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With the continuous advancement of carbon peaking and carbon neutrality goals worldwide, the concept of "hydrogen replacing carbon" is gradually becoming the mainstream for the future development of the steel industry. It plays a crucial role in achieving carbon reduction at the source and breaking away from dependence on fossil fuels. Based on this, this study focuses on the kinetic research of non-isothermal reduction of different iron-containing raw materials under a hydrogen atmosphere. The TG curve and DTG curve in the temperature range from room temperature to 1223K were obtained by thermogravimetric analysis. The research reveals that the hydrogen reduction of iron-containing raw materials can be divided into three stages. In the Stage Ⅰ, hydrogen exhibits strong reduction ability towards HM iron concentrate powder and BY iron concentrate powder, with apparent activation energies of 19.997 kJ/mol and 23.863 kJ/mol, respectively. In the Stage Ⅲ, the presence of Wüstite and MgFe 2 O 3 in HM iron concentrate powder and BY iron concentrate powder hinders the reduction rate. Throughout the reaction stages, the hydrogen reduction of HF ore powder and PB ore powder requires overcoming relatively small reaction barriers, with apparent activation energies of 62.274 kJ/mol and 64.568 kJ/mol, respectively. This analysis provides a theoretical basis for the effective hydrogen reduction of iron-containing raw materials. [Display omitted] • Exploring the reduction behavior of iron-containing raw materials during heating using non-isothermal methods. • Classifying reaction regions based on the variations in TG and DTG curve profiles. • It is proposed that in the Stage Ⅲ of the reaction, the formation of MgFe 2 O 4 leads to an increase in activation energy. • In proposing a deceleration in the Stage Ⅲ of the reaction, two factors may be considered. [ABSTRACT FROM AUTHOR]

Copper-promoted iron oxides are commonly utilized in high-temperature water-gas shift (WGS) reactions. Although the promotional effect of Cu has been previously documented, the nature of the active sites for Cu/Fe 3 O 4 remains debated and the role of the crystallite size of Fe 3 O 4 has not been tackled. In this study, a wide range of Cu/Fe 3 O 4 catalysts were designed by hosting Cu species onto Fe 3 O 4 of two contrasting crystallite sizes (approximately 10 and 160 nm) and by utilizing different preparation methods (ammonia evaporation and deposition-precipitation). The evaluation of their catalytic WGS performances revealed a remarkable and previously undocumented phenomenon: the addition of Cu resulted in universal activity enhancements only for small Fe 3 O 4 crystals, while the larger analogues displayed decreased activity. This peculiar phenomenon can be explained by the creation of Cu–Fe 3 O 4 interfaces present in the iron oxides of small crystallite sizes. Thorough characterizations, such as advanced electron microscopic, in situ powder X-ray diffractions, in situ diffuse reflectance infrared Fourier transform spectroscopy, and computational studies, suggest strong electronic interactions between the different metal species, facilitated reductions of the individual oxides, and more favorable CO activation at the interfacial sites, all accounting for the promoted activity. [Display omitted] • Influence of Fe 3 O 4 crystallite size in water-gas shift reaction was examined. • Performance of Cu/Fe 3 O 4 in water-gas shift reaction was studied. • The formation of Cu–Fe 3 O 4 interfaces existed on small Fe 3 O 4 crystals. • Promotional effect of Cu was only found on small Fe 3 O 4 crystals. [ABSTRACT FROM AUTHOR]

Biogas conversion is a renewable alternative for producing hydrogen. In this work, dry reforming of simulated biogas was performed in a 1 kW th continuous chemical looping reforming (CLR) unit in which the oxygen required for the partial oxidation of biogas to CO and H 2 is supplied by an oxygen carrier. The performance of two different oxygen carriers (an iron oxide-based residue and a synthetic material based on an iron-manganese mixed oxide) was evaluated. The residue was capable of performing the dry reforming of biogas to a larger extent than the synthetic oxygen carrier. To enhance hydrogen yield, NiO addition was also considered with both materials. The presence of NiO increased methane conversion and H 2 selectivity for both oxygen carriers. A value of approximately 2.6 mol H 2 /mol CH 4 was achieved with both materials with the presence of only 2.7 wt% NiO in the bed. • Dry-CLR of biogas was evaluated in a 0.5 kW th chemical looping unit. • Two Fe-based oxygen carriers tested: one residue and one iron-manganese mixed oxide. • The residue performed the dry reforming of biogas in a larger extent. • NiO addition to both oxygen carriers increased methane conversion and H 2 selectivity. • Yield of 2.6 mol H 2 /molCH 4 with both materials with 2.7 wt% NiO in the bed. [ABSTRACT FROM AUTHOR]

This work designed a mesoscale method of multi-step reduction of Fe 2 O 3 with H 2 based on Lattice Gas Cellular Automata (LGCA). Particles in the LGCA were marked to distinguish all the reactants, intermediates, products, and inert. A self-organized evolutionary mechanism is designed. The hydrogen reduction of Fe 2 O 3 in the temperature range of 460–550 °C and 650–800 °C was simulated. Results show that the intermediate product Fe 3 O 4 was found in both conditions, and its mass fraction quickly reach a peak at ∼0.8 and gradually decrease thereafter. An "induction period" can be identified in the initial stage of the reaction at 650–800 °C, where the reduction rate is slow due to the hindered formation of FeO. The porosity inside the Fe 2 O 3 particles increases continuously through the reduction process, resulting in significant changes in the flow field around the particles. Consequently, the wake vortex gradually decreases and disappears eventually. • The multiple step reduction of Fe 2 O 3 by hydrogen is investigated in mesoscale. • A mesoscale method with self-organized evolutionary mechanism is developed. • Three obvious reaction rate transitions can be identified at 650–800 °C by the method. • The flow field is altered from internal structural of Fe 2 O 3 changes during reduction. [ABSTRACT FROM AUTHOR]

