CO In H2-rich Stream Research Articles

Oxygen vacancy-regulated atomic dispersed Au on CeFeOx for preferential oxidation of CO in H2-rich stream

CO preferential oxidation in H2-rich stream (CO-PROX) is a critical reaction for H2 purification in emerging hydrogen economy including advanced fuel cell technology. Au-based catalysts are viewed as some of the most promising catalysts but achieving high catalytic efficiency and selectivity is still challenging. Defect engineering is deemed as a powerful strategy to improve the intrinsic catalytic activity. Herein, CeFeOx-supported Au catalysts with controllable oxygen vacancy (Ov) concentrations were obtained and applied to CO-PROX. The results of characterizations showed that the Ovs were preferentially generated in conjunction with Au single atoms (SAs) rather than nanoparticles (NPs), which further modulated the surface electronic properties via surplus electrons in Ovs and enhanced the interfical interaction between Ovs and Au SAs. The CO-PROX results indicated that the reduced Au SA catalyst (Au1/CeFeOx-R) with the highest Ov concentration completely converted CO at temperature of 80 °C with relatively low reactivity towards H2 oxidation. The remarkable catalytic activity and selectivity were attributed to the modified electronic properties by Ovs that played a bridging role in electron transfer and accelerated reaction process, as well as the coupling effect of Ovs and Au SAs that enhanced the dissociative adsorption of O2 and the adsorption-oxidation of CO, resulting in a reduced reaction energy barrier and making CO oxidation more favorable than H2 oxidation. This research opens up an alternative strategy to simultaneously stabilize and activate single-atom catalysts.

Synergistic effect of platinum single atoms and nanoclusters for preferential oxidation of carbon monoxide in hydrogen-rich stream

Despite the maximum atom-utilization efficiency and remarkable activity of single-atom catalysts, further improvement of catalytic activity can be obtained by the synergistic effect of single atoms and nanoclusters in some catalytic systems. Herein, CeFeOx-supported Pt single atoms coupling with subnanometric clusters (Pt1-Ptn) structures are developed via a facile strategy. They are applied as the highly efficient catalysts for the preferential oxidation of CO in H2-rich stream (CO-PROX), which achieve complete elimination of CO at low temperature of 50 °C, with a wide operating temperature window and extraordinary stability for over 500 h without noticeable deactivation. The exceptional performance is attributed to the synergistic effect of distinctive Pt1-Ptn structures, which couple the benefits of Pt single atoms and subnanometric clusters in a remarkable way. The disadvantages of single Pt species catalysts, such as sensibility to strong adsorption of CO or reduced lattice oxygen reactivity due to excessive coordination, can be well mitigated. The results of detailed characterizations and density functional theory calculations confirm that the unique structures possess moderate adsorption strength for CO and create abundant active interfacial oxygen species, because of the absence of bulk metallic Pt0 and appropriate coordination to lattice oxygen, which synergistically facilitate the catalytic performance.

Three birds, one-stone strategy for synthesis of hierarchically arrayed defective MnCo2O4@NF catalyst for photothermal preferential oxidation of CO in H2-rich streams

A novel strategy with the “three birds, one stone” effect has been proposed to enhance the catalytic performance of cobalt manganese spinel catalysts for photothermal CO-PROX in H2 streams. The approach involves fabricating hierarchically arrayed defective MnCo2O4@ Nickel foam (NF) through a simple hydrothermal post-treatment and partial recrystallization process. Three synergetic effects were induced by the hydrothermal posttreatment of MnCo2O4: (i) the creation of a hierarchically arrayed morphology that strengthens light absorption and photo-to-thermal conversion, supported by finite-element method (FEM) simulations; (ii) the increased vacancy structures to alleviate significant electron-hole recombination; and (iii) abundant oxygen vacancy to facilitate oxygen adsorption and activation. These effects result in the unique hierarchically arrayed morphology and superior structural properties of MnCo2O4 spinel, which significantly enhances the photothermal synergism and catalytic activity of MnCo2O4@NF in photothermal CO-PROX driven by simulated solar light. This work provides a simple and facile strategy for developing hierarchical and defective MnCo2O4 spinel photothermal materials.

