Utilizing electrocatalytic methods to efficiently convert harmful nitric oxide into derivatives of ammonia is undoubtedly a very economical way. Herein, we synthesized a series of different metal ratio NixCoy-layered double hydroxide nanoflower (NixCoy-LDH NF) material derived from the metal-organic framework (MOF), which can convert low concentration NO into ammonia. Among them, Ni50Co50-layered double hydroxide nanoflower can achieve a NH3 yield rate of 4.33mgh-1 cm-2 with a Faradaic efficiency of 74.6% in a H-cell. Notably, the yield can increase to 22.8mgh-1 cm-2 at -0.4V (V vs.RHE) with a current density over 250mAcm-2 in a gas diffusion electrode. The post-electrolysis electrolyte was then collected and a membrane permeation device was used to purify the free ammonia into ammonium chloride. Our work investigated the influence of different proportions of Ni on the nitric oxide reduction reaction performance of layered double hydroxide materials and provided a new strategy for efficient NO conversion catalyst design.
Heteroatoms can be doped into the crystal lattice to introduce defects by physical or chemical methods, which can adjust the band structure of the photocatalyst, and ultimately affect the photocatalytic performance of the photocatalyst. Herein, ZnIn2S4 (ZIS) nanoflowers with high content lattice-O doping were synthesized by one-pot ion-exchange method from solid ZnO source. The peaks of lattice-O (531.4 eV) and O vacancies (530.0 eV) presence in XPS spectra support the existence of lattice-O in the ZnIn2S4 (ZIS) nanoflowers. Numerous 2D ultrathin nanosheets assembled ZIS nanoflowers would resulted into hierarchical structure with high surface and mesoporous structure. With optimum Zn/In ratio in the obtained materials, ZIS (1:3:9) show enhanced CO2 to CO conversion activity(1038.4 μmol·g−1·h−1) and a low CH4-evolving rate of 4.9 μmol·g−1·h−1 under visible light irradiation. The obtained ZIS (1:3:9) material can significantly promote photogenerated charge separation, accelerate transfer of photogenerated electrons, delay the recombination of electrons and holes. This work opens up a new way for element doping and careful construction of heterojunctions to improve photocatalytic performance by improving photogenerated charge and hole separation and regulating band structure.
Aniline (PhNH2) finds widespread applications in dyes, pharmaceuticals, pesticides, rubber additives, and the polyurethane industry. However, PhNH2 is traditionally synthesized from nitrobenzene (PhNO2) via hydrogenation under harsh conditions (high-temperature and high-pressure). Hence, developing highly active catalysts for the electrocatalytic hydrogenation of PhNO2 under mild operating conditions is of paramount importance for both aniline synthesis and electrochemical energy storage technologies. Herein, twenty-five Co-TM-N6V4-G dual-atom catalysts (DACs) were constructed by coupling a Co single atom with various transition metal (TM) species. Density functional theory (DFT) calculations were performed to elucidate how interatomic d–d orbital coupling within the DACs regulates their catalytic performance toward nitrobenzene electroreduction. First, evaluations of the formation energies, dissolution potentials, and the differences between average binding and cohesive energies indicate that all 25 DACs exhibit excellent thermodynamic and electrochemical stability. Second, Gibbs free energy profiles and limiting potential calculations reveal that the Co-Cu-N6V4-G catalyst possesses the optimal catalytic activity and selectivity. Insights into the electronic structure and synergistic mechanism of Co-Cu-N6V4-G reveal that Cu single-atom doping successfully promotes d–d orbital hybridization between the adjacent Cu and Co atoms. Such electronic modulation substantially strengthens the adsorption and activation of the reactant, thereby lowering the thermodynamic barrier of the potential-determining step (PDS). Consequently, this work establishes a solid theoretical foundation for the rational design of advanced DACs toward efficient PhNO2 electroreduction.