The utilization of nanoparticles to enhance bacterial activity and boost hydrogen production in fermentation processes has gained significant attention due to their unique properties such as high specific surface area and quantum size. This research aimed to improve the biohydrogen yield from food waste by adding iron oxide nanoparticles (Fe 3 O 4) at various concentrations (50, 75, 100, 150, and 200 mg/l) and titanium dioxide (TiO 2) at different amounts (25–150 mg/l) to a single-stage hybrid (dark/photo) fermentation reactor. After obtaining the optimal amount of these two nanoparticles, the effect of synergic addition of nanoparticles on hydrogen production yield, was investigated at ratios of Fe 3 O 4 /TiO 2 = 50/50 and 100/50 mg/mg. At the ratio of Fe 3 O 4 /TiO 2 = 100/50, the cumulative hydrogen production and yield of hydrogen have increased from 1613 to 3392 ml and 101.60 to 213.66 mlH 2 /gVS, respectively, compared to the control experiment. We also found that the COD removal rate has enhanced from 28% to 40.1%. In the optimal value, the bacterial growth lag phase has also remarkably decreased from 8.19 to 4.81 h. • Synergic application of TiO 2 and Fe 3 O 4 significantly increased biohydrogen purity and production yield. • TiO 2 played an important role in the activity of bacteria in the photo fermentation process. • Fe 3 O 4 played an important role in the dark fermentation system. • Nanoparticles may act as a scaffold for enzyme and substrate binding. • Optimal nanoparticle concentration may differ for different bioreactors. [ABSTRACT FROM AUTHOR]

Chemical Looping Hydrogen (CLH) allows the direct production of pure hydrogen exploiting the redox properties of Fe, with high flexibility on the type of reductant used. In this work, a highly pure hydrogen stream suitable for the direct use into Proton Exchange membrane Fuel Cells was produced, using bioethanol as renewable fuel. The influence of both redox temperature (675°C–750 °C) and chemical composition of the Fe-based particles (2 wt% and 40 wt% of alumina added) on the carbon formation rate during reduction step was also deeply analyzed. Al 2 O 3 changed both Fe x O y redox kinetics and equilibrium phases, leading to a complete iron deactivation at high Al 2 O 3 concentration. The addition of an air oxidation step (3 steps CLH) is fundamental to restore the redox activity, with a constant efficiency of about 30% at 750 °C for 10 cycles. Furthermore, Al 2 O 3 promotes the ethanol conversion into carbon, undermining the hydrogen purity. [Display omitted] • Pure H 2 suitable for PEMFCs is obtained using bioethanol as renewable fuel. • The influence of Fe/Al interaction on H 2 yields and H 2 purity was studied. • 3 steps CLH allows the use of Fe 2 O 3 -40 wt% Al 2 O 3 with no reduction in performance. • Fe 2 O 3 -2 wt% Al 2 O 3 withstands 10 redox cycles in the temperature range 675–750 °C. • A process efficiency of 30% was achieved at 750 °C for 10 consecutive redox cycles. [ABSTRACT FROM AUTHOR]

Fe 2-x Sn x O 3 structures grown by RF-DC magnetron co-sputtering. The band gap of Fe 2 O 3 , SnO 2 , Fe 2-x Sn x O 3 structure was calculated as 2.86, 4.06, 2.77 eV, respectively. The Fe 2 O 3 thin film has shown a tetragonal as well as the SnO 2 structure, however, the Fe 2-x Sn x O 3 (0 < x < 1) has shown rhombohedral structure. XPS measurements have shown change in binding energy which is due to the electron exchange of tin-iron with oxygen, and iron - tin oxide structure. This binding energy increases slightly with the chemical environment effect. The films were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM). In AFM images was seen that the iron oxide structure was pyramidal and the tin oxide structure was spherical, similar to the SEM image. The response of the film to hydrogen gas was measured at flow values of 100, 500 and 1000 ppm at 300 °C. Fe 2 O 3 thin films show 46%, SnO 2 61% and, Fe 2-x Sn x O 3 6.5% response to 1000 ppm H 2 gas. It is seen that the gas sensor response was affected by the morphological and structural features of the grown film. Current vs. time graph for thin films gas sensor. [Display omitted] • Thin films were successfully grown by RF-DC co-sputtering system. • Metal oxide hydrogen gas sensor devices were measured depending on different grown structures. • Fe 2 O 3 , SnO 2 , Fe 2-x Sn x O 3 thin films show 46%, 61%, 6.5% response to 1000 ppm H 2 gas. • Iron oxide and tin oxide have n-type carrier, while iron tin oxide has p-type carrier. [ABSTRACT FROM AUTHOR]

Materials composed of various constituents with distinct physical or chemical features are named composites. Merging components in the composite structure leads to new properties creation or the intrinsic properties magnification of the components, or synergetic effects. Here, the ternary nanocomposite of copper, nickel, and iron oxides was electrodeposited on the glassy carbon electrode (GCE) surface to facilitate the ethanol electro-oxidation reaction (EOR) and overcome the electrode fouling problem while prolonging its efficiency. The GCEs were modified by three different procedures and activated by CV cycling in an alkaline solution, and their electro-catalytic activity was tested toward EOR. The ternary electrocatalysts prepared by two-steps electrodeposition of their components (Ni,Fe 2 O 3 /Cu and Cu/Ni,Fe 2 O 3) demonstrated higher peak current and more negative peak potential (E pa = 476 mV, I pa = 492 μA, and E pa = 510 mV, I pa = 644 μA, respectively) than the binary electrocatalyst of Ni,Fe 2 O 3 toward EOR. The best electro-catalytic efficiency was acquired for the simultaneous electrodeposition of nano Cu, Ni, and Fe 2 O 3 on the GCE surface (Cu,Ni,Fe 2 O 3 , E pa = 530 mV, I pa = 3179 μA). The physicochemical and electro-catalytic characterizations of the fabricated electrocatalysts were evaluated by various techniques. The fast and facile engineered design of the GCE modification with the ternary Cu,Ni,Fe 2 O 3 components led to a high current density of about 101 mA/cm2 with increased tolerance against poisoning intermediates resulting in longtime stability for EOR in alkaline media. The synergistic effect between nano Ni, Cu, and Fe oxides provided promising properties for the EOR pursuing the construction of a powerful device with commercialization potential. • On-step electrodeposition of Cu,Ni,Fe 2 O 3 ternary nano-composite • Improvement of the electron transfer kinetic of EOR • High tolerance against poisoning intermediates and longtime stability for EOR • Promising electro-catalytic performance of Cu,Ni,Fe 2 O 3 /GCE for EOR • Achievement of a high current density of ∼101 mA/cm2 for EOR [ABSTRACT FROM AUTHOR]