Atomically dispersed Au catalysts for preferential oxidation of CO in H2-rich stream

Carbon monoxide preferential oxidation (CO-PROX) is regarded as a promising strategy to remove trace amount of CO in H2-rich stream. Herein, atomically dispersed Au catalysts with different Au contents supported on cerium-zirconium solid solution supports were obtained by a deposition-precipitation method. The optimal catalyst, with 0.02 wt% Au, exhibits nearly 100 % CO conversion and 50 % CO2 selectivity for CO-PROX reaction under PEMFC working temperature range (80–120 ℃) and remains catalytically stable after 72 h testing at 80 ℃. The superior catalytic performances are attributed to the strong adsorption of CO and the low energy barrier of CO oxidation reaction, as well as the weak H2 adsorption and dissociation over highly dispersed Au single atoms, as supported by density functional theory calculations. Furthermore, combining characterization and experimental results, it is concluded that although catalysts are atomically dispersed, their performances can be adjusted by the synergetic interaction between neighboring Au single atoms.

Insights into the essential roles of tin and chloride species within Cu–CeO2 based catalysts for CO preferential oxidation in H2-rich stream

Sn modified Cu–Ce catalysts have been synthesized by the solvent-free combustion method for preferential oxidation of CO in H2-rich stream (CO-PROX) and characterized by N2 adsorption-desorption (BET), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), Raman, in-situ DRIFTS, X-ray photoelectron spectroscopy (XPS), and Oxygen storage capacity (OSC). The results show that the incorporation of Sn species accelerates the redox cycle among Sn, Cu and Ce, thus strengthening the Cu–Ce interaction and promoting the formation of surface and bulk lattice Cu-[Ox]-Ce structures Meanwhile, to balance the charge, more oxygen vacancies are formed and thus facilitate the migration of oxygen species. Combined with the more strong absorbed ability of SnO2 for O2, active Cu-[Ox]-Ce structures promotes the easier conversion of more CO into CO2. However, the existence of Cl ions decreases catalytic performance because the formation of CuCl makes the Cu–Ce interaction weakened, resulting in the formation of fewer Cu-[Ox]-Ce structures and oxygen vacancies. Although CuCl is prone to be in favor of absorbing more CO, there are not enough O species available, hence a decrease in performance is observed.

Local structure of Pt species dictates remarkable performance on Pt/Al2O3 for preferential oxidation of CO in H2

State-of-the-art production of industrial hydrogen predominantly derives from the reforming of hydrocarbons. However, the unavoidable ∼1 % CO in this hydrogen resource usually poisons proton-exchange-membrane fuel cells (PEMFCs) and other applications. An effective solution to eliminate CO involves the preferential oxidation of CO in H2-rich stream (PROX). Here, we report that ∼1.4 nm Pt nanoparticles supported on inert substrate (Al2O3) can catalyze total CO conversion and CO2 selectivity in a temperature range from −30 to 120 °C. Detailed characterizations indicate that this remarkable performance is determined by the local structure of Pt active centers. The ensemble of Pt(OH) and metallic Pt plays a more critical role compared with PtOx or the only Pt°. On this ensemble, O2 activation is favored while CO adsorption is weakened and H2 adsorption is inhibited, which facilitate the preferential oxidation of CO rather than H2, thus enabling a broad temperature window for 100 % selective CO removal.

Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream

The as-prepared (Co3O4) and hydrazine-treated (Co3O4(H)) cobalt catalysts were prepared using the precipitation method and evaluated at a temperature range of 40–220 °C for preferential oxidation (PROX) of CO in excess hydrogen. An improved surface reducibility with smaller crystallite size was noted on hydrazine-treated cobalt species (i.e., Co3O4(H) catalyst), which indicates some surface transformation. This finding correlates with the surface roughness formation (as depicted by scanning electron microscope (SEM) and transmission electron microscope (TEM) data), which was further confirmed by an increase in the Brunauer–Emmett–Teller (BET) surface area. The mesoporous structure of the Co3O4(H) catalyst remained intact, as compared to that of the Co3O4 catalyst. Interestingly, the in situ treatment of the standalone Co3O4(H) catalyst decreased the maximum CO conversion temperature (T100%) from 160 °C (over Co3O4) to 100 °C, with good selectivity. The Co3O4(H) catalyst showed good stability, with approximately 85% CO conversion at 100 °C for 21 h, as compared to a faster deactivation of the Co3O4 catalyst. However, the Co3O4(H) catalyst was unstable in both CO2 and the moisture environment. Based on the evaluation of spent hydrazine-treated (CoO(H)) cobalt catalyst, the high PROX activity is associated with the formation of Co3+ species as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and temperature-programmed reduction (TPR) data.

