ZrO2 Catalysts Research Articles

Transition Metals Modified Ni−M (M=Fe, Co, Cr and Mn) Catalysts Supported on Al2O3−ZrO2 for Low‐Temperature CO2 Methanation

AbstractAlthough considerable efforts have been made in transforming carbon dioxide into high value‐added products, it still remains a big challenge to convert CO2 to CH4 directly at low temperature. Here, we report transition metals (including Fe, Co, Cr and Mn) modified Ni catalysts supported on Al2O3−ZrO2 via a single‐step sol‐gel method for low temperature CO2 methanation. Specially, incorporation of Mn metal into the Ni/Al2O3−ZrO2 catalyst was the most beneficial to the reduction and dispersion of NiO particles on the surface of Al2O3−ZrO2 composite support in comparison to other transition metals such as Fe, Co and Cr, which promoted the formation of active metallic Ni sites. Furthermore, the addition of Mn promoter facilitated the formation of surface oxygen vacancies, which combined with more metallic Ni active sites, thus improving the low‐temperature CO2 methanation performance significantly. An optimized Ni−Mn/Al2O3−ZrO2‐1 catalyst exhibited a superior CO2 conversion of 78 % with CH4 selectivity almost 100 % at a lower temperature of 300 °C without any deactivation in the long term 100 h reaction, which presented a potential industrial application for CO2 methanation.

Construction of S-scheme g-C3N4/ZrO2 heterostructures for enhancing photocatalytic disposals of pollutants and electrocatalytic hydrogen evolution

In consideration of environmental protection and energy conversion, the development of semiconductor photocatalytic technology is as first choice. But the photocatalytic performance of typical ZrO2 catalyst is seriously inhibited since it can only been driven by ultraviolet light. Herein, constructing S-scheme g–C3N4–modified ZrO2 heterostructures can be conducive to enhance photocatalytic performance by separating rapidly the photogenerated carriers. In this work, a series of S-scheme g-C3N4/ZrO2 heterostructures were constructed via the simple calcination, and their photocatalytic performances were evaluated by degradating Rhodamine B (RhB), Methyl orange (MO) and Acid orange II (AO II) under visible light irradiation. Importantly, 15% g-C3N4/ZrO2 heterostructures exhibited superior photocatalytic activities (degradating 82% RhB, 50% MO and 98% AO II in 150 min) and electrocatalytic performance (possessing lower overpotential, Tafel slope as well as more exposed active sites). The enhanced performances were ascribed to the intensive light absorption, the larger specific surface area, more exposed active sites as well as the higher separation of photogenerated electrons/holes pairs, which were confirmed by UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectra, electrochemical and radicals trapping experiments. This research provides the platform for the application in environmental protection and energy conversion via constructing S-scheme heterostructures.

Mixed Oxide Catalyst for the Oxidation of Glycerol to Lactic Acid: Influence of the Preparation Method and Calcination Temperature

The selective oxidation reaction of glycerol to produce lactic acid is a high-temperature reaction, and requiring a catalyst with high thermal stability. The mixed metal oxide is one of the potential catalysts to be explored. In this study, prepared CaCe supported on ZrO2 catalyst with two preparation methods (co-precipitation and impregnation), and calcination temperatures (800 and 600 °C) were investigated. The oxidation reaction of glycerol to lactic acid was carried out at 250 °C for 2 h in a base-free condition using pure glycerol as a reactant. The catalysts were characterized using XRD, TGA, XPS, SEM and basicity test to evaluate and correlate the physical and chemical properties with their catalytic performance. It was found that the catalyst prepared by co-precipitation and calcined at 800 °C exhibited the highest catalytic performance. The high lactic acid yield of 38.8 and 95% glycerol conversion were achieved. The catalyst was successfully developed with sufficient porosity and high intensity of mixed metal structure that contributed to the desired high performance. Improvement in the basicity and formation of surface oxygen vacancies was attributed to cationic Ce4+/Ce3+ elements leading to the promotion of lactic acid yield and high glycerol conversion.