Spontaneous lattice oxygen reverse spillover from MgO(111) substrate to the surface of supported transition metal catalysts can influence the mechanisms and activities of this emerging class of catalysts for organic oxidation, hydrogen evolution, and ammonia synthesis or decomposition. In this study, we employed density functional theory calculations to analyze various models of metal/MgO catalysts to understand how metal size, MgO facet, metal species, and exposure to a hydrogen atmosphere could affect the occurrence of such lattice oxygen reverse spillover. Energetic analysis of Rux (x = 10, 4, 1) on MgO(111), (110), and (100) facets shows that lattice oxygen reverse spillover becomes more favorable with decreasing Ru size, but only on the MgO(111) facet. Electronic structure analyses reveal that the charge redistribution from Ru to the surface O species of MgO(111) stabilizes the polar substrate. Consistently, single atom models of all 30 d-block metals on MgO(111) reveal that metal species donating more electrons to the MgO(111) surface during lattice oxygen reverse spillover also facilitate more facile lattice oxygen reverse spillover, from both thermodynamic and kinetic perspectives. Particularly, lattice oxygen reverse spillover is maximized for Cr, Tc, and W among 3d, 4d, and 5d metals, respectively, and becomes less favored for metals with inhibited electron-donating capabilities due to either very few valence electrons or substantial electronegativity. Moreover, we demonstrate that chemisorption of atomic hydrogen intermediates on the MgO(111) substrate, known to occur on metal/MgO(111) catalysts applied under hydrogen-rich conditions, inhibits lattice oxygen reverse spillover. Hence, whereas lattice oxygen reverse spillover on metal/MgO(111) catalysts plays a significant role when applied under oxidative reaction conditions, it is inhibited under reducing hydrogen-rich environments. This study highlights lattice oxygen reverse spillover on MgO(111)-supported metal catalysts and provides a detailed mechanistic understanding that will be important to consider for the rational design and optimization of these MgO(111)-based catalysts.
Electroreduction of lignin into value-added chemicals offers an effective route for its high-value utilization. However, how the electronic states of catalytic sites govern lignin conversion efficiency and product yield remains poorly understood. Here, we use Pt and a Pd@Pt heterostructure as model catalysts to systematically investigate catalyst-intermediate interactions and their influence on lignin electroreduction. In the Pd@Pt heterostructure, electron transfer from Pd to Pt reconstructs the Pt 5d states and shifts the catalyst-intermediate interaction from a strong Pt 5dxz-O 2py interaction on pure Pt with C6H5OH/C6H5COCH3 to a weaker Pt 5dxy/yz-O 2px interaction on Pd@Pt. This reduced orbital overlap significantly lowers the activation barrier of the rate-determining step, thereby enhancing lignin reduction activity. These findings highlight the critical role of orbital interaction modes in regulating catalyst activity and provide mechanistic insight for the rational design of advanced electrocatalysts for lignin reduction.
Creating efficient active oxygen evolution catalysts (OECs) from inexpensive, abundant elements is critical, as the inherently slow kinetics of the oxygen evolution reaction (OER) remain a major bottleneck limiting the efficiency of many electrochemical energy conversion technologies. We present a straightforward approach for synthesizing a novel BPhTz-Bz conjugated microporous polymers (CMPs) through an ionothermal [3 + 3] Schiff-base condensation between 1,3,5-tris(3′-tert-butyl-4′-hydroxy-5′-formylphenyl)benzene (Bz-3CHO) and 4′,4‴,4‴″-(1,3,5-triazine-2,4,6-triyl)tris(([1,1′-biphenyl]-4-amine) (BPhTz-3NH2). Subsequently, the pristine BPhTz-Bz CMP was readily converted into a series of metal-coordinated materials, denoted as BPhTz-Bz-M CMPs (M2 + = Co2+, Ni2+, Cu2+), prepared by a simple metal ion incorporation of BPhTz-Bz CMP using the corresponding metal acetates. Both BPhTz-Bz CMP and BPhTz-Bz-M CMPs exhibited excellent thermal stability, with char yields reaching up to 60 wt% at 800 °C. Nitrogen adsorption–desorption (BET) analysis revealed that the original BPhTz-Bz CMP possesses a high specific surface area of 583 m2 g−1. After metal ion incorporation, the surface area decreased to 377, 355, and 392 m2 g−1 for the Co-, Ni-, and Cu-containing CMPs, respectively. Electrochemical measurements demonstrated that the metal-coordinated CMPs exhibit significantly improved catalytic activity toward the OER in 1 M KOH. Among them, the BPhTz-Bz-Co CMP and BPhTz-Bz-Ni CMP showed the best performance, showing high catalytic performance with a 540 and 396 mV overpotential at 10 mA cm−2, accompanied by a Tafel slopes of 123.3 and 71.4 mV dec−1, and a turnover frequency (TOF) of 0.032 and 0.115 s−1 at an overpotential of 420 mV. These findings demonstrate that the combination of rational ligand design and transition-metal coordination yields a synergistic effect, enhancing electrocatalytic OER efficiency.