Synthesis of CuOx–CeO2 catalyst with high-density interfaces for selective oxidation of CO in H2-rich stream

Constructing materials with high-density interfaces offers a very promising route to enable high-performance nanocatalysts. Herein, a one-pot method to synthetize CuOx–CeO2 spherical catalysts with high-density interfaces is developed by controlling the growth condition so that the CuOx can only nucleate and grow via heterogeneous mode. The synthesis method ensures fine dispersion of CuOx over CeO2 and the density of interface between CuOx and CeO2. The generation of the species of Cu+, Ce3+, and oxygen vacancies are enhanced by the interface interaction. And the reduction of copper ions to metals is effectively suppressed, which helps to avoid deactivation of catalyst at high temperature. When catalyzing the CO preferential oxidation reaction (CO-PROX), the CuOx–CeO2 composite with high-density interfaces exhibits a strikingly high catalytic oxidation activity at a broad operating temperature window (i.e. CO 100% conversion, 95–235 °C). The heterogeneous nucleation methodology of synthesizing composite with high-density interfaces reported in this work also applies to other materials system.

Catalytic Performance of Gold Supported on Mn, Fe and Ni Doped Ceria in the Preferential Oxidation of CO in H2-Rich Stream

Ceria supported metal catalysts often exhibit high activity in the preferential oxidation (PROX) of CO in H2-rich stream and doping the ceria support with other metals proves to be rather effective in further enhancing their catalytic performance. Therefore, in this work, a series of ceria materials doped with Mn, Fe and Ni (CeM, where M = Mn, Fe and Ni; M/Ce = 1/8) were synthesized by a modified hydrothermal method; with the doped ceria materials (CeM) as the support, various supported gold catalysts (Au/CeM) were prepared by the colloidal deposition method. The influence of metal dopant on the performance of these ceria materials supported with gold catalysts in CO PROX was then investigated in detail with the help of various characterization measures such as N2 sorption, XRD, TEM, Raman spectroscopy, H2-TPR, XPS and XAS. The results indicate that the incorporation of Mn, Fe and Ni metal ions into ceria can remarkably increase the amount of oxygen vacancies in the doped ceria support, which is beneficial for enhancing the reducibility of ceria, the metal-support interaction and the dispersion of gold species. Although the gold catalysts supported on various doped ceria are similar in the size and state of Au nanoparticles, the CO conversions for CO PROX over Au/CeMn, Au/CeFe and Au/CeNi catalysts are 65.6%, 93.0% and 48.2%, respectively, much higher than the value of 33.6% over the undoped Au/CeO2 catalyst at ambient temperature. For CO PROX over the Au/CeNi catalyst, the conversion of CO remains near 100% at 60–130 °C, with a PROX selectivity to CO2 of higher than 50%. The excellent performance of Au/CeNi catalyst can be ascribed to its large amount of oxygen vacancies and high reducibility on account of Ni incorporation. The insight shown in this work helps to clarify the doping effect of other metals on the physicochemical properties of ceria, which is then beneficial to building a structure-performance relation for ceria supported gold catalyst as well as developing a better catalyst for removing trace CO in the hydrogen stream and producing high purity hydrogen.

Preferential Oxidation of CO in H2-Rich Stream Over Au/CeO2–NiO Catalysts: Effect of the Preparation Method

Two methods, viz., the hydrothermal (HT) and co-precipitation (CP) methods, were used to prepare CeO2–NiO composite oxides; with them as the supports, Au/CeO2–NiO catalysts were prepared by the colloidal deposition method and used in the preferential oxidation (PROX) of CO in H2-rich stream. Various characterization measures such as N2 sorption, XRD, TEM, H2-TPR, Raman spectroscopy and XPS were used to clarify the influence of preparation method on the structure of CeO2–NiO support and the performance of Au/CeO2–NiO catalyst. The XPS and TEM results reveal that the CeO2–NiO(HT) support prepared by hydrothermal method displays a uniform rod-like shape and exposes preferentially the (110) and (100) planes of CeO2, whereas the CeO2–NiO(CP) support prepared by co-precipitation method is composed of nanorods and irregular nanoparticles dominated by (111) facets of CeO2. After deposition of gold, both the Au/CeO2–NiO(HT) and Au/CeO2–NiO(CP) catalysts are alike in the state and size distribution of deposited Au nanoparticles. The H2-TPR results indicate that the presence of Au strongly promotes the reduction of CeO2 in the Au/CeO2–NiO catalyst. Raman spectra illustrate that the incorporation of Ni ions into CeO2 remarkably increases the amount of oxygen vacancies in the CeO2–NiO supports, especially in CeO2–NiO(HT) prepared by hydrothermal method, which is beneficial to the dispersion and stabilization of gold species. The structure of CeO2–NiO support and catalytic activity of Au/CeO2–NiO in CO PROX is strongly related to the preparation method; Au/CeO2–NiO(HT) exhibits much higher activity than Au/CeO2–NiO(CP). The larger fraction of (110) and (100) CeO2 facets in CeO2–NiO(HT) can promote the dispersion of gold species, formation of oxygen vacancies and migration of oxygen species, which are effective to enhance the redox capacity and activity of the obtained Au/CeO2–NiO(HT) catalyst for CO PROX in H2-rich stream. Au supported on CeO2–NiO nanorods prepared by hydrothermal method exhibits much higher catalytic activity for CO PROX in H2-rich stream.