Hydrogen purification by removing CO traces was studied via the preferential CO oxidation (PROX) reaction using highly dispersed Pt catalysts supported on dual oxide FeO x /TiO 2. These catalysts were prepared by the strong electrostatic adsorption (SEA) method by varying the pH of synthesis and the calcination temperature. By measuring the point of zero charge (PZC) of the support components, it was possible to determine the pH in which Pt can be selectively deposited onto one of the support components, obtaining Pt dispersion values above 90%. The selective SEA of a Pt precursor onto the co-support (FeO x) was achieved at a synthesis pH between the PZCs of the support components (i.e., TiO 2 PZC = 5.2 and Fe 2 O 3 PZC = 6.9) by using a Pt anionic complex. The catalytic activity for the PROX reaction, expressed in terms of the CO conversion, O 2 selectivity to CO 2 , apparent activation energy, and turnover frequency, confirmed that the SEA prepared catalysts were active and selective for the PROX reaction. XPS and TPR results of the Pt/FeO x /TiO 2 catalysts showed the formation of Pt-FeO x interfaces, called as (Pt-FeO x) i interfacial sites, which enhanced the stability and catalytic activity for the PROX reaction. The concentration of these sites can be controlled by the synthesis conditions used, mainly pH and to a lower extent the calcination temperature. [Display omitted] • Pt/FeO x /TiO 2 catalysts were prepared by SEA at a pH that ensures a Pt selective deposition onto Fe-based support. • 1 nm Pt crystallites were selectively deposited over FeO x at a pH between the PZCs of the support components. • The formation of (Pt-FeO x) i interfacial sites were detected by XPS, TPR, TEM and operando DRIFTS analyses. • The concentration of (Pt-FeO x) i interfacial sites is affected by the calcination temperature and the synthesis pH. • The concentration of (Pt-FeO x) i interfacial sites was correlated with the activity of Pt–Fe catalysts in the PROX reaction. [ABSTRACT FROM AUTHOR]

A peerless inexpensive electrochemical engineering of spherical Pt nanoparticles (nano-Pt: ca. 100 nm in average diameter) was achieved with intersected ferric oxyhydroxide nanotubes (α-FeOOH (goethite): ca. 20 nm in average diameter). The FeOOH@Pt catalyst exhibited ca. 2.5 and 1.94-times increases in the catalytic activity and poisoning tolerance, respectively, of the formic acid electro−oxidation (FAO) – the anodic reaction in the direct formic acid fuel cells (DFAFCs). Surprisingly, with a post-activation of the FeOOH@Pt catalyst at 0.48 V vs. reversible hydrogen electrode (RHE) in 0.2 mol L−1 NaOH, a favorable Fe2+/Fe3+ transformation succeeded to eliminate the permanent CO poisoning of Pt that impaired the catalytic performance of DFAFCs. This was synchronized (relatively to nano-Pt) with a four-fold increase in the catalytic efficiency, ca. −174 mV shift in the onset potential, and eightfold enhancement in the catalyst's durability for FAO. The activated FeOOH@Pt catalyst also showed a mass activity of 296 mA mg−1 Pt (at 0.8 V), which was ca. nine times higher than that (34 mA mg−1 Pt) of the commercial Pt/C catalyst. The ascertained improvement in the electron transfer at the FeOOH@Pt surface foresees quick industrialization for DFAFCs. TOC. A simple layer-by-layer electrochemical assembly and a post-activation of a peerless inexpensive FeOOH/Pt/GC nanostructured catalyst was recommended for "mitigated CO-poisoning" formic acid electro−oxidation. [Display omitted] • An efficient and robust FeOOH/Pt anodic catalyst was developed for the direct formic acid fuel cells (DFAFCs). • The catalyst's activation at 0.48 V vs. RHE in NaOH resulted in a boosted (fourfold) catalytic performance. • The activation enriched the catalyst surface with α-FeOOH (goethite phase). • The electronic properties of Pt were tuned to accelerate the charge transfer of FAO. • The peerless inexpensive modification of Pt with FeOOH will sustain the market to realize DFAFCs. [ABSTRACT FROM AUTHOR]

Steam iron process represents a technology for H 2 production based on iron redox cycles. Fe x O y are reduced by syngas/carbon to iron, which is subsequently oxidized by steam to produce pure H 2. However, the system shows low stability. In this work, the effect of promoters (Al 2 O 3 , MgO and CeO 2) on Fe x O y stability is investigated (10 consecutive redox cycles). Bioethanol is used as a reducing agent. The particles are synthesized by coprecipitation method, analysed by BET, XRD, SEM and tested in a fixed bed reactor (675 °C, 1 bar). Pure H 2 is obtained controlling the Fe x O y reduction degree feeding different amounts of ethanol (4.56–1.14 mmol) until no CO is detected in oxidation. The results show that the promoters not only improve the thermal stability of Fe x O y but also affect its redox activity and react with iron forming spinel structures. MgO led to the highest activity and cyclability (H 2 = 0.15 NL; E = 35%). • Steam iron process is a promising alternative to obtain pure H 2 ideal for PEMFC. • Pure and renewable H 2 is achieved using bioethanol in the reduction step. • The promoters Al 2 O 3 , CeO 2 and MgO aim to improve the Fe redox cyclability. • Al 2 O 3 and MgO play an active role reacting with Fe and forming spinel structures. • MgO gives the highest pure H 2 yields (H2(NL)/EtOH(g) = 3.422) stable for 10 cycles. [ABSTRACT FROM AUTHOR]

Carcinogenic hexavalent Cr in the current iron oxide-based catalysts of high temperature water-gas shift (HT-WGS) reaction is great environmental concern. Interpreting the role of the Cr in this important industrial catalyst system is required. In the present study, we investigated substitution of Cr atoms into the most stable termination of Fe 3 O 4 (111) slab surface by spin-polarized periodic DFT approach to comprehend the role of Cr. We applied the projector augmented-wave (PAW) method within the Perdew-Wang 1991 (PW91) form of the generalized gradient approximation (GGA) on the Vienna Ab-initio Simulation Package (VASP). The calculations point out that Cr atoms choose being below the surface FeO 6 sites. Cr slightly affects the dissociative H 2 O adsorption. There is no effect on the CO adsorption. Oxygen vacancy is favored to form on the topmost layer with less vacancy formation energy. Substitution of Cr into the structure increases the oxygen vacancy formation energy. This indicates that Cr does not act as a chemical promoter and does not affect the catalytic activity positively, which is experimentally confirmed by the previous studies. [Display omitted] • Surface FeO 6 is catalytic active site for HT-WGS reaction. • Oxygen atom from the topmost layer most energetically favorable for vacancy formation. • Cr modifies surface FeO 6 site by acting as ligand from below. • Cr increases energy for oxygen vacancy formation (increases E act). [ABSTRACT FROM AUTHOR]

