Strong Electronic Orbit Coupling between Cobalt and Single-Atom Praseodymium for Boosted Nitrous Oxide Decomposition on Co3O4 Catalyst

Hybridizing Electrode Interface Structures in Protonic Ceramic Cells for Durable, Reversible Hydrogen and Power Generation

Protonic ceramic electrochemical cells (PCECs) represent a transformative technology for sustainable hydrogen production and power generation by converting energy between chemical and electrical forms. Operating at intermediate temperatures, PCECs utilize proton-conducting electrolytes, achieving high efficiency and reduced degradation. However, a major bottleneck lies at the oxygen electrode due to sluggish kinetics and limited active sites. To address this, we present a hybrid oxygen electrode featuring PrNi0.7Co0.3O3-δ (PNC) backbone infused with oxygen vacancy-rich praseodymium oxide (PrOx) nanoparticles. This design leverages the interplay between surface and bulk properties to enhance oxygen adsorption, diffusion, and catalytic kinetics. The PrOx introduces abundant oxygen vacancies and modulates the d-band center for optimal adsorption energy, while the PNC backbone provides robust proton conduction and stabilizes reaction intermediates. Cells incorporating this hybrid electrode demonstrate a peak power density of 1.56 W cm-2 at 600 °C in fuel cell mode and a current density of 2.25 A cm-2 at 1.30 V in electrolysis mode. Faradaic and energy efficiency reach 96.8% and 89.9%, respectively, with exceptional thermal cycling stability and reduced polarization resistance (0.079 Ω cm2). This study underscores the potential of advanced electrode architectures to enhance the efficiency, durability, and applicability of PCECs in renewable energy systems.

Oxide Support Inert in Its Interaction with Metal but Active in Its Interaction with Oxide and Vice Versa

Supported metal or oxide nanostructures catalyze many industrial reactions, where the interaction of metal or oxide overlayer with its support can have a substantial influence on catalytic performance. In this work, we show that small Pt species can be well stabilized on CeO2 under both H2-containing and O2-containing atmospheres but sintering happens on SiO2, indicating that CeO2 is active whereas SiO2 is inert in Pt-support interaction. On the other hand, Co oxide (CoOx) supported on SiO2 can maintain a low-valence Co2+ state both in air and during CO2 hydrogenation to CO, indicating a strong interaction of CoOx with SiO2. However, the CoOx overlayer has a weak interaction with CeO2 and is easily reduced to metallic Co during the CO2 hydrogenation reaction producing CH4. Thus, SiO2 is active, but CeO2 is inert for CoOx-support interaction, which is counter to the common sense from the Pt/oxide systems. Systematic studies in stability behaviors of Pt and CoOx nanocatalysts supported on various oxides show that the reducibility of the oxide supports can be used to describe the catalyst-support interaction. Oxide supports with high reducibility or low metal-oxygen bond strength interact strongly with Pt and other metals, showing high metalphilicity. Conversely, oxide supports with low reducibility or high metal-oxygen bond strength have strong interaction with CoOx and other oxides, having high oxidephilicity.

New Electromagnetic Interference Shielding Materials: Biochars, Scaffolds, Rare Earth, and Ferrite-Based Materials

In this review, a comprehensive systematic study of the research background, developments, classification, trends, and advances over the past few years in research on new electromagnetic interference (EMI) shielding materials will be described. The following groups of new materials for EMI shielding will be discussed: biochars, scaffolds, rare earth, and ferrite-based materials. We selected two novel, organic, lightweight materials (biochars and scaffolds) and compared their shielding effectiveness to inorganic materials (ferrite and rare earth materials). This article will broadly discuss the EMI shielding performance, the basic principles of EMI shielding, the preparation methods of selected materials, and their application prospects. Biochars are promising, eco-friendly, sustainable, and renewable materials that can be potentially used as a filter in polymer composites for EMI shielding, along with scaffolds. Scaffolds are new-generation, easy-to-manufacture materials with excellent EMI shielding performance. Rare earth (RE) plays an important role in developing high-performance electromagnetic wave absorption materials due to the unique electronic shell configurations and higher ionic radii of RE elements. Ferrite-based materials are often combined with other components to achieve enhanced EMI shielding, mechanical strength, and electrical and thermal conductivity. Finally, the current challenges and future outlook of new EMI shielding materials will be highlighted in the hope of obtaining guidelines for their future development and application.

