Energy CO2 Research Articles

Influencing mechanism of carbon monoxide on the hydrogen absorption performance of Zr2Fe

Zr2Fe is considered as the promising hydrogen isotopes trapping material to control the quantity of tritium generated in deuterium–tritium fusion reaction. However, the vulnerability to poisoning by impurity gases such as carbon monoxide is the bottleneck for their applications. In this study, we show from our DFT calculations that the Zr2Fe(101) surface is saturated with 13CO molecules and the hollow site is the most stable CO adsorption site. The adsorption energy of CO is much lower than that of hydrogen, resulting in the preferential adsorption of CO on Zr2Fe(101). The dependence of the Gibbs free energies of CO on the temperatures under UHV conditions were also obtained. The climbing-image nudged elastic band results reveal that CO pre-coverage would block the hydrogen adsorption sites and affect the hydrogen diffusion. The Sieverts analysis demonstrates that even the low concentration CO is a fatal poison to the hydrogenation process of Zr2Fe at ambient temperature. Hydrogen absorption may occur at a higher temperature with a lower absorption rate and capacity, as CO starts to desorpt from Zr2Fe(101) with the increase of temperature and thus making H2 absorption possible, even though the H diffusion energy barriers are relatively high. Our results provide the basis for exploring the influence mechanisms of the impurity gas CO on the hydrogen adsorption properties of the Zr-based alloys, which would be beneficial for the applications of metal getter of tritium-containing waste gas.

Dust removal ash coupled with high-temperature exhaust gas to produce energy gas CO and remove the heavy metals synchronously

In order to solve the utilization problem of dry quenching coke dust removal ash (DRA) and high-temperature exhaust gas (HTEG) at the same time, this study proposes a new technology that combines DRA and high-temperature exhaust gas to produce energy gas CO and realize the removal of heavy metals in dust removal ash. The reaction properties of DRA and high-temperature exhaust gases, as well as the migration law of heavy metals, are preliminarily evaluated using thermodynamic simulation software (FactSage) and a combination of thermogravimetric mass spectrometry (TG-MS). The dropper furnace (DF) experiments are used to verify the feasibility of the new technology by simulating the high-temperature flue gas environment. The findings reveal that as pressure rises, the content of gas products namely CO2 and CH4 rises while the content of gas products CO and H2 falls. At the same time, when the temperature rises, the CO and H2 contents rise. Heavy metals such as Cd, Pb, and Zn are also more volatile, whereas heavy metals such as Ni, Cr, and Cu, require higher temperatures to volatilize. As the temperature increases from 800 to 1200 °C, the Pb removal rate climbs from 34.6% to 92.5%, the Cd removal rate increases from 46.5% to 95.6%, and the Zn removal rate increases from 13.4% to 80.5%. The new technology captures CO2 from high-temperature exhaust gases and converts them into CO energy gases, simultaneously realizing the removal of heavy metals. This provides an innovative solution for the treatment of organic solid waste.

First Principles' Calculations of CO Adsorption on Bimetallic Nickel-Iron Clusters

Abstract: Density functional theory (DFT) calculations using the Generalized Gradient Approximation (GGA) functional are performed to investigate the structural, energetic and magnetic properties of bimetallic alloyed 〖〖Ni〗_n Fe〗_(N-n) isomers (N = 2-6 and N = 43, n = 0 to N). The negative mixing energies indicate the stability of these clusters as compared to Ni and Fe bare clusters. All clusters exhibit high spin ground states, with a significant decrease in the magnetization per atom for Fe19Ni24 cluster with the iron core. The adsorption energies of CO on the most stable isomers of alloyed clusters are lower than those on Fe clusters with the same structure. This behavior indicates a decrease of CO poisoning and an increase of methanol oxidation reaction (MOR) activity upon alloying. Keywords: Ni-Fe bimetallic clusters, DFT, CO adsorption, Methanol oxidation reaction, Catalytic activity.

