CO Disproportionation Research Articles

Modifying the Charge-Density of Tetrahedral Cobalt(II) Centers through Carbon-Layer Modulation Promotes C-H Activation in the Propane Dehydrogenation Reaction (PDH).

The electronic structure of active metal centers plays an indispensable role in regulating catalytic reactivity in heterogeneous catalysis, developing other metals as promoters to decorate electronic state is a common strategy, while non-metal component of carbon as electronic additives to regulate d-band center has rarely been studied in thermal-catalysis field. Herein, we report electron-deficient tetrahedral Co(II) (Td-cobalt(II)) centers through carbon-layer modulation for propane dehydrogenation (PDH). It is indicated that bifunctional sites of both Td-cobalt(II) and metallic-cobalt are designed, and the in situ generated carbon through the disproportionation of CO on metallic-cobalt can cover the inactive metallic-cobalt and tailor d-band of active Td-cobalt(II) simultaneously. More importantly, the pre-deposited carbon-layer is proposed to decrease electron density of Td-cobalt(II) and make d-band center closer to Fermi level, consequently promotes C-H activation in PDH reaction. This study provides new perspective for the utilization of inactive carbon as electronic promoters and unlocks new opportunity to fabricate efficient PDH and other heterogeneous catalysts.

Modifying the Charge‐Density of Tetrahedral Cobalt(II) Centers through Carbon‐Layer Modulation Promotes C‐H Activation in the Propane Dehydrogenation Reaction (PDH)

AbstractThe electronic structure of active metal centers plays an indispensable role in regulating catalytic reactivity in heterogeneous catalysis, developing other metals as promoters to decorate electronic state is a common strategy, while non‐metal component of carbon as electronic additives to regulate d‐band center has rarely been studied in thermal‐catalysis field. Herein, we report electron‐deficient tetrahedral Co(II) (Td‐cobalt(II)) centers through carbon‐layer modulation for propane dehydrogenation (PDH). It is indicated that bifunctional sites of both Td‐cobalt(II) and metallic‐cobalt are designed, and the in situ generated carbon through the disproportionation of CO on metallic‐cobalt can cover the inactive metallic‐cobalt and tailor d‐band of active Td‐cobalt(II) simultaneously. More importantly, the pre‐deposited carbon‐layer is proposed to decrease electron density of Td‐cobalt(II) and make d‐band center closer to Fermi level, consequently promotes C−H activation in PDH reaction. This study provides new perspective for the utilization of inactive carbon as electronic promoters and unlocks new opportunity to fabricate efficient PDH and other heterogeneous catalysts.

Investigation of limiting H2O/CO2 co-electrolysis to convert renewable electricity into chemical energy using solid oxide electrolysis cell

H2O/CO2 co-electrolysis offers an efficient way to convert renewable electricity into chemical energy. However, carbon deposition is a serious problem for H2O/CO2 co-electrolysis. In this work, limiting electrolytic potential, limiting electrolytic voltage and conversion ratios of H2O/CO2 co-electrolysis are investigated. At low temperatures, the limiting potential of H2O/CO2 co-electrolysis is low and the conversion ratio cannot reach high because solid carbon is easily formed through CO electrolysis or disproportionation reactions. At high temperatures, the electrolytic voltage and conversion ratios of H2O and CO2 can reach high because CO electrolysis or disproportionation reactions are not easy to take place. The conversion ratios of CO2 and H2O can reach 99.6 % and 99.4 % at the H2O/CO2 ratio of 1:1 and 1273 K without solid carbon formation. The polarization resistance of fuel electrode has different effects on the conversion ratios of CO2 and H2O under different conditions, which is obvious at low temperatures and high polarization resistance of fuel electrode. The conversion ratios of CO2 and H2O under limiting electrolysis condition decrease from 9.8 % to 36.6 %–1.8 % and 8.5 % when the polarization resistance of fuel electrode increases from 0 to 0.1 Ω cm2 at the H2O/CO2 ratio of 1:2 and 773 K.

