Search Results (1,712)

Controlling molecular catalyst speciation under reaction conditions can be an effective approach for extending catalyst lifetimes and controlling selectivity. Anchoring molecular catalysts to solid supports, to generate hybrid catalysts, is a means for preventing bimolecular catalyst interactions and preventing the formation of catalyst species such as dimers and multimers. Here we compare a series of different anchoring motifs for molecular nickel catalysts bound to metal oxide supports. The catalysts are anchored to the supports through functional groups on the ligand framework, and carboxylate, ester, and silanol groups are compared in terms of synthetic ease, anchoring stability, catalyst loading on the surface, and catalytic behavior with respect to Suzuki–Miyaura cross-coupling. The results show that covalent bonds between the molecular catalysts and the oxide support lead to increased catalyst surface loadings and higher surface loading, which helps avoid mass transport limitations during catalysis. In addition, the metal–ester-bound catalysts exhibit support-dependent reactivity, which is unique and different from the carboxylate and silanol anchoring groups. Infrared and X-ray photoelectron spectroscopy are used to characterize the molecular nature of the catalysts, and reactivity trends show that the covalent bonding of the catalysts to the surface controls catalyst speciation with respect to geometry and valency, which influences catalytic activity. Full article

Methane cracking has emerged as a promising route for sustainable hydrogen production because it avoids direct carbon dioxide emissions while simultaneously enabling carbon sequestration in the form of solid carbon. In this work, a comprehensive and systematic experimental investigation of catalytic methane cracking was performed by directly comparing a commercial nickel catalyst (KATALCO™ 25-4MQ), an in-house catalyst prepared by wet impregnation using Fe(NO₃)₃·9H₂O as the iron precursor and Puralox SCFa-160 Ce20 as the support, and non-catalytic thermal conditions under identical operating parameters. Experiments were carried out in a laboratory-scale fixed-bed reactor at atmospheric pressure by varying methane partial pressure (0.1–0.2 atm) and operating temperature (600–800 °C), while maintaining a constant methane-specific WHSV of 0.3 h⁻¹. Continuous online gas analysis was employed to monitor reactor performance, and a dedicated post-processing methodology, including nitrogen-tracer-based carbon balance calculations, was developed to validate the experimental results. The results demonstrated the strong beneficial effects of both temperature and catalytic materials on methane decomposition. The Fe-based catalysts exhibited the highest performance, achieving average methane conversions and hydrogen yields approaching 50%, with peak values exceeding 90% under the most favorable conditions. Commercial Ni catalysts also showed promising activity, although a more pronounced deactivation tendency was observed during prolonged operation. Conversely, non-catalytic tests resulted in substantially lower performance. Overall, this work provides an experimentally assessed and integrated methodology together with benchmark performance indicators that may serve as useful guidance for researchers, process designers, and practitioners involved in the development, optimization, and future scale-up of methane cracking technologies for turquoise hydrogen production. Full article

Sulfur hexafluoride (SF₆) serves as an essential insulating and arc-extinguishing medium in power facilities, while it is an extremely potent greenhouse gas with an ultra-long atmospheric lifetime. To realize efficient medium-temperature harmless disposal of waste SF₆, two-dimensional stable C₄N monolayers were adopted as substrates to load ZnO and CuO nanoparticles for composite catalyst fabrication. XRD, TEM, and EDS characterizations confirmed the uniform dispersion of the metal oxides without destroying the C₄N two-dimensional skeleton. Comparative experiments proved that an NH₃ reducing atmosphere significantly accelerates SF₆ decomposition. The 3:1 CuO-modified catalyst achieved a maximum SF₆ conversion of 91%, and a CaO additive effectively restrained high-temperature sintering and irreversible HF halogen poisoning, boosting overall catalytic efficiency by approximately 30%. DFT adsorption simulations revealed totally different active centers: hollow sites dominate ZnO-C₄N with broad adsorption capacity for SO₂, SO₂F₂, and other fluorinated intermediates, whereas surface O sites of CuO-C₄N exhibit exclusive strong chemisorption toward SO₂. Combined with macroscopic kinetics and atomic-scale interfacial interaction rules, their distinct stepwise defluorination pathways were illustrated. This study offers solid experimental data and microscopic theoretical guidance for designing advanced C₄N-based catalysts for waste SF₆ abatement. Full article