Mechanism of sulfur poisoning to Ru-based catalysts in supercritical water gasification of glycerol: From experiment to combined DFT and kinetics studies

Systematic experimental and kinetic studies were carried out to investigate the effect of sulfur toxicity on the performance of Ru-based catalysts in supercritical water gasification of glycerol. The principal display of catalyst sulfur poisoning is a reduction in catalytic activity for the water–gas shift reaction due to the competition of sulfur and CO in the active site. Consequently, CO production rose with increasing sulfur concentration, while H2 yield gradually decreased. DFT calculations confirmed that the adsorption energy of CO at Ru and Ni surfaces tends to decrease in the presence of surface S, thus promoting CO desorption. A kinetic model involving the adsorption and desorption process was developed based on the proposed reaction network and calculations provide clear evidence for experimental observation that the CO adsorption rate decreases with increasing sulfur concentration, from 9.36 × 10−2 to 6.24 × 10−2 L2·mol−1·min−1·gcat−1, while desorption rate rises, from 5.20 × 10−3 to 1.56 × 10−1 L2·mol−1·min−1·gcat−1.

Mechanism of gas production under microwave/conventional pyrolysis of sewage sludge: Mechanism of microwave energy action on oxygen-containing functional groups

Microwave pyrolysis (MWP) of sewage sludge (SS) has obvious advantages in the quality improvement of syngas. However, it is unclear the mechanism of syngas production and microwave energy on oxygen-containing functional groups during MWP of SS. In this paper, the effect of pyrolysis methods on syngas generation is investigated through macroscopic experimental quantitative analysis combined with microscopic DFT simulations. Compared with conventional pyrolysis (CP), MWP showed higher gas yields. Further quantitative analysis of the gas composition revealed that microwaves excited the gasification reaction of CO2 and promoted the production of H2 and CO, and increased by 39.89%. Kinetic calculations revealed that microwaves decreased the activation energy of H2 and CO by 50.84% and 29.59%, respectively. Tar analysis revealed that microwaves promoted a large number of oxygen-containing functional groups transferred to tar at low temperatures. As temperature increases, the oxygen-containing functional groups in the tar undergo a secondary reaction in response to microwave, resulting in numerous H radicals and O radicals being transferred to the gas phase, promoting the yield of H2 and CO. Combined with DFT to explore the decomposition path of all typical oxygen-containing functional groups in tar, it found that the decomposition of these functional groups into H2 and CO requires high energy to complete, and microwave was expected to achieve the process. Finally, the mechanism of microwave energy in the process of SS pyrolysis was proposed, which provides a feasible idea for the subsequent directional regulation of microwave pyrolysis of SS.

Alloying effects on site preference, mechanical properties, and deformation behavior of L12 Co–Ti-based alloys

Alloying plays an important role in controlling the phase stability, mechanical properties, and deformation behavior of ordered intermetallic compounds. In this study, the effects of 3d, 4d, and 5d transition elements on site preference, elastic properties, ideal shear strength, and planar fault energies of L12 Co–Ti-based alloys were systematically investigated by using first-principles calculations. The calculated transfer energy and formation enthalpy indicate that Sc, V, Cr, Y, Zr, Nb, Mo, W, Hf, Ta, and W tend to occupy the Ti site, which reduce the structural stability of L12-Co3Ti. The elastic moduli and ideal shear strength of L12-Co3(Ti,M) increase with average electron density. The electron localization function (ELF) analysis reveals that the Co–M bonds have a stronger covalent character than the Co–Ti bond, which plays an important role in the strengthening of the alloys. The ratio of superlattice intrinsic stacking fault (SISF) to anti-phase boundary (APB) energy of L12-Co3(Ti,M) decreases with increasing atomic number of alloying elements in each period in the range of studied elements, which tends to change the deformation mode from the APB-favored to SISF-favored ones. The APB anisotropy ratio of L12-Co3(Ti,M) decreases with increasing atomic number of alloying elements in each period, which enhances the yield strength anomaly. This study not only sheds insight into the fundamental understanding of phase stability and mechanical behavior of multicomponent L12 compounds, but also provides useful guidelines for designing novel L12-stregnthened Co-based superalloys with superior mechanical properties.

