O2 Desorption Research Articles

A Cardiac-Targeting and Anchoring Bimetallic Cluster Nanozyme Alleviates Chemotherapy-Induced Cardiac Ferroptosis and PANoptosis.

Doxorubicin (DOX), a potent antineoplastic agent, is commonly associated with cardiotoxicity, necessitating the development of strategies to reduce its adverse effects on cardiac function. Previous research has demonstrated a strong correlation between DOX-induced cardiotoxicity and the activation of oxidative stress pathways. This work introduces a novel antioxidant therapeutic approach, utilizing libraries of tannic acid and N-acetyl-L-cysteine-protected bimetallic cluster nanozymes. Through extensive screening for antioxidative enzyme-like activity, an optimal bimetallic nanozyme (AuRu) is identified that possess remarkable antioxidant characteristics, mimicking catalase-like enzymes. Theoretical calculations reveal the surface interactions of the prepared nanozymes that simulate the hydrogen peroxide decomposition process, showing that these bimetallic nanozymes readily undergo OH⁻ adsorption and O₂ desorption. To enhance cardiac targeting, the atrial natriuretic peptide is conjugated to the AuRu nanozyme. These cardiac-targeted bimetallic cluster nanozymes, with their anchoring capability, effectively reduce DOX-induced cardiomyocyte ferroptosis and PANoptosis without compromising tumor treatment efficacy. Thus, the therapeutic approach demonstrates significant reductions in chemotherapy-induced cardiac cell death and improvements in cardiac function, accompanied by exceptional in vivo biocompatibility and stability. This study presents a promising avenue for preventing chemotherapy-induced cardiotoxicity, offering potential clinical benefits for cancer patients.

Valence state and redox property of Fe‐CNTs added CeO2/TiO2 catalyst

AbstractThe investigation focused on examining the impact of incorporating Fe‐carbon nanotubes (CNTs) on the valence state and oxygen vacancies, and the physicochemical parameters of the catalytic system. For the CeO2/TiO2 catalyst with Fe‐CNTs, no distinct X‐ray diffraction (XRD) peaks corresponding to Fe‐CNTs were observed. This indicated their uniform dispersion, supported by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) imaging. X‐ray photoelectron spectroscopy (XPS) analysis was conducted to observe the changes in the valence state due to the addition of Fe‐CNTs. The concentration of Ce3+ on catalyst surface increased from 19.90% to 29.48% with an increased concentration of the chemisorbed oxygen species (Oα). This suggests that the addition of Fe‐CNTs into CeO2/TiO2 catalyst reduced Ce4+ on the catalyst surface, resulting in the formation of oxygen vacancies. Oxygen temperature‐programmed desorption (O2‐TPD) and hydrogen temperature‐programmed reduction (H2‐TPR) analyses showed both the adsorbed oxygen species and H2 consumption increased with adding Fe‐CNTs. Furthermore, the onset temperatures for O2 desorption and H2 consumption became lower, confirming the enhancement of catalytic redox properties.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

Effect of different skeleton structures on N2O decomposition from ammonia-fueled engines using Fe-based zeolite catalysts

This study systematically investigated the relationship between active species and the direct decomposition of nitrous oxide (N2O) over various Fe-based zeolites (Fe-ZSM-5, Fe-SSZ-13, and Fe-Beta) based upon a simulated gas test platform. A comprehensive analysis with XRD, N2 adsorption–desorption, TEM, UV-Raman, XPS, H2-TPR, O2-TPD, and NH3-TPD was performed for structure and species change to investigate the role of Fe sites and acidity. A series of experiment results revealed a distinct hierarchy in the overall N2O decomposition, with Fe-ZSM-5 demonstrating the highest efficacy, achieving exceptional conversion rates exceeding 72 % at 400 °C, followed by Fe-Beta and Fe-SSZ-13. Fe species primarily occurred as isolated Fe3+ of Fe-ZSM-5 catalysts, serving as the main active species in N2O decomposition. In contrast, Fe species loaded on Fe-Beta catalysts were predominantly present within the straight pore channels, mostly as low-polymerized FexOy clusters, while Fe-SSZ-13 catalysts contained Fe2+, influenced by the cage structure. It should be noted that the unique pore structure of Fe-ZSM-5 facilitated a higher concentration of isolated Fe3+. Additionally, the Fe-ZSM-5 catalysts contained more adsorbed oxygen, which facilitated the desorption of O2 during the decomposition of N2O and promoted the overall decomposition process. The performance of the catalysts in decomposing N2O improved with increasing adsorbed oxygen content, consistent with the activity evaluation.