Enhanced Nitrous Oxide Decomposition on Zirconium-Supported Rhodium Catalysts by Iridium Augmentation

The effective elimination of N2O from automobile exhaust at low temperatures poses significant challenges. Compared to other materials, supported RhOx catalysts exhibit high N2O decomposition activities, even in the presence of O2, CO2, and H2O. Metal additives can enhance the low-temperature N2O decomposition activities over supported RhOx catalysts; however, the enhancement mechanism and active sites require further investigation. In this study, we demonstrate the significant enhancement of the low-temperature N2O decomposition activity of a monoclinic ZrO2-supported Rh catalyst [Rh(1)/ZrO2] with Ir addition in the presence of N2O + O2 + CO2 + H2O. The promotional effect of Ir and the active sites on N2O decomposition in Rh(1)-Ir(1)/ZrO2 (Rh = 1 wt % and Ir = 1 wt %) were investigated by kinetic studies and in situ spectroscopic methods, including X-ray absorption spectroscopy, ambient-pressure X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. These results indicate that both surface Rh and Ir species in Rh(1)-Ir(1)/ZrO2 were active sites for N2O catalytic decomposition at low temperatures, and Ir augmentation promoted the desorption of gaseous O2, which are regarded as key steps in N2O decomposition.

Insights into the Roles of Different Iron Species on Zeolites for N2O Selective Catalytic Reduction by CO

Iron zeolites are promising candidates for mitigating nitrous oxide (N2O), a potent greenhouse gas and contributor to stratospheric ozone destruction. However, the atomic-level mechanisms by which different iron species, including isolated sites, clusters, and particles, participate in N2O decomposition in the presence of CO still remain poorly understood, which hinders the application of the reaction in practical technology. Herein, through experiments and density functional theory (DFT) calculations, we identified that isolated iron sites were active for N2O activation to generate adsorbed O* species, which readily reacted with CO following the Eley-Rideal (E-R) mechanism. In contrast, Fe2O3 particles exhibited a different reaction pathway, directly reacting with CO to generate oxygen vacancies (Ov), which could efficiently dissociate N2O following the Mars-van Krevelen (MvK) mechanism. Moreover, the transformation of iron oxide clusters into undercoordinated FeOx species by CO was also revealed through various techniques, such as CO-temperature-programmed reduction (TPR), and ab initio molecular dynamics (AIMD) simulations. Our study provides deeper insights into the roles of different iron species in N2O-SCR by CO, and is anticipated to facilitate the understanding of multicomponent catalysis and the design of efficient iron-containing catalysts for practical applications.

Highly active Mn-VO-Co sites by cobalt doping on cryptomethane for enhanced catalytic decomposition of N2O

Direct catalytic decomposition has shown great promise in controlling the greenhouse gas N2O. Herein, we synthesize a series of cobalt-doped cryptomethane (OMS-2) catalysts for N2O catalytic decomposition by a mild one-step sol-gel method. The Co0.1-OMS-2 exhibits superior catalytic performance with 90% N2O conversion at 398 °C, which is attributed to the formation of the Mn-VO-Co structure served as active sites. The increased electron density on oxygen vacancies promotes the electron transfer between oxygen vacancies and N2O molecules, in turn facilitating the adsorption and activation of N2O. Moreover, Co doping reduces the formation energy of oxygen vacancies. However, excessive Co doping results in the decrease of highly active Mn-VO-Co sites and the formation of Co3O4, which makes Co0.3-OMS-2 exhibit poor catalytic activity. The DFT calculation illustrates that Langmuir-Hinshelwood is the primary reaction mechanism over Co0.1-OMS-2. This study broadens the materials applicable for the catalytic decomposition of N2O, offering an effective approach to modulate the electronic structure at oxygen vacancies.

Promoting C-Cl Bond Activation via a Preoccupied Anchoring Strategy on Vanadia-Based Catalysts for Multi-Pollutant Control of NOx and Chlorinated Aromatics

Regulating vanadia-based oxides has been widely utilized for fabricating effective difunctional catalysts for the simultaneous elimination of NOx and chlorobenzene (CB). However, the notorious accumulation of polychlorinated species and excessively strong NH3 adsorption on the catalysts lead to the deterioration of multipollutant control (MPC) activity. Herein, protonated sulfate (-HSO4) supported on vanadium-titanium catalysts via a preoccupied anchoring strategy are designed to prevent polychlorinated species and alleviate NH3 adsorption for the multipollutant control. The obtained catalysts with -HSO4 modification achieve an excellent NOx and CB conversion with turnover frequency values of ∼ 3.63 and 17.7 times higher than those of the pristine, respectively. The protonated sulfate promotes the formation of polymeric vanadyl with a higher chemical state and d-band center of V. The modulated catalysts not only substantially alleviate the competitive adsorption of multipollutant via the "V 3d-O 2p-S 3p" network, but also distinctly strengthen the Brønsted acid sites. Besides, the introduced proton donor of the -HSO4 connecting polymeric structure could markedly reduce the reaction barrier of breaking the C-Cl bond. This work paves an advanced way for low-loading vanadium SCR catalysts to achieve highly efficient NOx and CB oxidation at a low temperature.

