Search Results (1,859)

The thermal decomposition performance of ammonium perchlorate (AP) is a key factor in regulating the combustion of composite solid propellants, and its catalytic decomposition process is considered a typical multiphase catalytic process. The exposure of catalytic centers during multiphase catalysis is a key factor affecting catalytic performance. In response to the problem of low atomic utilization efficiency of traditional metal oxide catalysts, this study successfully prepared nitrogen-doped carbon-supported single-atom cobalt catalyst (SACo-PC-X) using the “zinc volatilization pore formation and nitrogen anchoring” method with inexpensive biomass as the precursor. Aberration-corrected transmission electron microscopy, together with XPS and XRD analyses, suggests that Co species are predominantly stabilized in an atomically dispersed Co-N_x configuration. This catalyst exhibits excellent catalytic performance for the thermal decomposition of AP, significantly reducing its high-temperature decomposition temperature from 433.5 °C to 322.7 °C (The cobalt content in the system is less than 0.2%). Gas studies have shown that Co-N_x sites efficiently accelerate the oxidation process of NH₃ by promoting electron transfer, resulting in a significant increase in the proportion of N₂O gas. This work not only provides an efficient and stable new catalyst for AP decomposition, but also offers new ideas for designing energetic material decomposition catalysts at the atomic level. Full article

A sustainable and scalable one-pot impregnation protocol, avoiding high-temperature calcination/activation, was employed to prepare Pd/Al₂O₃ (0.24 wt%), Pd/TiO₂ (0.18 wt%), Pd/ZrO₂ (0.21 wt%), Pd/SiO₂ (0.37 wt%), Rh/Al₂O₃ (0.18 wt%), and Rh/TiO₂ (0.15 wt%). Support effects on activity, selectivity, and recyclability of these low-metal content heterogeneous catalysts were investigated, using (E)-cinnamaldehyde and levulinic acid as probe molecules. In cinnamaldehyde hydrogenation, Pd catalysts were highly effective for chemoselective C=C reduction to 3-phenylpropanal under mild conditions, with Pd/TiO₂ displaying the highest activity and robust performance over several recycles. However, the Lewis acidity of TiO₂ promoted a solvent-involving side reaction in 2-propanol, with hemiacetal and ether formation, highlighting that apparent selectivity is strongly shaped by support acidity and product residence time. Rh/Al₂O₃ exhibited lower activity than Pd analogues but near-quantitative selectivity to the saturated aldehyde, whereas Rh/TiO₂ again favored hemiacetal formation. In levulinic acid hydrogenation, Pd catalysts were essentially inactive toward ketone hydrogenation even at elevated temperature and H₂ pressure, while Rh catalysts achieved high productivity with exclusive formation of γ-valerolactone, Rh/Al₂O₃ being the most active at comparatively mild pressures. Full article

Nitrophenols, despite their wide synthetic utility in the specialty chemical industry, are recognized as toxic and can pose a serious environmental hazard. A popular strategy for the purification of wastewater containing nitrophenols is their catalytic reduction to the corresponding aminophenols in the presence of supported transition metal catalysts. However, the practical application of such systems is hindered by tedious catalyst manufacturing protocols and strong dependence on the catalyst/support microstructure. Herein, a series of CoO_x@SiO₂ composites was prepared by a direct reduction of aqueous solutions of Co(II) salts (Co(OAc)₂, CoCl₂, and CoF₂) with fumed silica having a triethoxysilane-modified surface. The prepared composites, despite the observed low cobalt content (0.1–0.2 wt%), proved highly effective in reducing 2-nitrophenol to 2-aminophenol, demonstrating a cost-effective, readily available non-precious-metal-based system for the remediation of nitrophenols from contaminated water. Full article