Built-in electric field construction and lattice oxygen activation for boosting alkaline electrochemical water/seawater oxidation

Oxygen evolution reaction (OER) remains a bottleneck for hydrogen production by water-alkali electrolysis at high industrial current density, but the structure–activity relationship of the catalyst and the underlying catalytic mechanism are still debated, which always limits the design of efficient catalysts. Herein, we report a proof-of-concept hierarchical hydroxide/sulfide (NiFe LDH/Ni3S2) heterostructure as model catalyst to simultaneously adjust the electronic states and activate lattice oxygen. As-activated NiFe LDH/Ni3S2 electrode displays promising OER capability with an ultra-low overpotential of 295 mV at the industrial current density of 500 mA·cm−2. The interface-induced built-in electric field effect promotes the asymmetric charge distribution on both sides. In-situ/ex-situ characterization demonstrates the adjusted intermediates adsorption/desorption and accelerated OER kinetics due to rapid electron transfer. A series of electrochemical probe experiments reveal that the OER mechanism of NiFe LDH/Ni3S2 follows the lattice oxygen mechanism. Especially, the super-strong wettability electrode design and structural advantages effectively enhance mass transfer and promote O2 desorption in alkaline water/seawater splitting systems. This work provides an avenue to break through OER limitations for efficient electrocatalytic water oxidation.

Mesoporous graphene-supported nanostructured nickel telluride for efficient electrocatalytic oxygen evolution reaction

The electrocatalytic oxygen evolution reaction (OER) imposes significant constraints on the operational overpotential of electrochemical energy devices, such as water electrolyzers, metal-air batteries, and fuel cells. However, the sluggish kinetics of OER reactions hinder these applications, which has prompted efforts to design more effective electrocatalysts. In this study, we have synthesized NiTe via in-situ growth into mesoporous graphene (MG), with varying nominal weight percentages (5- wt%, 10- wt%, and 15- wt%) of NiTe. The resulting NiTe/MG nanohybrids displayed hexagonally structured NiTe nanoparticles with a predominant (101) surface that promotes the OER kinetics. The wrinkled 3D mesoporous graphene scaffold facilitated the attachment and dispersion of NiTe particles of nanoscale on its surface, preventing their agglomeration. The porous characteristics of the MG significantly increased the high surface area of the NiTe/MG nanohybrids (583–671 m2 g−1), promoting enhanced accessibility of active sites and mass transport beneficial for the OER. Moreover, the altered electronic structure of the NiTe in the MG nanohybrid indicates enhancing O2 desorption during the OER. The optimized composition of the 10 wt% NiTe-loaded MG nanohybrid electrocatalyst demonstrates superior OER activity compared to other nanohybrids. It exhibits a small overpotential of 250 mV at 10 mA cm−2, a low Tafel slope of 63 mV dec−1 and maintained stability in 1 M KOH (pH = 14) as the electrolyte for a prolonged period. This enhanced OER activity is ascribed to the synergistic effect of MG’s high conductivity and the improved intrinsic activity of NiTe within the nanohybrid structure.

Assessing the dynamics of O2 desorption from cobalt phthalocyanine by in situ electrochemical scanning tunneling microscopy

We report here the in situ electrochemical scanning tunneling microscopy (ECSTM) study of cobalt phthalocyanine (CoPc)-catalyzed O2 evolution reaction (OER) and the dynamics of CoPc-O2 dissociation. The self-assembled CoPc monolayer is fabricated on Au(111) substrate and resolved by ECSTM in 0.1 M KOH electrolyte. The OH− adsorption on CoPc prior to OER is observed in ECSTM images. During OER, the generated O2 adsorbed on CoPc is observed in the CoPc monolayer. Potential step experiment is employed to monitor the desorption of OER-generated O2 from CoPc, which results in the decreasing surface coverage of CoPc-O2 with time. The rate constant of O2 desorption is evaluated through data fitting. The insights into the dynamics of Co-O2 dissociation at the molecular level via in situ imaging help understand the role of Co-O2 in oxygen reduction reaction (ORR) and OER.

Homogeneous In‐Plane Lattice Strain Enabling d‐Band Center Modulation and Efficient d–π Interaction for an Ag2Mo2O7 Cathode Catalyst With Ultralong Cycle Life in Li‐O2 Batteries