Experimental and ab initio Investigation on the Effect of CO and CO2 during Hydrodeoxygenation of m‐Cresol over Co/SBA‐15

AbstractThe hydrodeoxygenation (HDO) is a fundamental step in the production of biofuels from lignin, and the catalyst type and reaction conditions can play an important role. In this work, Co nanoparticles finely dispersed in the porosity of SBA‐15 stand out a high selectivity toward deoxygenated products (63 % of methylcyclohexenes and 16 % of methylcyclohexane) in the HDO of m‐cresol (30 bar of pressure, temperature of 350 °C). The effect of co‐feeding CO and CO2, which can be present in the pyrolysis gas after transformation of carboxylic acids, was investigated. An unexpected positive effect on the stability of the catalyst was observed when CO2 was added in the feed stream. On the contrary, the presence of CO led to a strong decrease of the m‐cresol conversion. These experimental findings are supported by DFT calculations which show that the m‐cresol is much more strongly adsorbed than CO2 at the Co@SiO2 interface while the interaction energy of CO is close to the one of m‐cresol.

Plasma nitrided CoCrFeNiMn high entropy alloy coating as a self-supporting electrode for oxygen evolution reaction

Noble metal electrocatalytic electrodes used in water electrolysis for hydrogen production are expensive and non-noble metal nanoparticle catalysts are not conducive to large-scale production. In this paper, the CoCrFeNiMn high entropy alloy (HEA) coating was prepared by high-velocity oxygen fuel (HVOF) spraying on the surface of stainless steel as a self-supporting oxygen evolution electrode, and the electrocatalytic activity of the electrode was further improved by plasma nitriding. The results show that the CoCrFeNiMn coating is mainly composed of FCC solid solution phase and MnCr2O4 spinel phase, and the thickness of the coating is approximately 100 μm. After nitriding, the surface of the coating is reshaped from the original semi-molten morphology to cauliflower-like structure, and the N atoms are mainly enriched in the MnCr2O4 phase. In addition, the binding energies of Co, Cr, and Ni to O in the nitrided coating decrease by 0.7 eV, while the binding energies of Fe and Mn to O are not significantly affected. The overpotential of the nitrided CoCrFeNiMn coating decreases from 363 mV to 309 mV at the current density of 10 mA cm−2, and it has a smaller Tafel slope and charge transfer resistance, and larger double-layer capacitance compared to the CoCrFeNiMn coating. Both the CoCrFeNiMn coated electrodes with and without nitriding show good long-term stability during the 60 h stability test. The high entropy alloy coating coupled with plasma nitriding technique provides a new research idea for the eletrocatalytic field of the water splitting.

The positive role of Ir0 and OV on the reduction of SO2 by CO over Ir/CeO2

Several Ir/CeO2 catalysts were synthesized with different preparation variable, the variable influences the SO2 reduction by CO over Ir/CeO2 catalyst through changing the specific surface area, the content of Ir0 species and the concentration of oxygen vacancies on the surface of catalysts. The characteristic results showed that the as-prepared Ir/CeO2-6 catalyst has the highest crystallinity, the smallest grain size and the largest lattice parameter among the synthesized catalysts. All these three catalysts are mesoporous structures, and Ir/CeO2-6 has the largest pore size and specific surface area. DFT results showed that the adsorption energies of CO and SO2 at higher Ir loading is consistent with the stoichiometric ratio. Combining the results of Raman, XPS and H2-TPR, Ir/CeO2-6 has the highest Ce3+ content, OVs content and Ir0 content which exhibited the strongest Ir-O-Ce interaction and caused better catalytic activity. All the as-prepared catalysts follow the redox mechanism during reactions. This study illustrates the preparation method affecting microstructure and then the reaction activity, providing research ideas for modulating the preparation of efficient CeO2-based catalyst for SO2 reduction by CO.