Direct methanol fuel cells (DMFCs) have attracted considerable attention recently for various applications ranging from portable ones to transportation. The efficiency of DMFCs depends on the kinetics of anodic and cathodic electrocatalysts. Due to sluggish anodic methanol oxidation reaction (MOR), DMFCs require an effective and bifunctional catalyst for promoting efficient MOR. The state-of-the-art MOR catalysts, such as Pt/C and Pt-Ru/C, have been shown to exhibit reasonable MOR activity; however, the insufficient mass activity and poor stability of carbon-supported catalysts have been a major limitation, requiring an alternative, efficient, electrocatalyst that exhibits high mass and specific activities. In addition, electrocatalysts without any carbon support (self-supported electrocatalysts) further mitigate their poor stability and therefore enhance their durability. In this regard, metal aerogel catalysts, which are entirely composed of metallic networks, recently attained special interest due to their specific advantages over conventional carbon supports, such as high catalyst utilization and improved electronic conductivity and stability. In this review, we systematically reviewed various metal aerogel catalysts developed for MOR since their first discovery in 2009. The metal aerogel demonstrated superior MOR performance relative to carbon-supported commercial catalysts, with enhancements ranging from 2-fold to 22-fold of mass activity. We also statistically compared the mass activity of metal aerogels with traditional carbon-supported, non-carbon-supported, and advanced shape-controlled catalysts and found that metal aerogels exhibited high mass activities compared to other catalyst systems. Therefore, we clearly establish that metal aerogel catalysts possess great potential as efficient MOR catalysts in DMFCs. In addition, we have provided several future research directions and strategies for further development of metal aerogel-integrated DMFC devices. Full article

Regulation of surface acidity is critical for steering reaction pathways in catalytic biomass conversion; however, the modulation of Lewis acidity in MXene-supported single-atom catalysts remains poorly understood. In this work, density functional theory calculations were performed to systematically investigate how surface terminations coupled with metal identity govern the Lewis acidity of single-atom sites on Ti₃C₂-based MXenes. Two representative terminations (-O and -OH) were considered, and various metal atoms were anchored to construct single-atom catalysts. Formation energies were evaluated to assess thermodynamic stability, while NH₃ adsorption energies were employed as a descriptor for Lewis acidity. The results reveal a pronounced termination-dependent modulation of acidity. Specifically, -OH termination disfavors single-atom stabilization, whereas -O termination ensures strong anchoring. Electronic structure analysis indicates that enhanced acidity originates from termination-induced electronic polarization and charge redistribution. This work establishes a structure–termination–acidity relationship and provides theoretical guidance for the rational design of MXene-based catalysts with tunable acidity. Full article

The great impact of carbon dioxide emissions on climate change motivates the development of technologies for carbon capture and utilization. CO₂ methanation, which transforms CO₂ into methane using renewable hydrogen, is a promising power-to-gas and carbon utilization pathway. Achieving high activity, strong CH₄ selectivity, and long-term stability remains challenging, as well as pushes to tailor catalyst properties for the methanation reaction. Cerium oxide is therefore widely explored as a support or promoter due to its redox behaviour and oxygen vacancy chemistry. This review surveys recent literature on catalysts based and containing CeO₂ applied for CO₂ methanation, covering not only thermal operation but also non-conventional catalytic routes as photothermal, electrocatalytic, and plasma-assisted, with emphasis on how synthesis and role of Ce tune physicochemical properties and catalytic activity. Across reported systems, dispersing active metals (notably Ni and Ru, Cu for electrochemical systems) on ceria frequently yields to high CH₄ selectivity. Redox properties of ceria enable optimal metal–support interactions and surface basicity to achieve effective CO₂ activation in thermo-catalytic route. Further enhancement of oxygen mobility is associated with doped CeO₂ and solid solutions such as Ce-Zr. The high oxygen storage capacity of CeO₂ promotes photogenerated charge separation for light-driven performance and optimal plasma–catalyst interactions. Full article

