Preferential Oxidation Reaction Research Articles

MOF-derived high oxygen vacancies CuO/CeO2 catalysts for low-temperature CO preferential oxidation

The CO preferential oxidation reaction (CO-PROX) is an effective strategy to remove residual poisonous CO in proton exchange membrane fuel cells, in which oxygen vacancies play a critical role in CO adsorption and activation. Herein, a series of CuO/CeO2 catalysts derived from Ce-MOFs precursors were synthesized using different organic ligands via the hydrothermal method and the CO-PROX performance was investigated. The CuO/CeO2-135 catalyst derived from homophthalic tricarboxylic acid (1,3,5-H3BTC) exhibited superior catalytic performance with 100 % CO conversion at a relatively low temperature (T100% = 100 °C), with a wide reaction temperature range and excellent stability. The superior catalytic properties were attributed to the structural improvements provided by the 1,3,5-H3BTC precursors and the promotional effects of oxygen vacancies. Additionally, in-situ Raman spectroscopy was performed to verify the dynamic roles of oxygen vacancies for CO adsorption and activation, while in-situ DRIFTS analysis revealed key intermediates in the CO-PROX reaction, shedding light on the mechanistic aspects of the catalytic process. This work not only demonstrates insights into the effective CuO/CeO2 catalysts for CO preferential oxidation, but also provides a feasible way to synthesize MOF-derived catalysts.

Effect of air depletion in the preferential oxidation reactor and fuel depletion in a proton exchange membrane fuel cell system fueled by natural gas

This study estimates the steady-state performance of a proton exchange membrane fuel cell (PEMFC) under conditions of air depletion in the preferential oxidation reactor (PrOx) and fuel depletion at the anode, which has not been previously studied. Considering the detailed chemical reactions of the reforming process, the composition of the reformed gas at the anode inlet is determined using the temperature and pressure data measured at various state points in the PEMFC system. To calculate the voltage loss at the anode due to the air depletion in PrOx or reformate gas depletion before the anode, the electrochemical reaction of the reformed gas in the anode catalyst layer is studied. The calculations show that when the fuel entering the anode or air entering the PrOx decreases, the amount of CO at the anode increases depending on the reduction, resulting in activation loss at the anode, and thereby leading to power loss. This analysis of the power loss in a PEMFC due to a lack of air or fuel can serve as an auxiliary diagnostic tool to identify faulty parts in the Balance of Plant (BOP).

Highly dispersed copper catalysts for CO preferential oxidation in hydrogen-rich atmosphere

CeO2 and ZnO with finely rod shape were used as carriers to support copper. High-resolution transmission electron microscopy demonstrated that copper species were existed mostly in bilayer clusters containing underlying Cu+ and upper Cu0 on CeO2, but in big particles of 5–10 nm consisting of only Cu0 on ZnO. The amounts of underlying Cu+ in bilayers and oxygen vacancies (Ov) at copper-ceria interface reached maximum when copper loading was about 10 wt%. In CO preferential oxidation reaction, the 10-Cu/CeO2 catalyst showed the highest activity suggesting that CO adsorbed on Cu+ in bilayer clusters reacted rapidly with O2 absorbed on adjacent Ov. The near synergistic effect not only reduced the CO reaction temperature but also enhanced the CO conversion. The Cu/ZnO catalyst had weak CO adsorption and long distance of Cu0 and Ov, thus it showed much low activity. By filling the 10-Cu/CeO2 catalysts in a two-stage reactor, 1 % CO in the methanol steam reforming gas could be removed to 2 ppm after two successive CO oxidation processes, which provided a new solution for H2 purification.

Selective electrocatalytic conversion of primary alcohols to nitriles on nickel-cobalt nitride/oxide tandem electrocatalyst