Catalytic pyrolysis of rice straw: Screening of various metal salts, metal basic oxide, acidic metal oxide and zeolite catalyst on products yield and characterization

Lignocellulosic biomass is a promising renewable feedstock for the production of chemicals and fuels in light of the extensive use of fossil fuels associated with increasingly serious environmental problems. In this study, pyrolysis of rice straw with different types of catalyst such as metal salts (FeCl3, CuCl2, MgCl2 and MnCl2), metal basic oxides (MgO, CaO, MgCO3 and CaCO3), acidic metals (ZnO, ZrO2, CeO2 and TiO2), zeolites catalysts (ZSM-5, Y-Zeolite, Mordenite and SBA-15), catalyst amount (5, 10, 15 and 20 wt%) and reaction temperatures (350, 400, 450 and 500 °C) were examined on product yield and products characterization. The maximum bio-oil (38.5 wt%) was obtained for non-catalytic reaction at 450 °C. However for catalytic reaction highest bio-oil yield were observed 55.2, 52.1, 48.7 and 48.4 wt% with Y-zeolite, MgO, ZrO2 and MgCl2 catalyst at 450 °C respectively. GC-MS, FT-IR, NMR, GPC, TGA, and CHNS were used for bio-oil characterization. Y-zeolite effectively produced phenolics monomers as compare to basic (MgO), acidic (CeO2) and metal salt (MgCl2) catalyst. The use of catalysts was increased the boiling point range and the higher boiling point range was observed in case of Y-zeolite and MgO catalytic bio-oil. The highest higher heating value (HHV) 36.7 MJ/kg and highest carbon 75.2% was observed for zeolite catalytic bio-oil. Moreover lower molecular weight in the catalytic bio-oil was observed as compare to non-catalytic bio-oil.

Catalytic methane decomposition over ZrO2 supported iron catalysts: Effect of WO3 and La2O3 addition on catalytic activity and stability

A leading method of hydrogen production that is free of carbon oxides is catalytic methane decomposition. In this research, Fe supported catalysts produced by wet impregnation method were employed in the methane decomposition. The effect of doping ZrO2 with La2O3 and WO3 on the catalytic performance was studied. Different techniques were used to characterize the catalysts. It was discovered that support doped with WO3 gave the best performance in terms of CH4 conversion, H2 yield and stability at the test condition (800 °C, 4000 ml/hgcat space velocity). The initial H2 yield was found to be 58%, 81% and 92% on Fe/ZrO2, Fe/La2O3–ZrO2 and Fe/WO3–ZrO2 catalysts, respectively. These values were significantly decreased to reach 20% and 25% over the Fe/ZrO2 and Fe/La2O3–ZrO2 catalysts after running for 240 min. On the contrary, the Fe/WO3–ZrO2 catalyst maintained its catalytic activity and stability within the reaction time. The BET results showed remarkable increase in the specific surface area of Fe/La2O3+ZrO2 and Fe/WO3+ZrO2 compared to Fe/ZrO2 catalyst. TPR profiles revealed progressive change in the valency of Fe in its combined form to the zero valence free metal. The Fe/WO3–ZrO2 catalyst showed the highest reduction temperature among the tested catalysts, probably due to the strong metal support interaction. The Fe/WO3–ZrO2 gave the best performance and maintained stability during the time on stream. Its stability was attributed to the higher dispersion and stabilization of iron nanoparticles on the surface of WO3–ZrO2 support. TEM and TPO results indicated that the deposited carbon was multi-walled carbon nanotubes with tabular structure.

The consequences of support identity on the oxidative conversion of furfural to maleic anhydride on vanadia catalysts

Maleic anhydride (MA) is a high value building block molecule whose synthesis from furfural (FUR) is proposed as a green and sustainable alternative. In this work, vanadia supported on SiO2, γ-Al2O3, ZrO2 and TiO2 catalysts were synthetized, characterized and investigated for the selective gas phase oxidation of FUR to MA. The catalytic properties depend on both, the nature of the support and the vanadia surface dispersion. V2O5/SiO2 and V2O5/γ-Al2O3 display ca. 50 % MA yield. Conversely, for the V2O5/ZrO2 and V2O5/TiO2 catalysts, complete FUR oxidation to CO2 and negligible MA production was obtained. By decreasing the oxidation potential of the reaction feed, V2O5/ZrO2 and V2O5/TiO2 catalysts achieve MA yields comparable to V2O5/SiO2 and V2O5/γ-Al2O3 catalysts. This behavior is attributed to the higher vanadia dispersion on ZrO2 and TiO2 and the reducible nature of these supports. The results obtained in this work offer new catalytic alternatives for the sustainable production of MA.