Ammonia electrosynthesis represents a pivotal sustainable technology for the energy transition towards carbon neutrality. Among others, single-atom catalysts (SACs) have drawn significant interest due to their advantages including maximum metal utilization, homogeneous and low-coordination metal active centers. However, the conventional design of SACs based on density functional theory is constrained by high computational costs and system complexity. Artificial intelligence (AI) emerged as a transformative paradigm, enabling the rational design of SACs and related catalytic architectures. This review systematically outlines the fundamental mechanisms of SACs towards ammonia electrosynthesis. We further elaborate on the data-driven strategies for building catalyst descriptors and databases, with emphasis on reviewing cutting-edge AI applications in high-throughput catalyst screening, structure-activity relationship modeling, reaction mechanism analysis, and multi-metal-atom catalyst design. Finally, we summarize the pivotal shift in the design workflows driven by AI, analyze the persistent challenges, and discuss future pathways toward industrial implementation.
Covalent organic frameworks (COFs) have emerged as a versatile class of crystalline porous materials for sustainable hydrogen peroxide (H2O2) synthesis through both photocatalytic and electrocatalytic pathways. This review provides a perspective on COF-enabled H2O2 production by examining photocatalytic and electrochemical two-electron oxygen reduction systems in parallel. By comparatively analyzing solar-to-chemical and electricity-to-chemical H2O2 conversion routes, this review reveals intrinsic connections and complementary design principles between photocatalysis and electrocatalysis. Finally, critical challenges and future research directions are outlined, encompassing efficiency enhancement, long term stability under realistic conditions, reactor engineering, and techno economic considerations, with the aim of guiding the rational development of COF based platforms for decentralized green and scalable H2O2 production.
The rapid rise in plastic waste, coupled with the limitations of existing recycling technologies, necessitates the development of efficient and sustainable catalytic systems for polymer depolymerization. In particular, the chemical recycling of polyethylene terephthalate (PET) requires robust system that enable high catalytic activity, facile recovery, reusability and improved process efficiency. In this study, a magnetically recoverable eucalyptus leaf ash-functionalized Fe3O4 (ELA@Fe3O4) nanocatalyst, derived from eucalyptus leaf ash, was synthesized via a green co-precipitation approach and applied for the efficient glycolysis of post-consumer polyethylene terephthalate (PET). Under optimized conditions (190 degrees C, 4 h, PET:EG = 1:8, 1 wt% catalyst), complete PET conversion with up to 93% yield of bis(2-hydroxyethyl) terephthalate (BHET) was achieved. The catalyst exhibited good recyclability over multiple cycles with moderate loss activity. Comprehensive spectroscopic and thermal analyses confirmed the high purity of the recovered BHET. Importantly, the depolymerized monomer was further upcycled into a dynamically crosslinked thermoset network via Diels-Alder chemistry, enabling thermal reprocessability. The thermo-reversible nature of this network facilitate the fabrication of complex threedimensional geometries, demonstrating its potential as a feedstock for additive manufacturing. By establishing a complete valorization chain from waste plastic to reprocessable, shape-programmable materials, this integrated approach presents a sustainable and scalable pathway for converting plastic waste into value-added functional materials.