Sustainable photo-assisted CO oxidation in H2-rich stream by simulated solar light response of Au nanoparticles supported on TiO2

In this study the photo-response behaviour of Au/TiO2 systems in the preferential CO oxidation in a H2-rich stream (CO-PROX) was investigated by the first time under simulated solar light irradiation at room temperature and atmospheric pressure. Au nanoparticles, with an average size of 2–5nm, were precipitated-deposited on a mesoporous TiO2, previously synthesized by sol-gel type procedure and thermally treated at different temperatures to obtain anatase/rutile mixed phases. Structural, chemical and optical properties were studied by means of AAS, N2 physisorption, XRD, HR-TEM, DRUV–vis and XPS, investigating the effects of TiO2 polymorphs (anatase, rutile and combination thereof). All samples, containing a very low amount of noble metal (0.5wt%), resulted very active in the photocatalytic CO-PROX at ambient conditions, attaining very high CO conversion and CO2 selectivity values. The Au/TiO2 sample containing both anatase/rutile polymorphs in the support displayed the highest activity, both in dark and under simulated solar light, due to the simultaneous presence of these two titania crystalline phases, capable to lower the effective band gap of the composite system (2.90eV) and improving the photocatalytic activity in the studied reaction. This kind of materials may provide a sustainable and feasible approach to selectively oxidize CO in H2-rich stream under solar light irradiation and ambient conditions.

Identification of the nano/micro structure of CeO2(rod) and the essential role of interfacial copper-ceria interaction in CuCe(rod) for selective oxidation of CO in H2-rich streams

CeO2(rod) has been found to be exposed four {111} planes and two {100} planes with a hexangular cross section, and the growth mechanism follows to the oriented attachment of the cube-like basic grains with a [110] growth direction and the subsequent Ostwald ripening, corresponding to the increasing lateral size and longitudinal size with prolonging the hydrothermal time. Equal amount of copper oxide totally highly distributed on the surface of CeO2(rod) supports with different abundance of oxygen vacancies facilitate to produce the strongly bound Cu-[Ox]-Ce species to different degrees (supported by XPS, H2-TPR and in situ DRIFTs results), which is encouraged by prolongation of hydrothermal time of CeO2(rod) supports. The essential role of interfacial Cu-Ce interaction in CuCe(rod) catalysts for CO-PROX was identified by the enhanced catalytic performance of CuCe(rod)-48h, on account of much stronger Cu-Ce interaction generated in it. Moreover, we proposed a potential structural model of strongly bound Cu-[Ox]-Ce to interpret the synergetic effect of copper and ceria species in CuO/CeO2 catalysts and generalized the possible reaction mechanism for CO-PROX over the CuCe(rod) catalyst.

Unexpected stability of CuO/Cryptomelane catalyst under Preferential Oxidation of CO reaction conditions in the presence of CO2 and H2O

