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Photocatalytic water-splitting represents a promising avenue for clean hydrogen production, necessitating an in-depth understanding of the photocatalytic reaction mechanism. The majority of the photocatalytic materials need cocatalysts to enhance the photo-oxidation or reduction reactions. However, the working mechanism, such as collecting charge carriers or reducing the reaction barrier, is not clear because they disperse inhomogeneously on a surface, and it is difficult to follow the local charge carrier behavior. This study employs the pattern-illumination time-resolved phase microscopy (PI-PM) method to unravel the spatial charge carrier behavior in photocatalytic systems, utilizing time-resolved microscopic image (refractive index change) sequences and their clustering analyses. This approach is robust for studying the change in local charge carrier behavior. We studied two major cocatalyst effects on photocatalysts: TiO2 with/without Pt and hematite with/without CoPi. The PI-PM method, supported by charge type clustering and the effects of scavengers, allowed for the analysis of local activity influenced by cocatalysts. This approach revealed that the introduction of cocatalysts alters the local distribution of charge carrier behavior and significantly impacts their decay rates. In TiO2 systems, the presence of Pt cocatalysts led to a local electron site on the micron scale, extending the lifetime to a few tens of microseconds from a few microseconds. Similarly, in hematite films with CoPi, we observed a notable accumulation of holes at cocatalyst sites, emphasizing the role of cocatalysts in enhancing photocatalytic efficiency. The study's findings highlight the complexity of charge carrier dynamics in photocatalytic processes and the significant influence of cocatalysts. [ABSTRACT FROM AUTHOR]

The present study investigated the performance of iron ore mixed with carbide slag (CS) as oxygen carrier in a batch-fluidized bed reactor using Datong bituminous coal as fuel. The effects of mixing mass ratio and reaction temperature on the CLC process of coal were investigated. The results showed that iron ore mixed with carbide slag accelerated the CLC process of coal compared with iron ore alone. Reaction temperature had a crucial effect on carbon conversion of coal, but higher than 900°C resulted in a decreased reactivity of CS-mixed oxygen carrier. Multiple redox cycle tests were also conducted to study the stability of CS-mixed oxygen carrier. It was found that though a continuing decreasing reactivity was observed for CS-mixed oxygen carrier, it still has higher CO2 yield and lower CO yield than those of undecorated one. SEM analysis revealed that sintering occurred on the surface of CS-mixed oxygen carrier, resulting in the deterioration of reactivity. The reason for the promoted performance of CS-mixed iron ore seems to be the catalytic effect of carbide slag on the water-gas shift reaction, converting CO to H2, for H2 is more reactive toward iron ore. [ABSTRACT FROM AUTHOR]

Due to the abundance of active components and low cost, pyrite cinder has great potential as an oxygen carrier in the process of chemical looping combustion (CLC). In order to improve the fuel combustion reactivity, we modified pyrite cinder with copper oxide (CuO). The addition of copper oxide could effectively increase the pore volume and oxygen vacancy concentration of pyrite cinder. The modified pyrite cinder with 20 wt% CuO possessed the highest pore volume (0.3 cm3/g) and oxygen vacancy concentration (55.61%). During the long-term redox cycles, the modified pyrite cinder samples showed higher fuel combustion reactivity than the undoped sample. The results of characterization indicated that the crystalline phases of CuO and CuFe 2 O 4 were formed in the CuO-modified pyrite cinder samples. The active components (Fe 2 O 3 , CuFe 2 O 4 and CuO) in the modified pyrite cinder samples were reduced to Fe 3 O 4 , FeO, CuFeO 2 and Cu during the reduction half cycle. The modified pyrite cinder with 20 wt% CuO possessed the highest CH 4 conversion (nearly 100%) and CO 2 selectivity (nearly 100%) in multiple redox testing. The CH 4 conversion of undoped pyrite cinder was only about 60%. When the content of CuO reached 30 wt%, surface sintering occurred for the modified pyrite cinder, resulting in the decrease of CH 4 conversion and surface area. After continuous redox cycles, the CuO-modified pyrite cinder samples could maintain the original crystal structure. [Display omitted] • Raw pyrite cinder was modified by CuO. • CuO promoted the formation of oxygen vacancies. • Fuel combustion reactivity of CuO-modified pyrite cinder was improved significantly. • CuO enhanced the reduction of iron oxide in pyrite cinder. • The optimum amount of CuO was 20 wt%. [ABSTRACT FROM AUTHOR]

Upscaling of the laboratory oxygen carriers while keeping comparable performance as laboratory powders remains a challenge in the field of chemical looping combustion (CLC). In this work, two perovskite compositions of CaMn0.375Ti0.5Fe0.125O3 (termed CMTF8341) and CaMn0.5Ti0.375Fe0.125O3 (CMTF8431) have been fabricated by means of spray granulation. The fabricated granules were evaluated by redox cycles under CLC conditions and showed comparable performance with laboratory-prepared powders, i.e. high oxygen transfer capacity and fast redox kinetics. Under chemical looping oxygen uncoupling (CLOU) conditions, it has been found that steam leads to a slower kinetics and lower oxygen transfer capacity for these two compositions. When it comes to sulphur effect on the oxygen carriers, redox cycles with deep reduction showed no influence with H2S since the CaSO4 formed in air decompose but it affected the materials under mild CLOU due to calcium sulphate formed under such condition. Nonetheless, redox performance can be recovered by deep reduction with an enhanced oxygen capacity. These two oxygen carriers showed no degradation as compared to other tested minerals in the field of CLC. Microstructure analyses from SEM showed high degree of structure integrity after redox cycles at temperatures up to 1050 °C for the CMTF8341. Good mechanical strength was evidenced from cold attrition test, and the lifetime of the two granules was also predicted based on a standard reference. [ABSTRACT FROM AUTHOR]

Iron or its oxides (FexOy) commonly exist in the ash of fossil fuel and biomass, and are used as oxygen carriers in chemical looping process, and Fe3O4 is a main occurrence. The NO reduction mechanisms by CO over Fe3O4 (111) surface was investigated via density functional theory (DFT) calculations. An optimized unit cell of Fe3O4 was constructed. The interaction between molecules and cell surface was described by the calculated adsorption properties and electronic structures. Results showed that the most stable adsorption of NO/CO belongs to chemisorption and NO has higher adsorption energy than CO. NO can be absorbed onto Fe3O4 surface to form (NO)2 dimer structure, which easily decomposes via a small energy barrier. (NO)2 dimer mechanism is a possible pathway for the reduction of NO by CO over Fe3O4, following three steps: 2NO → (NO)2*, (NO)2* → N2O + O*, O* + CO* → CO2. After the decomposition, the intermediate species N2O molecule and the remaining O atom adsorbed strongly on the Fe3O4 surface can be removed by CO. CO also promotes the gaseous decomposition of N2O. DFT results also showed O2 will prevent NO reduction reaction. The calculated reaction rate constants further verify the existence of (NO)2 dimer mechanism and the rate-limiting step is the removal of the surface O atom. [ABSTRACT FROM AUTHOR]

Chemical looping ammonia generation is a promising, efficient, and environmentally friendly synthesis of ammonia by cycling N-absorption and N-desorption reactions. A portion of the generated NH 3 decomposes at the reaction temperature of the N-desorption reaction. In order to promote the N-desorption reaction and inhibit the decomposition of NH 3 , the effect of α-Al 2 O 3 loading on the N-desorption reaction was investigated in this paper by fixed-bed experiments. The mechanism was revealed using Density functional theory (DFT) calculations. The results showed that when the reaction temperature increased, the conversion of AlN and the yield of NH 3 increased, but the actual NH 3 conversion decreased. When the steam concentration increased, the conversion of AlN, the yield of NH 3, and the actual NH 3 conversion increased. The loading of α-Al 2 O 3 could facilitate the N-desorption reaction and inhibit the decomposition of NH 3. The 40 wt% α-Al 2 O 3 had the highest conversion of AlN. The 80 wt% α-Al 2 O 3 had the highest yield of NH 3. The actual efficiency of ammonia production at 1075 °C with 80 wt% load increased from 45.5% without load to 58.5%. The DFT calculations revealed the mechanism: α-Al 2 O 3 surface promotes the dissociation of H 2 O molecules to make more hydroxyl groups in the reaction system, which promotes the transfer of H+ and the N-desorption reaction. Meanwhile, the adsorption of NH 3 by the α-Al 2 O 3 surface protected NH 3 and inhibited its decomposition. [Display omitted] • The loading of α-Al 2 O 3 could promote the N-desorption reaction and inhibit the decomposition of NH 3. • The inhibition of NH 3 decomposition by α-Al 2 O 3 increased with increasing reaction temperature. • α-Al 2 O 3 promotes H 2 O dissociation and NH 3 adsorption thereby increasing the actual yield of NH 3. [ABSTRACT FROM AUTHOR]