Unveiling the promotional performance of CO oxidation over Na-doped Pt-0.5P&W/TiO2 catalyst: “SMSI” effect of Na in catalysis

The dopant WO3 of the catalyst Pt-0.5P&W/TiO2 enhanced the SO2 resistance of the catalyst for CO oxidation in sintering waste gas, but it also had an impact on strong metal-support interactions (SMSI), which decreased the CO catalytic activity. Adding alkali metal Na to Pt-0.5P&W/TiO2 can effectively improve the CO catalytic performance. The Pt–O–Na bond replaced the Pt–O–Ti bond, allowing Na to act as an electron and structure promoter instead of TiO2 to contribute the electronic and synergistic effects in catalysis. XPS and EPR date indicated that the positively charged group centered on Pt adsorbed hydroxyl groups by electrostatic interaction, which co-acted with Na to form Pt-Ox(OH)yNa. In situ infrared data indicated that Na promoted the electron density on the Pt surface leading to the disproportionation of CO on the Pt surface to produce inactive C*. The production of C* facilitated the adsorption and activation of O2 by blocking the single-layer adsorption of CO on Pt. The active oxygen species adsorbed on the catalyst surface increased the CO activity of the catalyst. In sulfur-containing flue gas conditions, SO2 reacted with Na around Pt to generate sodium sulfate, which enhanced the local acidity of the active site and the sulfur resistance of the catalyst.

Enhanced CO2 conversion with CH4 for greenfuel generation using coke-neutral nickel-loaded fibrous silica titania catalysts

This study reveals a groundbreaking advancement in utilizing carbon dioxide (CO2) for syngas production through methane (CH4) dry reforming using Fibrous Silica Titania (FST) as a support, loaded with different (1%, 3%, and 5%) nickel dosages. FST is distinguished by its fibrous structure, maintains a stable temperature, facilitates the confinement and dispersion of active metal, and is exceptionally effective at preventing carbon deposition. For a thorough examination of the new catalysts, characterization methods including XRD, FESEM, EDX mapping, N2 physisorption, FTIR-KBr, H2-TPR, and CO2-TPD were employed. Importantly, TEM lattice fringes verified the existence of XRD peaks and planes of Ni (111), Ni (200), and TiO2 (101). Aspects such as O-H stretching, Si-O-Si asymmetry, vibrations caused by external Si-OH groups, and Si-O-Si bending were identified using FTIR-KBr analysis. The study ingeniously identified the superior (3Ni/FST) catalyst, which exhibited moderate basicity sites on the CO2-TPD at approximately 350 °C. The catalyst converted nearly 100% CH4 at 750 °C with minimal coke production and 80% CO2 at 850 °C. Surprisingly, the 3Ni/FST catalyst demonstrated remarkable stability during a 72 h TOS stability test at 650 °C, effectively preventing coke-forming side reactions such as CO disproportionation, CO hydrogenation, CO2 and CH4 cracking with syngas ratio around unity and little coke production. The FST support exhibited exceptional attributes for low temperature carbon neutral CH4 reforming.

In-situ exsolved ultrafine Ni nanoparticles from CeZrNiO2 solid solution for efficient photothermal catalytic CO2 reduction by CH4

CO2 reduction by CH4 (CRM) to produce fuel is of great significance for solar energy storage and eliminating greenhouse gas. Herein, the catalyst of ultrafine Ni nanoparticles supported on CeZrNiO2 solid solution (Ni@CZNO) was synthesized by the sol-gel method. High yield of H2 and CO (58.0 and 69.8 ​mmol ​min−1 ​g−1) and excellent durability (50 ​h) were achieved by photothermal catalytic CRM merely under focused light irradiation. Structural characterization and DFT calculations reveal that CZNO has rich oxygen vacancies that can adsorb and activate CO2 to produce reactive oxygen species. Oxygen species are transferred to ultrafine Ni nanoparticles through the rich Ni-CZNO interface to accelerate carbon oxidation, thereby maintaining the excellent catalytic stability of the catalyst. Moreover, the experimental results reveal that light irradiation can not only enhance the photothermal catalytic CRM activity through photothermal conversion and molecular activation, but also improve the stability by increasing the concentration of oxygen vacancies and inhibiting CO disproportionation.