Copper-based catalysts supported on γ-Al₂O₃ were prepared by wet impregnation and evaluated for the catalytic wet peroxide oxidation (CWPO) of phenol. Citric acid was used as a complexing agent to enhance copper stabilization, and lanthanum was incorporated as a structural promoter. The effects of calcination temperature, heating rate, Cu loading, and La incorporation route on catalyst structure and performance were systematically investigated. Thermal treatment and La incorporation-controlled phase evolution and copper oxidation state. Calcination at 900 °C promoted the development of CuAl₂O₄- and CuAlO₂-type phases, as suggested by XRD, while XPS showed that the Cu²⁺/Cu⁺ ratio increased progressively with temperature, consistent with stronger metal–support interactions. Citric acid, incorporated at a CA:Cu molar ratio of 1:1, reduced copper leaching by up to 50% compared to catalysts prepared without the complexing agent, regardless of calcination temperature. Co-impregnated Cu–La catalysts achieved complete phenol conversion within 20–30 min and TOC removals of 84–95%, depending on synthesis conditions. The combination of La incorporation, calcination at 900 °C, and citric acid-assisted impregnation yielded the best stability–activity balance, with Cu5.0/La-A-900-1 showing 91% TOC removal and only 18% Cu leaching after 2 h of reaction. XPS, catalytic performance, and leaching results indicate that CWPO activity is governed by the balance between redox accessibility (Cu²⁺/Cu⁺) and structural stabilization of copper species. The results indicate that CWPO proceeds through a combined surface-mediated and homogeneous Fenton-like pathway, where the relative contribution of each depends on copper stabilization and leaching. Full article

Developing high-performance non-precious metal catalysts for the methanol oxidation reaction remains a challenge for direct methanol fuel cells. Herein, a nickel-doped Beta (Ni-Beta) zeolite was successfully synthesized via a template-free one-pot hydrothermal route followed by protonation via ammonium exchange. In this work, the protonation process strengthened metal–support interaction to form Ni²⁺/Ni³⁺ redox pairs, introduced abundant acidic sites, and optimized the zeolitic pore structure. Optimized Ni-H-Beta-170 (Si/Ni = 170) achieved a remarkable mass activity of 71.6 A g⁻¹ at 0.66 V vs. Hg/HgO, around 10-fold higher than unprotonated Ni-Beta zeolite. The improved activity originates from reversible Ni²⁺/Ni³⁺ cycles for eliminating toxic CO_ads, enriched acid sites accelerating C–H cleavage of methanol and formation of active NiOOH, and enlarged pore volume facilitating mass transfer. This work offers a low-cost strategy toward advanced non-precious methanol oxidation reaction electrocatalysts. Full article

Methods for the preparation of aluminum hydroxides and alumina-supported catalysts through the interaction of activated Al–In–Ga alloys with water were developed. Bayerite was obtained from an alloy containing 99.0% Al + 0.5% In + 0.5% Ga at 303 K, while pseudoboehmite was synthesized from 90% Al + 5% In + 5% Ga at 363 K. The maximum specific surface area of aluminum oxide reached 700 m²/g. Dehydration of aluminum hydroxides proceeds via a sigmoidal mechanism with induction, acceleration, and deceleration stages. The dehydration rate increases with calcination temperature. Kinetic analysis revealed both kinetic and diffusion-controlled transformation regions for pseudoboehmite and bayerite. Transformation of pseudoboehmite into γ-Al₂O₃ at 523–673 K preserves a high specific surface area of 630–640 m²/g. Two platinum deposition methods were proposed: synthesis in the presence of soluble platinum salts and incorporation of Pt into the Al–Ga–In alloy followed by reaction with water. Alongside metallic Pt, Ptδ⁺, Pt²⁺, and Pt⁴⁺ species were detected and reduced to Pt⁰ at 900 K. Alumina–platinum catalysts showed high activity in cyclohexane dehydrogenation. A Zn–Al catalyst for methanol decomposition was developed, providing up to 70% H₂ in gaseous fuel and complete methanol conversion at 573 K. Full article