The electrochemical CO2 reduction reaction (e-CO2RR) represents a sustainable approach to convert CO2 into valuable fuels and chemicals using renewable electricity to close the carbon loop and mitigate the climate change. In this scenario, oxide-derived Cu catalysts (i.e., Cu oxides precursor modified by the application of a negative electrochemical bias to perform the CO2 reduction) have emerged as promising materials for the e-CO2RR, demonstrating an enhanced Faradaic Efficiency (FE) toward C-2 products, while significantly suppressing the CH4 formation. In this work, CuO systems were synthesized using different soft-chemistry approaches (i.e., precipitation vs. hydrothermal routes), and characterized through several advanced techniques such as TEM, SEM, XRD, BET analysis, Raman and FT-IR spectroscopies of adsorbed probe molecules. Catalytic performances were determined in terms of FE by monitoring the production of the main CO2 reduction derivatives in a flow cell. By performing a systematic study, it was demonstrated that both starting CuO particles size and morphology represent critical factors determining the C-C coupling reaction, mandatory to obtain C-2 products. In particular, oxide-derived Cu catalysts presenting particles with sheet-like morphology showed superior selectivity for the CO2 conversion into C-2 derivatives (i.e., 50% at 200 mA cm(-2)), with > 40% of C2H4 formation at high production rate (400 mA cm(-2)). Interestingly, both CuO particles size increase and their morphological changes toward either tabular-prismatic or spheroidal shapes determine a substantial drop of the performances accompanied by a rise in the parasite hydrogen evolution reaction (HER).
Porous Poly(vinylidene fluoride)/BaFe12O19 (PVDF/BAF) composite membranes with different BaFe12O19 (BAF) loadings were fabricated via a non-solvent/thermally induced phase separation (NIPS-TIPS) approach and systematically investigated in photo-, piezo-, piezophotocatalytic, and magnetically induced piezocatalytic degradation of methylene blue. Structural, phase, and surface analyses performed by scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray photoelectron spectroscopy (XPS) revealed the formation of a developed interfacial region and stabilization of the electroactive (beta + gamma) phase of PVDF upon incorporation of BAF, while preserving the phase integrity and chemical stability of the f BAF component within the polymer matrix. It was experimentally established that under ultrasonic activation the piezocatalytic mechanism dominates, providing a high dye degradation efficiency (up to similar to 95-96%), with the maximum performance already achieved at a low filler loading (2 wt%). Using selective scavenger tests and a fluorescent terephthalic acid probe (TA-probe) method, hydroxyl radicals (& centerdot;OH) were identified as the primary reactive species governing the piezocatalytic oxidation mechanism; the apparent steady-state & centerdot;OH concentration was estimated to be on the order of 10(-14)-10(-15) M. The results obtained by both independent approaches are in good agreement and confirm the radical oxidative nature of the process. Magnetically induced piezocatalysis was demonstrated for the first time in PVDF/BAF membrane composites without direct mechanical contact and without optical excitation. Under an alternating magnetic field, the catalytic activity increases monotonically with increasing ferrimagnetic phase content, reaching similar to 81% degradation after 240 min for the membrane containing 10 wt% BAF. This behavior is attributed to magnetostriction-induced local deformations of BAF particles and their efficient transfer to the piezoactive polymer matrix. Piezoelectric response measurements using a piezoelectric nanogenerator (PENG) revealed a non-monotonic dependence of the output voltage amplitude on composition and showed a maximum piezopotential for the PVDF/BAF2 membrane (similar to 1.3-1.4 V), which directly correlates with its highest piezocatalytic activity. Overall, the results experimentally demonstrate the key role of interfacial interactions, morphology, and mechanical compliance in controlling the efficiency of piezo- and magnetically induced catalytic processes and identify PVDF/BAF membranes as a promising platform for energy-efficient water treatment systems activated by remote physical fields.