Disproportionation of Co2+ in the Topochemically Reduced Oxide LaSrCoRuO5

AbstractComplex transition‐metal oxides exhibit a wide variety of chemical and physical properties which are a strong function the local electronic states of the transition‐metal centres, as determined by a combination of metal oxidation state and local coordination environment. Topochemical reduction of the double perovskite oxide, LaSrCoRuO6, using Zr, yields LaSrCoRuO5. This reduced phase contains an ordered array of apex‐linked square‐based pyramidal Ru3+O5, square‐planar Co1+O4 and octahedral Co3+O6 units, consistent with the coordination‐geometry driven disproportionation of Co2+. Coordination‐geometry driven disproportionation of d7 transition‐metal cations (e.g. Rh2+, Pd3+, Pt3+) is common in complex oxides containing 4d and 5d metals. However, the weak ligand field experienced by a 3d transition‐metal such as cobalt leads to the expectation that d7+ Co2+ should be stable to disproportionation in oxide environments, so the presence of Co1+O4 and Co3+O6 units in LaSrCoRuO5 is surprising. Low‐temperature measurements indicate LaSrCoRuO5 adopts a ferromagnetically ordered state below 120 K due to couplings between S=1/2 Ru3+ and S=1 Co1+.

Boosting CO-based synthesis of single-walled carbon nanotubes with hydrogen

Aerosol (floating catalyst) chemical vapor deposition method based on CO disproportionation (the Boudouard reaction) is one of the most promising techniques for the synthesis of single-walled carbon nanotubes (SWCNTs), especially in the form of thin films. However, despite its advantages (i.e., high quality of nanotubes, absence of double- or multi-walled nanotubes, and high controllability of the process), synthesis based on CO disproportionation fails to provide high-yield production. In this work, we examined the effect of hydrogen, admixed to the CO atmosphere as a growth promoter, on the synthesis and properties of SWCNTs. Using optical spectroscopy techniques, conductivity tests, TEM and SEM analysis, and thermodynamic calculations, we revealed hydrogen affects both catalyst activation and nanotube growth. We found a positive H2 effect in two different temperature regimes: the yield increased by a factor of ∼15 at a low temperature (880 °C), which, after doping, led to one of the lowest ratios of the equivalent sheet resistance (R90) and yield (i) and SWCNT lengthening by a factor of 2.4 leading to a 3-fold decrease in an R90 coupled with a noticeable increase in the yield at a high temperature (1000 °C) (ii). We believe the presented results are fruitful for the fundamental understanding of the mechanism for nanotube growth and practical opportunity to fine-tune the production rate of SWCNT films.

Investigation into the coking-related key reaction steps in dry reforming of methane over NiMgOx catalyst

With pre-reduced NiMgOx catalyst, the structure evolution, catalytic performance, surface species and coking-related reaction steps are investigated in methane dry reforming (DRM) at selected temperatures. Satisfactory conversion of CH4 and CO2, H2/CO ratio, and anti-coke stability are achieved in long-term (78 h) reaction at 650 °C as a proper temperature. The characterizations evidence co-existence of metallic Ni0 and solid solution phases in the working catalysts. Combined catalytic evaluation and coke analysis reveal that, at 650 °C, endothermic CO2-free CH4 decomposition shows a high initial rate for H2 production but severe coke deposition for rapid deactivation, serving as the primary coking process. In contrast, exothermic CO disproportionation exhibits a lower reaction rate and a higher coke graphitization degree. The in-situ DRIFT spectra demonstrate that carbonates and bicarbonates serve as the primary adsorbates during CO2 dissociation process, whereas formate intermediates dominate in DRM reactions. Such evolution of the surface species verifies facile dissociation of both CH4 and CO2 in well-matched rates, promoting coke-resistance DRM reaction over NiMgOx catalyst.