A novel cyclic molecular designed dispersion (CMDD) method was employed to uniformly deposit 0.0–6.5 wt% Fe on CeO 2. The gold catalysts (0.0–3.8 wt%) supported on Fe 2 O 3 -CeO 2 were tested for CO preferential oxidation (PROX). As the CMDD method involved grafting of Fe (acac) 3 onto the surface –OH groups, 2.7 surface –OH/nm2 was determined for the CeO 2 by using the Grignard reagent. The performance of CMDD catalysts was compared with the corresponding catalysts prepared by impregnation. The catalysts were characterized by XPS, XRD, TPR, HRTEM-EDX, BET and ICP. The results suggested that Au/Fe 2 O 3 -CeO 2 was significantly more active and selective than Au/CeO 2. The CMDD-prepared catalysts with 1.4–2.5 wt% iron showed the highest activity and selectivity, especially at temperatures as low as 323 K. The formation of Ce-Fe solid solution for CMDD catalysts promoted the dispersion of both iron and gold. Highly dispersed gold nanoparticles mainly as small as 2.2 nm were observed in HRTEM. Image 1 • Cyclic molecular designed dispersion (CMDD) method was used to graft Fe 2 O 3 on CeO 2. • CMDD of Fe 2 O 3 enhanced iron dispersion and its interaction with Au and CeO 2. • CMDD PROX catalysts are more active and selective than impregnation ones. • An Au/Fe ratio of about 0.4 on CeO 2 reduces complete oxidation of CO to 318 K. • Highly dispersed nanosized gold particles with diameter of 1–3 nm were achieved. [ABSTRACT FROM AUTHOR]

In this work, PdFe 2 O 3 bimetallic materials containing oxygen vacancies (O v , from 10 to 75%) and two bimetallic nanoparticles based on noble metals (PdAu and PdPt) were obtained and evaluated for the ethanol electro‒oxidation reaction (EOR) in alkaline medium. For this purpose, bimetallic nanoparticles were synthesized keeping similar crystallite sizes (~6 nm), particle sizes (~6 nm), mass compositions (18 ± 4% co‒metal) and metallic loadings (18.3 ± 5.1%). PdAu/C, PdPt/C and the most active PdFe 2 O 3 /C material (75% of O v) displayed an improved onset potential (E onset) during the oxidation of 1.5 M ethanol in 0.3 M KOH in comparison with a monometallic Pd/C material, finding the trend: PdAu/C (−0.56 V vs. NHE) > PdPt/C (−0.55 V) > PdFe 2 O 3 /C (−0.51 V) > Pd/C (−0.50 V). In addition, these bimetallic materials presented an increase in the current density; being PdPt/C and PdFe 2 O 3 /C the most active materials for EOR. A spectroelectrochemical analysis was performed by coupling a μRaman spectroscope with an electrochemical cell. This analysis allowed to conclude that the improvement of the E onset is related to changes in chemisorption energies as was suggested by Raman shifts found for the C 1 ‒M (metal) bond, while the high activity of PdPt/C can be attributed to a higher adsorption of ethanol molecules. Additionally, it was found that the activity of PdFe 2 O 3 /C is associated with an energy decrease to form the C 1 ‒M bond, which could be promoted by the abundance of oxygen vacancies. PdFe 2 O 3 and two bimetallic nanoparticles based on noble metals (PdAu and PdPt) were synthesized and tested for ethanol electro-oxidation. The presence of oxygen vacancies in PdFe 2 O 3 improved the activity displaying similar mass activity than PdPt and higher than PdAu. Spectroelectrochemical tests revealed that the improved activity was related to changes in chemisorption energies due to shifts found for the C 1 ‒M (metal) bond. Image 1 • PdFe 2 O 3 , PdAu and PdPt with similar particle size (6 nm) and loading were obtained. • Improvements on E onset were found to be related to changes in C 1 ‒M (metal) bond. • PdFe 2 O 3 displayed higher activity than PdAu and similar activity than PdPt. • The improved activity of PdFe 2 O 3 was related to the presence of oxygen vacancies. [ABSTRACT FROM AUTHOR]

Solar redox reforming is a process that uses solar radiation to drive the production of syngas from natural gas. This approach caught attention in recent years, because of substantially lower reduction temperatures compared to other redox cycles. However, a detailed and profound comparison to conventional solar reforming has yet to be performed. We investigate a two-step redox cycle with iron oxide and ceria as candidates for redox materials. Process simulations were performed to study both steam and dry methane reforming. Conventional solar reforming of methane without a redox cycle, i.e. on an established catalyst was used as reference. We found the highest efficiency of a redox cycle to be that of steam methane reforming with iron oxide. Here the solar-to-fuel efficiency is 43.5% at an oxidation temperature of 873 K, a reduction temperature of 1190 K, a pressure of 3 MPa and a solar heat flux of 1000 kW/m2. In terms of efficiency, this process appears to be competitive with the reference process. In addition, production of high purity H 2 or CO is a benefit, which redox reforming has over the conventional approach. • Solar redox reforming and solar conventional reforming are simulated. • Iron oxide and ceria-based redox cycles are compared. • Efficiency and product quality are evaluated. • Impact of solar flux and solid-solid heat recovery is analyzed. [ABSTRACT FROM AUTHOR]

ReaxFF molecular dynamics simulation has been employed to investigate the iron oxide-catalyzed supercritical water gasification (SCWG) of naphthalene (NAP), a common component of refractory polycyclic aromatic hydrocarbons. Simulation results showed that synergistic effects between SCW and iron oxide catalyst enormously promoted the degradation of NAP and the production of H 2 and CO. During the gasification process, SCW served not only as H source for H 2 generation but also as O source for CO generation and lattice oxygen recompense, while the major roles of iron oxide catalyst were to provide lattice oxygen with high hydrogen-abstraction ability, catalyze SCW to produce more active species, and weaken the C–C bonds. The effects of different parameters were subsequently revealed: increasing the use of H 2 O molecules raised H 2 and CO yields along with the lattice oxygen supplement but slowed the rate of CO generation, high hydrogen recovery was achieved at high NAP concentration accompanied by a low carbon gasification efficiency. Our simulated results further demonstrated that the deactivation of iron oxide catalyst was caused by carbon deposition, lattice oxygen exhaustion and iron loss. SCW media effectively inhibited the iron loss, while calcination in O 2 environment could successfully regenerate the iron oxide catalyst by cleaning up the carbon deposition and replenishing the lattice oxygen. Image 1 • SCW served not only as H source but also as O source. • Iron oxide provided lattice oxygen, catalyze SCW and C–C breaking. • Carbon deposition, lattice oxygen and iron loss caused catalyst deactivation. • Catalyst regeneration mechanism in O 2 environment was also revealed. [ABSTRACT FROM AUTHOR]