Nitriles are vital precursors in the production of pharmaceuticals, advanced materials and many other commercial chemicals. Conventional approaches for nitrile synthesis are limited by the utilization of highly toxic cyanide ion and harsh conditions. The electrochemical conversion of primary alcohols and ammonia to nitriles offers a cost-effective and green approach to prepare nitriles, which requires highly efficient and selective catalysts to drive the cascade reaction and minimize side reactions. Here, we demonstrate how nitriles can be selectively synthesized by electrocatalytic oxidation of benzyl alcohol and ammonia on NiCo nitride and oxide that are co-localized on carbon cloth (NiCo-N,O/CC) electrode. In this electrocatalyst, the oxidation from alcohols to aldehydes is mainly catalyzed by NiCo oxide, while the oxidation from imine to nitrile is mainly catalyzed by NiCo nitride, endorsing preferential oxidation and cascade reactions on these catalytic interfaces. A total faradaic efficiency of 52%, productivity rate of 35 μmol cm-2h−1 and 70.1% selectivity of nitriles was achieved at 1.53 V vs RHE. The two interface NiCo-N,O/CC tandem electrocatalyst revealed synergistic activity and selectivity superior to NiCo-O/CC with single interface. Our results demonstrate that the utilization of tandem catalytic mechanisms could create new prospects in designing electrocatalysts for cascade reactions.

Electrochemical Performance of a Spatially Distributed ECPrOx Reactor

In this contribution a spatially distributed Electrochemical Preferential Oxidation (ECPrOx) reactor is evaluated and the influence of the temperature, CO inlet concentration, feed flow rate and relative humidity on the polarization curve, the local current distribution and the CO outlet concentration, selectivity and conversion are investigated. For that, six different cases are studied under galvanostatic and potentiostatic operation. For Galvanostatic operation, it was observed that depending on the operation conditions, the bifurcation point as well as the frequency and amplitude of the oscillations can be modified. Additionally, several spatiotemporal profiles of the local current density were found. For potentiostatic operation, the spatiotemporal profiles are constant with time, however they are affected by the anode overvoltage. Finally, after the bifurcation point, the temporal averaged anode overvoltage and the CO outlet concentration is always lower for galvanostatic control.

A methanol autothermal reforming system for the enhanced hydrogen production: Process simulation and thermodynamic optimization

Methanol autothermal reforming is a potential way to produce hydrogen that can be used for vehicle power batteries like PEMFC. Combining a reformer with a combustor to produce substantial hydrogen is promising, but the challenge of heat transfer efficiency between the reformer and combustor must be considered. Furthermore, the complexity of the system structure is not conducive to its large-scale operation level. In this paper, a novel methanol autothermal reforming hydrogen production system without catalytic combustion was built and developed, aiming to produce hydrogen-rich gas with low CO concentration. Process simulation and thermodynamic optimization on the target system were detailedly performed using Aspen Plus software and parameter sensitivity analysis methods. In addition, a methanol autothermal reforming hydrogen production system using catalytic combustion was taken as the reference system. The results indicated that the novel system could achieve a self-sustaining operation by the coupled methanol partial oxidation and steam reforming. And the product gas contained very low CO concentration (<10 ppm) due to the combined effects of water-gas shifting and CO preferential oxidation reactions. It was verified that under the maximal exergy efficiency condition, the exergy efficiency of the novel system is not significantly improved compared with the reference system, but the hydrogen yield is increased by about 27.65%, the thermal efficiency is increased by about 17.51%, and the exergy loss when generating unit molar H2 is reduced by 20.53 kJ/mol; Under the condition of maximum hydrogen yield, the indicators of the novel system also perform better. Notably, the reformer is the main exergy loss source in the novel system, which provides a theoretical basis for further optimization of parameter configuration. This work will be beneficial to researchers who study the miniaturization design of the integrated system of methanol hydrogen production coupled vehicle power battery.

Understanding the role of K on PtCo/Al2O3 for preferential oxidation of CO in H2

CO preferential oxidation reaction (CO-PROX) can effectively eliminate CO in H2 rich atmosphere to avoid CO poison the Pt anode of Proton Exchange Membrane Fuel Cell (PEMFC). To match the operation temperature window for PEMFC, PtCo nanoparticles supported on K modified Al2O3 (PtCo/K–Al2O3) were prepared to promote CO-PROX activity. The addition of K species weakened the interaction between PtCo nanoparticle and support, which improved the dispersion of Pt particles and redox property of PtCo/Al2O3. It also facilitated the formation of Pt3Co species and active surface −OH groups, which were involved in CO-PROX reaction. According to in situ DRIFTS spectra, HCO3− and HCOO− were intermediates of PtCo/K–Al2O3 catalyzed CO-PROX at low temperature and high temperature, respectively. Thus, the addition of 1 wt% K to PtCo/Al2O3 (PtCo/1K–Al2O3) could completely oxidize CO in the temperature range of 127–230 °C with O2 selectivity at 50%. The 100% CO conversion temperature window of PtCo/1K–Al2O3 is expanded by 100 °C in comparison of PtCo/Al2O3.