Catalytic Steam-Reforming of Glycerol over LDHs-Derived Ni-Al Nanosheet Array Catalysts for Stable Hydrogen Production

In the present work, LDHs–derived Ni–Al nanosheet arrays (NiAl/NA) were successfully synthesized via a one–step hydrothermal method, and applied in the steam-reforming of glycerol reaction for enhanced and stable hydrogen production. The physicochemical properties of catalysts were characterized using various techniques, including XRD, SEM–EDS, XPS, N2–physisorption, Raman, and TG–DTG. The results indicate that smooth and cross–linked Ni–Al mixed metal oxide nanosheets were orderly and perpendicularly grown on the Ni foam substrate. The SEM line scan characterization reveals the metal concentration gradient from the bottom to the top of nanosheet, which leads to distinctly optimized Ni valence states and an optimized binding strength to oxygen species. Owing to the improved reducibility and more exposed active sites afforded by its array structures, the NiAl/NA catalyst shows enhanced glycerol conversion (83.1%) and a higher H2 yield (85.4%), as well as longer stability (1000 min), compared to the traditional Ni–Al nanosheet powder. According to the characterization results of spent catalysts and to density functional theory (DFT) calculations, coke deposition is effectively suppressed via array construction, with only 1.25 wt.% of amorphous carbons formed on NiAl/NA catalyst via CO disproportionation.

Anodic Reaction in Syngas-Fueled Proton-Conducting Solid Oxide Fuel Cells

Anode-supported proton-conducting solid oxide fuel cells (PC-SOFCs) fabricated with two representative proton-conducting oxides, BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) and BaZr0.8Y0.2O3-δ (BZY), were compared to obtain the insight into the electrochemical performances when fueled with syngas at 700°C and the correlation between the anode thickness (0.4, 0.8, and 1.6 mm) and operational stability. We have demonstrated that, in stability tests, the BCZYYb cells exhibited significantly higher maximum power density (MPD) than the BZY cells when operating on H2, 1.22 and 0.48 W/cm2 for the BCZYYb and BZY cells, but the BCZYYb cells degraded more rapidly than the BZY cells when operating on syngas. In addition, decreasing the anode thickness significantly enhanced the stability of BCZYYb cells operating on syngas, a reduction of 81, 76, and 71% in MPD for 1.6, 0.8, and 0.4 mm anode after 30 min. The electrochemical impedance spectra and X-ray diffraction patterns indicated that the rapid degradation of cerate-based cells with syngas could be mainly attributed to the considerable increase in polarization resistance due to the phase decomposition of the electrolyte powder in the anode. Heterogeneous catalysis was performed to study the catalytic reaction of the H2–CO mixture over anode powders prepared with the two proton-conducting oxides (Ni-BCZYYb and Ni-BZY) in a fixed bed reactor, and the CO conversion and selectivity to CO2 and CH4 were determined. For all anode powders, continuous CO2 production was initially observed with CH4 formation, and no significant difference in catalytic activity trends was observed between both anode powders. An increased residence time substantially decreased the normalized CO2 yield, which was associated with the potential secondary reaction of CO2 with H2, CH4, or perovskite oxide. Based on the results of heterogeneous catalysis with both anode powders, the observed cell degradation on both cells during operation with syngas may be primarily attributed to carbon coking due to CO disproportionation; however, more than 4 times rapid degradation of the cerate-based cell when operating with syngas was clearly demonstrated to be attributed to the decomposition of the electrolyte powder in anode by the resulting CO2 from the catalytic reaction of the H2–CO mixture.