Objective Molten catalytic methane pyrolysis coupled with chemical looping combustion technology was developed, and natural gas was used as material gas. It can produce hydrogen along with power generation and solid carbon. Methods The process was simulated by Aspen Plus, and techno-economic feasibility in terms of economic benefits was analysed. The main influencing factors of methane conversion rate, pyrolysis reaction temperature, and PSA separation efficiency were discussed. Results When the feedstock was 600 kmol/h, the system could produce 956 kmol/h hydrogen and 503 kmol/h solid carbon, and the system generating capacity was 9.43 MW. The CO2 capture amount was 208 kmol/h while the capture ratio was 99.75%. The system performance was examined, and the results showed that the total system efficiency was 77.044%, wherein the hydrogen efficiency was 41.059%, the rate of solid carbon production was 31.453%, and the electricity efficiency was 4.532%. Conclusion It was concluded that improving methane conversion and PSA efficiency, and reducing thermal cracking reaction temperature were significantly helpful in increasing product yield and total system efficiency. [ABSTRACT FROM AUTHOR]

Indirect combustion with the chemical looping combustion (CLC) of solid oxygen carriers is one of the most promising technologies for capturing carbon dioxide (CO2) in energy production from fossil fuels since the separation of the generated CO2 is inherent to the process itself. Therefore, the cost associated with capturing this gas will be significantly reduced. This technology transfers oxygen from air to fuel through a metal oxide that acts as an oxygen carrier, avoiding direct contact between air and fuel. This oxygen carrier circulates in a fluidized bed reactor called a reduction reactor and an oxidation reactor. (1) This research work has focused on evaluating the behavior of oxygen carriers based on the original and improved manganese mineral (copper-impregnated mineral) named for this study, OXMN009 and OXMN009P, respectively. (2) Equilibrium experiments were carried out on a thermogravimetric balance (TGA) to evaluate the kinetic behavior of these oxygen transporters OXMN009 and OXMN009P, using the gases methane (CH4), carbon monoxide (CO), and hydrogen (H2). (3) The enhanced solid oxygen carrier OXMN009P exhibited good performance for the CLC process with gaseous fuels in terms of reactivity and combustion efficiency, having high reactivity and oxygen transfer properties due to copper impregnation. (4) The results show that OXMN009P has comparable reactivity to other manganese-based materials reported in the literature. It may be an effective option for carbon dioxide capture, as it uses metal oxides as the oxygen transporters (TO). (5) These oxygen transporters, OXMN009 and OXMN009P, are used in a cyclic process that prevents the formation of nitrogen oxides by keeping the air and fuel separate. (6) Thermogravimetric balance (TGA) experiments were conducted to evaluate the kinetic behavior of these copper-modified oxygen transporters. (7) It was found that OXMN009P improved the reactivity and oxygen transfer properties due to copper impregnation. The kinetic parameters obtained in the TGA indicate that the reaction is non-thermal and requires less energy to initiate. (8) The results show that OXMN009P has reactivity comparable to other manganese-based materials reported in the literature and can be an effective option for carbon dioxide capture. [ABSTRACT FROM AUTHOR]

We have successfully constructed a PDI supramolecular material, s-PDI- P 1, with an intermolecular double hydrogen bonding structure, which has a compact H-type π-π stacking structure and achieves high carrier separation and migration efficiency. The oxygen evolution rate of the s-PDI- P 1 was 3.23 mmolg-1h−1, without the use of precious metal co-catalysts. [Display omitted] • In the absence of a noble metal co-catalyst, the s-PDI- P 1 molecule exhibited the highest oxygen evolution rate of 3.23 mmolg-1h−1. • The formation of a double hydrogen-bonded structure resulted in a tight H-type π-π stacking between the s-PDI- P 1 molecules, leading to the creation of an ultrathin nanosheet structure with a thickness of 4.7 nm. • s-PDI- P 1 with higher photocurrent intensity (87.2 μA) and lower internal resistance (0.32 KΩ). • s-PDI- P 1 has a higher valence band position (+1.5 V). Perylene diimides (PDI) are widely used in photocatalytic oxygen evolution due to their deep valence band potentials. Here, we report the synthesis of a unique supramolecular photocatalyst (designated s-PDI- P 1) by introducing hydroxyl and carboxyl groups at the imide position of PDI. This modification allows the formation of intermolecular double hydrogen bond structures between the hydroxyl groups, oxygen atoms on the perylene cores and the carboxyl groups. The resulting double hydrogen bonding structures reduce lateral slip and promote the formation of supramolecular structures with H-type π-π stacking. In addition, the intermolecular hydrogen bonding interactions between the hydroxyl groups and the oxygen atoms on the perylene cores bring the PDI molecules closer together, enhancing the conjugation of the PDI supramolecules and facilitating the formation of ultrathin nanosheet-like structures. In this study, we successfully constructed ultrathin nanosheets of the supramolecular photocatalyst s-PDI- P 1 with a compact H-type π-π stacking structure, which exhibited enhanced charge transfer capability, shorter charge migration distance, and achieved a high photocatalytic oxygen evolution rate of 3.23 mmolg-1h−1. These results highlight the potential of intermolecular double hydrogen bond structures to improve the separation and migration driving force of photogenerated charges, thus providing a novel design strategy for organic photocatalysts. [ABSTRACT FROM AUTHOR]

Climate change incurred by the increasing amount of CO2 released into the atmosphere has become a global priority, and triggers the development of carbon capture, utilization, and storage. Low energy requirement and cost by employing moisture swing process make quaternary ammonium-based materials applicable for CO2 capture. The moisture-sensitive sorbents suffer decreased CO2 affinity and cyclic capacities with moderate or high humidity, while water vapor ubiquitously exists in flue gas or ambient air. The effect of applying electric field on CO2 adsorption, especially the water-involved proton transfer step, by quaternary ammonium-based sorbents in the existence of water, is analyzed. The discrepancy in the hydrophilicity between reactant and product species is enhanced by the electric field, which indicates more favorable chemisorption. Thermodynamics of CO2 adsorption coupling interfacial water evaporation under the electric field are depicted with changes of enthalpy and free energy calculated. Therefore, the rationality of electric field enhanced CO2 capture of quaternary ammonium-based sorbents in moist circumstance is theoretically validated, providing the methodology of optimizing moisture swing adsorption from process intensification apart from material design. [ABSTRACT FROM AUTHOR]