Iron oxide has been widely studied in chemical looping hydrogen generation (CLHG) process as an oxygen carrier, but fast decline of its activity in redox cycles due to sintering and agglomeration is one of the main drawbacks. In this work, the colloidal crystal templated (CCT) method was applied to synthesize Fe 2 O 3 /CeO 2 oxygen carrier and the mole ratio of Fe/Ce was 8:2, aiming to inhibit adjacent grains from agglomerating and improve the contact between the fuel gas and the oxygen carrier. The redox performances were evaluated with CO as fuel in a batch fixed bed reactor for 20 redox cycles, with oxygen carriers prepared by co-precipitation (CP) and sol-gel (SG) methods as references. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and H 2 -temperature programmed reduction (H 2 -TPR) were used for characterization. The results showed that the calcination temperature lower than 750 °C was suitable for the CCT. The redox experiments showed that the H 2 yield and the redox stability for the oxygen carrier prepared by CCT were higher than those by co-precipitation and sol-gel methods. The H 2 yield of CCT oxygen carrier kept stable from the 3rd cycle and was 8.5 mmol/gOC in the 20th cycle. The pore structures resulting from CCT were different from another two oxygen carriers before and after the cycles, but maintained well through SEM images, leading to high activity and stability during redox cycles. The crystallite sizes of Fe 2 O 3 and CeO 2 before and after redox cycles were the smallest for the CCT oxygen carrier from XRD patterns. In addition, H 2 -TPR demonstrated that CCT oxygen carrier exhibited the highest reactivity. • Colloidal crystal templated (CCT) is desirable for Fe 2 O 3 /CeO 2 preparation in CLHG. • The calcination temperature lower than 750 °C was suitable for the CCT. • The superior performance of CCT oxygen carrier can be ascribed to its pore structure. • The H 2 yield of the CCT oxygen carrier was 8.5 mmol/gOC after 20 cycles. [ABSTRACT FROM AUTHOR]

Abstract CeO 2 -supported Fe 2 O 3 is a satisfactory oxygen carrier for chemical looping hydrogen generation (CLHG). However, the sintering problem restrains its further improvement on redox reactivity and stability. In the present work, a core-shell-structured Fe 2 O 3 /CeO 2 (labeled Fe 2 O 3 @CeO 2) oxygen carrier prepared by the sol-gel method was studied in a fixed bed. The effect of the core-shell structure on the sintering resistance and redox performance was investigated with a homogenous composite sample of Fe 2 O 3 /CeO 2 as a reference. The results showed that the Fe 2 O 3 @CeO 2 exhibited much higher redox reactivity and stability than the Fe 2 O 3 /CeO 2 with no CO or CO 2 observed in the generated hydrogen, while the hydrogen yield for Fe 2 O 3 /CeO 2 decreased with redox cycles due to serious sintering. The satisfactory performance of Fe 2 O 3 @CeO 2 can be ascribed to its high sintering resistance, since the core-shell structure suppressed the outward migration of Fe cations from the bulk to the surface of the particles. On the other hand, the migration of Fe cations and their subsequent enrichment on the particle surface led to the serious sintering of Fe 2 O 3 /CeO 2. The crystallite size evolution of Fe 2 O 3 and CeO 2 in redox cycles further demonstrated the higher sintering resistance of Fe 2 O 3 @CeO 2. Further, the particle size distribution (PSD) results indicated the agglomeration of Fe 2 O 3 /CeO 2 after cycles. In addition, the CeO 2 shell could facilitate the transport of oxygen ions between the iron oxide nanoparticle core and the shell surface. Therefore, the coating of nanoscale Fe 2 O 3 with a CeO 2 shell did not reduce the redox reactivity and stability of Fe 2 O 3 @CeO 2 , but rather promoted it, though less oxygen-ionic-conductive CeFeO 3 was generated. Graphical abstract Image 1 Highlights • A core-shell structured Fe 2 O 3 @CeO 2 prepared by sol-gel method was studied for CLHG. • Fe 2 O 3 @CeO 2 exhibited significantly enhanced sintering resistance. • Fe 2 O 3 @CeO 2 showed much higher activity and stability than the composite Fe 2 O 3 /CeO 2. • Fe 2 O 3 @CeO 2 prevented the outward migration of Fe cations from the bulk to surface. • CeO 2 shell facilitated oxygen mobility between the Fe 2 O 3 core and the shell surface. [ABSTRACT FROM AUTHOR]

Abstract The iron-oxide nanoparticles (IONPs) filled multi-walled carbon nanotubes (IONP-MWCNTs hybrid) were directly synthesized via chemical vapour deposition method with acetylene as a carbon source. The bare IONPs were synthesized by hydrothermal method and the prepared bare IONPs were employed as a catalytic-support as well as a filling agent for the synthesis of IONP-MWCNTs hybrid at about 800 °C under atmospheric pressure. The synthesized IONP-MWCNTs hybrid was characterized by various physicochemical techniques including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results demonstrate that the carbon nanotubes were successfully generated on the IONPs with the high yield because of unique carbon-iron metal interactions. An average diameter of synthesized IONPs and MWCNTs are around 9 and 50 nm, respectively. In addition, the HRTEM images and Raman spectrum confirms the obtained IONP-MWCNTs hybrid is well graphitic without major carbonaceous impurities. The electrochemical activity of the synthesized IONP-MWCNTs hybrid was performed in 2 M KOH using a three-electrode cell setup with a saturated Ag/AgCl as a reference electrode and a platinum plate as a counter-electrode by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. This electrode active material (IONP-MWCNTs hybrid) possess excellent supercapacitive behaviour and has excellent cyclic stability, even after 5000 cycles of charge-discharge at 4 A g−1 as current density. Thus, the synthesized IONP-MWCNTs hybrid will be a suitable as well as an economical electrode active material for high-performance supercapacitors. Graphical abstract Image 1 Highlights • IONPs was successfully filled inside of the MWCNTs by a simple CVD method. • Fabricated IONP MWCNTs delivered a high C s about 231 F g−1 at 4 A g−1. • This electrode material has excellent cyclic stability even after 5000 cycles. • Moreover, this method offers an economical way to get high-performance capacitors. [ABSTRACT FROM AUTHOR]