Sorbitol-derived carbon overlayers encapsulated Cu nanoparticles on SiO2: Stable and efficient for the continuous hydrogenation of ethylene carbonate

SummaryAn ultrastable and efficient Cu@C/SiO2 nanocatalyst was fabricated for the hydrogenation of ethylene carbonate, in which Cu nanoparticles are encapsulated by sorbitol-derived graphitized carbon overlayers. During the calcination of Cu-sorbitol/SiO2 precursors under N2 atmosphere, sorbitol decomposed to CO and CO2. The in situ generated CO not only reduced Cu2+ to Cu0/Cu+, but also formed graphitized carbon overlayers on the Cu surface via the disproportionation of CO. The Cu@C/SiO2 catalyst exhibited superior catalytic performance (91% MeOH yield and 43.6 h−1 TOF) at a H2/EC molar ratio of 20. Of particular note, the Cu@C/SiO2 catalyst showed remarkable long-term stability during 736 h time-on-stream test without any deactivation. The graphitized carbon overlayers on the surface of Cu nanoparticles not only functioned synergistically with the surface Cu0/Cu+ sites to promote the EC hydrogenation but also suppressed the sintering of Cu nanoparticles. Furthermore, the interaction of Cu nanoparticles and graphitized carbon overlayers stabilized the surface Cu+/(Cu0+Cu+) ratio.

High Fuel Yields, Solar‐to‐Fuel Efficiency, and Excellent Durability Achieved for Confined NiCo Alloy Nanoparticles Using MgO Overlayers for Photothermocatalytic CO2 Reduction

Solar‐energy‐driven CO2 reduction to produce fuel is of great importance for alleviating the greenhouse effect and energy shortage. Here, a composite of MgO overlayers confined NiCo alloy nanoparticles supported on MgO (NiCo@MgO/MgO) is prepared. Extremely high production rates of H2 (rH2) and CO (rCO) (112.98 and 127.13 mmol min−1 g−1, respectively) and large solar‐to‐fuel efficiency (η, 39.3%) are achieved on NiCo@MgO/MgO for photothermocatalytic CO2 reduction by CH4 under ultraviolet–visible–infrared (UV–VIS–IR) illumination. The high fuel production rates and η originate from efficient light–thermal conversion and photoactivation, which can boost the photothermocatalytic activity by reducing the activation energy. Importantly, NiCo@MgO/MgO does not show deactivation during a 90 h photothermocatalytic CO2 reduction by the CH4 durability test, owing to its low carbon deposition rate. Experimental evidence reveals that the NiCo alloy and MgO overlayers can inhibit CO disproportionation and accelerate the oxidation of carbon species, thereby significantly decreasing the carbon deposition rate.

CO Adsorption and Disproportionation on Smooth and Defect-Rich Ir(111).

CO adsorption and dissociation on “perfect” and “defect-rich” Ir(111) surfaces were studied by a combination of surface-analytical techniques, including polarization-dependent (PPP and SSP) sum frequency generation (SFG) vibrational spectroscopy, low-energy electron diffraction (LEED), Auger electron spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. CO was found to be ordered and tilted from the surface normal at high coverage on the “perfect” surface (e.g., θ = 30° at 0.70 ML), whereas it was less ordered and preferentially upright (θ = 4–10°) on the “defect-rich” surface for coverages of 0.55–0.70 ML. SFG, LEED, and XPS revealed that CO adsorption at low pressure/high temperature and high pressure/low temperature was reversible. In contrast, upon heating to ∼600 K in near mbar CO pressure, “perfect” and even more “defect-rich” Ir(111) surfaces were irreversibly modified by carbon deposits, which, according to DFT, result from CO disproportionation.

Pyrolysis gas from biomass and plastics over X-Mo@MgO (X = Ni, Fe, Co) catalysts into functional carbon nanocomposite: Gas reforming reaction and proper process mechanisms

The metal catalysts X-Mo@MgO (X = Ni, Fe, Co) was studied as excellent catalyst for catalytic pyrolysis conversion of biomass and plastics into functional carbon nanocomposite. The proper reaction mechanism of the process was explored through the gas composition, and explored the bactericidal performance of functional carbon nanocomposite. The results showed that the Ni, Fe and Co-based catalysts elevated H2 gas yield reached to 57%, 34% and 44% as the addition of Mo, due to Mo or its oxide species for scission of small molecule compound. The introduction of NiMo@MgO catalyst produced lower CH4, and higher H2 and MWCNTs, which indicated that the formation of MWCNTs is mainly attributed to CH4 dehydrogenation. As a comparison, FeMo@MgO catalyst for CO disproportionation reaction could generate more MWCNTs and lower H2. The functional carbon nanocomposite from FeMo@MgO catalyst were comprehensively evaluated by multiple characterizations. TPO and Raman results confirmed that FeMo@MgO catalyst can provide an excellent carrier to generate MWCNTs with few defects and high graphitization. The functional carbon nanocomposite were initially applied to E.coli extinguishing. The core-shell structure catalyst not only has excellent bactericidal performance, but also has strong resistance to metal leaching.

