalytic performance of D-NiFeAl-LDHs was even better than those of most of the reported NiFe-LDHs electrocatalysts.     

Direct methanol fuel cells using Se/Ru core/shell cathodes provide high catalytic activity and stability

We have synthesized Se/Ru core/shell nanoparticles (NPs) as cathode electrocatalysts. By controlling the concentration of RuCl₃, we obtained Se/Ru_0.2, Se/Ru_0.7, and Se/Ru_1.1 core/shell NPs. The mass activities of as-prepared catalysts were 58.0, 32.1, and 12.5 A/g, respectively; part of these values are higher than that (2.2 A/g) of a commercial PtRu electrode and those (22.8, 28.0, and 24.5 A/g) of traditional carbon-supported Ru_xSe_y electrodes. The Se/Ru_1.1 electrode generated the greatest current density and was more tolerant toward poisoning in the presence of 1 M MeOH; cyclic voltammetry measurements revealed that this electrode was stable for at least 100 cycles. This is the first example demonstrating preparation of Se/Ru core/shell NPs that provided excellent catalytic activity and stability toward oxidation of MeOH. With their ease of large-scale preparation, low cost, high electroactivity, and high stability, such Se/Ru core/shell NPs have great potential for use as cathode electrocatalysts in direct MeOH fuel cells.     

Hydrogen production over Rh/Ce-MCM-41 catalysts via ethanol steam reforming

1 wt%Rh/Ce-MCM-41 catalysts were synthesized using Ce-MCM-41 as support where Si/Ce molar ratio varied from 10 to 30 and 50. During hydrogen reduction process, metallic Rh particles were formed on the Ce-MCM-41 at around 130 °C with an average particle size 6.8 nm. These catalysts were tested in the ethanol steam reforming (ESR) under atmospheric pressure between 225 and 425 °C. Compared to Rh/MCM-41 catalyst, cerium introduction would significantly enhance both the catalytic activity and hydrogen yield by approximately 2–3 times. However, the amount and the method of Ce incorporation in the framework of MCM-41 could greatly impact the catalytic performance of the Rh/Ce-MCM-41 catalysts. The ethanol conversion at 425 °C over the Rh/Ce-MCM-41 catalysts increased from 90.0% to 95.1% and 99.9%, as the Si/Ce molar ratio increases from 10 to 30 and 50. However, product selectivity is almost independent of the cerium content. The direct hydrothermal method of introducing Ce into the framework of MCM-41 is much superior to the impregnation route in the ESR reaction. After 6 h of reaction, the catalysts remain the mesostructure and the chemical state of cerium ions unchanged. Trace coke with graphite-like structure deposited on the surface does not modify the catalytic performance.