Highly Efficient Catalysts of Bimetallic Pt-Ru Nanocrystals Supported on Ordered ZrO2 Nanotube for Toluene Oxidation.

ZrO2 nanotube arrays and their supported bimetallic platinum and ruthenium (PtxRuy/ZrO2; x + y = 1 mmol %, x/y = 1:0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.5:0.5, 0:1) nanocomposites were fabricated by employing SBA-15-OH as a hard template and an impregnation method, respectively. A controlled ordered nanotube array structure formed from the fabricated catalysts, and it showed a good performance for toluene oxidation. The specific physicochemical properties of the catalysts were examined through various analytical means. The PtxRuy/ZrO2 possessed a high surface area, and the Pt-Ru nanoparticles were dispersed uniformly on the ZrO2 nanotube surface. The Pt0.7Ru0.3/ZrO2 catalyst performed best among all of the samples, with T90% and T100% (temperatures for 90 and 100% conversion of toluene) of 140 and 160 °C, respectively, at a weight hourly space velocity of 36 000 mL/(h·g). These bimetallic catalysts exhibit excellent characteristics for toluene oxidation, such as higher turnover frequencies and lower apparent activation energy (Ea) values, which probably result from the synergistic effect of the Pt-Ru noble metals that leads to a high reducibility and oxygen adsorption capacity. The excellent activity, stability, and economics of the Pt0.7Ru0.3/ZrO2 catalyst allow for its application in toluene removal.

Mechanism and catalytic performance for direct dimethyl ether synthesis by CO2 hydrogenation over CuZnZr/ferrierite hybrid catalyst

Direct synthesis of dimethyl ether (DME) by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods: co-precipitation, sol-gel, and solid grinding to produce mixed Cu, ZnO, ZrO2 catalysts that were physically mixed with a commercial ferrierite (FER) zeolite. The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of CO2 (CO2-TPD), temperature programmed desorption of NH3 (NH3-TPD), and temperature programmed H2 reduction (H2-TPR). The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases, higher surface area, and lower reduction temperature are all favorable for catalytic activity. The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Methanol appears to be formed via the bidentate-formate (b-HCOO) species undergoing stepwise hydrogenation, while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.

Dry Reforming of Methane Using Ce-modified Ni Supported on 8%PO4 + ZrO2 Catalysts

Dry reforming of methane (DRM) was studied in the light of Ni supported on 8%PO4 + ZrO2 catalysts. Cerium was used to modify the Ni active metal. Different percentage loadings of Ce (1%, 1.5%, 2%, 2.5%, 3%, and 5%) were tested. The wet incipient impregnation method was used for the preparation of all catalysts. The catalysts were activated at 700 °C for ½ h. The reactions were performed at 800 °C using a gas hourly space velocity of 28,000 mL (h·gcat)−1. X-ray diffraction (XRD), N2 physisorption, hydrogen temperature programmed reduction (H2-TPR), temperature programmed oxidation (TPO), temperature programmed desorption (TPD), and thermogravimetric analysis (TGA) were used for characterizing the catalysts. The TGA analysis depicted minor amounts of carbon deposition. The CO2-TPD results showed that Ce enhanced the basicity of the catalysts. The 3% Ce loading possessed the highest surface area, the largest pore volume, and the greatest pore diameter. All the promoted catalysts enhanced the conversions of CH4 and CO2. Among the promoted catalysts tested, the 10Ni + 3%Ce/8%PO4 + ZrO2 catalyst system operated at 1 bar and at 800 °C gave the highest conversions of CH4 (95%) and CO2 (96%). The stability profile of Cerium-modified catalysts (10%Ni/8%PO4 + ZrO2) depicted steady CH4 and CO2 conversions during the 7.5 h time on stream.