Investigation of a methanol processing system comprising of a steam reformer and two preferential oxidation reactors for fuel cells

Methanol steam reforming is able to produce hydrogen-rich syngas onsite for fuel cells and avoids the problems of hydrogen storage. Nevertheless, CO in the reformate needs to be further removed to ppm level before it can be fed into proton exchange membrane fuel cells. In this study, a methanol processing system consisting of a methanol reformer and two-stage preferential oxidation reactors is developed. The hydrogen production performance and scalability of the reformer are experimentally investigated under various operating conditions. The methanol reformer system shows stable methanol conversion rate and linearly increased H2 flow rate as the number of repeating unit increases. Methanol conversion rate of 96.8% with CO concentration of 1.78% are achieved in the scaled-up system. CO cleanup ability of the two-stage preferential oxidation reactors is experimentally investigated based on the reformate compositions by varying the operating temperature and O2 to CO ratios. The results demonstrate that the developed CO cleanup train can decrease the CO concentration from 1.6% to below 10 ppm, which meets the requirement of the fuel cell. Finally, stability of the integrated methanol processing system is tested for 180 h operation.

Promotional Effect of H2 Pretreatment on the CO PROX Performance of Pt1/Co3O4: A First-Principles-Based Microkinetic Analysis.

Atomic Pt studded on cobalt oxide is a promising catalyst for CO preferential oxidation (PROX) dependent on its surface treatment. In this work, the CO PROX reaction mechanism on Co3O4 supported single Pt atom is investigated by a comprehensive first-principles based microkinetic analysis. It is found that as synthesized Pt1/Co3O4 interface is poisoned by CO in a wide low temperature window, leading to its low reactivity. The CO poisoning effect can be effectively mitigated by a H2 prereduction treatment, that exposes Co ∼ Co dimer sites for a noncompetitive Langmuir-Hinshelhood mechanism. In addition, surface H atoms assist O2 dissociation via "twisting" mechanism, avoiding the high barriers associated with direct O2 dissociation path. Microkinetic analysis reveals that the promotion of H-assisted pathway on H2 treated sample helps improve the activity and selectivity at low temperatures.

Viability of Au/La2O3/HAP catalysts for the CO preferential oxidation reaction under reformate gas conditions

The viability of gold supported on lanthanum-modified HAP catalysts is investigated for CO preferential oxidation (PROX) in H2-rich stream. All samples comprise small nanoparticles (NPs) of Au (< 4 nm). Addition of La enhances the chemisorption of CO, whereas it lowers that of H2 and H2O. Moreover, lanthanum improves the reducibility of the catalysts and the mobility of oxygen. FTIR studies show that under CO oxidation conditions Au exists in two distinct forms on La-promoted samples, namely Auσ+ and Au+ species. The catalytic tests under different PROX conditions show an improvement of the performance with lanthanum addition. The observed improvement is linked to suitable chemical properties, whereas efficiency dependence on Au NP sizes is rather secondary. At 80 °C, La-rich catalysts completely eliminate CO and prove to be selective (66%) under realistic PROX conditions (in the presence of H2O and CO2). Moreover, they are exceptionally stable during an extended period (240 h).

Dynamic analysis of a CCHP system based on fuel cells integrated with methanol-reforming and dehumidification for data centers

For data centers with strict requirements on temperature and humidity, this study proposes a combined cooling, heating and power (CCHP) system integrated with methanol-reforming and dehumidification based on proton exchange membrane fuel cells (PEMFCs). The system consists of a methanol-reformer, preferential oxidation (PROX) reactor, PEMFC stack, adsorption chiller, desiccant air conditioning (DAC), and phase change material(PCM) heat storage tank. Taking a data center in Harbin as the research object, the dynamic response characteristics of the system are studied, and the system has good dynamic response characteristics. The CO concentration in the reformed gas is controlled by controlling the O2/CO ratio in the PROX. The CO concentration in the transformation gas can be controlled below 4 ppm. The cooling and dehumidification requirements of the data center are met by controlling the cooling power of the system and the air intake conditions of the data center. The results show that the cooling power of the system rises for 400 s at the beginning of the operation, and stabilizes after about 2 h, and the temperature and relative humidity of the data center can be controlled at 25 °C and 55–63%. The novel system develops an efficient way to recover low-grade waste heat of PEMFC stacks for cooling and dehumidification in data centers.

