Rotating gliding arc assisted methane decomposition in nitrogen for hydrogen production

Hydrogen production from methane decomposition via an atmospheric pressure rotating gliding arc (RGA) discharge reactor co-driven by a magnetic field and tangential flow is investigated. The motion and V–I characteristics of the RGA are studied with a high-speed camera and oscilloscope. Optical emission spectroscopy (OES) is used to characterize RGA plasmas in N₂ and CH₄ + N_2, and the RGA plasma is shown to occur as a warm plasma. For the CH₄ + N₂ plasma, CN, C₂, and CH spectral lines are observed. The vibrational and rotational temperatures are 0.56–0.86 eV and 1325–1986 K, respectively. The effects of load resistance, the CH₄/N₂ ratio, and the feed flow rate on the performance of methane decomposition are investigated. The maximum CH₄ conversion rate and H₂ selectivity are 91.8% and 80.7% when the CH₄/N₂ ratio is 0.1 and 0.05, respectively, at a flow rate of 6 L/min. The possible reaction mechanisms of the methane decomposition process are discussed. This study is expected to establish a basis for the further industrial applications of H₂ production.     

Performance improvement of the proton-conducting solid oxide electrolysis cell coupled with dry methane reforming

The proton-conducting solid oxide electrolysis cell (H-SOEC) is a clean technology for syngas production from H₂O and CO₂ through electrochemical and chemical reactions. However, it provides a low CO₂ conversion and produces a syngas product with a high H₂O content. To improve the H-SOEC for syngas production, H-SOEC coupled with a dry methane reforming process (H-SOEC/DMR) was proposed in this work. The process flowsheet of the H-SOEC/DMR was developed and further used to evaluate the performance of the H-SOEC/DMR process. From the performance analysis of the H-SOEC/DMR process, it was found that the CO₂ and CH₄ conversions were higher than 90% and 80%, respectively, when the process was operated in the temperature range of 1073–1273 K. In addition, the result showed that a syngas product with a low H₂O content could be obtained. Energy efficiency was then considered and the results indicated that the highest energy efficiency of 72.80% could be achieved when the H-SOEC/DMR process was operated at a temperature of 1123 K, pressure of 1 atm, and current density of 2500 A m^?2. Based on a pinch analysis, a heat exchanger network was applied to the H-SOEC/DMR process that improved the energy efficiency to 81.46%. Finally, an exergy analysis was performed and showed that the H-SOEC/DMR unit had the lowest exergy efficiency as a high-temperature exhaust gas was released.     

Analysis of the carbon anode in carbon conversion cells

We examine further the electrochemical oxidation of carbon in molten carbonate, based on analysis of published research. Ascending and descending branches of voltage hysteresis found in current sweeps of atomically-ordered graphite and of disordered carbon (coal char) are separated by about 0.20–0.25 V and by 0.10–0.15 V for ordered and disordered forms, respectively, over a wide band of current density, 0.03–0.10 A/cm². The higher voltage of the descending branch is in rough agreement with prediction of the Y. Li model for the carbon/carbonate electrode in the same current range, for ordered graphite (L_a = 70–100 nm) and for disordered structures (L_a = 3–5 nm), respectively. We suggest that the amplitude of the hysteresis represents the difference between the overvoltage requirements for 2- and 4 electron net transfer processes, respectively. The 2 e− reaction (C + CO₃²⁻ = CO + CO₂ + 2e⁻) dominates the low current segment (LCS) of our previous analysis, and the more hindered 4e− transfer reaction (C + 2CO₃²⁻ = 3CO₂ + 4e⁻) dominates the high current segment (HCS). The voltage increase separating LCS from HCS is effected by accumulation of CO₂ within small, melt-filled pores to form highly supersaturated solutions of CO₂, which enhance anode voltage by a concentration overpotential of 0.10–0.25 V. Overpotential increases with reaction extent until (1) overall polarization inhibits the interior reaction and shifts CO₂ production to the more accessible exterior surface, or, (2) at a critical concentration (dependent on surface tension and pore diameter) bubbles nucleate and block current flow in the pores. Further support for this picture comes from the often-reported deviation of the gas composition from the CO/CO₂ ratio of the Boudouard equilibrium at atmospheric pressure, as open circuit conditions are approached in an electrochemical cell. Our interpretation accounts for the mole fraction of CO₂ at open circuit being greater than predicted from the Boudouard equilibrium.     