Computational screening of chemically active metal center in coordinated dipyridyl tetrazine network

Creation, stabilization, characterization, and control of single transition metal (TM) atoms may lead to significant advancement of the next-generation catalyst. Metal organic network (MON) in which single TM atoms are coordinated and separated by organic ligands is a promising class of material that may serve as a single atom catalyst. Our density functional theory-based calculations of MONs in which dipyridyl tetrazine (DPTZ) ligands coordinate with a TM atom to form linear chains leads to two types of geometries of the chains. Those with V, Cr, Mo, Fe, Co, Pt, or Pd atoms at the coordination center are planar while those with Au, Ag, Cu, or Ni are non-planar. The formation energies of the chains are high (∼2.0–7.9 eV), suggesting that these MON can be stabilized. Moreover, the calculated adsorption energies of CO and O2 on the metal atom at center of the chains with the planar configuration lie in the range 1.0–3.0 eV for V, Cr, Mo, Fe, and Co at the coordination center, paving the way for future studies of CO oxidation on TM-DPTZ chains with the above five atoms at the coordination center.

Zn Modification of Pd/TiO2/Ti Catalyst for CO Oxidation.

The main goal of this study was to modify the activity of Pd/TiO2/Ti catalyst in the reaction of CO oxidation by the addition of Zn. Plasma electrolytic oxidation (PEO) of Ti wire was conducted to produce a uniform porous layer of TiO2. A mixture of Pd and Zn was then introduced by means of adsorption. After reduction treatment, the activity of the samples was examined by oxidation of 5% CO in a temperature range from 80-350 °C. Model catalysts with sufficient amounts of the metals for physico-chemical investigation were prepared to further investigate the reaction between Pd and Zn during CO oxidation. The structures and compositions of the samples were investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), inductively coupled plasma mass spectrometry (ICP-MS), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). Modification of Pd/TiO2/Ti catalyst by Zn with a Pd:Zn atomic ratio of 2:1 decreased the temperature of complete CO oxidation from 220 °C for Pd/TiO2/Ti to 180 °C for Pd-Zn/TiO2/Ti. The temperature of 50% CO conversion on Pd-Zn(2:1)/TiO2/Ti was around 55 °C lower than in the reaction on monometallic Pd catalyst. The addition of Zn to the Pd catalyst lowered the binding energy of CO on the surface and improved the dissociative adsorption of oxygen, facilitating the oxidation of CO. FTIR showed that the bridging form of adsorbed CO is preferred on bimetallic systems. Analysis of the surface compositions of the samples (SEM-EDS, TOF-SIMS) showed higher amounts of oxygen on the bimetallic systems.

DFT-based Machine Learning for Ensemble Effect of Pd@Au Electrocatalysts on CO2 Reduction Reaction.

The ensemble effect due to variation of Pd content in Pd-Au alloys have been widely investigated for several important reactions, including CO2 reduction reaction (CO2 RR), however, identifying the stable Pd arrangements on the alloyed surface and picking out the active sites are still challenging. Here we use a density functional theory (DFT) based machine-learning (ML) approach to efficiently find the low-energy configurations of Pd-Au(111) surface alloys and the potentially active sites for CO2 RR, fully covering the Pd content from 0 to 100 %. The ML model is actively learning process to improve the predicting accuracy for the configuration formation energy and to find the stable Pd-Au(111) alloyed surfaces, respectively. The local surface properties of adsorption sites are classified into two classes by the K-means clustering approach, which are closely related to the Pd content on Au surface. The classification is reflected in the variation of adsorption energy of CO and H: In the low Pd content range (0-60 %) the adsorption energies over the surface alloys can be tuned significantly, and in the medium Pd content (37-68 %), the catalytic activity of surface alloys for CO2 RR can be increased by increase the Pd content and attributed to the meta-stable active site over the surface. Thus, the active site-dependent reaction mechanism is elucidated based on the ensemble effect, which provides new physical insights to understand the surface-related properties of catalysts.

Nonthermal Ultrafast Optical Control of Magnetization Dynamics by Linearly Polarized Light in Metallic Ferromagnet.

Coherent optical control of the magnetization in ferromagnetic (FM) mediums using ultrafast nonthermal effect paves a promising avenue to improve the speed and repetition rate of the magnetization manipulation. Whereas previously, only heat-induced or helicity-dependent magnetization dynamics are demonstrated in metallic ferromagnets. Here, the linearly-polarized light control of magnetization is demonstrated in FM Co coupled with ferroelectric (FE) BiFeO3 by tuning the light polarization direction. It is revealed that in the Co/BiFeO3 heterostructure excited by femtosecond laser pulses, the magnetization precession amplitude follows a sinusoidal dependence on the laser polarization direction. This nonthermal control of coherent magnetization rotation is attributed to the optical rectification effect in the BiFeO3 layer, which yields a FE polarization depending on the light polarization, and the subsequent modulation of magnetic energy in Co by the electrostriction-induced strain. This work demonstrates an effective route to nonthermally manipulate the ultrafast magnetization dynamics in metallic ferromagnets.