Nanostructured catalysts have become a core component of energy conversion in electrocatalysis and photocatalysis; however, successfully translating their performance from laboratory scale to industrial applications remains a long-standing challenge. This paper provides a critical assessment of the field, systematically tracing the entire development trajectory from catalyst design to practical application. We focus on five major classes of catalysts—monometallic catalysts, bimetallic/multimetallic alloy catalysts, metal compound catalysts, carbon-based composite catalysts, and single-atom catalysts—and explore synthetic strategies for achieving precise structural control, including hydrothermal/solvothermal methods, electrodeposition, template-assisted and MOF-derived syntheses, high-temperature pyrolysis, and post-treatment defect engineering. This paper delves into the mechanisms and performance descriptors governing the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), urea oxidation, photocatalytic water splitting, and CO₂ reduction. Based on the above analysis, this paper lays the mechanistic foundation for five core strategies to improve catalyst performance: morphology control, elemental doping, heterostructure and interface engineering, defect and vacancy engineering, and support modification. Furthermore, this paper provides an in-depth evaluation of the applications of these catalysts in water splitting, CO₂ valorization, fuel cells, metal–air batteries, and energy-saving electrolysis, with a particular focus on earth-abundant alternatives to precious metals. We argue that in many well-studied reactions, intrinsic activity may no longer be the primary bottleneck restricting their development; instead, the core challenge now lies in maintaining excellent catalytic performance under harsh and industrially relevant conditions, especially under high-current densities, impurity-containing feed systems, and long-term operating conditions. In response to this shift in research focus, this paper clearly identifies the key obstacles hindering the industrial application of catalysts and proposes practical directions for future research. Full article

The influence of carbon support and Cu loading on the structural, surface, and catalytic properties of Cu-based catalysts for furfural hydrogenation was systematically investigated. Two activated carbons with distinct textural and chemical characteristics were evaluated: a biomass-derived carbon (ACS) and commercial carbon (ACC). The ACC support exhibited a higher density of thermally stable oxygen-containing functional groups, which promoted stronger metal-support interactions and an increased proportion of surface reduced Cu species (Cu⁰/Cu⁺), resulting in superior catalytic performance compared to ACS. Based on these results, the effect of Cu loading (5–20 wt.%) was further studied on the ACC support. The catalysts were characterized by N₂ physisorption, XRD, TEM, H₂-TPR, He-TPD, NH₃-TPD, and XPS. Increasing Cu loading enhanced the amount and reducibility of Cu species; however, excessive loading led to particle growth, pore blockage, and reduced metal dispersion. Catalytic activity exhibited volcano-type behavior, reaching a maximum at 15 wt.% Cu, where an optimal balance between reduced availability of Cu species and metal-support interaction was achieved. Selectivity toward furfuryl alcohol remained essentially unchanged across all catalysts, indicating that the catalytic performance is closely related to the surface chemistry and relative concentration of reduced Cu sites and is not significantly affected by acidity. These results highlight the critical role of support properties and metal loading in controlling catalyst performance, providing insights for the rational design of efficient Cu-based catalysts for biomass valorization. Full article

The rational design of metal-free catalysts capable of efficiently converting CO₂ under atmospheric pressure remains a significant challenge in sustainable chemistry. Herein, we report a series of clamp-shaped dihydrogen-bonded iodide catalysts (CDBI catalysts) featuring a preorganized bifunctional framework that integrates dual hydrogen-bond donors and an intrinsic iodide nucleophile within a single molecular scaffold. Systematic structural variation revealed that catalytic activity is highly sensitive to electronic modulation, steric accessibility, and precise spatial arrangement between the hydrogen-bonding units and the iodide center. The optimal catalyst enabled solvent-free cycloaddition of CO₂ with epoxides at 1 atm CO₂, affording up to 99% conversion and >99% selectivity at 80 °C within 12 h. Substrate scope studies demonstrated efficient transformation of a wide range of terminal epoxides, while sterically demanding substrates exhibited reduced reactivity consistent with a confined activation mode. Mechanistic investigations support a cooperative pathway in which dual hydrogen-bond activation and proximal halide nucleophilicity operate synergistically within a preorganized clamp-shaped pocket. Comparative analysis with representative catalytic systems highlights the ability of this metal-free design to achieve high efficiency under atmospheric CO₂ without cocatalysts or solvents. These findings demonstrate that structural preorganization represents an effective strategy for promoting sustainable CO₂ utilization under operationally simple conditions. Full article