Effect of Support on CO Oxidation Performance over the Pd/CeO2 and Pd/CeO2–ZrO2 Catalyst

In this study, we investigated different palladium-support interactions over the Pd/CeO2 and Pd/CeO2–ZrO2 catalyst and illuminated the effect of support on CO oxidation performance. Pd/CeO2, Pd/Ce0...

Manganese promoted TiO2 and ZrO2 nanostructures for soot combustion with boosted efficiency

TiO2, ZrO2 and mixed-oxide (TiO2-ZrO2) materials with manganese as active promoter were synthesized. The performance of these catalysts was tested in the diesel soot oxidation reaction. The soot conversion light-off temperature was remarkably lowered by manganese in the mixed-oxide (TiO2-ZrO2) in comparison with manganese in the TiO2 and ZrO2 catalysts. On the other hand, the mixed oxide enhanced surface defects because of the promotional role played by the ZrO2 interface, which led to the formation and stabilization of defect sites. In addition, the O2/TPD characterization revealed two peaks corresponding to desorption of oxygen species and desorption of lattice oxygen between 120 and 500 °C, which was correlated with the catalytic activity. The manganese-doped-mixed-oxide (TiO2-ZrO2) catalyst displayed structural stability, higher surface area, presence of Mn3+ and Mn4+ species and soot conversion light-off temperature of 260 °C, which was preserved after three reaction cycles.

Effect of cobalt on titania, ceria and zirconia oxide supported catalysts on the oxidative depolymerization of prot and alkali lignin

The production of phenolics by oxidative depolymerization of prot lignin and alkali lignin were studied in the presence of cobalt impregnated TiO2, CeO2 and ZrO2 catalysts at 140 °C for 1 h. Maximum bio-oil yield of 78.0 and 60.2 wt% were observed with Co/CeO2 catalyst for prot lignin and alkali lignin, respectively. The characterizations of the bio-oils were carried out using GC–MS, FTIR, and 1H NMR. The GC–MS compounds have been classified into four categories (G, H, S-type and others). The depolymerization of prot lignin showed a mixture of G, H and S type phenolic monomers. Interestingly, higher selectivity of acetosyringone (47.1%) was obtained in the presence of Co/TiO2 catalyst with prot lignin. The depolymerization of alkali lignin exhibited only G-type phenolic monomers production, and was effectively produced 67.4% (G-type monomer) in the presence of Co/ZrO2 catalyst.

Endothermic reactions of 1-propanamine on a zirconia catalyst

Cooling of critical engine components is important for hypersonic aircraft and endothermic reforming reactions on the fuel could play an important role by taking up some of the heat. Here, we propose using alkylamines that dehydrogenate to nitriles and H2 over ZrO2 catalysts as the endothermic fuel. Temperature programmed desorption (TPD) revealed that 1-propanamine on ZrO2 undergoes dehydrogenation at temperatures below 600 K. At 723 K and below, the selectivity to form H2 and propionitrile is greater than 90 %. Heat measurements at 60 bar show heat uptakes as large as 2000 kJ kg−1 of fuel reacted could be achieved at 723 K. Side reactions at higher conversions and temperatures lowered this value but values above 1000 kJ kg−1 were still obtained at nearly 100 % conversion of the amine. The observation of a significant endothermic effect suggests that the unconventional functional groups in the fuels merit further investigation to achieve a more profound chemical heat sink. Possible ways to apply this approach are discussed.

Lewis acid-oxygen vacancy interfacial synergistic catalysis over SO42−/Ce0.84Zr0.16O2–WO3–ZrO2 for N,N-diethylation of aniline with ethanol