Chemical looping combustion (CLC) has been validated as one of the most promising technologies for fossil fuel combustion, which can produce high-purity CO2 streams ready for capture and sequestration in power production. The selection of an appropriate oxygen carrier is one of the most important issues for the CLC process, and the reduction kinetics investigation of the oxygen carrier with fuel gas can provide the basis for CLC reactor design and simulation optimization. In this study, copper ore was chosen as an oxygen carrier, and the oxygen release property of copper ore under a nitrogen environment at various temperatures (1073–1193 K) was first investigated in a thermogravimetric analyzer (TGA). Subsequently, the reduction kinetics of copper ore with CO and H2 were evaluated by the TGA at temperatures ranging from 773 K to 1073 K, using a continuous stream of 5, 10, 15, 20, 25, and 30 vol. % of CO or H2 balanced by CO2 or N2. It was found that the reaction rates of these reactions accelerated with the increase in temperature and fuel gas concentration in inlet gas. Both the oxygen release process of copper ore and the reduction process of copper ore with reducing gases can be described by the unreacted shrinking core model (USCM). The reaction mechanism function for the oxygen-releasing and reduction process of copper ore oxygen carrier was varied. The activation energy of the oxygen-releasing process, reduction process with CO, and reduction process with H2 were calculated as 99.35, 5.08, and 4.28 kJ/mol, respectively. The pre-exponential factor ranged from 1.96 × 10−1 to 1.84 × 103. The reaction order depended on the fuel gas, which was 1 and 0.86, respectively, for reaction with CO and H2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cations serve as cross-linkers to induce MXene gelation and impede the restacking. • Melamine sponge as a support loads MXene aerogels with mechanical strength. • Mg-induced MXene@MS aerogel exhibits the maximum area capacity of 702.22 mF cm−2. The self-assembled aerogels are considered as an efficient strategy to address the aggregation and restacking of Ti 3 C 2 T x MXene nanosheets for high-performance supercapacitors. However, the low mechanical strength of the MXene aerogel results in the structural collapse of the self-standing supercapacitor electrode materials. Herein, a low-cost melamine sponge (MS) absorbed different cations (H+, K+, Mg2+, Fe2+, Co2+, Ni2+ and Al3+), serves as a carrier and crosslinker for loading MXene hydrogel induced by the absorbed cations on the skeleton surface and the pores of MS, resulting in the high loading mass MXene aerogels with high mechanical strength. The experimental results show that the Mg-Ti 3 C 2 T x @MS aerogel exhibits the maximum area capacitance of 702.22 mF cm−2 at 3 mA cm−2, and the area capacitance is still 603.12 mF cm−2 even at 100 mA cm−2, indicating the high rate capability with a capacitance retention of 85.89 %. It is worth noting that the constructed asymmetric supercapacitor with activated carbon achieves high energy densities of 104.53 μWh cm−2 and 93.87 μWh cm−2 at 800 μW cm−2 and 7999 μW cm−2, respectively. Furthermore, the asymmetric supercapacitor shows the high cycling stability with 90.2 % capacity retention after 10,000 cycles. This work provides a feasible strategy to prepare Ti 3 C 2 T x MXene aerogels with large layer spacing and high strength for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Chemical looping combustion (CLC) offers a novel approach to simultaneous power generation and carbon capture. However, the commercial viability of CLC depends on durable and cost‐effective oxygen carriers (OCs). This study assesses the impact of water vapor (WV) on the attrition of red mud OC, crucial for industrial CLC deployment. Findings indicate a significant reduction in the average attrition rate, from 0.06%/h to 0.03%/h, attributed to the limitation of Fe2O3 reduction, resulting in reduced volumetric and temperature changes in the presence of WV. A developed volume‐based model reveals attrition contributions in the order of chemical > mechanical >> thermal stresses, influencing OC particle surface morphology. Remarkably, the formation of the iron‐oxide layer remains unaffected by WV, reducing agents (CO or H2), or superficial velocities, suggesting scalable iron recovery from attrition with enhanced flexibility in future applications. [ABSTRACT FROM AUTHOR]

Even though the energy penalties and solvent regeneration costs associated with amine-based absorption/stripping systems are important challenges, this technology remains highly recommended for post-combustion decarbonization systems given its proven capture efficacy and technical maturity. This study introduces a novel centralized and decentralized hybrid control strategy for the post-combustion carbon capture plant, aimed at mitigating main disturbances and sustaining high system performance. The strategy is rooted in a comprehensive mathematical model encompassing absorption and desorption columns, heat exchangers and a buffer tank, ensuring smooth operation and energy efficiency. The buffer tank is equipped with three control loops to finely regulate absorber inlet solvent solution parameters, preventing disturbance recirculation from the desorber. Additionally, a model-based controller, utilizing the model predictive control (MPC) algorithm, maintains a carbon capture yield of 90% and stabilizes the reboiler liquid temperature at 394.5 K by manipulating the influent flue gas to the lean solvent flowrates ratio and the heat duty of the reboiler. The hybrid MPC approach reveals efficiency in simultaneously managing targeted variables and handling complex input–output interactions. It consistently maintains the controlled variables at desired setpoints despite CO2 flue gas flow disturbances, achieving reduced settling time and low overshoot results. The hybrid control strategy, benefitting from the constraint handling ability of MPC, succeeds in keeping the carbon capture yield above the preset minimum value of 86% at all times, while the energy performance index remains below the favorable value of 3.1 MJ/kgCO2. [ABSTRACT FROM AUTHOR]

Mn-doped cobalt ferrite nanoparticles were synthesized via the green route combustion-assisted method using tamarind seed powder as a fuel with the chemical formula Mn x Co 1-x Fe 2 O 4 , where x = 0.0, 0.2, 0.4, and 0.6, and named as CF, MCF-1, MCF-2, and MCF-3 NPs, respectively. XRD, FT-IR, SEM with EDS, XPS, TEM, CV, PL, and UV–visible spectroscopy have been employed to characterize the synthesized nanoparticles. The average crystalline sizes of NPs were 5.7, 6.1, 6.8, and 7.6 nm, and the lattice parameters increases as the manganese dopant level rises, owing to the XRD patterns. FT-IR spectra verified the observation of the metal-oxygen bond's vibrational stretching frequency in the tetrahedral and octahedral lattices. Using X-ray photoelectron spectroscopy, the elemental composition, oxidation state, and transition state of the synthesized nanoparticles were identified. The structure resembles nanoflakes with agglomeration, as revealed by SEM and HRTEM, and the elemental composition was verified by EDS. UV–visible spectroscopy was employed to figure out the bandgap, which decreases as the level of manganese doping rises. As the dose of manganese dopant was increased, the peak intensity of the luminescence spectra reduces. Synthesized NPs showed good electrochemical behaviour in CV studies. Under visible light illumination, the photocatalytic efficacy of synthesized nanoparticles was evaluated with methylene blue dye. [Display omitted] [ABSTRACT FROM AUTHOR]

Efficient activation and the conversion of methane to value‐added products have long attracted interest. Chemical looping reforming has become a competitive technology to transform methane into syngas that can act as raw material for various chemicals. In this paper, the methane chemical looping reforming reactivity of the Ce−Co composite oxygen carriers fabricated with different preparation methods, including solution combustion, ball‐milling, hydrothermal, and co‐precipitation method, are investigated on a fixed‐bed. Various bulk/surface characterizations (TEM, XRD, BET, XPS, Raman, etc.) were applied to reveal the effect of preparation methods on the properties of these oxygen carriers. The results indicate that the oxygen carrier prepared by the solution combustion method exhibits excellent methane conversion, high syngas yield, and desirable H2/CO ratio, as well as stable regenerability because of its relatively small crystal size, large specific surface area, high oxygen vacancy concentration and Ce3+/Ce4+ ratio. This work may be helpful in the preparation of highly active and stable oxygen carriers for chemical looping reforming reaction of methane. [ABSTRACT FROM AUTHOR]

Amine-functionalized adsorbents offer substantial potential for CO2 capture owing to their selectivity and diverse application scenarios. However, their effectiveness is hindered by low efficiency and unstable cyclic performance. Here we introduce an amine-support system designed to achieve efficient and stable CO2 capture. Through atom-level design, each polyethyleneimine (PEI) molecule is precisely impregnated into the cage-like pore of MIL–101(Cr), forming stable composites via strong coordination with unsaturated Cr acid sites within the crystal lattice. The resulting adsorbent demonstrates a low regeneration energy (39.6 kJ/molCO2), excellent cyclic stability (0.18% decay per cycle under dry CO2 regeneration), high CO2 adsorption capacity (4.0 mmol/g), and rapid adsorption kinetics (15 min for saturation at 30 °C). These properties stem from the unique electron-level interaction between the amine and the support, effectively preventing carbamate products' dehydration. This work presents a feasible and promising cost-effective and sustainable CO2 capture strategy. An amine-support system has been introduced through atom-level design, achieving low regeneration energy, excellent cyclic stability, high capacity, and rapid kinetics, stemming from electron-level interactions preventing carbamate dehydration. [ABSTRACT FROM AUTHOR]

Herein, a robust microporous aluminum tetracarboxylate framework, MIL‐120(Al)‐AP, (MIL, AP: Institute Lavoisier and Ambient Pressure synthesis, respectively) is reported, which exhibits high CO2 uptake (1.9 mmol g−1 at 0.1 bar, 298 K). In situ Synchrotron X‐ray diffraction measurements together with Monte Carlo simulations reveal that this structure offers a favorable CO2 capture configuration with the pores being decorated with a high density of µ2‐OH groups and accessible aromatic rings. Meanwhile, based on calculations and experimental evidence, moderate host‐guest interactions Qst (CO2) value of MIL‐120(Al)‐AP (−40 kJ mol−1) is deduced, suggesting a relatively low energy penalty for full regeneration. Moreover, an environmentally friendly ambient pressure green route, relying on inexpensive raw materials, is developed to prepare MIL‐120(Al)‐AP at the kilogram scale with a high yield while the Metal‐ Organic Framework (MOF) is further shaped with inorganic binders as millimeter‐sized mechanically stable beads. First evidences of its efficient CO2/N2 separation ability are validated by breakthrough experiments while operando IR experiments indicate a kinetically favorable CO2 adsorption over water. Finally, a techno‐economic analysis gives an estimated production cost of ≈ 13 $ kg−1, significantly lower than for other benchmark MOFs. These advancements make MIL‐120(Al)‐AP an excellent candidate as an adsorbent for industrial‐scale CO2 capture processes. [ABSTRACT FROM AUTHOR]