Abstract Coal-direct chemical looping hydrogen generation (CLHG) is an innovative technology developed to produce hydrogen with in situ CO 2 capture. Most oxygen carrier (OC) candidates for other chemical looping processes are not suitable for the technology. In this work, potassium modified Fe 2 O 3 /Al 2 O 3 OCs were prepared by co-precipitation method, and screening tests were conducted to selected appropriate OC and char particle size. Experiments on the technology were carried out in a fixed bed reactor to evaluate the redox and cyclic performance of the composite OCs using Shenmu char as fuel. The OC residues in the process were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and N 2 adsorption analyzer. Moreover, the variations of potassium content in OC residues were also discussed. The results show that the appropriate particle ranges were 425 μm–600 μm for OC and less than 75 μm for char. During the first cycle, the carbon conversion could reach about more than 95% within 45 min and the total H 2 concentration under an N 2 -free basis in steam oxidation period was about 99.3%. In the multi-cycle tests, the carbon conversion and hydrogen yield remained almost unchanged during the first three cycles and decreased thereafter. The selectivity toward CO 2 was less than 80% during the first three cycles, increased in the next five cycles and reached about 99.3% in the 8th cycle. The OC exhibited a good anti-sintering ability and stable pore structure in the eight cycles. The decrease of potassium content in OCs was the reason for the decline of carbon conversion and hydrogen yield, and the supplement of K 2 CO 3 could recover the reactivity of OCs. Highlights • A new type oxygen carrier for coal-direct chemical looping hydrogen generation. • The oxygen carrier had a good anti-sintering and stable pore structure. • The total H 2 concentration under an N 2 -free basis was about 99.3%. • Potassium content in oxygen carrier was related to the reactivity of oxygen carrier. [ABSTRACT FROM AUTHOR]

Electrode materials with high specific capacity and cycle stability are the key factors that determine the overall performance of lithium ion batteries (LIBs) for new smart electronic device, and such materials with high performance are still challenging. Here, we report a composite material Carbon nanotube @ Iron oxide @ Carbon (γ-CNTs@γ-Fe 2 O 3 @C) with coaxial cable structure in hydrothermal method with the assistance of glucose. The as-prepared composite materials show superior electrochemical properties with good rate capability and excellent cycling performance, which show the great potential of CNTs@γ-Fe 2 O 3 @C for practical production and application in energy devices. [ABSTRACT FROM AUTHOR]

Several novel materials were synthesized by precipitating iron oxide (using the previously optimized 10% Fe loading by weight) onto mixtures of nanoparticle zirconia and ceria to investigate the effects of adding CeO 2 to FeO x /ZrO 2 materials in the thermochemical water splitting reaction. At water splitting temperatures of 1000 °C (after thermal reduction at 1450 °C), the stability of the CeO 2 -containing materials was lower than for the FeO x /ZrO 2 material, and there was no advantage to adding CeO 2 to the FeO x /ZrO 2 material. However, when operating at a water splitting (WS) temperature of 1200 °C, the stability increased and the hydrogen production was significantly higher over most materials compared with a water splitting temperature of 1000 °C. At a WS temperature of 1200 °C the FeO x /Zr 75 Ce 25 O 2 (75% Zr 75 O 2 and 25% CeO 2 by weight) and FeO x /Zr 50 Ce 50 O 2 materials performed slightly better than the FeO x /ZrO 2 material, and X-ray photoelectron spectroscopy data revealed that the surface concertation of iron is less important compared with water splitting at 1000 °C. The temperature programmed reduction data indicated that the FeO x -CeO 2 interactions were weaker compared with FeO x -ZrO 2 interactions, since the FeO x reduction occurred at lower temperatures for the CeO 2 -containing materials. The weaker interactions can explain why the stability was lower for the materials containing CeO 2 (sintering of FeO x was likely more pronounced) The X-ray diffraction data revealed that ZrO 2 -CeO 2 solid solutions formed after activation at 1450 °C and lattice volume calculations indicated that iron did incorporate into the ZrO 2 -CeO 2 matrices. More incorporation was observed after water-splitting at 1200 °C compared with a lower temperature (1000 °C), and likely explains why the materials were more stable during water-splitting at 1200 °C. [ABSTRACT FROM AUTHOR]

Iron oxide nanostructures are an attractive option for being used as photocatalyst in photoelectrochemical applications such as water splitting for hydrogen production. Nanostructures can be obtained by different techniques, and electrochemical anodization is one of the simplest methods which allows high control of the obtained morphology by controlling its different operational parameters. In the present study, the influence of the electrolyte temperature during electrochemical anodization under stagnant and hydrodynamic conditions was evaluated. Temperature considerably affected the morphology of the obtained nanostructures and their photoelectrochemical behavior. Several techniques were used in order to characterize the obtained nanostructures, such as Field Emission Scanning Electron Microscopy (before and after the annealing treatment in order to evaluate the changes in morphology), Raman spectroscopy, photocurrent vs. potential measurements and Mott-Schottky analysis. Results revealed that the nanostructures synthesized at an electrolyte temperature of 25 °C and 1000 rpm are the most suitable for being used as photocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Fe 2 O 3 is currently the most proper active metal oxide for chemical looping hydrogen generation (CLHG). However, supports are necessary to improve the reactivity and redox stability. CeO 2 can enhance the oxygen mobility, leading to high redox reactivity and carbon deposition resistance, which can be an excellent alternative support for oxygen carriers. In this paper, Fe 2 O 3 /CeO 2 oxygen carriers prepared by the co-precipitation method with different Fe 2 O 3 loadings were investigated on a batch fluidized bed regarding the hydrogen yield and purity, redox reactivity and stability in CLHG with CO as fuel. The results showed that Fe6Ce4 is the best given comprehensive performance with no CO or CO 2 observed in the obtained hydrogen (detection limit 0.01% in volume). The oxygen mobility property for the reducible support CeO 2 and the physical contact between un-integrated Fe 2 O 3 and CeO 2 could improve the reduction of Fe 2 O 3 . In addition, the formation of the hematite-like solid solution and perovskite-type CeFeO 3 could bring about abundant oxygen vacancies and promote the oxygen mobility, which contributes to the elimination of carbon deposition, counteracts the negative effect of serious sintering and guarantees the reactivity and redox stability of the Fe 2 O 3 /CeO 2 oxygen carriers. The Fe 2 O 3 /CeO 2 oxygen carriers were characterized by carbon monoxide temperature-programmed reduction measurement and X-ray diffraction patterns, and Fe6Ce4 was also selected to be characterized by scanning electron microscopy images and energy dispersive X-ray spectrometer analysis. [ABSTRACT FROM AUTHOR]