An experimental and theoretical approach for the biogas steam reforming reaction

An experimental and theoretical study for the biogas steam reforming reaction over 5%Ru/Al₂O₃ catalyst have been performed. An apparatus was constructed for the conduction of the experiments, the core of which was a tube reactor, filled with the catalyst in form of pellets. The inlet gas mixture consisted of CH₄ and CO₂ in various composition ratios as a model biogas and steam. A theoretical model of the process was developed. The experimental reactor was modelled as an isothermal pseudo homogeneous fixed bed reactor. Internal and external transport phenomena were neglected and appropriate effectiveness factors were employed instead. A physical properties model was used for the calculation of the physicochemical properties of the real mixture. Five reactant species, CH₄, CO₂, H₂O, CO and H₂, were included in the model, whereas the feed consisted of the first three. Steam reforming and water gas shift were the main reactions. Experimental results and theoretical predictions match closely, stability of the catalyst was assured and an optimal operational window was identified, at GHSV = 10,000–20,000 h⁻¹, T = 700–800 °C, CH₄/CO₂ = 1.0–1.5 and H₂O/CH₄ = 3.0–5.0.     

Rapid release of 1.5 equivalents of hydrogen from CO2-treated ammonia borane

This work addresses the accelerated dehydrogenation of ammonia borane (AB, NH₃BH₃) in two separate processes of CO₂ pre-treatment of AB and dehydrogenation of the treated AB. Decoupling these two processes can still keep the dehydrogenation activity of CO₂-treated AB and eliminate the purification step of H₂ from gas phase. When AB is exposed to 1.38 MPa of carbon dioxide (CO₂) at 70 °C, it shows the most favorable and controllable operating condition for the CO₂ pre-treatment. The pre-treatment enhances not only the rate but also the amount of hydrogen release at the dehydrogenation step; 1.5 mol H₂ per mol of AB rapidly desorbs at 85 °C in 1 h, corresponding to 10.1 wt.% of hydrogen with regard to pristine AB. Also, our observations show that the fast dehydrogenation resulted from the CO₂ pre-treatment is preserved for more than four days of storage. The degree of dehydrogenation is further confirmed by ATR-FTIR spectroscopic and elemental analyses of the solid product. The spectra display the N–H stretching mode involving π-bonded nitrogen (sp² N) at ca. 3434 cm⁻¹,while the atom ratio of H:B is found to be 2.84:1. Based on the hydrogen release measurements, spectroscopic observations and elemental analyses, we deduce that the predominant solid product of dehydrogenation of CO₂-treated AB at 85 °C is a polymer with an empirical formula of (NBH₃)_n. It corresponds to the solid product after 1.5 equivalent hydrogen release of AB.     

Y2O3-promoted NiO/SBA-15 catalysts highly active for CO2/CH4 reforming

A series of Y₂O₃-promoted NiO/SBA-15 (9 wt% Ni) catalysts (Ni:Y weight ratio = 9:0, 3:1, 3:2, 1:1) were prepared using a sol–gel method. The fresh as well as the catalysts used in CO₂ reforming of methane were characterized using N₂-physisorption, XRD, FT-IR, XPS, UV, HRTEM, H₂-TPR, O₂-TPD and TG techniques. The results indicate that upon Y₂O₃ promotion, the Ni nanoparticles are highly dispersed on the mesoporous walls of SBA-15 via strong interaction between metal ions and the HO–Si-groups of SBA-15. The catalytic performance of the catalysts were evaluated at 700 °C during CH₄/CO₂ reforming at a gas hourly space velocity of 24 L g_cat⁻¹ h⁻¹(at 25 ^°C and 1 atm) and CH₄/CO₂molar ratio of 1. The presence of Y₂O₃ in NiO/SBA-15 results in enhancement of initial catalytic activity. It was observed that the 9 wt% Y–NiO/SBA-15 catalyst performs the best, exhibiting excellent catalytic activity, superior stability and low carbon deposition in a time on stream of 50 h.     

Syngas production from greenhouse gases using Ni–W bimetallic catalyst via dry methane reforming: Effect of W addition

DMR is a promising technique to utilize the rising greenhouse gases and produce an alternative energy source. The main hurdle in the commercialization of DMR is the catalyst deactivation. Presently, the effect of Tungsten (W) addition on Ni-based catalysts supported on mixed oxide (Al₂O₃–MgO) support is tested for DMR. The Ni–W bimetallic catalysts are synthesized via co-precipitation followed by the impregnation technique. An equimolar stream of feed (CH₄:CO₂) is used for DMR at 800 °C. The Ni–W catalyst with 4 wt% of W showed steady performance with elevated conversions of CH₄ and CO₂, even after 24 h of DMR. The freshly and spent catalysts are characterized by BET, XRD, FESEM, EDX, elemental mapping, TPR-H₂, TPD-CO₂, and XPS to confirm the elemental composition and the type of carbon formed on the catalysts. The activity of Ni catalyst declined due to formation of amorphous carbon-nanosheets, whereas Ni–W catalyst remained active due to formation of MWCNT.     