The chemical looping reforming and combustion of methane have attracted increasing interest as processes for clean energy and syngas production, with potential to reduce carbon dioxide emissions. Previous literature on the development of oxygen carriers evidenced the effects that oxygen availability exerts on the selectivity of the oxidation reaction. In the present paper, we evaluate the performance of chromite sand (Chro), cerium dioxide (CeO2), and mixed cerium–copper oxide (Ce–Cu) as oxygen carriers for either reforming or combustion according to their oxygen availability. The oxides are tested in 2 to 5 min reduction intervals in a CH4/N2 mixture (5, 10 and 20% vol.) followed by regeneration in O2/N2 (3, 5, or 21% vol.), with redox cycles conducted either at 850 °C or 950 °C. The obtained rank of selectivity towards complete CH4 combustion is Ce–Cu > CeO2 > Chro. Another relevant finding is the role of the degree of carrier conversion in promoting partial or total oxidation. In particular, the selectivity towards CO2 markedly decreases at increasing carrier conversion, disclosing new strategies for process design and optimization by controlling the carrier conversion degree. [ABSTRACT FROM AUTHOR]

Bioenergy with carbon capture and storage (BECCS) or utilization (BECCU) allows net zero or negative carbon emissions and can be a breakthrough technology for climate change mitigation. This work consists of an energetic, exergetic, and economic analysis of an integrated process based on chemical looping combustion of solar-torrefied agro-industrial residues, followed by methanation of the concentrated CO2 stream with green H2. Four agro-industrial residues and four Italian site locations are considered. Depending on the considered biomass, the integrated plant processes about 18–93 kg h−1 of raw biomass and produces 55–70 t y−1 of synthetic methane. Global exergetic efficiencies ranged within 45–60% and 67–77% when neglecting and considering, respectively, the valorization of torgas. Sugar beet pulp and grape marc required a non-negligible input exergy flow for the torrefaction, due to the high moisture content of the raw biomasses. However, for these biomasses, the water released during drying/torrefaction and CO2 methanation could be recycled to the electrolyzer to eliminate external water consumption, thus allowing for a more sustainable use of water resources. For olive stones and hemp hurd, this water recycling brings, instead, a reduction of approximately 65% in water needs. A round-trip electric efficiency of 28% was estimated assuming an electric conversion efficiency of 40%. According to the economic analysis, the total plant costs ranged within 3–5 M€ depending on the biomass and site location considered. The levelized cost of methane (LCOM) ranged within 4.3–8.9 € kgCH4−1 but, if implementing strategies to avoid the use of a large temporary H2 storage vessel, can be decreased to 2.6–5.3 € kgCH4−1. Lower values are obtained when considering hemp hurd and grape marc as raw biomasses, and when locating the PV field in the south of Italy. Even in the best scenario, values of LCOM are out of the market if compared to current natural gas prices, but they might become competitive with the introduction of a carbon tax or through government incentives for the purchase of the PV field and/or electrolyzer. [ABSTRACT FROM AUTHOR]

Conventional Carbon Capture and Storage (CCS) operations use the direct injection of CO2 in a gaseous phase from the surface as a carbon carrier. Due to CO2 properties under reservoir conditions with lower density and viscosity than in situ brine, CO2 flux is mainly gravity-dominated. CO2 moves toward the top and accumulates below the top seal, thus reinforcing the risk of possible leakage to the surface through unexpected hydraulic paths (e.g., reactivated faults, fractures, and abandoned wells) or in sites without an effective sealing caprock. Considering the risks, the potential benefits of the interplay between CO2 and an aqueous solution of formate ions (HCOO¯) were evaluated when combined to control CO2 gravity segregation in porous media. Three combined strategies were evaluated and compared with those where either pure CO2 or a formate solution was injected. The first strategy consisted of a pre-flush of formate solution followed by continuous CO2 injection, and it was not effective in controlling the vertical propagation of the CO2 plume. However, the injection of a formate solution slug in a continuous or alternated way, simultaneously with the CO2 continuous injection, was effective in slowing down the vertical migration of the CO2 plume and keeping it permanently stationary deeper than the surface depth. [ABSTRACT FROM AUTHOR]

Drop-in fuels for aviation gas-turbine engines have been introduced recently to mitigate global warming. Despite their similarity to the fossil fuel Jet A-1, their combustion in traditional combustors should be thoroughly analyzed to maintain engine health and low emissions. The paper introduces criteria for assessing the impact of the chemical composition of fuels on combustion in the DEGN 380 turbofan. Based on previous emission-test results, the power functions of carbon monoxide and its emission index were adopted as the model of combustion. Based on the general notation of chemical reactions leading to the production of CO in combustion, the regression coefficients were given a physical meaning by linking them with the parameters of the kinetic equations, i.e., the reaction rate constant of CO and CO2 formation expressed as exponential functions of combustor outlet temperature and the concentration of O2 in the exhaust gas, as well as stoichiometric combustion reactions. The obtained empirical functions show that, in the entire range of engine operating parameters, synthetic components affect the values of the rate constants of CO and CO2 formation. It can be explained by the change in activation energy determined for all chain-of-combustion reactions. The activation energy for the CO formation chain changes in the range between 8.5 kJ/mol for A0 and 24.7 kJ/mol for A30, while for the CO2 formation chain between 29.8 kJ/mol for A0 and 30.8 kJ/mol for A30. The reactivity coefficient lnαiCOACODCO changes between 2.29 for A0 and 6.44 for A30, while lnαiCO2ACO2DCO2 changes between 7.90 for A0 and 8.08 for A30. [ABSTRACT FROM AUTHOR]

Nickel ferrite (NFO), cobalt ferrite (CFO), and nickel-cobalt (NCFO) ferrite were produced by a green synthesis method utilizing olive leaf extract as a fuel (OLE). The study aims to assess the structural and magnetic characteristics of ferrite nanoparticles produced via green synthesis with olive leaf extract. This method seeks to decrease toxicity and environmental impact while enhancing properties like size, shape, and composition to improve performance. Crystal structure, microstructure, and magnetic properties were studied using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. The NFO, CFO, and NCFO ferrites display a single cubic spinel structure belonging to the Fd-3 m space group with crystallite sizes ranging from 123 to 170 nm. The lattice parameter (a) increases from 8.3499±10-4Å for NFO to 8.3673±10-4 Å and 8.3872±10-4 Å for Co-containing NCFO and CFO ferrites, respectively. The estimation of the cation distribution from the Rietveld refinement reveals that the CFO shows a higher inversion degree of 0.67 compared to that of NFO and NCFO ferrites (δ = 0.46). The CFO, NFO, and NCFO samples exhibit mixed ferrite structures. Fourier-Transform Infrared spectroscopy measurements confirm the formation of the spinel structures. The saturation magnetization, coercivity, remanence, and constant anisotropy K1 of the cobalt-containing CFO and NCFO ferrites are higher than those of NFO. [ABSTRACT FROM AUTHOR]