AbstractAlthough lithium–oxygen batteries (LOBs) hold great promise as future energy storage systems, they are impeded by insulated discharge product Li2O2 and sluggish oxygen reduction reaction/oxygen evolution revolution (ORR/OER) kinetics. The application of a highly efficient cathode catalyst determines the LOBs performance. The d‐band modulation and catalytic kinetics promotion are important concept guidelines for the performance enhancement of cathode catalysts. In this work, the homogeneous in‐plane distortion‐derived synergistic catalytic capability of an Ag2Mo2O7 catalyst with modulated d‐band centers and promoted ORR/OER kinetics is demontrated. The uniform elongation of Ag─O bonds and compression of Mo─O bonds in (020) plane leads to d‐band splitting and d‐band center optimization and delivers improved adsorption behavior for high ORR/OER capability. Furthermore, the spatial and energy overlap of Ag dxz and O2 anti‐bonding π* orbitals facilitate electron injection during ORR process and reduce the energy barrier for charge transfer and O2 desorption during OER process, accelerating the ORR/OER kinetics. As a result, the (020) plane‐exposed Ag2Mo2O7 cathode exhibits ultralong cycle stability of 817 cycles at 500 mA g−1 and large specific discharge/charge capacities of 15898/15180 mAh g−1. This work provides facile concept guidance for optimizing catalytic capability through controlled lattice distortion in cathode catalysts for LOBs.

Effect of N2/CO2 Injection on O2 Desorption in Coal Rocks Containing CH4

Effect of N2/CO2 Injection on O2 Desorption in Coal Rocks Containing CH4

Spatially Axial Boron Coordinated Single‐Atom Nanozymes with Boosted Multi‐Enzymatic Performances for Periodontitis Treatment

AbstractSingle‐atom nanozymes (SAzymes) have made significant strides in antibacterial treatment but fall short as natural enzyme and drug replacements due to limited catalytic performance. Here, a rational strategy is presented for incorporating spatially axial boron (B) ligands to effectively modulate the local coordination environment of planar Fe─N4 motifs (Fe─B/N─C SAzymes). With electronic modulation, the Fe─B/N─C SAzymes exhibit significantly enhanced oxidase‐, peroxidase‐, and catalase‐like activities. Theoretical calculations highlight that the spatially axial B ligands effectively adjust the charge distribution around the planar Fe─N4 active center, which facilitates the heterolysis of H2O2 and the desorption of O2, resulting in accelerated H2O2 decomposition. Furthermore, the intrinsic photothermal effect of Fe─B/N─C SAzymes enhances multienzyme‐like activities, rapidly generating abundant reactive oxygen species (ROS), and achieving chemodynamic/photothermal synergistic therapy for impressive disinfection against periodontal‐related pathogenic bacteria. These findings offer a distinctive viewpoint for optimizing the local coordination environment of SAzymes with axial ligand to enhance their catalytic performance and effectiveness in periodontitis therapy.

Inter-site structural heterogeneity induction of single atom Fe catalysts for robust oxygen reduction

Metal-nitrogen-carbon catalysts with hierarchically dispersed porosity are deemed as efficient geometry for oxygen reduction reaction (ORR). However, catalytic performance determined by individual and interacting sites originating from structural heterogeneity is particularly elusive and yet remains to be understood. Here, an efficient hierarchically porous Fe single atom catalyst (Fe SAs-HP) is prepared with Fe atoms densely resided at micropores and mesopores. Fe SAs-HP exhibits robust ORR performance with half-wave potential of 0.94 V and turnover frequency of 5.99 e−1s−1site−1 at 0.80 V. Theoretical simulations unravel a structural heterogeneity induced optimization, where mesoporous Fe-N4 acts as real active centers as a result of long-range electron regulation by adjacent microporous sites, facilitating O2 activation and desorption of key intermediate *OH. Multilevel operando characterization results identify active Fe sites undergo a dynamic evolution from basic Fe-N4 to active Fe-N3 under working conditions. Our findings reveal the structural origin of enhanced intrinsic activity for hierarchically porous Fe-N4 sites.

Non-Noble-Metal-Doped Carbon Nitride Photocatalysts for Water Splitting Screened Out by Empty Defect States and the d-Band Center.

A rational design of water-splitting photocatalysts from the perspective of the electronic structure is highly desirable for optimizing catalytic activities. However, the structure-activity relationship is still unclear, which impedes the development of efficient catalysts. Herein, by comparing systematically the overall water-splitting capability of 20 kinds of metallic elements anchored at three sites (including cavity, carbon vacancy, and nitrogen vacancy) of graphitic carbon nitride (g-C3N4) through density functional theory calculations, we uncover that availability of in-gap empty defect states and the d-band center position are paramount parameters to determine activities of g-C3N4 on photocatalytic water splitting. In-gap empty states play a role in accommodating electrons from H2O to facilitate its splitting. A lower d-band center weakens the interaction between reaction intermediates and g-C3N4, thereby promoting O2 desorption. Metals embedded at carbon vacancies are found to be superior to those at cavities and nitrogen vacancies because the former not only provides ample in-gap empty states but also has a lower d-band center. We also discover a rule that, for a reaction in which the bond order between the metal and intermediate enlarges (reduces), its reaction difficulty increases (decreases) with the increasing atomic number for elements in the same period. After screening, we find that non-noble metals Co, Ni, and Ga anchored at carbon vacancies possess catalytic performances comparable to Pd- and Pt-doped systems, with the rate-determining barriers less than 0.55 eV. Our findings may provide useful information for designing effective photocatalysts.