Herein, a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis for aniline N,N-diethylation with ethanol was proposed, and the SO42−/Ce0.84Zr0.16O2–WO3–ZrO2 catalyst (SCWZ) with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method, which shows better catalytic activity than the reported solid acidic catalysts. Besides, the SO42−/ZrO2 (SZ) and SO42−/WO3–ZrO2 (SWZ) catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component. The SO42− and WO3 mainly generate Lewis acid by bonding with ZrO2, which is beneficial for the fracture of the N–H bond in aniline. The Ce0.84Zr0.16O2 solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species, which can participate in stripping –OH from ethanol, then the carbocation will also be released, which only needs 1.3805 kcal/mol energy, calculated by density functional theory (DFT), to be input. In comparison, the traditional reaction mechanism needs the Brønsted acidic sites to promote the protonation of ethanol, then dehydration and subsequent formation of carbocation followed, and 108.6846 kcal/mol energy needs to be input, which is far higher than that of the new mechanism. The apparent activation energy (Ea) over SCWZ was measured by experiment to be 34.09 kJ/mol, which is much lower than that of SWZ (47.10 kJ/mol) and SZ (54.37 kJ/mol), illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ. Besides, the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100% and 73%, respectively. The SCWZ can be renewed for 4 times without rapid deactivation, and the longevity of SCWZ is longer than that of SWZ and SZ, as the loaded SO42− and tetragonal ZrO2 are stabilized by Ce0.84Zr0.16O2 and WO3, respectively.

Activity and stability of mesoporous CeO2 and ZrO2 catalysts for the self-condensation of cyclopentanone

Metal oxides containing acid-base pairs are widely used as catalysts for aldol condensation reactions, but they are often prone to secondary condensation and fast deactivation. In this contribution, high-surface area mesoporous CeO2 and ZrO2 have been synthesized and tested as catalysts for the self-condensation of cyclopentanone, an attractive molecular building block for several biomass upgrading strategies. The catalytic activity, stability, and overall kinetics behavior of these two catalysts have been compared in the liquid phase. A detailed kinetics analysis shows that on both oxides, the reaction is controlled by the initial unimolecular α-H abstraction step, in which cyclopentanone forms the crucial enolate intermediate. Subsequently, the enolate couples with another cyclopentanone molecule in a bimolecular C-C coupling step. CO2-TPD analysis and site titration with probe molecules indicate that initially the most active catalyst is the mesoporous ZrO2 sample with strong base character. However, this catalyst exhibits a very rapid deactivation. By contrast, the mesoporous CeO2 prepared in this study has lower basicity strength, which results in lower initial activity, but enhanced stability.

Comparative studies for CO oxidation and hydrogenation over supported Pt catalysts prepared by different synthesis methods

Pt supported on TiO2 and ZrO2 catalysts were synthesized via wet impregnation and deposition precipitation methods. The catalysts were tested for CO removal from reformate gas following the water-gas shift reaction for on-board fuel processors. Tests included oxidation of CO to CO2, preferential oxidation of CO to CO2 in the presence of H2 (PROX), and hydrogenation of CO to CH4 (selective methanation, SMET). The Pt–ZrO2 catalysts showed better metal dispersions, particle sizes, lower degrees of reduction and higher oxygen storage capacities than the TiO2 supported catalysts. All catalysts showed low activity for the oxidation of CO in the PROX reaction, due to H2 and O2 spillover effects. ZrO2, with its high reducing properties and strong metal-support interactions, was found to be the best support for hydrogenation of CO. ZrO2 induced small well-dispersed Pt particles that were key parameters in this reaction. Both Pt–ZrO2 catalysts showed CO conversions over 99% above 350 °C with high CH4 selectivities (99%). The study shows advantageous effects of strong metal to support interactions, like participation of MOx (support) species in activating the CO molecule. The CO concentration was effectively reduced to the desired ppm levels (<10 ppm) required for optimum fuel cell operation.

Preparation and Characterization of Mixed-Oxide Catalyst

Solid heterogeneous CuO-MoO3/ZrO2 catalyst was prepared by impregnation using suitable precursor materials supported over zirconia. Upon calcination at 450°C for 2 hours, available techniques were employed for the characterization. The available oxides and minerals in the catalyst were revealed by the XRF and XRD profiles respectively. The catalyst crystallite size (131.6nm) was obtained using the Bragg’s equation from the latter. Thermal analysis showed three weight loss stages between (49.25-152.06°C), (152.06-559.47°C) and (559.47-752.0°C) while presence of sulphate and zirconia oxides was revealed by the FTIR analysis due to appearance of absorption bands around 1225-980cm-1 and 700-600 cm-1 respectively.

Ga Ion-doped ZrO2 Catalyst Characterized by XRD, XAFS, and 2-Butanol Decomposition.