Calcium‐looping dry reforming of methane (CaL‐DRM) strategy mainly relies on novel Ni/CaO‐based dual‐functional materials, in which its microscopic mechanism remains to be further explored. In this work, molecular simulation of the adsorption and dissociation processes of CO2 was performed on the surface of Ni/CaO dual‐functional materials (DFMs) based on density functional theory (DFT). The analyses of electron density, partial density of states, and formation energy suggest that the Ni/CaO model has higher stability and activity than the CaO model. The analyses of the evolution of chemical bonds, adsorption energy, density of states, and charge population after the adsorption of CO2 on the CaO surface and Ni/CaO shows that the modification with Ni made the adsorption of CO2 on Ni/CaO more stable. The transient calculations indicate that the path with the lowest activation energy is the H‐mediated dissociation path of chemisorption carboxyl COOH* as an intermediate, which is the possible dissociation path of CO2 on the surface of Ni/CaO DFMs. The dissociation of COOH* into CO* and OH* is the rate‐controlling step of the reaction. The DFT results demonstrate that the doping of Ni during the preparation of CaO materials can realize and enhance the CaL‐DRM processes, which provide a theoretical basis for the optimum preparation of Ni/CaO‐based DFMs. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, in situ hybrid (Al3Ni + Al2O3)/Al composites were prepared successfully by the solid-state combustion via Al–NiO system. The effects of Al3Ni + Al2O3 on the corrosion features of composites were analyzed using potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion corrosion in 3.5 wt% NaCl solution. The results show that with the increase of NiO addition, the corrosion resistance of composites is improved, and the corrosion resistance of 15 % NiO–Al composite is almost comparable to the Al matrix. The increased quantity and dispersive distribution of Al3Ni and Al2O3 particles can effectively prevent the occurrence of corrosion and the movement of free electrons. Besides, more fine Al2O3 particles distributed in grain boundaries can increase the impedance and hinder the electrochemical corrosion preferentially starting at the boundary. Also, in the composite with high NiO addition, a better and compact interface bonding can be formed due to reduction of large size Al3Ni particles and improvement in the dispersion of particles, thereby inhibiting interface damage. This study has advanced understanding of corrosion. [ABSTRACT FROM AUTHOR]

The pure H2 production procedure for polymer fuel cell applications by the chemical loop reforming of methanol in the presence of 0.3CoFe2O4-0.4ZrO2 as an oxygen carrier in a micro-channel reactor was studied and the results of this study showed that the production of pure H2 is possible only if the coke deposition is controlled. By optimizing the reduction time to 7 minutes, the coke deposition controlled and pure H2 flow was produced with an average yield of 2.6%, which was an interesting result and so far, this degree of purity of H2 has not been reported by the chemical loop reforming of methanol. To increase the yield of pure H2 in this study, a two-layer catalyst concept is proposed in the form of an additional layer coating with high resistance to coke and suitable reactivity with methanol from NiO/MgAl2O4 to 10% on 0.3CoFe2O4-0.4ZrO2 layer. Optimizing the reduction time using the concept of double-layer oxygen carrier showed that the use of 20% nickel concentration with a reduction time of 11 minutes increased the yield of H2 with 100% purity, which increased by 42% in the double-layer arrangement compared to the singlelayer state, and it is a promising result for the concept of double-layer oxygen carrier in this process. [ABSTRACT FROM AUTHOR]

Hydrogen has a key role to play in decarbonising industry and other sectors of society. It is important to develop low-carbon hydrogen production technologies that are cost-effective and energy-efficient. Sorption-enhanced steam methane reforming (SE-SMR) is a developing low-carbon (blue) hydrogen production process, which enables combined hydrogen production and carbon capture. Despite a number of key benefits, the process is yet to be fully realised in terms of efficiency. In this work, a sorption-enhanced steam methane reforming process has been intensified via exergy analysis. Assessing the exergy efficiency of these processes is key to ensuring the effective deployment of low-carbon hydrogen production technologies. An exergy analysis was performed on an SE-SMR process and was then subsequently used to incorporate process improvements, developing a process that has, theoretically, an extremely high CO2 capture rate of nearly 100 %, whilst simultaneously demonstrating a high exergy efficiency (77.58 %), showcasing the potential of blue hydrogen as an effective tool to ensure decarbonisation, in an energy-efficient manner.

The low-carbon, clean, and efficient utilization of the Zhundong coal is greatly limited by some severe problems such as ash accumulation, slagging, and CO2 emissions in the conventional combustion and utilization processes. The adoption of low-rank coal pyrolysis at low and moderate temperatures to produce semicoke, tar, and pyrolysis gas is a leading technology for the utilization of classified coal. Based on the characteristic of high alkali gasification activity of pyrolysis semicoke, the chemical-looping combustion technology is adopted to achieve a low-carbon, clean, and efficient conversion of the Zhundong coal semicoke. The in-situ gasification chemical-looping combustion characteristics of the Zhundong coal semicoke are studied in a fixed bed, in which CO2 is selected as the gasification agent and hematite is considered as the oxygen carrier. The study of migration and transformation laws of alkali and alkaline earth metals (AAEMs) in the Zhundong coal semicoke also is performed. The experimental result indicates that the addition of the hematite oxygen carrier can significantly improve the CO2 concentration of the flue gas at the outlet of the fixed bed reactor. However, CO2 concentration increases first and then remains constant with the increase in the mass ratio of the oxygen carrier and semicoke (mOC/mC). The optimal mOC/mC is determined as 50∶1. In this case, the CO2 selectivity of the flue gas at the outlet of the fixed-bed reactor is decreased by 8.95 percentage points at the pyrolysis temperature of 700 ℃ after acid washing and deashing treatment, indicating that the chemical-looping combustion performance of the Zhundong coal semicoke can be significantly affected by the catalytic activity of AAEMs in the semicoke. The distribution of AAEMs on the surface of the Zhundong coal semicoke is affected by the hematite oxygen carrier. Compared with the absence of the hematite oxygen carrier, more obvious cluster enrichment on the surface of semicoke for Na and K elements is found. An obvious dependency relationship for the distribution of Ca and Mg elements is observed. When the in-situ gasification chemical-looping combustion is adopted, the active AAEMs elements in the semicoke are migrated and transformed into hematite. High melting point minerals such as nepheline (NaAlSiO4), potassium feldspar (KAlSi3O8), gehlenite (Ca2Al2SiO7), and magnesium olivine (Mg2SiO4) are generated, effectively suppressing the volatilization of AAEMs in the Zhundong coal semicoke.

Effective decarbonization of the power generation sector requires a multi-pronged approach, including the implementation of CO2 capture and storage (CCS) technologies. The Graz cycle features oxy-combustion CO2 capture in a power production scheme which can result in higher thermal efficiencies than that of a combined cycle. However, the auxiliary consumption required by the air separation unit to provide pure O2 results in a significant energy penalty relative to an unabated plant. In order to mitigate this penalty, the present study explores the possibility of chemical looping combustion (CLC) as an alternative means to supply oxygen for conversion of the fuel. For a midscale power plant, despite reducing the levelized cost of electricity (LCOE) by approximately 12.6% at a CO2 tax of EUR 100/ton and a natural gas price of EUR 6.5/GJ and eliminating the energy penalty of CCS relative to an unabated combined cycle, the cost reductions of CLC in the Graz cycle were not compelling relative to commercially available post-combustion CO2 capture with amines. Although the central assumptions yielded a 3% lower cost for the Graz-CLC cycle, an uncertainty quantification study revealed an 85.3% overlap in the interquartile LCOE range with that of the amine benchmark, indicating that the potential economic benefit is small compared to the uncertainty of the assessment. Thus, this study indicates that the potential of CLC in gas-fired power production is limited, even when considering highly efficient advanced configurations like the Graz cycle. [ABSTRACT FROM AUTHOR]

Immobilized Pd‐catalyzed Suzuki‐Miyaura coupling under continuous‐flow conditions using a packed‐bed reactor, representing an efficient, automated, practical, and safe technology compared to conventional batch‐type reactions. The core objective of this study is the development of an active and durable catalyst. In contrast to supported Pd nanoparticles, the attachment of Pd complexes onto solid supports through well‐defined coordination sites is considered a favorable approach for preparing highly dispersed and stabilized Pd species. These species can be directly employed in various flow reactions without the need for pre‐treatment. This concept paper explores recent achievements involving the application of immobilized Pd complexes as precatalysts for continuous‐flow Suzuki‐Miyaura coupling. Our focus is to elucidate the significance of the designed catalyst structures in relation to their catalytic performance under flow conditions. Additionally, we highlight various reaction systems and catalyst packing methods, emphasizing their crucial roles in establishing a practical synthesis process. [ABSTRACT FROM AUTHOR]