Good prospect of ionic liquid based-poly(vinyl alcohol) polymer electrolytes for supercapacitors with excellent electrical,electrochemical and thermal properties

Poly(vinyl alcohol) (PVA)/ammonium acetate (CH₃COONH₄)/1–butyl–3–methylimidazolium chloride (BmImCl) based polymer electrolytes were prepared by solution casting method. The ionic conductivity increased with temperature as shown in temperature dependent-ionic conductivity study. The maximum ionic conductivity of (7.31 ± 0.01) mS cm⁻¹ was achieved at 120 °C upon adulteration of 50 wt% of BmImCl. The samples obeyed Vogel–Tamman–Fulcher (VTF) relationship. The glass transition temperature (T_g) of the polymer matrix was reduced by doping it with salt and ionic liquid as shown in differential scanning calorimetry (DSC). Supercapacitor was thus assembled. Wider potential stability range has been observed with addition of ionic liquid. Inclusion of ionic liquid also improved the electrochemical behavior of EDLC. The capacitance of supercapacitor were determined by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tester. The cell also illustrated energy density of 2.39 Wh kg⁻¹ and power density of 19.79 W kg⁻¹ with Coulombic efficiency above 90%.     

Effect of Ce on 5 wt% Ni/ZSM-5 catalysts in the CO2 reforming of CH4 reaction

The aim of this study is to investigate the promotional effect of Ce on Ni/ZSM-5 catalysts in the CO₂ reforming of CH₄ reaction. The evaluation of the catalytic performances of the composite catalysts was conducted in a fixed-bed reactor at atmospheric pressure. The influencing factors, including temperature, Ni and Ce loadings, molar feed ratio of CO₂/CH₄, and time-on-stream (TOS), were investigated. The characteristics of the catalysts were checked with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The reduction and the basic properties of the composite catalysts were elucidated by temperature-programmed reduction by H₂ (H₂-TPR) and temperature-programmed desorption of CO₂ (CO₂-TPD), respectively. The reactivity of deposited carbon was studied by sequential temperature-programmed surface reaction of CH₄ (CH₄-TPSR) and temperature-programmed oxidation using CO₂ and O₂ (CO₂-TPO and O₂-TPO). Results indicate that higher CH₄ conversion, H₂ selectivity, and desired H₂/CO ratio for 5 wt% Ni & 5 wt% Ce/ZSM-5 could be achieved with CO₂/CH₄ feed ratio close to unity over the temperature range of 500–900 °C. Moreover, the addition of Ce could not only promote CH₄ decomposition for H₂ production but also the gasification of deposited carbon with CO₂. The dispersion of Ni particles could be improved with Ce presence as well. A partial reduction of CeO₂ to CeAlO₃ was observed from XPS spectra over 5 wt% Ni & 5 wt% Ce/ZSM-5 after H₂ reduction and 24 h CO₂–CH₄ reforming reaction. Benefiting from the introduction of 5 wt% Ce, the calculated apparent activation energies of CH₄ and CO₂ over the temperature range of 700–900 °C could be reduced by 30% and 40%, respectively.     

Hydrogen generation from polyethylene by milling and heating with Ca(OH)2 and Ni(OH)2

A process to produce hydrogen from polyethylene [–CH₂–]_n (PE) is developed by milling with Ca(OH)₂ and Ni(OH)₂ followed by heating the milled product. Characterizations by a set of analytical methods of X-ray diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetry–mass spectroscopy (TG/MS) and gas chromatography (GC) were performed on the milled and heated samples to monitor the process. It has been observed that addition of nickel hydroxide as well as increases in milling time and rotational speed of the mill is beneficial to the gas generation, mainly composed of H₂ and CH₄, CO, CO₂. Gaseous compositions from the milled samples vary depending on the added molar ratio of calcium hydroxide. H₂ emission occurs between 400 and 500 °C, and H₂ concentration of 95% is obtained from the mixture of PE/Ca(OH)₂/Ni(OH)₂ (C:Ca:Ni = 6:14:1) sample, and the concentrations of CO and CO₂ remain below 0.5%. The process offers a novel approach to treat waste plastic by transforming it into hydrogen.     