Accelerating explicit solvent models of heterogeneous catalysts with machine learning interatomic potentials.

Realistically modelling how solvents affect catalytic reactions is a longstanding challenge due to its prohibitive computational cost. Typically, an explicit atomistic treatment of the solvent molecules is needed together with molecular dynamics (MD) simulations and enhanced sampling methods. Here, we demonstrate the utility of machine learning interatomic potentials (MLIPs), coupled with active learning, to enable fast and accurate explicit solvent modelling of adsorption and reactions on heterogeneous catalysts. MLIPs trained on-the-fly were able to accelerate ab initio MD simulations by up to 4 orders of magnitude while reproducing with high fidelity the geometrical features of water in the bulk and at metal-water interfaces. Using these ML-accelerated simulations, we accurately predicted key catalytic quantities such as the adsorption energies of CO*, OH*, COH*, HCO*, and OCCHO* on Cu surfaces and the free energy barriers of C-H scission of ethylene glycol over Cu and Pd surfaces, as validated with ab initio calculations. We envision that such simulations will pave the way towards detailed and realistic studies of solvated catalysts at large time- and length-scales.

Performance study of a novel supercritical CO2 solar-coal supplementary power generation system

• New supercritical CO 2 solar-coal supplementary power generation system is proposed. • The annual solar generating power accounts for 61.29% of the total power output. • Standard coal consumption rate is 161.11 g/kWh lower than pure coal-fired system. • The new system performances with the change of the load rate are revealed. • Effects of solar multiple and thermal energy storage capacity on new system are studied. To reduce the CO 2 emission and improve the solar energy utilization rate, a novel supercritical CO 2 solar-coal supplementary power generation system is proposed. Compared with the previous studies on supplementary systems, the novel system takes solar energy as the main heat source instead of coal, which greatly increases the proportion of solar energy input. The results show that, when the solar multiple (parameter representing the area of the heliostat field) is 3 and the thermal energy storage capacity is 16 h, on the summer and winter solstices, the proportions of solar generating power are 100% and 57.15%, respectively. The novel system can operate steadily during the whole year. The annual solar generating power is 161.07 GWh, accounting for 61.29%. The standard coal consumption rate of the novel system is 101.76 g/kWh, 161.11 g/kWh lower than that of the pure coal-fired system. The exergy efficiency for the novel system increases with an increasing operation load rate. Under 50%, 75%, 100%, and 125% load rates, the exergy efficiencies are 16.7%, 25.0%, 33.4%, and 38.0%, respectively. It is the first time to study the effects of the solar multiple and the thermal energy storage capacity on the energy, exergy, environmental, and economic performances of the supercritical CO 2 solar-coal supplementary power generation system. When the thermal energy storage capacity is 16 h, the solar multiple corresponding to the optimal economic performance is 2.5.

Full-spectrum utilization of solar energy for simultaneous CO2 reduction and seawater desalination

To address the underutilization of infrared light in photocatalysis, a synergistic CO2 photoreduction and seawater desalination system was developed, which exhibited a good bifunctional performance.

A graphene-like BeS monolayer as a promising gas sensor material with strain and electric field induced tunable response: a first-principles study.

A comprehensive investigation of the gas sensing potential of BeS monolayer has been conducted using DFT calculations. Twelve common pollutant gases: NH3, NO2, NO, CO, CO2, CH4, H2, O2, N2, H2S, H2O and SO2, have been studied. Our analysis reveals defect states in the band structure near the Fermi level and strong hybridization between gas molecule orbitals and the BeS monolayer. We observe higher adsorption energies for NH3 and CO compared to other popular gas sensing materials. The optical properties of CO2 and NO2 adsorbed on the BeS monolayer show increased reflectivity and absorption coefficient in the UV and far infrared region. Tensile strain has minimal impact on adsorption energy, while biaxial compressive strains enhance the gas sensing capability of the BeS monolayer. The application of an electric field offers control over gas adsorption and desorption. We propose the BeS monolayer as a promising candidate for future gas molecule sensing applications due to its high adsorption energy, rapid recovery time, and distinct optical properties.