During chemical looping combustion (CLC) and chemical looping gasification (CLG) of coal, the release, migration, and speciation of mercury in coal are significantly influenced by oxygen-carrier materials; however, the underlying mechanism remains inadequately addressed. In this work, the effect of a typical iron-based oxygen carrier on the release behavior of mercury from a bituminous coal and a lignite was investigated based on the Ontario-Hydro method. It is found that the effect of the iron-based oxygen carrier is attributed to three aspects: the enhanced release rate of mercury from coal, the adsorption of the released mercury, and the oxidization of gaseous Hg0 into Hg2+. With the increasing temperature, the adsorbance of mercury by the iron-based oxygen carrier decreases, while the oxidation of mercury enhances. Even at 900 °C, the adsorbance of mercury by the oxygen carrier remained at 0.1687 g/g, with a relative content of Hg2+ at 22.55%. Additionally, it was observed that iron-based oxygen carriers can physically absorb both Hg0 and Hg2+, while chemisorption refers to complex-compound formation between the iron-based oxygen carrier and mercury. [ABSTRACT FROM AUTHOR]

This study demonstrates the reaction behavior during the purification of model automotive exhaust gases over Pd catalysts before and after thermal degradation. In particular, to investigate the relationship between the Pd state and the reaction behavior of Pd/Al2O3 and Pd/CeO2−ZrO2 (CZ), operando X‐ray absorption spectroscopy measurements were performed during purifying exhaust gases over real and model catalysts mimicking the degradation of Pd particles and CZ supports after accelerated aging tests. The NO reduction activity of the aggregated Pd metal species was as high as that of the highly dispersed Pd species, but hydrocarbon (HC) poisoning was significantly enhanced by the aggregation of Pd metal particles caused by thermal aging. The existence of a three‐phase boundary (TPB) between the CZ, the Pd particles, and the gas phase strongly affected the catalytic activity at low temperatures, and the presence of a sufficient TPB facilitated the combustion of unburned HCs owing to the oxygen storage performance of CZ. Thus, the TPB reduced the poisoning of the precious metal surface by HC species at low temperatures. Therefore, the findings of this study will facilitate the development of next‐generation gas purification catalysts with high activity and durability. [ABSTRACT FROM AUTHOR]

To reach their net‐zero targets, countries will have to compensate hard‐to‐abate CO2 emissions through carbon dioxide removal (CDR). Yet, current assessments rarely include socio‐cultural or institutional aspects or fail to contextualize CDR options for implementation. Here we present a context‐specific feasibility assessment of CDR options for the example of Germany. We assess 14 CDR options, including three chemical carbon capture options, six options for bioenergy combined with carbon capture and storage (BECCS), and five options that aim to increase ecosystem carbon uptake. The assessment addresses technological, economic, environmental, institutional, social‐cultural and systemic considerations using a traffic‐light system to evaluate implementation opportunities and hurdles. We find that in Germany CDR options like cover crops or seagrass restoration currently face comparably low implementation hurdles in terms of technological, economic, or environmental feasibility and low institutional or social opposition but show comparably small CO2 removal potentials. In contrast, some BECCS options that show high CDR potentials face significant techno‐economic, societal and institutional hurdles when it comes to the geological storage of CO2. While a combination of CDR options is likely required to meet the net‐zero target in Germany, the current climate protection law includes a limited set of options. Our analysis aims to provide comprehensive information on CDR hurdles and possibilities for Germany for use in further research on CDR options, climate, and energy scenario development, as well as an effective decision support basis for various actors. Plain Language Summary: Countries aiming to achieve net‐zero emissions will have to remove the remaining carbon dioxide from the atmosphere through carbon dioxide removal (CDR). However, current assessments of CDR options rarely consider socio‐cultural or institutional aspects or set the CDR options in the specific context of their implementation. In this study, researchers conducted the first context‐specific feasibility assessment of CDR options in Germany, considering six dimensions, including technological, economic, environmental, institutional, and social‐cultural aspects. The study assessed 14 CDR options, including chemical carbon capture options, bioenergy combined with carbon capture and storage, and options to increase ecosystem carbon uptake. The study found that CDR options like cover crops or seagrass restoration face low implementation hurdles but have small CO2 removal potentials, while options like woody‐biomass combustion or mixed‐feedstock biogas production have high CDR potentials but face large economic and institutional hurdles. The analysis aims to provide comprehensive information on CDR options for use in further research and as an effective decision support basis for a range of actors. Key Points: More context‐specific assessments of carbon dioxide removal (CDR) options are needed to guide national net‐zero decision makingEcosystem‐based CDR options with comparably low implementation hurdles in Germany show relatively small CO2 removal potentialsHigh CDR potential options in Germany face high institutional, technological and societal hurdles linked in many ways to geological storage [ABSTRACT FROM AUTHOR]

Global population growth requires the use of various natural resources to satisfy the basic needs of humanity. Fossil fuels are mainly used to produce electricity, transportation and the artificial air conditioning of habitats. Nevertheless, countries around the world are looking for alternative energy sources due to the decrease in the availability of these fuels and their high environmental impact. The mixture of hydrogen and carbon monoxide (H2 + CO), commonly called syngas, is a high-value feedstock for various industrial applications. By varying the composition of syngas, especially the H2/CO molar ratio, it can be used to produce methanol, fuels or synthetic natural gas. However, when this ratio is very low, the separation of this gas usually represents a great problem when making the energy balance, which is why it is proposed to adapt a combustion process in chemical cycles, taking advantage of the energy of this gas, reducing the energy impact of the process. During the present project, mass and energy balances were developed for combustion in chemical cycles, using ilmenite as a carrier, integrating heat exchangers to take advantage of the residual energy at the output of the process, to preheat the inlet current in the regenerator. Here, a comparative was made at different temperatures of the air stream and evaluating the mechanism of the ilmenite when a syngas stream is used as fuel. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) impacts the greenhouse effect significantly and results in global warming, prompting urgent attention to climate change concerns. In response, CO2 capture has emerged as a crucial process to capture carbon produced in industrial and power processes before its release into the atmosphere. The main aim of CO2 capture is to mitigate the emissions of greenhouse gas and reduce the anthropogenic impact on climate change. Biopolymer nanocomposites offer a promising avenue for CO2 capture due to their renewable nature. These composites consist of biopolymers derived from biological sources and nanofillers like nanoparticles and nanotubes, enhancing the properties of the composite. Various biopolymers like chitosan, cellulose, carrageenan, and others, possessing unique functional groups, can interact with CO2 molecules. Nanofillers are incorporated to improve mechanical, thermal, and sorption properties, with materials such as graphene, carbon nanotubes, and metallic nanoparticles enhancing surface area and porosity. The CO2 capture mechanism within biopolymer nanocomposites involves physical absorption, chemisorption, and physisorption, driven by functional groups like amino and hydroxyl groups in the biopolymer matrix. The integration of nanofillers further boosts CO2 adsorption capacity by increasing surface area and porosity. Numerous advanced materials, including biopolymeric derivatives like cellulose, alginate, and chitosan, are developed for CO2 capture technology, offering accessibility and cost-effectiveness. This semi-systematic literature review focuses on recent studies involving biopolymer-based materials for CO2 capture, providing an overview of composite materials enriched with nanomaterials, specifically based on cellulose, alginate, chitosan, and carrageenan; the choice of these biopolymers is dictated by the lack of a literature perspective focused on a currently relevant topic such as these biorenewable resources in the framework of carbon capture. The production and efficacy of biopolymer-based adsorbents and membranes are examined, shedding light on potential trends in global CO2 capture technology enhancement. [ABSTRACT FROM AUTHOR]