Two-component Fe Mg O oxide system was prepared via sol-gel technique. An aqueous solution of iron nitrate was used to hydrolyze the magnesium methoxide instead of distilled water. The iron loading in a final sample was 15 wt% with respect to Fe 2 O 3 . The method was shown to provide a uniform distribution of iron oxide within MgO matrix. The sample was characterized by means of a low-temperature nitrogen adsorption and scanning electron microscopy. Reduction behavior of the sample was studied in a temperature-programmed regime using hydrogen as a reducing agent. In order to follow the possible phase transformations, the sample was examined by an in situ X-ray diffraction analysis in both reductive and oxidative atmospheres within the temperature range of 25–700 °C. It was found that after the first cycle of reduction/re-oxidation, the sample stabilizes in a novel state, and hydrogen uptake profiles of further cycles of reductive/oxidative treatment become completely reproducible. According to X-ray diffraction data, the sample consists of small particles (9 nm) of Fe 3 O 4 phase well-dispersed within the structure of nanocrystalline MgO. [ABSTRACT FROM AUTHOR]

Chemical looping hydrogen generation (CLHG) can produce high purity hydrogen from fuel gases with inherent separation of CO 2 . However, the performance of oxygen carrier in CLHG varies with the support materials. In this paper, the reactivity, carbon deposition, redox stability, hydrogen yield and purity, and sintering behavior of the Fe-based oxygen carriers were analyzed to investigate the effects of supports, i.e. Al 2 O 3 , SiO 2 , MgAl 2 O 4 , ZrO 2 and YSZ (yttrium-stabilized zirconia). The results showed that the properties of the oxygen carriers, e.g. carbon deposition, reactivity and stability, mainly depended on the support and its interaction with iron oxides. The reactivity and hydrogen yield for the oxygen carriers investigated followed the order: Fe 2 O 3 /MgAl 2 O 4 > Fe 2 O 3 /ZrO 2 > Fe 2 O 3 /YSZ > Fe 2 O 3 /Al 2 O 3 > Fe 2 O 3 /SiO 2 , and the order of hydrogen purity was identical with that of hydrogen yield as a result of carbon deposition. Furthermore, the hydrogen purity of the Fe-based oxygen carriers supported by MgAl 2 O 4 , ZrO 2 , or YSZ could reach above 99.5% and Fe 2 O 3 /YSZ showed the lowest carbon deposition. The oxygen carriers, Fe 2 O 3 /MgAl 2 O 4 and Fe 2 O 3 /SiO 2 , were selected to be characterized by SEM images and XRD patterns before and after the redox cycles. [ABSTRACT FROM AUTHOR]

Chemical reduction behaviour of 3% chromium doped (Cr–Fe 2 O 3 ) and undoped iron oxides (Fe 2 O 3 ) were investigated by using temperature programmed reduction (TPR). The reduced phases were characterized by X-ray diffraction spectroscopy (XRD). The reduction processes were achieved with 10% H 2 in nitrogen (%, v/v), 10% and 20% of carbon monoxide (CO) in nitrogen (%, v/v). In hydrogen atmosphere, the TPR results indicate that the reduction of Cr–Fe 2 O 3 and Fe 2 O 3 proceed in three steps (Fe 2 O 3 → Fe 3 O 4 → FeO → Fe) with Fe 3 O 4 and FeO as intermediate states. A complete reduction to metallic iron for both samples occurred at 900 °C. As for CO reductant, the profiles show the reduction of Fe 2 O 3 also proceeded in three steps with a complete reduction occurs at 900 °C in 10% CO with no sign of carbide formation. Nevertheless, a 20% CO was able to reduce the completely at lower temperature at 700 °C and there is a formation of iron carbide at 500 °C but the carbide disappeared as the reduction temperature increase. Meanwhile in 10% CO atmosphere, Cr–Fe 2 O 3 shows a better reducibility compared to Fe 2 O 3 with a complete reduction at 700 °C, which is 200 °C lower than Fe 2 O 3 . A Cr dopant in the Fe 2 O 3 can lead to formation of various forms of iron carbides such as F 2 C, Fe 5 C 2 , Fe 23 C 6 and Fe 3 C as the CO concentration was increased to 20%. The transformation profile of iron phases during carburization follows the following forms, Fe 2 O 3 → Fe 3 O 4 → iron carbides (Fe x C). The XRD pattern shows the diffraction peaks of Cr–Fe 2 O 3 are more intense with improved crystallinity for the characteristic peaks of Fe 2 O 3 compare to undoped Fe 2 O 3 . No visible sign of chromium particles peaks in the XRD spectrum that indicates the Cr particles loaded onto the iron oxide are well dispersed. The uniform dispersion with no sign of sintering effects of the Cr dopant on the Fe 2 O 3 was confirmed by FESEM. The study shows that Cr dopant gives a better reducibility of iron oxide but promotes the formation of carbides in an excess CO concentration. [ABSTRACT FROM AUTHOR]

A novel sorbent (SCX) composed of mixed iron oxides and hydroxides was studied to assess its suitability for H 2 S removal from biogas finalized to high temperature fuel cell systems. From an industrial point of view, the potential usage of this product would have a beneficial impact on operational costs, since it is less expensive than activated carbons. Moreover, it is a non-hazardous landfilled product with a reduced environmental impact and it can be easily regenerated. Sorbent SCX was tested in different operative conditions, evaluating the influence on sorption capacity of gas hourly space velocity (GHSV), gas composition (inlet H 2 S concentration, gas matrix, humidity), reactor temperature and filter geometry. As main outcomes, the experimentation highlighted: i) a hyperbolic increase in adsorption capacity as GHSV decreased, ii) a parabolic performance enhancement with increasing temperature and iii) a negative effect of humidity. Moreover, a comparison with commercial activated carbons typically used for the same purpose (Cu–Cr or KOH–KI treated) was performed, identifying the optimal operative parameters to obtain higher H 2 S sorption capacity for SCX sorbent. Specifically, SCX showed its potential in terms of H 2 S removal for GHSV lower than 330 h −1 , values of particular interest for many practical applications. In this case, an improved removal capability is obtained with respect to the ones exhibited by the considered carbons. Moreover, quantitative evaluations provided for unitary installed power (1 kW e fuel cell-based systems) highlighted the possibility to have more compact (volume reduction of about 50%) and cheaper (cost reduction up to six times) filters. [ABSTRACT FROM AUTHOR]