The catalytic activity of CuO/Cryptomelane for the preferential oxidation of CO in H2-rich streams has been studied in the absence and presence of H2O and CO2, paying special attention to the catalyst stability and to changes on its physical-chemical properties under CO-PROX reaction conditions.For fresh CuO/cryptomelane catalyst, the presence of CO2 and/or H2O in the CO-PROX feed partially inhibits CO oxidation due to chemisorption of H2O and CO2 on the catalyst. H2O chemisorption on CuO/Cryptomelane is stronger than CO2 chemisorption, and simultaneous CO2 and H2O adsorption has a synergetic effect that enhances co-adsorption and significantly hinders CO oxidation.On the contrary, the presence of CO2+H2O in the CO-PROX reaction mixture has a positive effect in the CuO/Cryptomelane stability upon several consecutive reaction cycles in the 25–200°C range. XRD showed that chemisorbed CO2+H2O species partially prevent the catalyst deactivation due to cryptomelane reduction to hausmannite (Mn3O4) under the strongly reductive environment of the CO-PROX reaction, and H2-TPR and Raman spectroscopy characterisation support that the cryptomelane structure is less damaged under CO-PROX conditions in the presence of CO2 and H2O than in the absence of these species. Therefore, interestingly under CO2+H2O environment (realistic CO-PROX conditions) CuO/Cryptomelane catalyst performs an improved catalytic activity.

Improved Low-Temperature Activity of CuO–CeO2–ZrO2 Catalysts for Preferential Oxidation of CO in H2-Rich Streams

In this work, CuO–CeO2–ZrO2 catalysts for CO preferential oxidation have been prepared by ultrasound assisted reverse coprecipitation and slow coprecipitation, and characterized via BET, XRD, XPS and H2-TPR techniques, respectively. It is found that the catalyst prepared with ultrasound assisted reverse coprecipitation preserves large specific surface area, fine crystalline grain and high dispersion of active copper species. Meanwhile, the reducibility is improved significantly and more active copper species and oxygen vacancies are formed in the copper–ceria boundaries. The ultrasound assisted reverse coprecipitation prepared CuO–CeO2–ZrO2 catalyst exhibits superior low-temperature activity and CO2 selectivity, over which the temperature responding to 50 % CO conversion is as low as 67 °C, and the temperature window of full CO conversion is significantly widen from 100 to 160 °C. The ultrasound assisted reverse coprecipitation prepared CuO–CeO2–ZrO2 catalyst exhibits superior low-temperature activity for CO preferential oxidation and wide temperature window of full CO conversion comparing with the catalyst prepared with slow coprecipitation.

Ceria-Praseodymia Mixed Oxides: Relationships Between Redox Properties and Catalytic Activities Towards NO Oxidation to NO2 and CO-PROX Reactions

A series of CexPr1−xO2−δ catalysts was prepared by co-precipitation method in alkali media. These catalysts were characterized by N2 adsorption–desorption isotherms at −196 °C, X-ray diffraction, thermogravimetry combined with mass spectrometry (TG-MS), and temperature-programmed reduction with H2 and CO (H2-TPR and CO-TPR, respectively). Catalytic tests were performed for temperature programmed NO oxidation to NO2 (from 25 to 750 °C) and for the preferential oxidation of CO in H2 rich stream (CO-PROX reaction) in the range of 150–500 °C. The trends in the order of catalytic activities towards NO oxidation and CO-PROX are correlated with the redox properties of the catalysts and their composition. CexPr1−xO2−δ mixed oxides present very different catalytic behaviours towards NO oxidation and CO-PROX reactions. These experimental trends might be explained by the balance of several factors: the acid character of the NO and CO molecules, the different lattice oxygen mobility of the catalysts, the presence of surface carbonates species in the samples, and the catalysts’ reducibility under H2 and CO. The understanding of the features that govern the activity towards these environmentally relevant oxidation reactions is important in the designing of effective catalysts.

Selective oxidation of CO in H2-rich stream over ZSM5 zeolites supported Ru catalysts: An investigation on the role of the support and the Ru particle size

Selective oxidation of CO in H2-rich stream was studied over ZSM5 zeolite supported Ru catalysts and the results were compared with those obtained over Ru samples supported on alumina, silica and ceria. ZSM5 zeolite supported Ru catalysts exhibited higher yields to CO2 than Ru samples on other supports. The SiO2/Al2O3 ratio of the zeolite was found to strongly affect the performance of the Ru/ZSM5 system, the Ru sample supported on the H-ZSM5 with the highest SiO2/Al2O3 ratio (280) being the most efficient towards the CO selective oxidation. The form of the zeolite (H- or Na-) had instead a lower influence. On the basis of characterization data (TEM, XPS, H2-TPR, NH3-TPD) it was pointed out that the performance of the Ru/ZSM5 samples are strongly dependent on the Lewis acidity of the zeolite and/or the Ru particle size, a lower number of Lewis acid sites and bigger Ru particles resulting in higher CO2 yields.