Group 2, 3, and 13 element-doped zirconium oxide catalysts M-ZrO2 (M = Mg, Sr, Y, La, Ce, Sm, Er, Yb, B, Al, Ga, In, and Tl; 5 mol%) were prepared by impregnation of each metal salt aqueous solution on amorphous zirconium hydroxide, followed by calcination at 773 K. The M-ZrO2 samples were characterized by the catalytic performance of 2-butanol decomposition at 573 K, XRD, XANES and EXAFS spectroscopic techniques. Detailed analyses were performed herein for a series of Ga-ZrO2 with various doping amounts in the range of 1 - 60 mol%. The addition of Group 2 and 3 elements little influenced the catalytic performance of ZrO2 itself to promote dehydration to produce 1-butene with 90% selectivity. Ga-ZrO2 and In-ZrO2 gave methyl ethyl ketone as the main product via dehydrogenation. The doped Ga ion mainly existed inside the bulk of zirconia by forming the GaxZr1-xO2 solid solution up to 5 mol%. Highly doped species more than 10 mol% aggregated to form ε-Ga2O3. Each fraction forming the solid solution and Ga2O3-like species was evaluated by XANES analysis.

Facile precipitation synthesis, structural, morphological, photoluminescence and photocatalytic properties of Ni doped ZrO2 nanoparticles

In this study, Pure ZrO2 (600 °C) and Ni (0.02, 0.04, 0.06, 0.8 M) doped ZrO2 (600 °C) nanoparticles were obtained by facile precipitation method. The obtained products have been characterized by XRD, FTIR, UV-DRS, PL, FESEM-EDX, TEM-SAED pattern and XPS. The tetragonal structure of ZrO2 (600 °C) gradually increases with the increasing Ni doping concentration and then a small NiO diffraction peak was detected at increasing Ni content. The Ni (0.08 M) doped ZrO2 (600 °C) nanoparticles were approximately in spherical morphology was confirmed by FESEM and TEM results. The energy gap value of the pure ZrO2 (600 °C) and Ni doped ZrO2 (600 °C) nanoparticles decreased from 5.12 to 3.2 eV with enhancing nickel concentration. The surface defects and oxygen vacancies were analyzed by PL spectroscopy. This peak intensity gradually decreased with increase in nickel concentration. The photocatalytic activities of the Ni (0.08 M) doped ZrO2 (600 °C) catalysts were studied by the photodegradation of MV and MB aqueous solution under sunlight irradiation. The Ni (0.08 M) doped ZrO2 (600 °C) catalyst exhibited good photocatalytic efficiency and the enhanced photocatalytic mechanism was discussed.

Effect of Preparation Method on ZrO2-Based Catalysts Performance for Isobutanol Synthesis from Syngas

Two types of amorphous ZrO2 (am-ZrO2) catalysts were prepared by different co-precipitation/reflux digestion methods (with ethylenediamine and ammonia as the precipitant respectively). Then, copper and potassium were introduced for modifying ZrO2 via an impregnation method to enhance the catalytic performance. The obtained catalysts were further characterized by means of Brunauer-Emmett-Teller surface areas (BET), X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), and In situ diffuse reflectance infrared spectroscopy (in situ DRIFTS). CO hydrogenation experiments were performed in a fixed-bed reactor for isobutanol synthesis. Great differences were observed on the distribution of alcohols over the two types of ZrO2 catalysts, which were promoted with the same content of Cu and K. The selectivity of isobutanol on K-CuZrO2 (ammonia as precipitant, A-KCZ) was three times higher than that on K-CuZrO2 (ethylenediamine as precipitant, E-KCZ). The characterization results indicated that the A-KCZ catalyst supplied more active hydroxyls (isolated hydroxyls) for anchoring and dispersing Cu. More importantly, it was found that bicarbonate species were formed, which were ascribed as important C1 species for isobutanol formation on the A-KCZ catalyst surface. These C1 intermediates had relatively stronger adsorption strength than those adsorbed on the E-KCZ catalyst, indicating that the bicarbonate species on the A-KCZ catalyst had a longer residence time for further carbon chain growth. Therefore, the selectivity of isobutanol was greatly enhanced. These findings would extend the horizontal of direct alcohols synthesis from syngas.