Thermal stability study of La0.9Sr0.1Ga0.8Mg0.2O2.85–(Li/Na)2CO3 composite electrolytes for low-temperature solid oxide fuel cells

Novel composite materials based on La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 (LSGM) and a binary eutectic carbonates (52 mol% Li₂CO₃:48 mol% Na₂CO₃) are potential electrolytes for low-temperature solid oxide fuel cells (LTSOFCs) operating at 400–600 °C. However, thermal stability of the LSGM–(Li/Na)₂CO₃ composites remains in doubt due to the molten state of the carbonates at elevated temperature. In this paper, XRD, SEM, TGA and EIS were employed for thermal ageing and cycling studies of the LSGM–(Li/Na)₂CO₃ composites. XRD and SEM results showed that ageing induced a slight effect on the structure and morphology of the composites. TGA and EIS results indicated that the composites had a good stability during cycling. The LSGM–20 wt% (Li/Na)₂CO₃ sample showed a relatively stable conductivity (7–9 × 10⁻² S cm⁻¹) during a 650 h measurement under air at 600 °C. Single cell based on the composite electrolytes was reported for the first time, a maximum power density of 617 W cm⁻² and the open circuit voltage (OCV) of 1.01 V were achieved at 600 °C for the composite containing 20 wt% carbonates. The notable thermal stability together with fairly high performance emphasize the promise of LSGM–(Li/Na)₂CO₃ composite electrolytes for long-term LTSOFCs.     

A comparative study of electrochemical methods on Pt–Ru DMFC anode catalysts: The effect of Ru addition

In the present study comparative electrochemical study of methanol electro-oxidation reaction, the effect of ruthenium addition and experimental parameters on methanol electro-oxidation reaction at high performance carbon supported Pt and Pt–Ru catalysts have been studied by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in H₂SO₄ (0.05–2.00 M) + CH₃OH (0.01–4.00 M) at 20–70 °C. Tafel plots for the methanol oxidation reaction on Pt and Pt–Ru catalysts show reasonably well-defined linear region with the slopes of 128–174 mV dec⁻¹(α = 0.34–0.46). The activation energies from Arrhenius plots have been found as 39.06–50.65 kJ mol⁻¹. As a result, methanol oxidation is enhanced by the addition of ruthenium. Furthermore, Pt–Ru (25:1) catalyst shows best electro–catalytic activity, higher resistance to CO, and better long term stability compared to Pt–Ru (3:1), Pt–Ru (1:1), and Pt. Finally, the EIS measurements on Pt–Ru (25:1) catalyst reveals that methanol electro-oxidation reaction consists of two process: methanol dehydrogenation step at low potentials (<700 mV) and the oxidation removal of CO_ads by OH_ads at higher potentials (>700 mV).     

Thermal desorption processes of H2 and CH4 from Li2ZrO3 and Li4SiO4 materials absorbed H2O and CO2 in air at room temperature

The thermal desorption processes of hydrogen (H₂) and methane (CH₄) from lithium-based materials, Li₂ZrO₃ and Li₄SiO₄, exposed to air at room temperature of 293 K with a relative humidity of 80%, were investigated using gas chromatography (GC). The GC analysis revealed that the absolute values of the released H₂ and CH₄ gases at 523 K were approximately 7.42 × 10^?6 and 1.54 × 10^?6 ml/g for Li₂ZrO₃, and 3.24 × 10^?6 and 0 ml/g for Li₄SiO₄. The amounts of H₂ and CH₄ released increased with increase in annealing temperatures and considerably depended on absorption properties of water (H₂O) and carbon dioxide (CO₂) present in air at room temperature. The production of CH₄ at low temperature is due to the intermediate species including CH_x precursors produced by the reaction between H split from H₂O and Li₂CO₃ resulting in the CO₂ absorption of Li₂ZrO₃ and Li₄SiO₄ materials.     