Temperature-dependent selective nucleation of single-walled carbon nanotubes from stabilized catalyst nanoparticles

• Enriched (6,5) and (7,5) SWCNTs are respectively synthesized at ambient pressure. • Highly stabilized cobalt nanoparticles are generated from catalyst reduction. • Thermodynamic stability of different tube nuclei accounts for SWCNT selectivity. The utilization of metal nanoparticles supported on oxides substrate as a catalyst for rational single-walled carbon nanotube (SWCNT) growth is hindered by particle coarsening at high synthesis temperature, despite many empirical advances in supported catalyst design. In this study, a newly developed MgO-supported cobalt (Co-MgO) catalyst affords the formation of well-stabilized Co nanoparticles upon reduction, which is attributed to the electronic metal-support interaction and electrostatic stabilization at the Co-MgO interface. The highly stabilized Co nanoparticles led to the predominant growth of (6, 5) SWCNTs at 700 °C by CO disproportionation and the major SWCNT species was found to be (7, 5) SWCNTs at a reaction temperature of 800 °C. The temperature-dependent selective growth of the two SWCNT species was found, by density functional theory calculation, to be strongly correlated with the change of the relative thermodynamic stability of the SWCNT nuclei in the chirality assigning process at different temperatures.

Carbon deposition behaviors in dry reforming of CH4 at elevated pressures over Ni/MoCeZr/MgAl2O4-MgO catalysts

Carbon deposition is a major bottleneck for the development of durable catalysts applicable for the dry reforming of CH4 (DRM). In this work, the carbon deposition behaviors in dry reforming of CH4 at elevated pressures over Ni/MoCeZr/MgAl2O4-MgO catalysts which exhibited a durable stability and excellent coking resistance at atmospheric pressure DRM reaction in our previous report were examined. The differences in the types and sources of carbon deposition under atmospheric pressure and elevated pressure were clarified by XRD, TPO, TEM and Raman spectroscopy as well as the comparative experiments conducted in CH4, CO and CH4/CO atmospheres. It was found that the stability of the catalyst declined rapidly at elevated reaction pressure, and the sources and types of carbon deposition in DRM reaction under atmospheric pressure and pressurized conditions were significantly different at temperatures above 800 °C, but barely differed at temperatures below 700 °C. Under atmospheric pressure, the filamentous carbon (carbon nanotubes, CNTs) was produced by CH4 decomposition reaction and CO disproportionation reaction at 500 and 600 °C, the encapsulated graphitic carbon was generated by CH4 decomposition reaction at 800 and 850 °C, and the filamentous carbon and encapsulated graphitic carbon deriving from CH4 decomposition reaction and CO disproportionation reaction coexisted at 700 °C. Under high pressure, CH4 decomposition reaction and CO disproportionation reaction were jointly involved in the formation of carbon deposition. The filamentous carbon was formed regardless of the reaction temperature, and accompanied by the encapsulated graphitic carbon at 700, 800 and 850 °C. It is concluded that stable DRM catalysts at atmospheric pressure may not be competent for the pressurized DRM because the sources and types of carbon deposition at pressurized conditions are different and the methods of carbon removal and suppression at atmospheric pressure are not fully applicable, thus further study is needed to develop durable catalysts at pressurized DRM.