New insights into engineering the core size and carbon shell thickness of Co@C core–shell catalysts for efficient and stable Fenton-like catalysis

Herein, we engineered the cobalt core size and carbon shell thickness of Co@C by molten salt electrolysis (MSE) to investigate the enhanced essence of decreasing core size as well as the shell thickness dependence-mediated transition of catalytic mechanisms. We found that the reaction activation energy (RAE) of Co@C/peroxymonosulfate (PMS) systems was intimately dependent on the core sizes for sulfamethoxazole (SMX) degradation. The smaller core size of 26 nm provided a lower RAE of 13.39 kJ mol−1. In addition, increasing carbon shell thicknesses of Co@C altered the catalytic mechanisms from a radical pathway of SO4•– and •OH to to a non-radical pathway of 1O2 and electron-transfer process (ETP), which were verified by experimental results and density functional theory (DFT) calculations. Interestingly, increasing carbon shell thicknesses promoted the charge transfer between Co metal slab and carbon shell, increased the adsorption energy of PMS molecule on the Co@C slab, and decreased the length of OO, which favoured the occurrence of non-free radical processes.

Efficient recovery of valuable metals from spent Lithium-ion batteries by pyrite method with hydrometallurgy process

With the generation of a large number of spent lithium-ion batteries (LIBs), a large amount of valuable metals in spent LIBs is in urgent need of recovery for resource recycling and environmental protection. In the hydrometallurgy recycling process of cathode materials, reducing agents are essential, while traditional ones suffer from high dosage, high price and environmental unfriendliness. Herein, pyrite (FeS2) is developed as an alternative to achieve efficient recovery of valuable metals. Leaching parameters such as sulphuric acid concentration, liquid/solid ratio, FeS2 dosage, temperature, and leaching duration were systematically optimized to obtain 98 %∼99.9 % leaching efficiencies of Ni, Co, Mn, and Li from spent LIBs. Thermodynamically, the entire leaching process is feasible. Kinetic studies have shown that the reaction activation energies for Ni, Co, Mn, and Li are in the range of 20 kJ mol−1 to 30 kJ mol−1, implying that the limiting step of the reaction is the diffusion process. Apart from this, the present work provides that the Fe and S in pyrite play a synergistic role in the reduction process based on the application of XRD, SEM, XPS, redox potential testing, ICP and other detection methods. The entire process greatly reduces the involvement of chemical reagents, achieves efficient leaching of valuable metals by the pioneering pyrite method, and compliance with environment-friendly regulations as much as possible.

Leaching NCM cathode materials of spent lithium-ion batteries with phosphate acid-based deep eutectic solvent

Deep eutectic solvents (DESs) play an important role in efficient recovery of spent lithium-ion batteries (LIBs). In this study, we proposed an efficient and safe method by using a choline chloride-phenylphosphinic acid DES as a lixiviant for the leaching of LiNixCoyMnzO2 (NCM) cathode active materials of spent LIBs. The leaching conditions were optimized based on the leaching time, liquid–solid ratio, and leaching temperature. Under optimal experimental conditions, the leaching efficiencies of Li, Co, Ni, and Mn reached 97.7 %, 97.0 %, 96.4 %, and 93.0 %, respectively. The kinetics of the leaching process were well-fitted using the logarithmic law equation. The apparent activation energies for Li, Co, Ni, and Mn have been reported to be 60.3 kJ/mol, 78.9 kJ/mol, 99.3 kJ/mol, and 82.1 kJ/mol, respectively. UV–visible spectroscopy and Fourier transform infrared analysis revealed that the coordination configurations of Ni and Co in the leaching solution were octahedral and tetrahedral, respectively. In addition, the PO bond in phenylphosphinic acid was involved in coordination during leaching. This finding may provide an effective and safe approach for leaching valuable metals from spent LIBs.