In this paper, OpenFOAM was employed to numerically investigate syngas (H 2 and CO) production by the simultaneous splitting of H 2 O and CO 2 via thermochemical redox cycle based on iron oxide (Fe 3 O 4 ). The effects of operating conditions such as pressure, temperature and species reactant ratios on syngas yield were investigated. The results indicated that amount of syngas yield was highly dependent on the reduction temperature. It was found that the process at high pressure could lower the reaction temperature and increased species production rate. The overall syngas yield increased from 1.34% up to 98.65% when the pressure increased from 5 to 20 atm. The analysis of the results showed that the syngas yield and the syngas composition were strongly influenced by the ratio of H 2 O/CO 2 ( γ g ). The highest syngas purity (ratio of H 2 /CO ( γ s )) = 3.36 was reached at γ g = 2. The optimum operating conditions for hydrogen-rich syngas production were obtained when γ g = 2 under 1600 K at 20 atm. [ABSTRACT FROM AUTHOR]

Au/α-Fe 2 O 3 catalysts have been prepared by deposition-precipitation. The support α-Fe 2 O 3 has been previously synthesized by precipitation technique. The effect of thermal treatment on structural, morphological and redox properties of Au/α-Fe 2 O 3 samples have been thoroughly studied for the samples calcined at 150, 200 and 300 °C, together with a non-calcined sample. Their catalytic activity toward CO oxidation in the presence of hydrogen (CO-PROX) has been tested. The results showed that the gold particle size and surface adsorbed oxygen changed with the calcination temperature, being the minimum for the sample calcined at 200 °C. There was not detected cationic gold by X-ray photoelectron spectroscopy (XPS) in none of the samples. The presence of gold promoted notably the reduction of the iron oxide. The highest activity for CO-PROX was achieved by the non-calcined catalysts (simply dried at 110 °C), while the sample calcined at 200 °C was the least active. The catalysts activity was assigned to the gold particle size and surface adsorbed oxygen. [ABSTRACT FROM AUTHOR]

Alternating reductions with hydrogen and oxidations with steam have been carried out on solids with improved redox capacity showing the benefits of different synthesis methods in the steam-iron process (SIP). Solids chosen were a commercial hematite, a lab-made iron oxide doped with ceria and alumina and hematite synthesized by freeze-casting technique. The first one shows a high loss of reactivity from the first cycle on while the others keep their reduction capacity along three consecutive cycles and beyond. Isothermal experiments were also performed with the best two solids. Although all of them had hematite as the starting material, they have shown significant differences in behaviour respecting the original commercial hematite depending on the chemical (inclusion of additives that account for only 2 wt% of the solid mass) or physical (macroporosity) properties. Also the effect of long lasting runs with up to 10 cycles (reduction + oxidation) have been performed at different reduction temperatures showing a slightly higher stability of the pure iron oxide pellets produced by freeze-casting versus an iron oxide with alumina and ceria selected as structural stabilizers and accelerators of the reduction/oxidation reaction. [ABSTRACT FROM AUTHOR]

Two-step solar thermochemical water splitting offers a viable solution for employing renewable energy pathways for production of high-purity hydrogen, which can be used in fuel cells or for the production of liquid fuels. One promising thermochemical cycle uses iron oxide as the reactive material to split water in a relatively simple two-step process. However, this cycle requires high temperatures, on the order of 1500 °C. Therefore, to increase stability and thermal shock resistance, iron oxide was deposited onto high-temperature-stable ceramic oxides, such as zirconia (ZrO 2 ) and yttria-stabilized zirconia (YSZ). Nanoparticle zirconia samples (n-ZrO 2 and n-YSZ) were used in this study to increase the interactions between the iron oxide and the zirconia, and the resulting materials were compared with an iron oxide supported on a commercially available porous zirconia support (p-ZrO 2 ). After heat treatment, these FeO x /n-ZrO 2 and FeO x /n-YSZ materials were surprisingly stable and yielded consistent hydrogen production over several cycles. The hydrogen yield per cycle for the FeO x /n-YSZ material was consistently higher for all iron loadings compared with the FeO x /n-ZrO 2 materials, and they both yielded significantly more hydrogen compared to the FeO x supported on the commercial ZrO 2 support. Compared with the FeO x /n-YSZ, the iron loading had a larger effect on the hydrogen production over n-ZrO 2 -supported materials. X-ray diffraction (XRD) data indicated that iron was incorporated into the unit cell lattice of the n-YSZ supported material, which alleviated some of the detrimental iron oxide sintering inherent at the high-temperatures of the thermochemical water splitting reaction, and resulted in a more consistent and higher hydrogen production compared with the FeO x /n-ZrO 2 material. [ABSTRACT FROM AUTHOR]

A series of Au supported on Fe 2 O 3 –TiO 2 catalysts were prepared, characterized and investigated the catalytic activity in the preferential CO oxidation (PROX) under a H 2 -rich stream. The effects of the different metal support ratio, the calcination temperature, the gold loading, and the pre-treatment condition were studied on both the characteristics and catalytic activity of the catalysts. The results obviously showed that 1% Au/Fe 2 O 3 –TiO 2 (1:4) exhibited higher CO conversion than the 1% Au/TiO 2 and 1% Au/Fe 2 O 3 catalysts, especially temperature lower than 100 °C, which due to the formation of reducible gold species at lower temperature. TPR results suggested the improvement of Au–Au and metal–metal (in support) interaction. Additionally, XPS spectra suggested the Au 0 could be the predominant active site. The effect of O 2 pretreatment showed a negative effect in both activity and selectivity which suggested the formation of adsorbed oxygen species on the surface of the catalyst. Moreover, the deactivation was affected by injection H 2 O, CO 2 or the combination of CO 2 –H 2 O into the typical feed. [ABSTRACT FROM AUTHOR]