The design and manufacture of bifunctional electrocatalysts are of great significance in the electrolysis of water. Herein, porous organic polymers (POPs) of metal–N-heterocyclic carbene were synthesized from imidazolium borate ionic POPs and supported on a nickel foam surface (Pd–NHC/NF, Ag–NHC/NF, and Cu–NHC/NF). Among them, Pd–NHC/NF exhibited high activity for both hydrogen evolution reaction and oxygen evolution reaction. The oxygen evolution overpotential of Pd–NHC/NF was 245 mV with a Tafel slope of 83 mV dec⁻¹; the hydrogen evolution overpotential was 139 mV with a Tafel slope of 94 mV dec⁻¹ at 10 mA cm⁻² in alkaline media. Additionally, the assembled Pd–NHC/NF||Pd–NHC/NF electrolyzer demonstrated excellent performance in electrocatalytic water-splitting, achieving a voltage of 1.55 V at 10 mA cm⁻² and showing outstanding stability for over 90 h in the long-term test. The results highlighted the substantial capability of Pd–NHC as a bifunctional catalyst for electrocatalytic water-splitting. Full article

Ammonia decomposition over non-precious metal thermos-catalysts offers a viable and cost-effective pathway for sustainable hydrogen production. In this study, LaCeO₃ perovskite was synthesized using a citric acid complexation method and employed as a support for mono- and bimetallic catalysts prepared by incipient wetness impregnation, maintaining a total metal loading of 10 wt%. Structural and surface properties were systematically investigated using BET, XRD, H₂-TPR, SEM, TEM, and CO₂-TPD. Among the monometallic catalysts (Ni, Co, and Fe), 10%Ni/LaCeO₃ exhibited the highest activity, which is attributed to its enhanced reducibility and optimal surface basicity, facilitating NH₃ activation. Bimetallic systems (Ni-Co, Ni-Fe, and Co-Fe) with equal metal loadings (5 wt% each) showed better activity compared to their monometallic counterparts following the order: 5%Ni–5%Co/LaCeO₃ > 5%Ni–5%Fe/LaCeO₃ > 5%Co–5%Fe/LaCeO₃. The improved performance of the Ni-Co system is due to structural interactions between Ni and Co, which promote hydrogen desorption and accelerate N–H bond cleavage, while suppressing nitrogen recombination as the rate-limiting step. Further systematic optimization of the Ni/Co ratio showed that 8%Ni–2%Co/LaCeO₃ had the highest catalytic activity with consistent performance over 50 h. This optimal composition provides a balanced distribution of active metallic sites and moderate-to-strong basic sites, enhancing NH₃ adsorption and intermediate transformation. These findings show that LaCeO₃-supported Ni-Co catalysts are promising candidates for efficient hydrogen production from ammonia without using noble metals. Full article

Hydrogen (H₂) has emerged as a promising next-generation energy carrier with significant potential to mitigate climate change and environmental pollution. The hydrogen evolution reaction (HER) is the critical half-reaction directly responsible for hydrogen production. Efficient HER electrocatalysts must exhibit low overpotential values and fast reaction kinetics to achieve high catalytic performance. While platinum (Pt) remains the benchmark catalyst due to its ideal hydrogen adsorption energy, high electrical conductivity, and superior chemical stability, further innovations are essential. This review summarizes recent advances in Pt-based HER catalysts, focusing on two primary design strategies: metal-level engineering and support-level engineering. These approaches allow for precise control over electronic structures, active site distributions, and interfacial properties, paving the way for next-generation HER electrocatalysts. Full article