This study provides the main performance estimates for new concepts, using flexible gasification operation modes, adaptable to prevailing market conditions, for the production of bio-synthetic natural gas (bio-SNG) and biochar from biogenic residues and waste, such as bark, straw, and Solid Recovered Fuel (SRF). Dedicated integrated process models were developed in Aspen Plus based on and validated against data from experimental campaigns in a gasification and gas cleaning pilot plant. Simulation runs show that the proposed concepts convert biomass to bio-SNG 10% more efficiently than the reference case, mainly due to the considerably reduced oxygen demand at the Autothermal Reformer (ATR) enabled by the improved catalyst. The co-production mode schemes showed promising results in terms of overall plant efficiency, at 76.5–78.2%, and total carbon utilisation, at 41–55.3%. The hybrid cases require an electrolyser with a power capacity almost 70% of the biomass thermal input to the gasifier, resulting in a total electricity consumption of up to 0.769 kWhe/kWh of biofuel. In return, they achieve over 50% utilisation of the carbon contained in the feedstock for biofuel production and a 70.1–76.5% total plant energy efficiency. Efficient biofuel and biochar production unlock negative emission potential, further strengthening the value of these flexible concepts. Full article

The ever-increasing output of coal gasification slag from coal gasification technology has created an urgent need for its efficient disposal. In this study, the fine-slag fraction is uti-lized as a precursor to prepare a carbon electrocatalyst for Li-O₂ batteries. Residual carbon was extracted from coal gasification fine slag via an integrated alkali-acid co-activation process. Subsequently, hydrothermal modification reconstructed the carbon microstructure and strengthened its coupling with intrinsic Ca-containing species. The as-prepared slag-derived catalyst improved oxygen-reaction kinetics at the battery cathode and effectively reduced polarization. The Li-O₂ cells delivered a low charge–discharge voltage gap of 1.02 V, a high discharge specific capacity of 9480 mAh g⁻¹, and stable long-term cycling for more than 870 h. The enhanced electrochemical performance arises from the synergistic interplay among the reconstructed carbon framework, surface defects, oxygen-containing functional groups, and Ca-containing species, with the latter serving as a major source of active sites for the oxygen electrocatalytic reactions. This work establishes a resource-utilization pathway from coal gasification slag to high-end energy-storage applications, aligning with green development goals to address both mining-area energy demands and solid-waste pollution. Full article

The Zeta-Minimizer Theorem provides a fully deductive variational foundation for the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Starting from three primitive thermodynamic axioms and the helical geometry of the phase functional, a multi-extent dynamical system is constructed that simultaneously treats the electrochemical reaction coordinates and the adsorption extents of the participating species at the solid–electrolyte interface. The combined Hessian of the phase functional yields a complete spectrum of relaxation rates whose eigenvalues and eigenvectors emerge directly from the solid blackbox constants C_k and the helical partition functions of the reactive species. Adiabatic elimination of the fast surface modes produces an effective single-extent description in which voltage (or overpotential) appears as the conjugate variable, exactly analogous to the role of pressure in the corresponding gas-phase ammonia synthesis framework. The resulting nonlinear rate law is thermodynamically consistent at all conditions, recovers the Butler–Volmer and Tafel forms as well-defined limiting cases, and incorporates the effects of temperature, dilution, and catalyst-specific interface constants without empirical activation energies or adjustable reaction orders. The framework therefore unifies equilibrium, kinetics, and modal dynamics of HOR and ORR within a single variational structure, offering a parameter-light, first-principles alternative to classical empirical electrocatalytic rate expressions while preserving transparent contact with established limiting laws. Full article