Biogas results from the anaerobic digestion of organic materials, a reliable and sustainable process that simultaneously manages organic waste and generates renewable energy. However, the presence of secondary impurities, such as carbon dioxide (CO2) and other gases, in raw biogas diminishes its efficacy, significantly lowering its energy content and restricting its utility across industry sectors. Moreover, these impurities contribute to various health and environmental concerns, including their role in exacerbating climate change and global warming. Consequently, efficient separation of CO2 is essential for upgrading biogas. The interest in utilizing biogas as a transportation fuel or as a substitute for natural gas has spurred the advancement of biogas upgrading technologies. While various methods exist for biogas upgrading, those relying on carbon dioxide absorption stand out as particularly significant. Carbon capture efficiency in biogas upgrading pertains to the ability of a method to effectively capture and separate CO2 from biogas, typically composed of methane (CH4) and other gases. This process is crucial for producing high-quality biogas with minimal carbon emissions, thus promoting environmental sustainability. Enhancing the carbon capture efficiency of the biogas upgrading process is essential for reducing greenhouse gas emissions and promoting cleaner energy production. The efficacy of CO2 separation relies on adsorbents and adsorption isotherms, which are integral components of this process. Improving these elements is vital for enhancing biogas purity, ensuring its suitability for various applications, and mitigating its environmental footprint. Traditional methods enhance the carbon capture efficiency by employing adsorbents, such as zeolites and activated carbon, as well as by optimizing adsorption isotherms. Surface modifications and adjustments to process parameters have also led to improved CO2 selectivity over other gases. Traditional methods still have drawbacks, such poor selectivity, difficulties with regeneration, and scalability. These limitations draw attention to the necessity of ongoing optimization, investigating substitute materials, and gaining a thorough grasp of how capacities, kinetics, and selectivity interact. Adsorbents and adsorption isotherms are the main topics of this study's thorough analysis, which examines the state of the art in increasing carbon capture efficiency in biogas upgrading. It discusses conventional methods, their drawbacks, and suggests alternate materials, customized adjustments, and optimization techniques as a means of achieving ongoing progress. It is suggested that customized changes, ongoing optimization, and investigation of substitute materials be used to increase the effectiveness of carbon capture. To guarantee consistency, the study suggested specific rules for the procurement, preparation, and calcining of materials such as eggshells. In addition, to balancing CO2 and CH4 adsorption, improving adsorbent composition and addressing scalability, long-term stability, and practical implementation challenges are critical. The results of this study direct future studies toward a more sustainable and efficient energy landscape by adding to our understanding of carbon capture in biogas upgrading. [ABSTRACT FROM AUTHOR]

A new catalytic combustion hydrogen (H 2) sensor is developed using the electrodeposition method and the Pd catalyst layer is directly deposited on a Pt filament without carrier. The sensing performance was investigated by altering the electroplating time to control the thickness of the Pd catalyst layer. The sensitivity is changed with the increase of the Pd layer's thickness and the highest sensitivity (26.8) was obtained when the thickness is 1.635 μm. In addition, the new sensor exhibits great selectivity, while having the advantages of low power consumption (25 mW) and high vibration resistance. The achievement of this carrier-free sensor is expected to meet the requirement for H 2 energy vehicles. • A carrier-free catalytic combustion H 2 sensor has been fabricated using the electrodeposition method. • The influence of catalytic layer on sensing performance was discussed. • The vibration resistance of sensors was demonstrated. [ABSTRACT FROM AUTHOR]

Carbanion‐based ionic liquids are proposed and utilized as the key components for the construction of five super‐nucleophilic deep eutectic solvents (SNDESs) in the paper. The super‐nucleophilic nature of carbanion‐based ionic liquids (ILs) is found to enable the capture of CO2 with large absorption capacity. However, the absorption is very slow in the IL due to high viscosity. The synergy of carbanion siting and hydrogen bonding is found to enable high and fast absorption of CO2 in [N2222][CH(CN)2]‐ethylimidazole (Eim), and a synergistic absorption mechanism is proposed and validated from spectroscopic analyses and quantum calculations. The enthalpy change of CO2 absorption in [N2222][CH(CN)2]‐Eim is calculated to be −39.6 kJ mol−1 according to the thermodynamic model, and the moderate value implies that both absorption and desorption of CO2 in the DES are favored and well balanced. The carbanion and hydrogen bond mediated by SNDESs provides a novel insight into the efficient CO2 capture. [ABSTRACT FROM AUTHOR]

In this work, different proportions of N-doped carbon quantum dots/porous Co3O4 (NCQDs/p-Co3O4) NCQDs/Co3O4 composite photocatalysts were prepared by a simple self-assembly method. It was demonstrated by a series of characterizations that 50% NCQDs/Co3O4 has a good visible light response and low electrochemical impedance. The photocatalytic degradation of TC was investigated by the 50% NCQDs/p-Co3O4 composite photocatalyst, and the results showed that the degradation effect of TC reached 81.2% within 120 min. The higher photocatalytic activity of 50% NCQDs/p-Co3O4 was analyzed probably because NCQDs can improve the separation efficiency of photogenerated electron–hole pairs and p-Co3O4 can provide a larger specific surface area and thus has more active sites. This study provides a new strategy for improving the photodegradation activity of Co3O4 photocatalysts. [ABSTRACT FROM AUTHOR]

Hygroscopic and acidic nature of organic hole transport layers (HTLs) insisted to replace it with metal oxide semiconductors due to their favorable charge carrier transport with long chemical stability. Apart from large direct bandgap and high optical transmittance, ionization energy in the range of −5.0 to −5.4 eV leads to use NiO as HTL due to good energetic matching with lead halide perovskites. Analyzing X-ray photoelectron spectroscopic (XPS) data of NiO, it is speculated that p-type conductivity is related to the NiOOH or Ni2O3 states in the structure and the electrical conductivity can be modified by altering the concentration of nickel or oxygen vacancies. However, it is difficult to separate the contribution from nonlocal screening, surface effect and the presence of vacancy induced Ni3+ ion due to very strong satellite structure in the Ni 2p XPS spectrum of NiO. Thus, an effective approach to analyze the NiO XPS spectrum is presented and the way to correlate the presence of Ni3+ with the conductivity results which will help to avoid overestimation in finding the oxygen-rich/deficient conditions in NiO. [ABSTRACT FROM AUTHOR]

• Mixed Cu/Mg ferrites were characterized for the first time as oxygen carriers. • Positive impact of Mg doping on mechanical durability was proven. • Highest reaction rate toward fuel was achieved for Cu 0.75 Mg 0.25 Fe 2 O 4 (1.19 wt.%/min). • Mg-rich OCs exhibited increased reactivity toward fuel in 610–730 °C. Waste wood biomass is considered a renewable energy source. Combining biomass combustion with emerging clean combustion technologies such as chemical looping combustion (CLC) can yield effective and affordable carbon capture and, consequently, lead to negative net emissions of greenhouse gases. Oxygen carrier (OC) is a crucial material in CLC technology that must exhibit certain properties, such as high durability, good chemical stability during numerous red-ox cycles and, important for the combustion of solid fuels, the capability of spontaneously releasing oxygen in a process referred to as chemical looping with oxygen uncoupling (CLOU). In this work, a series of nine Cu x Mg 1-x Fe 2 O 4 spinel-based materials were synthetized and evaluated for the first time as potential OCs for a waste biomass combustion. Their properties, such as oxygen transport capacity and reactivity with biomass (wood chips) as a fuel, were evaluated in a function of temperature (900–1000 °C). Tested oxygen carriers were characterized with an excellent oxygen transport capacity in CLOU process (up to 2.78 wt%) and good reaction rates with the fuel (up to 1.19 wt. %/min), and regeneration rates (up to 3.8 wt. %/min). High conversion of the waste biomass was also achieved (98.9 %). Moreover, new findings revealed a strong positive effect of magnesium addition on mechanical strength (crushing strength > 4 N for samples with Mg content above 0.5). [ABSTRACT FROM AUTHOR]

Plastic waste has captured considerable attention in gasification studies as it not only generates precious syngas rich in hydrogen but also aids in mitigating the environmental concerns linked to these substances. The proposed system employs the process of plastic waste gasification (PWG) to generate synthetic gas, which undergoes processing within multiple subsystems. Crucially, this ingenious system uses the liberated heat from the biogas-fueled chemical looping combustion (CLC) to facilitate the efficient decomposition and gasification of the plastic waste, which the CLC holds great potential as a technology for capturing CO 2 without any energy penalty. In the Aspen Plus software, a comprehensive simulation is conducted for the proposed system, with a focus on detailed modeling of CLC. Through this analysis, it is determined that the optimal operating condition for CLC occurs at a molar ratio of 2.6 between the oxygen carrier and biogas. Also, the results show that the overall thermal and exergy efficiencies of the CLC-PWG system are found to be 77.08% and 67.62%, respectively. Regarding exergy destruction distribution, it is noteworthy that the air reactor significantly contributes to the highest proportion, accounting for 35.3% of the total exergy destruction. Subsequently, the fuel reactor and gasifier also play significant roles, accounting for 13.6% and 13.1%, respectively. In addition, the proposed system has a power, heat and hydrogen production rate of 97 kW, 388 kW and 105.6 kg/hr, respectively. Moreover, the thermodynamic efficiencies increase through the elevation of the gasification reactor temperature and the mass ratio of steam to plastic waste. [Display omitted] [ABSTRACT FROM AUTHOR]