4d-2p-4f Gradient Orbital Coupling Enables Tandem Catalysis for Simultaneous Abatement of N2O and CO on Atomically Dispersed Rh/CeO2 Catalyst

N2O and CO coexist in various industrial and mobile sources. The synergistic reaction of N2O and CO to generate N2 and CO2 has garnered significant research interest, but it remains extremely challenging. Herein, we constructed an atomically dispersed Rh-supported CeO2 catalyst with asymmetric Rh-O-Ce sites through gradient Rh 4d-O 2p-Ce 4f orbital coupling. This design effectively regulates the 4f electron states of Ce and promotes the electron filling of the O 3π* antibonding orbital to facilitate N-O bond cleavage. Near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) reveals that CO reacts with the surface-adsorbed O* generated by N2O decomposition through self-tandem catalysis, accelerating the rate-limiting step in N2O decomposition and activating the synergistic reaction of N2O and CO at temperatures as low as 115 °C. This work can guide the development of high-performance catalysts using the strategy of high-order orbital hybridization combined with the tandem concept to achieve versatile catalytic applications.

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Unlocking Spin Gates of Transition Metal Oxides via Strain Stimuli to Augment Potassium Ion Storage

Transition metal oxides (TMOs) are key in electrochemical energy storage, offering cost-effectiveness and a broad potential window. However, their full potential is limited by poor understanding of their slow reaction kinetics and stability issues. This study diverges from conventional complex nano-structuring, concentrating instead on spin-related charge transfer and orbital interactions to enhance the reaction dynamics and stability of TMOs during energy storage processes. We successfully reconfigured the orbital degeneracy and spin-dependent electronic occupancy by disrupting the symmetry of magnetic cobalt (Co) sites through straightforward strain stimuli. The key to this approach lies in the unfilled Co 3d shell, which serves as a spin-dependent regulator for carrier transfer and orbital interactions within the reaction. We observed that the opening of these 'spin gates' occurs during a transition from a symmetric low-spin state to an asymmetric high-spin state, resulting in enhanced reaction kinetics and maintained structural stability. Specifically, the spin-rearranged Al-Co3O4 exhibited a specific capacitance of 1371 F g-1, which is 38 % higher than that of unaltered Co3O4. These results not only shed light on the spin effects in magnetic TMOs but also establish a new paradigm for designing electrochemical energy storage materials with improved efficiency.

High-Efficiency Electrocatalytic Reduction of N2O with Single-Atom Cu Supported on Nitrogen-Doped Carbon

Nitrous oxide (N2O) is a potent greenhouse gas with a high global warming potential, emphasizing the critical need to develop efficient elimination methods. Electrocatalytic N2O reduction reaction (N2ORR) stands out as a promising approach, offering room temperature conversion of N2O to N2 without the production of NOx byproducts. In this study, we present the synthesis of a copper-based single-atom catalyst featuring atomic Cu on nitrogen-doped carbon black (Cu1-NCB). Attributed to the highly dispersed single-atom Cu sites and the effective suppression of the hydrogen evolution reaction, Cu1-NCB demonstrated an optimal N2 faradaic efficiency (82.1%) and yield rate (3.53 mmol h-1 mgmetal-1) at -0.2 and -0.5 V vs RHE, respectively, outperforming previously reported N2ORR electrocatalysts. Further, a gas diffusion electrode cell was employed to improve mass transfer and achieved a 28.6% conversion rate of 30% N2O with only a 14 s residence time, demonstrating the potential for practical application. Density functional theory calculations identified Cu-N4 as the crucial active site for N2ORR, highlighting the significance of the unsaturated coordination and metal-support electronic structure. O-terminal adsorption of N2O was favored, and the dissociative adsorption (*ON2 → *O + N2) was the rate-determining step. These findings reveal the broad prospects of N2O decomposition via electrocatalysis.

Boosting N2O Decomposition by Fabricating the Cs-O-Co Structure over Co3O4 with Single-Layer Atoms of Cs