The ubiquitous presence of (3-lactam antibiotics like amoxicillin (AMX) in aquatic environments is increasingly becoming a threat to ecosystems and human health through its promotion of antimicrobial resistance. Herein, we report a Ce-UNH-MOF-derived cerium oxide (CNC) catalyst designed through MOF-to-oxide conversion with a high degree of control to sonophoto-Fenton degrade amoxicillin in a highly efficient manner. Thermal conversion of Ce-UNH produces a porous, oxygen-vacancy-enriched cerium oxide with an abundance of Ce3+/Ce4+ redox centers with high electron conductivity. With the combined action of visible light, ultrasonic irradiation and H2O2, the derived oxide is able to degrade AMX by 90% in 60 min with a high apparent rate constant of 0.038 min(-1), which is significantly higher than pristine MOF (79%) and other processes like photocatalysis (71%) or sonocatalysis (56%). Mechanistic studies convey that ultrasonic cavitation boosts mass transfer and Ce3+ regeneration whereas photoexcitation supports the growth of exciton separation and ROS production. Radical scavenging test and electron spin resonance (ESR) analyses identify hydroxyl radicals ((OH)-O-center dot) as the dominant active species, with auxiliary contributions from superoxide (center dot O-2(-)). The catalyst demonstrates excellent stability and reusability after five cycles. This work establishes MOF-to-Oxide engineering as an effective strategy to design redox-active cerium catalysts for advanced sonophoto-Fenton oxidation and antibiotic remediation.
The continuing usage of antibiotics such as ciprofloxacin (CIP) in our water systems raises significant concerns for both the environment and public health. Traditional methods for treating wastewater frequently fall short in completely removing contaminants, highlighting the necessity for more advanced catalytic solutions. This study offers a CrFeCoNiZn high-entropy metal nitride (HEMN) magnetic sonocatalyst that has been thoughtfully engineered with nitrogen vacancies (NVs). The synthesis process involved hydrothermal treatment followed by ammonia nitridation and hydrogenation. The HEMN catalyst from optimized condition, HEMN600A, showcases a single-phase cubic anti-perovskite structure, containing a uniform distribution of Cr, Fe, Co, Ni, Zn, and N. The structure has been confirmed using various analyses, including XRD, XPS, SEM, and XAS. The presence of NVs increases the electron density surrounding metal centers, alters the d-band center, and greatly enhances the generation of reactive oxygen species (ROS) when exposed to ultrasonic irradiation. Consequently, HEMN600A successfully degraded 93% of CIP in 15 min. Additionally, HEMN600A shows improved magnetization, making it easier to recover magnetically, while also maintaining stable performance through several cycles. Studies involving radical scavengers and mass spectrometry provide additional confirmation of the degradation pathways mediated by reactive oxygen species. This study shows NVs-engineered HEMNs as novel and magnetically recoverable sonocatalysts, offering a sustainable solution for the removal of antibiotics in water treatment.
Nitric oxide (NO) is a major air pollutant requiring efficient conversion. Using first-principles calculations, this study investigates the electrocatalytic NO reduction reaction (NORR) as an integrated solution for pollution abatement and value-added synthesis. Among the various metal atom/metal clusters anchored SnS2 nanosheet, Pd3@SnS2 is identified as an efficient single-cluster catalyst (SCC) for NORR to generate NH3, exhibiting a thermodynamically downhill reaction pathway at zero potential versus the standard hydrogen electrode. Charge transfer analyses reveal that the superior electron-donation capacity of the Pd3 cluster to key intermediates is the critical factor for its outstanding catalytic activity, enabling efficient N-O bond activation. The Pd3@SnS2 also demonstrates exceptional selectivity towards NH3 production over N2. Moreover, Ag1@SnS2 exhibits high activity for N-N coupling to reduce the NO into N2, which serves as suitable electrocatalyst for NO remediation.
Dopants influence the anatase-rutile phase transition of titanium dioxide, primarily affecting the temperature at which this transformation occurs. The specific effect (promotion or inhibition) depends on the dopant type (metal or non-metal), its ionic radius, and its concentration. Phosphorus (P) doping, in particular, retards the formation of rutile at high annealing temperatures. However, there are no reports on P doping in predominantly rutile TiO2 or the influence of P concentration on preferential anatase formation for a rutile-driven synthesis process. Herein, phosphorus-doped titanium dioxide (P-TiO2) photocatalysts were synthesized via a modified inverse micelle sol-gel route. At 0.5-1mol% P concentration, the materials retain a rutile composition of 97-98%, indicating a critical doping threshold where phosphorus has minimal effect on rutile inhibition. At 2mol% P, the anatase-to-rutile ratio shifts to 55% anatase and 45% rutile, whereas 3% loading results in 99% anatase TiO2. The P-TiO2 photocatalysts exhibited enhanced visible-light Methylene Blue (MB) degradation compared with commercial P25. MB dye degradation mechanistic studies were conducted through reactive oxygen species (ROS) probing and quenching experiments. Electrospray Ionization-Mass Spectrometry (ESI-MS) studies led to the proposal of MB degradation via oxidation and cleavage of the central thiazine ring.