Performance of fuel cells using biogas and its sensitivity analysis

The use of renewable fuels has been currently increased since the non-renewable sources of energy are depleting. H₂ is one of the main energy carriers which can be derived from various renewable and non-renewable fuels. Biogas has high methane content and that can be converted to H₂ using reforming reaction followed by water–gas shift reaction. The main objective of this study is to optimize H₂ yield by using autothermal reforming followed by the water–gas shift reaction and preferential oxidation and to analyze the performance of polymer electrolyte membrane fuel cell under different operating parameters. Sensitivity analysis using methane, steam and air flowrate, conversion of methane and oxygen, reactor temperature and pressure on the yield of H₂ and carbon-monoxide yield has been performed. The H₂ yield obtained from Autothermal reactor is 64.73 % which is increased to the value of 75.21 % after the preferential oxidation reactor. The H₂ yield achieved after the optimization is 68.64 % from the Autothermal reactor. The Optimum Air/Steam/Feed ratio obtained is 1:2.23:4.60. H₂ is produced at the rate of 330 kg/hr. Results showed that Polymer Electrolyte Membrane fuel cell efficiency and stack consumption is decreased with the increase in fuel flowrate. There is slight variation in polymer electrolyte membrane fuel cell efficiency and stack consumption with the increase in fuel and air supply pressure. Stack efficiency remained constant with increasing fuel and oxidant composition. Polymer Electrolyte Membrane fuel cell operates effectively at both the temperatures of 65 °C and 600 °C.

CO removal for hydrogen purification via Water Gas Shift and COPROX reactions with monolithic catalysts

A combination of Water Gas Shift (WGS) and CO preferential oxidation (COPROX) reactions is considered a promising approach for CO removal in an H2 feed employed for PEM fuel cells. Honeycomb monolithic catalysts were studied for this purpose, firstly coated with Ce or Ce-Pr, then with Cu or Cu-Ni, (mass gained ∼35%). Computational Fluid Dynamics simulation showed that outer channels (close to reactor wall) presented a slightly lower flow in comparison with flow in inner ones. The Pr content in WGS monoliths modulated the activity-selectivity ratio showing an optimal value for 15 at.% in case of Ni-containing samples due to a significant selectivity improvement towards WGS (hindering methanation). A Cu/ceria monolithic sample was tested as COPROX catalyst. The CO conversion presented a maximum value with the increase of the operation temperature. Besides, a larger contact time (achieved by modifying monolith length) also enhanced the undesired H2 oxidation reaction as same as a larger O2/CO ratio. As a consequence, a temperature window around to 130 °C, a contact time close to 0.1 g.s/cm3, and a O2/CO = 1 M ratio was determined as the most adequate parameters set.

Cu–Mn–O nano-particle/nano-sheet spinel-type materials as catalysts in methanol steam reforming (MSR) and preferential oxidation (PROX) reaction for purified hydrogen production

Nanocomposite Cu–Mn–O nano-particle (CuMnNP) and nano-sheet (CuMnNS) catalyst were successfully prepared using a one-step hydrothermal method in the absence of any templating reagent. Materials were characterised applying various structural techniques. SEM images showed that composite Cu–Mn oxide sheets were tailor-made synthesised by a one-pot urea-abetted protocol. Conversely, upon replacing carbamate by Na2CO3, oxidised metal Cu–Mn particles could be obtained. The formation of bulk mixed Cu–Mn phases resulted in an enhanced crystal lattice oxygen reactivity in CuMnNS. XPS, XRD and TPR measurements confirmed the presence of the Cu+ and Cu2+ species in nano-catalysts, and CuMnNS nanomaterials possessed more surface defects, thus causing a higher O2 adsorption/storage capacity. CuMnNS presented a superior catalytic activity as opposed to CuMnNP in the preferential oxidation (PROX) pathway of CO. With both CO2 and H2O in feed, a decrease in CO turnover was observed, due to a competitive interface binding of CO, CO2 and H2O. Compared to CuMnNP, CuMnNS also demonstrated a high time-on-stream conversion of methanol for the reforming for all operating conditions.