Thermochemical conversion of nitrogen- and sulfur-rich biomass-derived wastes, such as sewage sludge, algae, and agricultural residues, is a promising route for renewable fuel production and waste valorization. However, fuel-bound nitrogen can be released as NH₃, HCN, and HNCO, while sulfur species such as H₂S, SO₂, and COS accelerate catalyst deactivation and generate NO_x/SO_x precursors. Metal-loaded ZSM-5 catalysts are attractive for clean catalytic pyrolysis because they combine the MFI pore confinement and tunable Brønsted/Lewis acidity of ZSM-5 with the hydrogen transfer, dehydrogenation, cracking, redox, and sulfur-tolerance functions of metal species. This review critically summarizes recent advances in metal-loaded ZSM-5 catalysts for catalytic denitrogenation of biomass-derived solid wastes. The formation and migration of NH₃, HCN, HNCO, tar-N, and char-N are first discussed to clarify the chemical basis of fuel-N conversion. The effects of ZSM-5 pore structure, acid-site distribution, Si/Al ratio, hierarchical porosity, and synergy on adsorption, diffusion, C-N bond cleavage, heterocyclic-N ring-opening, aromatization, and nitrogen redistribution are then analyzed. Catalyst deactivation under realistic pyrolysis atmospheres is also highlighted, including coke deposition, metal sintering, framework dealumination, mineral poisoning, and H₂S/SO₂/COS-induced sulfur poisoning. Finally, future directions are proposed for designing multifunctional ZSM-5-based catalysts integrating denitrogenation activity, sulfur resistance, coke resistance, regenerability, and quantitative nitrogen/sulfur mass balance. Full article

Hydrogen storage represents a key technological challenge to the widespread use of hydrogen as a fuel and energy carrier. For this purpose, the hydrogen storage properties of medium-entropy and high-entropy alloys are under extensive investigation, including the study of the effects of compositional variations, nanostructuring, and catalyst additions. The present work characterizes the hydrogen storage behavior of a medium-entropy, near equiatomic Ti-V-Cr-Mn alloy, both in the as-cast condition and after nanostructuring by severe plastic deformation. The alloy consists of a matrix of BCC solid solution and a dispersed C14 Laves phase. Processing by high-pressure torsion results in the refinement of the crystallite size of the BCC phase down to about 30 nm. The absorption capacity of the alloy at 45 °C and 2.5 MPa is 1.6 wt%. Regardless of its initial condition, the first hydrogenation of the Ti-V-Cr-Mn alloy at room temperature and 2.5 MPa occurs without any pre-activation treatment. On the other hand, hydrogen is partially released at room temperature, while full dehydrogenation requires a temperature of 300 °C. Severe plastic deformation considerably reduces the susceptibility of the alloy to become deactivated for hydrogen absorption. These results highlight the potential of plastic straining to tailor the hydrogen storage properties of metallic BCC alloys. Full article

Performance and durability of solid oxide cells are ruled by surface and interface phenomena occurring under operation. Electrode elementary reactions involve adsorption, charge transfer, surface diffusion and incorporation processes that are sensitive to the applied operating conditions and defect concentration. However, key degradation mechanisms such as cation segregation, catalyst deactivation, phase transformations and microstructural evolution originate at/near the electrode surface. Consequently, understanding the surface chemistry of electrode materials is essential for the development of the next generation electrodes. In this frame, Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) has emerged as a powerful tool to probe chemically active surfaces under more realistic environments, thus correlating surface science and electrochemistry. This review covers the principles of NAP-XPS and its application to solid oxide cell materials, including ceria-based model electrodes, Ni-containing fuel electrodes, exsolved perovskites and mixed ionic-electronic conducting air electrodes. NAP-XPS demonstrated the ability to directly monitor the dynamic state of the electrode surface under controlled operating conditions. Common mechanistic insights and emerging trends are highlighted, together with potential limitations associated with current experimental configurations. Overall, combined NAP-XPS and electrochemical analyses appear to hold the potential for linking surface chemistry with electrode performance and degradation, thus supporting the rational design of the next-generation solid oxide cell materials. Full article

Co–Mg–Fe oxide systems are promising candidates for thermally stable deep oxidation catalysts because they potentially combine redox-active cobalt and iron components with stabilizing magnesium-containing phases. In this work, phase formation in a Co–Mg–Fe oxide system obtained by thermal decomposition of nitrate precursors with a Co:Mg:Fe ratio of 1:1:1 was studied over a wide range of heat-treatment temperatures from 400 to 1300 °C. The samples were characterized by X-ray diffraction, Mössbauer spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy mapping, and temperature-programmed oxygen desorption. The results show that the system undergoes staged phase evolution. At 400 °C, α-Fe₂O₃, including Mg-modified hematite-like states, cobalt-containing spinel phases, and a rocksalt oxide phase, is formed. Starting from 550 °C, a mixed ferrite spinel phase appears and its content increases with temperature. The transition through 800–900 °C is accompanied by decomposition of cobalt-containing spinels, a sharp change in the inversion parameter of the mixed ferrite, and formation of a stable high-temperature combination of ferrite spinel and rocksalt oxide solid solution. Oxygen desorption is most pronounced for the low- and medium-temperature samples and decreases strongly after high-temperature treatment. The obtained results provide the basis for the design of thermally stable Co–Mg–Fe oxide catalysts for deep oxidation processes. Full article