Developing effective catalysts for N2O decomposition at low temperatures is challenging. Herein, the Cs-O-Co structure, as the active species fabricated by single-layer atoms of Cs over pure Co3O4, originally exhibited great catalytic activity of N2O decomposition in simulated vehicle exhaust and flue gas from nitric acid plants. A similar catalytic performance was also observed for Na, K, and Rb alkali metals over Co3O4 catalysts for N2O decomposition, illustrating the prevalence of alkali-metal-promotion over Co3O4 in practical applications. The catalytic results indicated that the TOF of Co3O4 catalysts loaded by 4 wt% Cs was nearly 2 orders of magnitude higher than that of pure Co3O4 catalysts at 300 °C. Interestingly, the conversions of N2O decomposition over Co3O4 catalysts doped by the same Cs loadings were significantly inhibited. Characterization results indicated that the primary active Cs-O-Co structure was formed by highly orbital hybridization between the Cs 6s and the O 2p orbital over the supported Co3O4 catalysts, where Cs could donate electrons to Co3+ and produce much more Co2+. In contrast, the doped Co3O4 catalysts were dominated by Cs2O2 species; meanwhile, CsOH species was generated by adsorbed water vapor led to a significant decrease in catalytic activity. In situ DRIFTS, rigorous kinetics, and DFT results elaborated the reaction mechanism of N2O decomposition, where the direct decomposition of adsorbed N2O was the kinetically relevant step over supported catalysts in the absence of O2. Meanwhile, the assistance of adsorbed N2O decomposition by activated oxygen was observed as the kinetically relevant step in the presence of O2. The results may pave a promising path toward developing alkali-metal-promotion catalysts for efficient N2O decomposition.

High Flux and Stability of Cationic Intercalation in Transition-Metal Oxides: Unleashing the Potential of Mn t2g Orbital via Enhanced π-Donation

Transition-metal oxides (TMOs) often struggle with challenges related to low electronic conductivity and unsatisfactory cyclic stability toward cationic intercalation. In this work, we tackle these issues by exploring an innovative strategy: leveraging heightened π-donation to activate the t2g orbital, thereby enhancing both electron/ion conductivity and structural stability of TMOs. We engineered Ni-doped layered manganese dioxide (Ni-MnO2), which is characterized by a distinctive Ni-O-Mn bridging configuration. Remarkably, Ni-MnO2 presents an impressive capacitance of 317 F g-1 and exhibits a robust cyclic stability, maintaining 81.58% of its original capacity even after 20,000 cycles. Mechanism investigations reveal that the incorporation of Ni-O-Mn configurations stimulates a heightened π-donation effect, which is beneficial to the π-type orbital hybridization involving the O 2p and the t2g orbital of Mn, thereby accelerating charge-transfer kinetics and activating the redox capacity of the t2g orbital. Additionally, the charge redistribution from Ni to the t2g orbital of Mn effectively elevates the low-energy orbital level of Mn, thus mitigating the undesirable Jahn-Teller distortion. This results in a subsequent decrease in the electron occupancy of the π*-antibonding orbital, which promotes an overall enhancement in structural stability. Our findings pave the way for an innovative paradigm in the development of fast and stable electrode materials for intercalation energy storage by activating the low orbitals of the TM center from a molecular orbital perspective.

Single-Atom Catalysts in Environmental Engineering: Progress, Outlook and Challenges

Recently, single-atom catalysts (SACs) have attracted wide attention in the field of environmental engineering. Compared with their nanoparticle counterparts, SACs possess high atomic efficiency, unique catalytic activity, and selectivity. This review summarizes recent studies on the environmental remediation applications of SACs in (1) gaseous: volatile organic compounds (VOCs) treatment, NO_x reduction, CO₂ reduction, and CO oxidation; (2) aqueous: Fenton-like advanced oxidation processes (AOPs), hydrodehalogenation, and nitrate/nitrite reduction. We present the treatment activities and reaction mechanisms of various SACs and propose challenges and future opportunities. We believe that this review will provide constructive inspiration and direction for future SAC research in environmental engineering.

Beyond Purification: Highly Efficient and Selective Conversion of NO into Ammonia by Coupling Continuous Absorption and Photoreduction under Ambient Conditions

Although the selective catalytic reduction technology has been confirmed to be effective for nitrogen oxide (NO_x) removal, green and sustainable NO_x re-utilization under ambient conditions is still a great challenge. Herein, we develop an on-site system by coupling the continuous chemical absorption and photocatalytic reduction of NO in simulated flue gas (C_NO = 500 ppm, GHSV = 18,000 h^-1), which accomplishes an exceptional NO conversion into value-added ammonia with competitive conversion efficiency (89.05 ± 0.71%), ammonia production selectivity (95.58 ± 0.95%), and ammonia recovery efficiency (>90%) under ambient conditions. The anti-poisoning capacities, including the resistance against factors of H₂O, SO₂, and alkali/alkaline/heavy metals, are also achieved, which presents strong environmental practicability for treating NO_x in flue gas. In addition, the critical roles of corresponding chemical absorption and catalytic reduction components are also revealed by in situ characterizations. The emerging strategy herein not only achieves a milestone efficiency for sustainable NO purification but also opens a new route for contaminant resourcing in the near future of carbon neutrality.