Hydrogen-rich gas with low-level CO produced with autothermal methanol reforming providing a real-time supply used to drive a kW-scale PEMFC system

An integrated system was developed to produce hydrogen-rich gas with low-level CO via autothermal reforming (ATR) of methanol for the purpose of real-time use in a kW-scale proton exchange membrane fuel cell (PEMFC) system. Methanol was converted into a hydrogen-rich gas through ATR in conjunction with water gas shifting (WGS) and preferential oxidation (PrOX) reactors to reduce the CO concentration. A 29.5% hydrogen-rich gas with a CO concentration of approximately 20 ppm was achieved under the optimal parameter settings (i.e., an H2O/CH3OH ratio = 0.5 and an O2/CH3OH ratio = 0.55 for the ATR reaction, an H2O/CO ratio = 5.6 for the WGS reaction, and an O2/CO ratio = 1.08 for the PrOX reaction). Specifically, the reformer system steadily produced low CO, hydrogen-rich gas after 4 h of durability testing. This system was then combined with 40-cell fuel cell stacks with air bleeding and tested for its durability over a period of 6 h. It was verified that the hydrogen-rich gas produced by the reformer system enabled the fuel cell to steadily generate 1040 W of power. Notably, the hydrogen-rich gas (the actual reformate gas) produced herein could generate better performance than the simulated reformate gas reported in the literature.

Catalytic performance of copper oxide supported α-MnO2 nanowires for the CO preferential oxidation in H2-rich stream

In this article, the catalytic activity of the copper catalysts with different loadings of copper oxides supported on α-MnO2 nanowires prepared by the simple hydrothermal route was studied in the CO preferential oxidation reaction. The x-ray diffraction (XRD), N2 adsorption/desorption, Fourier transform infrared (FT-IR) spectroscopy, H2-temperature-programmed reduction (H2-TPR), and scanning electron microscopy (SEM) analyses were used to characterize the synthesized samples. The obtained results showed that the 10 wt% CuO/MnO2 catalyst with the highest specific surface area and the lowest particle size demonstrated the highest CO conversion and CO2 selectivity in this reaction. The good catalytic performance of this catalyst was due to the beneficial synergistic interaction between copper and manganese. However, adding CO2 and/or H2O to the feedstock decreased the conversion and selectivity. Moreover, the effect of different parameters such as calcination temperature, O2/CO ratio, gas hourly space velocity (GHSV), and pretreatment conditions were investigated.

In-situ experimental and computational approach to investigate the nature of active site in low-temperature CO-PROX over CuOx-CeO2 catalyst

Preferential oxidation (PROX) of carbon monoxide (CO) in presence of excess hydrogen is a necessity to prevent poisoning of the Pt-anode by CO in PEMFCs (Polymer Electrolyte Membrane Fuel Cell). A highly active catalyst, 5 wt% Cu-CeO2 showed 100 % CO conversion at 65 °C without any undesirable oxidation of H2. The catalyst showed no deactivation even after 100 h on stream, making it viable for practical fuel cell application. Operando EPR in the PROX reaction condition revealed highly dispersed mixed valent cations with oxygen vacancies, responsible for the low-temperature PROX activity. At the active site, both Cu and Ce ions were shown to reversibly change their valence states to facilitate the abstraction of bridging lattice oxygen for CO oxidation to CO2. This surface oxygen mediated CO oxidation was found to be much faster than that of H2 to H2O, which could explain the complete selectivity of oxygen for CO2 formation.

High Catalytic Performance of Au/Bi2O3 for Preferential Oxidation of CO in H2.

Preferential oxidation (PROX) of CO in hydrogen is of great significance for proton exchange membrane fuel cells (PEMFCs) that need a CO-free hydrogen stream as fuel. The key technical problem is developing catalysts that can efficiently remove CO from the H2-rich stream within the working temperature range of PEMFCs. Herein, we design a Au/Bi2O3 interfacial catalyst for PROX with excellent catalytic performance, which can achieve 100% CO conversion in the PROX reaction over a wide temperature window (70-200 °C) and is perfectly compatible with the operating temperature window (80-180 °C) of PEMFCs. Moreover, the catalyst also demonstrates excellent high flow performance and long-term stability. Density functional theory (DFT) calculations reveal that the electrons transferring from Bi2O3 to Au and then to adsorbed perimeter CO and O2 molecules promote the activation of CO and O2, thus enhancing the catalytic performance of PROX.