Antibiotic residues pose a serious threat to environmental safety. In this study, nitrogen/boron co-doped biochar (NBLB) was successfully prepared using lignosulfonate, an industrial byproduct, as the precursor via a one-step impregnation–pyrolysis method. NBLB was applied to activate peroxymonosulfate (PMS) to degrade tetracycline (TC) in water. The results showed that NBLB-activated PMS degraded 93.4% of TC within 60 min, which was 42.6%, 20.4%, and 27.8% higher than those of undoped biochar, nitrogen-doped biochar, and boron-doped biochar, respectively. Additionally, the NBLB/PMS system exhibited high tolerance to common aqueous anions such as Cl⁻, $\mathrm{C}{\mathrm{O}}_3^{2-}$, ${\mathrm{PO}}_4^{3-}$, ${\mathrm{NO}}_3^{-}$ and $\mathrm{S}{\mathrm{O}}_4^{2-}$. BET tests indicated that the specific surface areas of undoped, N-doped, B-doped, and NBLB were 133.98, 280.22, 304.13, and 342.35 m² g⁻¹, respectively, exhibiting a significant enhancement in the specific surface area of NBLB. The co-doping of N and B constructed a hierarchical pore structure, providing an efficient dispersion platform for active sites such as C=O, BC₂O, and pyridinic-N. Quenching experiments and EPR detection demonstrated that the degradation of tetracycline (TC) in the NBLB/PMS system followed a synergistic oxidation mechanism dominated by ¹O₂ and ${\mathrm{O}}_2^{•-}$, supplemented by ^•OH and $\mathrm{S}{\mathrm{O}}_4^{•-}$. This study prepared high-performance nonmetallic catalysts through a solid waste resource utilization strategy, providing a green and feasible path for the treatment of antibiotic pollution. Full article

Methane is an abundant energy carrier and carbon resource. However, its efficient utilization remains challenging because the strong C-H bonds in methane hinder low-temperature activation, whereas high-temperature conversion often leads to undesired side reactions and reduced product selectivity. Solid oxide cells (SOCs) provide a promising platform for methane conversion by integrating high-temperature electrochemistry, catalytic reactions, and ion transport within a single system, enabling efficient energy and chemical production. This review summarizes recent advances in SOC-based methane conversion through three representative pathways: direct electricity generation in methane-fueled solid oxide fuel cell (SOFC), syngas production via SOC-assisted methane reforming, and value-added C₂ hydrocarbon synthesis through methane oxidative coupling in solid oxide electrolysis cell (SOEC). For methane-fueled SOFC, the relationships among fuel-electrode materials, microstructural characteristics, carbon deposition behavior, and electrochemical performance are discussed, together with current strategies for improving carbon resistance and operational stability. In methane reforming and upgrading processes, SOCs can regulate oxygen-ion transport, local reaction environments, and electrode reaction pathways, thereby enhancing methane conversion and product selectivity toward syngas, hydrogen, and C₂ hydrocarbons. The roles of electrode design, catalyst development, and operating conditions in determining reaction performance are also highlighted. Finally, the major challenges facing SOC-based methane conversion are critically discussed. Future research directions involving advanced electrode materials, microstructure engineering, and multiscale modeling are proposed to support the development of efficient and durable SOC technologies for methane utilization. Full article