This study examines the performance of Ni-based catalysts (herein called NLH) promoted with noble metals (1-2 wt.% of Rh or Ru) supported on hydrotalcite-derived mixed oxides (HDMO) modified with La. These catalysts were tested, for the first time, for the steam reforming of distillery wastewater (DW), a problematic effluent of the wine distillery industry (generated during the production of ethanol or wine spirits), to produce renewable hydrogen. Characterization techniques, including hydrogen temperature-programmed reduction (TPR-H-2), temperature-programmed desorption of NH3 and CO2 (TPD-NH3, TPD-CO2), transmission electron microscopy (TEM), Raman spectroscopy and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), were employed to get insights about the prepared materials. Steam reforming tests were performed, the results of which showed H-2 yields in the following order: 2Rh/NLH similar to 1Rh/NLH > 2Ru/NLH > 1Ru/NLH > NLH. Stability tests demonstrated no H-2 yield loss for 2Rh/NLH or NLH after 24 h on-stream. Coke formation rate was relatively low for all catalysts, and the conversion of total organic carbon and chemical oxygen demand in the condensate was above 99 %. A test with real effluent, sourced from a Portuguese wine distillery, was also performed, providing a proof of concept as to the feasibility of the steam reforming of DW. The conversion of organic carbon and chemical oxygen demand in this test were both ca. 99 %.
The electrification of the chemical industry is a crucial step toward moving away from fossil fuels and achieving a more sustainable energy future. In this context, induction heating has emerged as a promising strategy to enhance catalytic performance in both metal-free carbon catalysts and metal-supported systems. This perspective emphasizes its strong potential, showing that induction heating improves performance not only through localized thermal effects but also through possible non-thermal contributions from alternating current magnetic fields. These fields can influence radical lifetimes, spin states, adsorption–desorption equilibria, and defect reactivity, thereby enabling reaction pathways and selectivities that remain inaccessible under conventional heating. Coupling carbon and supported metal catalysts with induction heating also offers an effective way to mitigate deactivation, as defect sites can act as adsorption centers that, under magnetic field stimulation, promote targeted transformations. Direct evidence for non-thermal contributions to catalytic performance remains scarce, mainly due to the limited availability of operando investigations. Nevertheless, the substantial gains in activity and selectivity observed under induction heating cannot be explained solely by localized thermal effects, suggesting an additional non-thermal influence. These findings point toward new opportunities for designing next-generation catalysts with improved operability and stability. In addition, the combined evidence of localized thermal effects, non-thermal field interactions, and the advantages of carbon-based catalysts shows that the synergy between advanced material design and induction heating provides a powerful pathway for electricity-driven catalysis, with significant implications for decarbonizing the chemical industry and advancing the energy transition.
Heterogeneous catalysis is essential in industrial chemical processes, particularly selective oxidation reactions. Oxidative reactions are complex due to the occurrence of multiple reaction pathways, kinetic and thermodynamic effects, and the involvement of reactive oxygen species (ROS). ROS, including superoxide radical anions (O2·-), hydrogen peroxide (H2O2), hydroxyl radicals (•OH), and singlet oxygen (1O2), can enhance selectivity or lead to overoxidation of reactants. Thus, ROS identification on a catalyst’s surface or under real-time conditions is crucial for determining mechanistic pathways and the key ROS species that contribute to high selectivity for oxidation processes. Tracking these reactive species can be challenging within heterogeneous systems. Most detection methods are hindered by the rapid decay of ROS, the complexity and cost of spin-trapping probes, lack of probe selectivity, and interference from other species in the reaction, which limits real-time ROS monitoring. There remains a need for reliable detection and scavenging methods, further combined with characterization techniques such as EPR, XPS, in situ DRIFTS, and oxygen isotope labeling. Prior review articles on ROS focus on applications in medicine, biological fields, and photocatalysis. This review examines the chemistry of molecular oxygen, generation mechanisms, and the detection of ROS in heterogeneous selective catalytic oxidations and our contribution to the field; we focus on literature published over the last five decades, highlight the specific challenges associated with studying these systems, and provide strategies for overcoming these limitations. Finally, we discuss in situ vs. ex situ ROS probing techniques and demonstrate their importance in dynamic catalytic systems.