Tunable CO Dissociation Assisted by H2 over Cobalt Species: A Mechanistic Study by In‐situ DRIFTS

AbstractFischer‐Tropsch synthesis (FTS) is an important heterogeneous catalytic process that can effectively reduce human dependence on the non‐renewable petroleum resources. Cobalt is a crucial active metal center in most catalysts, which effectively catalyzes syngas into valuable products such as liquid fuels. On this basis, we systematically investigated the adsorption of CO on the surface of different cobalt species and its dissociation characteristics assisted by H2 are studied by the in‐situ DRIFTS. For the metallic cobalt phase, H2‐assisted CO dissociation not only possessed the FTS activity, but also inhibited the CO disproportionation reaction. However, for the CoO phase, the bidentate carbonate species were decomposed into CO2. In addition, CoO presented a high‐chain propagation ability than that of Co under the same operation conditions. Co2O3 and Co3O4 also exhibited similar CO dissociation patterns with the assistance of H2. However, different from CoO phase, formate species also formed under the H2 atmosphere over these two Co species. In summary, CO dissociation would be well tuned via the assistance of H2 as demonstrated by the in‐situ DRIFTS. This work provides a new sight on the rational design of efficient cobalt catalysts toward the FTS processes.

Photothermocatalytic CO2 Reduction on Magnesium Oxide‐Cluster‐Modified Ni Nanoparticles with High Fuel Production Rate, Large Light‐to‐Fuel Efficiency and Excellent Durability

Highly efficient CO2 reduction to produce fuel driven by solar energy is of great significance to alleviate the greenhouse effect and realize solar energy storage. Herein, a unique nanocomposite of MgO‐cluster‐modified Ni nanoparticles supported on Ni‐doped MgO (MCM–Ni/Ni–MgO) is synthetized by a simple approach. Very high fuel production rate for H2 and CO (78.01 and 88.44 mmol min−1 g−1) as well as a large light‐to‐fuel efficiency (31.7%) are achieved by photothermocatalytic CO2 reduction by CH4 on MCM–Ni/Ni–MgO merely using focused UV–vis–IR illumination. This arises from efficient light‐driven thermocatalysis that is further enhanced by a photoactivation due to the activation energy being considerably reduced upon the illumination. More importantly, it exhibits excellent photothermocatalytic durability due to its extremely low carbon deposition rate of 8.85 × 10−4 gc h−1 g−1 catalyst, reduced by 39.2 times as compared with that of a reference sample of Ni nanoparticles supported on Ni‐doped MgO (Ni/Ni–MgO). The experimental evidences and the functional theory calculations reveal that the surface modification of Ni nanoparticles by MgO cluster not only inhibits the carbon deposition side reactions of CO disproportionation and CH4 complete dissociation, but also significantly accelerates the oxidation of carbon species, thus tremendously decreasing carbon deposition rate.

Yolk–Shell Pt-NiCe@SiO2 Single-Atom-Alloy Catalysts for Low-Temperature Dry Reforming of Methane

Herein, we report a highly carbon resistant nanotubular yolk–shell Pt-NiCe@SiO2 single-atom-alloy (SAA) catalyst for low-temperature dry reforming of methane (DRM). A synergetic combination of the confined yolk–shell morphology and Pt–Ni SAA structures prevents carbon formation and provides excellent catalyst stability. The confined morphology of the yolk–shell structures can impede carbon deposition due to the facile CO desorption from the surface. Carbon formation can be further minimized by 0.25 wt % Pt promotion, showing an excellent stability for 120 h during DRM at 500 °C. The enhanced stability of the Pt0.25-NiCe@SiO2 catalyst can be attributed to the atomically dispersed Pt on the yolks forming Pt–Ni SAA structures encapsulated by a nanotubular SiO2 shell. The Pt–Ni SAA facilitates Pt–Ni interactions and enhances the reducibility of the Ni species, which further suppresses carbon formation during DRM. The developed bifunctional catalyst exhibits excellent resistance to coking by decreasing the effect of both main carbon formation reactions: i.e., CO disproportionation and CH4 decomposition. When the Pt loading is increased above 0.25 wt %, Pt nanoparticles form, leading to oligomerization of C–H species. Our results show that advantageous effects of both confined morphology and Pt–Ni SAA structures can lower the operating temperature of DRM without showing any catalyst deactivation.