High-performance Ni–SiO2 for pressurized carbon dioxide reforming of methane

The SiO₂ and Ni–SiO₂ were synthesized via the complex-decomposition method by using different organic acids as the complexing agent and fuel. The Ni-supported SiO₂ from different sources was prepared by the incipient impregnation method. The Ni–SiO₂ and Ni/SiO₂ were comparatively evaluated for carbon dioxide reforming of methane (CDR) under severe conditions of CH₄/CO₂ = 1.0, T = 750 °C, GHSV = 53200 mL g⁻¹ h⁻¹, and P = 0.1–1.0 MPa. The materials were fully characterized by XRD, XPS, TEM, TG-DSC, H₂-TPR, and N₂ adsorption-desorption at −196 °C. It was found that the complexing agent and preparation method of the catalyst significantly affected its surface area, the size and dispersion of Ni, the reduction behavior, and the coking and sintering properties, which determine the activity and stability of the catalyst for CDR. As a result, a highly active and stable Ni–SiO₂ for pressurized CDR was obtained by optimizing the complexing agent.     

Co and Ni supported on CeO2 as selective bimetallic catalyst for dry reforming of methane

Co/CeO₂ (Co 7.5 wt.%), Ni/CeO₂ (Ni 7.5 wt.%) and Co–Ni/CeO₂ (Co 3.75 wt.%, Ni 3.75 wt.%) catalysts were prepared by surfactant assisted co-precipitation method. Samples were characterized by X-Ray diffraction, BET surface areas measurements, temperature programmed reduction and tested for the dry reforming of methane CH₄ + CO₂ → 2CO + 2H₂ in the temperature range 600–800 °C with a CH₄:CO₂:Ar 20:20:60 vol.% feed mixture and a total flow rate of 50 cm³ min⁻¹ (GHSW = 30,000 mL g⁻¹ h⁻¹). The bimetallic Co–Ni/CeO₂ catalyst showed higher CH₄ conversion in comparison with monometallic systems in the whole temperature range, being 50% at 600 °C and 97% at 800 °C. H₂/CO selectivity decreased in the following order: Co–Ni/CeO₂ > Ni/CeO₂ > Co/CeO₂. Carbon deposition on spent catalysts was analyzed by thermal analysis (TG-DTA). After 20 h under stream at 750 °C, cobalt-containing catalysts, Co/CeO₂ and Co–Ni/CeO₂, showed a stable operation in presence of a deposited amorphous carbon of 6 wt.%, whereas Ni/CeO₂ showed an 8% decrease of catalytic activity due to a massive presence of amorphous and graphitic carbon (25 wt.%).     

Preparation and characterization of nanocrystalline Ce0.8Sm0.2O1.9 for low temperature solid oxide fuel cells based on composite electrolyte

Nanocrystalline Ce_0.8Sm_0.2O_1.9 (SDC) has been synthesized by a combined EDTA–citrate complexing sol–gel process for low temperature solid oxide fuel cells (SOFCs) based on composite electrolyte. A range of techniques including X-ray diffraction (XRD), and electron microscopy (SEM and TEM) have been employed to characterize the SDC and the composite electrolyte. The influence of pH values and citric acid-to-metal ions ratios (C/M) on lattice constant, crystallite size and conductivity has been investigated. Composite electrolyte consisting of SDC derived from different synthesis conditions and binary carbonates (Li₂CO₃–Na₂CO₃) has been prepared and conduction mechanism is discussed. Water was observed on both anode and cathode side during the fuel cell operation, indicating the composite electrolyte is co-ionic conductor possessing H⁺ and O²⁻ conduction. The variation of composite electrolyte conductivity and fuel cell power output with different synthesis conditions was in accordance with that of the SDC originated from different precursors, demonstrating O²⁻ conduction is predominant in the conduction process. A maximum power density of 817 mW cm⁻² at 600 °C and 605 mW cm⁻² at 500 °C was achieved for fuel cell based on composite electrolyte.     

The effect of non-uniform temperature on the sorption-enhanced steam methane reforming in a tubular fixed-bed reactor