Owing to its high hydrogen storage capacity (7.6 wt%), MgH2 is regarded as a highly promising solid-state hydrogen storage material. Nonetheless, its commercialization is constrained by high thermodynamic stability and sluggish hydrogen sorption kinetics. Thus, catalyst introduction is essential to enhance MgH2’s hydrogen storage performance. This study designed and synthesized a hydrogen storage high-entropy alloy, TiVCrZrNbCe. Upon doping with Ce to enhance activation, the alloy was combined with MgH2 to fabricate a composite hydrogen storage system, thereby boosting the overall hydrogen storage properties of MgH2. Results indicate that the Ce-doped alloy eliminates the initial long hydrogen absorption induction period and exhibits rapid hydrogen absorption capability. The optimal MgH2/10 wt% HEA composite for hydrogen storage incorporates a Ce-doped alloy and MgH2. MgH2/10 wt% HEA shows initial/peak dehydrogenation temperatures of 205/270 °C, releases 6.05 wt% hydrogen, and enables rapid hydrogen absorption at room temperature. The hydrogen sorption activation energies are reduced to 40.8/76.8 kJ mol−1, and the capacity maintains well over ten cycles. Microstructure and mechanism analyses reveal that during ball milling of the MgH2-alloy, the Ce element in the alloy will interact with MgH2 to partially absorb hydrogen to form CeH2.51 in situ and generate a hydride FCC-MH phase. During hydrogen absorption/desorption, CeH2.51 and the alloy serve as nucleation sites for MgH2, effectively promoting its hydrogenation/dehydrogenation reactions and exerting a “hydrogen overflow” effect. Additionally, the alloy’s self hydrogen absorption/desorption drives MgH2’s hydrogenation/dehydrogenation, functioning as a “hydrogen pump”. The hydrogen absorption/desorption properties of MgH2 were notably optimized via the synergistic catalysis of CeH2.51 and the alloy. This work offers novel insights for designing and catalytically modifying new MgH2 catalysts.
Developing efficient electrocatalysts for the electrochemical nitrogen (N-2) reduction reaction (eNRR) under ambient conditions is essential for sustainable ammonia (NH3) production. In this study, we have used density functional theory (DFT) calculations to investigate the eNRR performance of two perovskite oxynitrides, BaTaO2N and BaNbO2N. We have systematically analyzed the reduction pathways and free energy profiles along both distal and alternating pathways on the (0 0 1) and (1 0 0) facets to evaluate the influence of surface orientation on catalytic performance. Our results show that the pristine surfaces exhibit weak N-2 adsorption and require a high Gibbs free energy (Delta G > 1.8 eV) for the initial protonation step, thereby limiting their intrinsic catalytic activity for direct NH3 formation. We further explore defect engineering via the Mars-van Krevelen (MvK) mechanism, wherein lattice anions (nitrogen and oxygen) participate in vacancy formation and subsequent N-2 activation. On the BaNbO2N (0 0 1) surface, lattice nitrogen can be readily protonated and reduced to NH3, forming nitrogen vacancies that act as catalytic sites to facilitate N-2 adsorption and activation, thereby restoring the catalytic surface for sustained NH3 production. Notably, the nitrogen-vacant surface (N-v-BaNbO2N (0 0 1)) exhibits significantly enhanced N-2 adsorption, with a lower Gibbs free energy change (Delta G = 0.18 eV) for the first protonation step, and a thermodynamically favorable NH3 desorption process. Furthermore, the reduced surface strongly suppresses the competing hydrogen evolution reaction (HER), thereby promoting high selectivity for NH3 production under ambient conditions. This theoretical study offers valuable insights into the design of perovskite oxynitride-based electrocatalysts, offering a promising strategy for sustainable and economically viable NH3 synthesis.