Blocking the non-selective sites through surface plasmon-induced deposition of metal oxide on Au/TiO2 for CO-PROX reaction

CO preferential oxidation (PROX) in excess hydrogen is a promising strategy for CO removal in hydrogen-rich reformate. However, the CO conversion and CO 2 selectivity in the PROX reaction dramatically decrease with rising temperature, resulting in a major challenge to complete CO removal across a wide temperature window. Here, we developed a photoexcited deposition of metal oxide (PDMO) method based on surface plasmonic resonance of Au nanoparticles, which can tune the interfacial properties by depositing lead oxide at the Au-TiO 2 interface. The interface modified Pb 3 O 4 /Au/TiO 2 catalyst can successfully eliminate CO in a wide temperature range (70°C–140°C) and exhibit superior stability in the PROX reaction. Further experiments demonstrated that the improved PROX performance is due to the severely depressed hydrogen oxidation through simultaneously inhibiting the activation of hydrogen and oxygen. The results further reveal that the interface of Au/TiO 2 is the superactive but non-selective site for H 2 and CO oxidation. • Photoexcited deposition of metal oxide method is employed for interface engineering • Interface-engineered Au-TiO 2 helps to identify the active site in CO and H 2 oxidation • Blocking the non-selective sites greatly improves the CO-PROX performance • Interface anchoring with inert lead oxide enhances long-term thermal stability Against the background of the carbon-neutral era, the liquid sunshine industry is booming due to the consumption of greenhouse gas (CO 2 ) and the solution of storage and transportation of H 2 energy. However, before the terminal application of H 2 energy, CO must be removed in the H 2 -rich reformate to avoid poisoning the noble metal catalysts. Gold-catalyzed CO preferential oxidation (PROX) has great potential in the removal of CO from H 2 -rich reformate. The competition oxidation of CO and H 2 at the interface of gold support always results in a decrease in CO oxidation conversion and selectivity, especially at high temperature. However, it is a major challenge to distinguish the interfacial sites from the other parts of nanoparticle surface. We show here that the interface of Au-TiO 2 is modified by our photoexcited deposition of metal oxide (PDMO) method, which greatly affects the performance of the CO-PROX reaction. The interfacial area of metal support is the ultrahigh active site in catalysis. However, the ultrahigh active sites are normally adverse for chemoselective oxidation or hydrogenation reaction. Interface-engineered catalyst is prepared based on a selective photoexcited deposition of metal oxide method and shows greatly improved performance in CO preferential oxidation in H 2 -rich stream (PROX reaction).

AuCu/TiO2 Catalysts prepared using electron beam irradiation for the preferential oxidation of carbon monoxide in hydrogen-rich mixtures

The major part of the world production of hydrogen (H2) is originated from a combination of methane steam reforming and water-gas shift reaction resulting in an H2-rich mixture known as reformate gas, which contains about 1% vol (10,000 ppm) of carbon monoxide (CO). The preferential oxidation reaction of CO in H2-rich mixtures (CO-PROX) has been considered a very promising process for H2 purification, reducing CO for values below 50 ppm allowing its use in PEMFC Fuel Cells. Au nanoparticles supported on TiO2 (Au/TiO2) catalysts have been shown good activity and selectivity for CO-PROX reaction in the temperature range between 20-80 ºC; however, the catalytic activity strongly depends on the preparation method. Also, the addition of Cu to the Au/TiO2 catalyst could increase the activity and selectivity for CO-PROX reaction. In this work, AuCu/TiO2 catalysts with composition 0.5%Au0.5%Cu/TiO2 were prepared in a single step using electron beam irradiation, where the Au3+ and Cu2+ ions were dissolved in water/2-propanol solution, the TiO2 support was dispersed and the obtained mixture was irradiated under stirring at room temperature using different dose rates (8 – 64 kGy s-1) and total doses (144 – 576 kGy). The catalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction transmission electron microscopy, temperature-programmed reduction and tested for CO-PROX reaction. The best result was obtained with a catalyst prepared with a dose rate of 64 kGy s-1 and a total dose of 576 kGy showed a CO conversion of 45% and a CO2 selectivity of 30% at 150 oC.