Characterization and catalytic properties of CuO/CeO2/MgAl2O4 for preferential oxidation of CO in H2-rich streams

Catalysts of copper (1wt.%) supported on a CeO2/MgAl2O4 mixed support have been prepared by using different pH values (pH∼4, 8 and 10) in the impregnating solution of copper with the aim of favoring different situations of interaction between copper and the two support components. The catalysts have been characterized in detail by XRD, SBET measurement, HREM and associated techniques, XPS, H2-TPR and EPR which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of the catalytic properties of the samples for preferential oxidation of CO in a H2-rich stream (CO-PROX) complemented by operando-DRIFTS. Important structural/chemical/catalytic differences as a function of the pH of the impregnating solution are revealed. These are explained on the basis of the characteristics of the interfaces formed between the different components present in each catalyst which basically determine the catalytic properties in each case.

Highly active subnano Rh/Fe(OH)x catalyst for preferential oxidation of CO in H2-rich stream

A novel catalyst formulation of 3.1wt.% Rh/Fe(OH)x was prepared via a co-precipitation method and investigated for CO preferential oxidation in H2-rich stream. This catalyst exhibited a wider temperature range of 20–70°C for CO total removal and better resistance to CO2 and H2O compared with the standard gold catalyst, standing out as the best Rh-based catalyst ever. The Rh species were highly dispersed in a subnano scale of ∼1nm and improved the reducibility of Fe(OH)x support. The adsorption of O2 was thus promoted over the reduced support, together with the weakened CO adsorption over the Rh clusters, permitting a non-competitive Langmuir–Hinshelwood mechanism through the elementary reaction of CO(ad)+O(ad). The reaction rate equation of r=k[CO]0.73[O2]0.64 and small apparent activation energy of 24kJmol−1 were then derived from the kinetic studies.

The preferential oxidation of CO in hydrogen rich streams over platinum doped nickel oxide catalysts

NiO/Al2O3, Pt/Al2O3 and Pt/NiO/Al2O3 catalysts were prepared by the incipient wetness technique with a Ni loading of 25wt% and Pt loading of 0.5wt%. These catalysts were characterized by ICP-OES, XRD, BET, TPR, N2 adsorption–desorption isotherms, CO chemisorption, FTIR-CO, XPS, SEM-EDX and TEM. XRD and XPS results of the catalysts showed the presence of NiO and PtO phases on the respective supports and in situ redox reactions showed that the catalysts underwent reversible phase changes (oxide and metallic) that were stable. FTIR-CO studies showed that the Pt containing samples exhibited both linear and bridged CO adsorption with higher intensities observed for the Pt/NiO/Al2O3 catalyst. The catalysts were tested for the oxidation of CO in H2 rich streams (preferential oxidation-PROX) in a continuous flow fixed bed stainless steel reactor. The NiO/Al2O3 catalyst produced very low conversions of CO in the stipulated PROX temperature range and showed highest conversion of 11% with a selectivity of 25% toward CO2. The Pt/Al2O3 catalyst showed improved activity within the PROX temperature range with highest CO conversion of 56% and selectivity toward CO2 of 68% at 200°C. The Pt/NiO/Al2O3 catalyst revealed synergistic effects, obtaining much higher CO conversions within the PROX temperature ranges compared to both the mono-metallic catalysts. The highest CO conversion, of 99.9%, for this catalyst was at 200°C, with a selectivity of 72.8% toward CO2 using a C:O2 ratio of 1:2.

CO methanation promoted by UV irradiation over Ni/TiO2

Thermo-catalytic CO methanation has been widely investigated as an attractive strategy for the removal of CO in H2-rich stream. In this paper, UV irradiation was introduced into the system of thermo-catalytic CO methanation over a noble-metal-free Ni/TiO2 catalyst. It is found that UV irradiation can remarkably promote the CO conversion and CH4 selectivity, as well as an excellent catalytic stability under the thermo-catalytic reaction conditions. Results of XPS, FT-IR, and TPO measurements for the Ni/TiO2 catalyst indicate that upon UV light irradiation, the photo-generated electrons are transferred from the TiO2 support to the adjacent Ni sites, and causes the Ni sites with increased surface electron density which subsequently enhances the adsorption and activation of CO molecules at Ni sites, and ultimately promotes the catalytic performance of CO methanation. This result shows that photo-excitation of TiO2 can act as an electron donor to promote the thermo-catalytic performance of CO methanation over Ni/TiO2.