Syngas tars are responsible for clogging and corrosion of pipelines and equipments due to their high condensation temperatures. At the same time, considering their energy content they cause a reduction in the energy efficiency of the conversion process. To overcome these drawbacks, the addition of a downstream reactor to perform hot catalytic gas cleaning has been proposed. However, the occurrence of significant carbon deposition and sulphide formation on the catalytically active surfaces can easily lead to early deactivation of the catalyst. Chemical looping tar reforming is based on a solid material, known as oxygen carrier, that undergoes two reactions steps: (1) reduction by interaction with the gas and tar streams; (2) regeneration by oxidation with ambient air, which also involves the combustion of any deposits on the particle surface. In this work, the first reaction step of the process is investigated in an integrated setup involving the pyrolysis or the gasification of hazelnut shells and the reaction with the oxygen carrier for tar abatement. Two reactor configurations have been considered: (1) single reactor, where the biomass and the oxygen carrier beds are loaded in series into the same reactor; (2) two reactors, where the two beds are loaded into different reactors in series. Blank tests for pyrolysis and gasification are also carried out for comparison. The results indicate that the two beds configuration enables higher tar conversion (89% wt for pyrolysis and 75% wt for steam gasification), though the presence of the oxygen carrier causes a reduction in the energy content of the syngas, especially in terms of H2 concentration, which is reduced from around 34% to 21% mol for pyrolysis and from 28% to 21% mol for steam gasification [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of H2O2 addition on OH radical formation on the surfaces of visible-light-irradiated BiVO4–TiO2 nanocomposite photocatalysts. Additionally, we examined the possible roles of OH radicals formed by the reduction reaction of H2O2 on the visible-light-irradiated surfaces of photocatalytic BiVO4–TiO2 nanocomposites. The BiVO4–TiO2 nanocomposite photocatalysts were prepared by mixing a BiVO4 photocatalytic film with commercially available semiconductor particulate TiO2 photocatalysts. By removing oxygen gas from the photocatalytic reactor, the effects of oxygen molecules on OH radical formation during the visible-light irradiation of BiVO4–TiO2 nanocomposite photocatalysts were examined. During visible-light irradiation, BiVO4 and BiVO4–TiO2 photocatalysts play different roles in OH radical formation because of two characteristic reduction reaction channels: (a) the direct reduction of H2O2 on photocatalytic surfaces and (b) the indirect reduction reaction of H2O2 by superoxide radical anions (O2−). [ABSTRACT FROM AUTHOR]

The redox kinetics of the oxygen carriers are crucial in Chemical‐Looping Combustion (CLC) systems. The random pore model (RPM) was widely used to investigate the macroscale redox kinetics of oxygen carriers in previous studies, in which the reaction rate constants were obtained just by fitting the experimental data. This study presents a first principle based rate equation (1pRE) applied to the RPM to calculate the reaction rate constants directly using density functional theory (DFT). The 1pRE is integrated with the RPM that accounts for the effect of pore size distribution derived from the surface area evolution of reaction interface and product layer diffusion, thus bridging the gap between the microscale elementary surface reactions and macroscale overall conversion. The developed 1pRE predicts the reduction kinetics of Fe2O3 oxygen carriers accurately, thereby facilitating the optimization of design processes for oxygen carrier materials and the scale up of CLC reactors. [ABSTRACT FROM AUTHOR]

Climate change caused by the greenhouse gases CO2 remains a topic of global concern. To mitigate the excessive levels of anthrophonic CO2 in the atmosphere, CO2 capture methods have been developed and among these, adsorption is an especially promising method. This paper presents a series of amine functionalized biochar obtained from desiccated coconut waste (amine-biochar@DCW) for use as CO2 adsorbent. They are ethylenediamine-functionalized biochar@DCW (EDA-biochar@DCW), diethylenetriamine-functionalized biochar@DCW (DETA-biochar@DCW), triethylenetetramine-functionalized biochar@DCW (TETA-biochar@DCW), tetraethylenepentamine-functionalized biochar@DCW (TEPA-biochar@DCW), and pentaethylenehexamine-functionalized biochar@DCW (PEHA-biochar@DCW). The adsorbents were obtained through amine functionalization of biochar and they are characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Brunauer–Emmett–Teller (BET), and thermogravimetric analysis (TGA). The CO2 adsorption study was conducted isothermally and using a thermogravimetric analyzer. From the results of the characterization analyses, a series of amine-biochar@DCW adsorbents had larger specific surface area in the range of 16.2 m2/g–37.1 m2/g as compare to surface area of pristine DCW (1.34 m2/g). Furthermore, the results showed an increase in C and N contents as well as the appearance of NH stretching, NH bending, CN stretching, and CN bending, suggesting the presence of amine on the surface of biochar@DCW. The CO2 adsorption experiment shows that among the amine modified biochar adsorbents, TETA-biochar@DCW has the highest CO2 adsorption capacity (61.78 mg/g) when using a mass ratio (m:m) of biochar@DCW:TETA (1:2). The adsorption kinetics on the TETA-biochar@DCW was best fitted by the pseudo-second model (R2 = 0.9998), suggesting the adsorption process occurs through chemisorption. Additionally, TETA-biochar@DCW was found to have high selectivity toward CO2 gas and good reusability even after five CO2 adsorption–desorption cycles. The results demonstrate the potential of novel CO2 adsorbents based on amine functionalized on desiccated coconut waste biochar. [ABSTRACT FROM AUTHOR]

The low electronic conductivity of hematite (α-Fe2O3) limits its best performance in many applications. Though highly reducing conditions induce an intrinsic n-type behavior, reaching extremely low oxygen partial pressure (p O 2) values is not practical. Alternatively, certain dopants provide hematite with excess electrons at practical p O 2 values. This study employs density functional theory with thermodynamic analysis to compute the concentration of electronic defects in hematite as a function of p O 2 , upon doping with 1% of 3d, 4d, and 5d transition metals. Isothermal Kröger–Vink diagrams at 1100 K are plotted to reveal the charge compensation mechanism controlling the electronic carriers in doped hematite and the maximum attainable p O 2 value, which achieves approximately one electron per dopant. A higher p O 2 value is a metric for an effective donor. Ti, Zr, Hf, Nb, Ta, Mo, and W are shown to be effective donors, especially Nb, Ta, and W, which achieve a 1:1 electron/dopant ratio around atmospheric pressure and a maximum electron/dopant ratio greater than one. The latter is a new metric introduced in this study to quantify the doping efficacy of a donor. Moreover, our study shows that W, Ta, and Nb co-doping in specific percentages with any of the other investigated dopants ensures the n-type behavior of the co-doped hematite while opening the possibility of improving other properties via the other dopant. The other dopant can be Ni or Co to enhance the surface catalytic properties or Zn to increase the minority hole carriers. Both properties are desirable in applications such as photoelectrochemical cells. [ABSTRACT FROM AUTHOR]

Green Hydrogen emerges as a promising energy solution in the quest for achieving Net Zero goals. The application of particulate semiconductors in photocatalytic water splitting introduces a potentially scalable and economically viable technology for converting solar energy into hydrogen. Overcoming the challenge of efficiently transferring photoelectrons and photoholes for both reduction and oxidation on the same catalyst is a significant hurdle in photocatalysis. In this context, we introduce highly efficient crystalline elemental boron nanostructures as photocatalysts, employing a straightforward and scalable synthesis method yield green hydrogen production without the need for additional co-catalysts or sacrificial agents. The resulting photocatalyst demonstrates stability and high activity in H 2 production, achieving over 1 % solar-to-hydrogen energy conversion efficiency (>15,000 μmol. g−1.h−1) during continuous 12-h illumination. This efficiency is credited to broad optical absorption and the crystalline nature of boron nanostructures, paving the way for potential scale-up of reactors using crystalline boron photocatalysts. [Display omitted] • Inexpensive, scalable, and novel synthesis process for Non-metallic single element catalysts. • Wide range optical absorption (UV–Vis–NIR). The H 2 production was achieved by only illuminating visible and NIR regions of light. • The H 2 production efficiency is more than 15,000 μM/gm/hr. • The high yield of H 2 production was achieved without the aid of co-catalysts and sacrificial reagents. • Long term stable performance H 2 production over 72 h is reported. [ABSTRACT FROM AUTHOR]