The effect of non-uniform temperature on the sorption-enhanced steam methane reforming (SE-SMR) in a tubular fixed-bed reactor with a constant wall temperature of 600 °C is investigated numerically by an experimentally verified unsteady two-dimensional model. The reactor uses Ni/Al₂O₃ as the reforming catalyst and CaO as the sorbent. The reaction of SMR is enhanced by removing the CO₂ through the reaction of CaO + CO₂ → CaCO₃ based on the Le Chatelier's principle. A non-uniform temperature distribution instead of a uniform temperature in the reactor appears due to the rapid endothermic reaction of SMR followed by an exothermic reaction of CO₂ sorption. For a small weight hourly space velocity (WHSV) of 0.67 h^?1 before the CO₂ breakthrough, both a low and a high temperature regions exist simultaneously in the catalyst/sorbent bed, and their sizes are enlarged and the temperature distribution is more non-uniform for a larger tube diameter (D). Both the CH₄ conversion and the H₂ molar fraction are slightly increased with the increase of D. Based on the parameters adopted in this work, the CH₄ conversion, the H₂ and CO molar fractions at D = 60 mm are 84.6%, 94.4%, and 0.63%, respectively. After CO₂ breakthrough, the reaction of SMR dominates, and the reactor performance is remarkably reduced due to low reactor temperature.For a higher value of WHSV (4.03 h^?1) before CO₂ breakthrough, both the reaction times for SMR and CO₂ sorption become much shorter. The size of low temperature region becomes larger, and the high temperature region inside the catalyst/sorbent bed doesn't exist for D ≥ 30 mm. The maximum temperature difference inside the catalyst/sorbent bed is greater than 67 °C. Both the CH₄ conversion and H₂ molar fraction are slightly decreased with the increase of D. However, this phenomenon is qualitatively opposite to that for small WHSV of 0.67 h^?1. The CH₄ conversion and H₂ molar fraction at D = 60 mm are 52.6% and 78.7%, respectively, which are much lower than those for WHSV = 0.67 h^?1.     

H2 and CO production over a stable Ni–MgO–Ce0.8Zr0.2O2 catalyst from CO2 reforming of CH4

Ni–Ce_0.8Zr_0.2O₂ and Ni–MgO–Ce_0.8Zr_0.2O₂ catalysts were investigated for H₂ production from CO₂ reforming of CH₄ reaction at a very high gas hourly space velocity of 480,000 h⁻¹. Ni–MgO–Ce_0.8Zr_0.2O₂ exhibited higher catalytic activity and stability (CH₄ conversion >95% at 800 °C for 200 h). The outstanding catalytic performance is mainly due to the basic nature of MgO and an intimate interaction between Ni and MgO.     

Strategies to enhance dry reforming of methane: Synthesis of ceria-zirconia/nickel–cobalt catalysts by freeze-drying and NO calcination

To improve the activity of nickel–cobalt (NiCo) catalyst supported on ceria-zirconia (CeZr) in the dry reforming of methane (DRM) with carbon dioxide, and to lower the coking rate in this process, 1.5 wt.% and 2.5 wt.% NiCo catalysts were prepared using two approaches, i.e. freeze-drying (FD) and NO calcination for comparison against oven-drying (OD) and air calcination (air), respectively. Their impact was studied for 20 h of DRM at 750 ^°C and 1.2 bar, with undiluted CH₄–CO₂ feed simulating the real conditions. NO-calcined samples show, on average, more pronounced improvement through increased conversion of CH₄ (90%), followed by FD samples (85%) from the air and OD-prepared samples (both 82%). Coking content varied between 0.67 and 0.82 wt.%. The observed slow catalyst deactivation might be caused by sintering of the catalysts. Higher quantity of CO than H₂ for syngas production was obtained, owing to concurrent reverse water-gas shift side reaction, and high redox properties of the defective CeZr lattice that enabled surface carbon gasification by continuous replenishment of oxygen from the support to produce CO, of which the latter phenomenon also explains the low carbon deposition. H₂/CO ratio between 0.42 and 0.85 was achieved, with FD and NO samples fared better (0.83–0.85) over the ones prepared by conventional methods (0.73–0.82) for 2.5%NiCo loaded catalysts.     

Visible light response photocatalytic water splitting over CdS-pillared zirconium–titanium phosphate (ZTP)

With an attempt to extend the light absorption towards the visible range and inhibit the rapid recombination of excited electrons/holes, a new type photocatalysts, cadmium sulfide intercalated zirconium–titanium phosphate (CdS–ZTP) was synthesized. The photocatalysts were characterized by small angle X-ray diffraction studies (SAXS), N₂ adsorption–desorption studies, diffused reflectance UV–vis (DRUV–vis) spectroscopic analysis, photoluminescence studies (PL), scanning electron microscopic/energy dispersive spectroscopic (SEM/EDS), X-ray photoelectron spectroscopic (XPS) studies etc. The samples exhibit a unique property of optical absorption in UV and visible regions with a wavelength, λ ≤ 450 nm followed by a clear long tail up to 700 nm. The pillared materials showed excellent activity for UV–visible light driven hydrogen production from photocatalytic splitting of water without using any co-catalyst. The photocatalytic activity of this cadmium sulfide pillared catalyst, as well as that of neat cadmium sulfide powder, was monitored for the visible light-induced evolution of hydrogen from water in the presence of hole scavenger, sulfide (S²⁻).