The conversion of waste textiles into valuable products is an effective route to mitigate low-value solid waste accumulation and recover energy. In this work, nickel and potassium were introduced into textile waste via an impregnation method, and their roles in microwave-assisted catalytic pyrolysis were investigated with a focus on hydrogen production. The results show that co-loading 1 wt.% Ni and 0.4 wt.% K significantly enhances gas formation, with a total gas yield of 67.47% and a hydrogen yield of 52.57 mmol/g. Hydrogen production was markedly improved compared with the untreated textiles, the physical mixing methods, and the conventional pyrolysis. Structural characterization by XRD and SEM mapping confirmed that K addition effectively suppressed the agglomeration of Ni species. FTIR analysis suggests that a synergistic catalytic effect between K and Ni promotes the conversion of macromolecular components into smaller gaseous products. The improved hydrogen production can be associated with the combined effect of enhanced Ni dispersion and promoted decomposition reactions. This work provides new insights into the design of alkali-promoted Ni catalysts for efficient hydrogen production from textile waste under microwave pyrolysis conditions. Full article

This study used red mud (RM), steel slag (SS), and desulfurization slag (DS) as raw materials to construct three catalytic oxidation systems, namely RM-DCDA/H₂O₂, SS-DS/H₂O₂, and SS-DS/peroxymonosulfate (PMS), to promote the utilization of industrial solid waste and enhance the treatment of recalcitrant antibiotic wastewater. The ciprofloxacin (CIP) degradation performances, influencing factors, and preliminary reaction mechanisms of these systems were investigated. RM formed an Fe₃N/C composite structure after acidification and dicyandiamide-assisted calcination. The Fe₃N active phase, coexistence of Fe²⁺/Fe³⁺, and N-doped C structure facilitated H₂O₂ activation and electron transfer. The SS-DS catalyst exhibited a rough and porous structure and contained Fe, Ca, and S species, which could provide reactive sites for H₂O₂ and PMS activation, following acid modification and urea-assisted calcination. Under the necessary reaction conditions, the CIP degradation efficiencies of the RM-DCDA/H₂O₂, SS-DS/H₂O₂, and SS-DS/PMS systems reached 94.60%, 92.58%, and 95.17%, respectively. These results indicate that RM- and SS-derived materials can be used for CIP oxidative degradation; however, the values should not be interpreted as a strict comparison of the intrinsic catalytic activity because the operating conditions differed among the systems. Parametric experiments showed that the catalyst dosage, oxidant concentration, and initial pH influenced the degradation efficiency. The H₂O₂-based systems were more suitable under acidic conditions, whereas the SS-DS/PMS system showed wider pH adaptability. Coexisting anion and humic acid experiments indicated that the systems were tolerant to natural organic matter, whereas HCO₃⁻ and HPO₄²⁻ inhibited degradation. CIP was further oxidized in total organic C and recycling experiments; however, it was difficult to completely mineralize it within a short reaction time, and the catalyst retained relatively high activity after repeated use. Radical quenching experiments suggested that ·OH and ·O₂⁻ participated in the degradation reactions in the RM-DCDA/H₂O₂ and SS-DS/H₂O₂ systems. In the SS-DS/PMS system, comparative quenching experiments revealed that non-radical singlet oxygen (¹O₂) was the dominant reactive species, while SO₄⁻· and ·OH contributed only marginally. In conclusion, RM and SS-DS can be used as low-cost raw materials to prepare industrial solid-waste-derived catalysts for the oxidative degradation of CIP, thereby providing a reference for industrial solid waste valorization and antibiotic wastewater treatment. Full article

Hydrolysis of cellulose to produce ethanol has become an effective way to utilize biological resources, but its large-scale industrial application has been limited. In this study, a one-pot catalytic conversion process for transforming cellulose into ethanol was developed. Meanwhile, multifunctional Mo/Pt/WO_x/Al₂O₃ catalysts were prepared by loading nano-alumina (Nano-Al₂O₃) via a stepwise impregnation method. The influence of catalysts with varying metal ratios on the types of products generated during the cellulose hydrolysis process to ethanol was examined. The catalyst with 0.1% Mo, 2% Pt, and 7.5% W loadings showed the best selectivity. With an ethanol yield of 45.3% after heating at 5 MPa H₂ and 518 K for 2 h. Nano-Al₂O₃ can provide suitable active sites. The addition of W⁵⁺ and Mo⁰ increased the surface oxygen vacancy density and enhanced the hydrodeoxidation and metal anchoring capacity of the catalyst. The solid solution structure facilitates electron transfer from W and Mo atoms to Pt atoms, forming electron-rich Pt^δ- species, promoting the hydrolysis of cellulose and the formation of ethanol. Full article