Lattice oxygen activation and local electric field enhancement by co-doping Fe and F in CoO nanoneedle arrays for industrial electrocatalytic water oxidation

Oxygen evolution reaction (OER) is critical to renewable energy conversion technologies, but the structure-activity relationships and underlying catalytic mechanisms in catalysts are not fully understood. We herein demonstrate a strategy to promote OER with simultaneously achieved lattice oxygen activation and enhanced local electric field by dual doping of cations and anions. Rough arrays of Fe and F co-doped CoO nanoneedles are constructed, and a low overpotential of 277 mV at 500 mA cm−2 is achieved. The dually doped Fe and F could cooperatively tailor the electronic properties of CoO, leading to improved metal-oxygen covalency and stimulated lattice oxygen activation. Particularly, Fe doping induces a synergetic effect of tip enhancement and proximity effect, which effectively concentrates OH− ions, optimizes reaction energy barrier and promotes O2 desorption. This work demonstrates a conceptual strategy to couple lattice oxygen and local electric field for effective electrocatalytic water oxidation.

Selective Adsorption of Oxygen from Humid Air in a Metal-Organic Framework with Trigonal Pyramidal Copper(I) Sites.

High or enriched-purity O2 is used in numerous industries and is predominantly produced from the cryogenic distillation of air, an extremely capital- and energy-intensive process. There is significant interest in the development of new approaches for O2-selective air separations, including the use of metal-organic frameworks featuring coordinatively unsaturated metal sites that can selectively bind O2 over N2 via electron transfer. However, most of these materials exhibit appreciable and/or reversible O2 uptake only at low temperatures, and their open metal sites are also potential strong binding sites for the water present in air. Here, we study the framework CuI-MFU-4l (CuxZn5-xCl4-x(btdd)3; H2btdd = bis(1H-1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin), which binds O2 reversibly at ambient temperature. We develop an optimized synthesis for the material to access a high density of trigonal pyramidal CuI sites, and we show that this material reversibly captures O2 from air at 25 °C, even in the presence of water. When exposed to air up to 100% relative humidity, CuI-MFU-4l retains a constant O2 capacity over the course of repeated cycling under dynamic breakthrough conditions. While this material simultaneously adsorbs N2, differences in O2 and N2 desorption kinetics allow for the isolation of high-purity O2 (>99%) under relatively mild regeneration conditions. Spectroscopic, magnetic, and computational analyses reveal that O2 binds to the copper(I) sites to form copper(II)-superoxide moieties that exhibit temperature-dependent side-on and end-on binding modes. Overall, these results suggest that CuI-MFU-4l is a promising material for the separation of O2 from ambient air, even without dehumidification.

An asymmetric electrode matching reversible kinetics of oxygen reaction for a rechargeable Zn-air battery

The development of zinc-air batteries (ZABs) is hindered by the sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) which occur in the complex interfaces between gaseous oxygen, liquid electrolyte and solid catalyst. Designing a rational interface that aligns with the kinetics of these multi-phase reactions is of utmost importance. Herein, an asymmetric cathode (Asy-electrode) has been designed and fabricated that the carbon nanotubes arrays (CNAs) encapsulating Co nanoparticles grown on carbon cloth is used as the aerophilic side (AI-side) to match and catalyze the ORR kinetics, the other side that deposition of NiFe layered double hydroxide (NiFe-LDH) on the CNAs plays as aerophobic side (AO-side) to accelerate the OER kinetics. The Asy-electrode effectively balances the adsorption and desorption of O2 and OH–, and promotes the efficient transport of gaseous and liquid reactants and products. Therefore, the efficiency of ORR and OER onto the corresponding catalytic sites of Co/CNAs and NiFe-LDH/CNAs are significantly enhanced. Consequently, the ZAB employing the asymmetric cathode can acquire a remarkable higher power density (236.26 mW cm−2) and an excellent long-term cycling stability (over 1920 cycles at 10 mA cm−2) due to the enhanced kinetic and the improved reversibility of the charge–discharge reaction on the cathode benefiting from the aerophilic/hydrophilic interfacial construction on each side of electrode. The present study could explore a route to design the catalysts from the view of matching the multi-phase reaction characteristics.

Porosity in Sr1−xCaxFeO3-δ oxygen carriers: The role of surface area and pretreatment on storage activity

Perovskite oxides have generated interest as robust, low-temperature oxygen carrier materials for a variety of clean energy applications, including chemical looping gasification and air separations. Methods to improve O2 desorption kinetics are vital to allow these carriers to compete economically with traditional metal oxide carriers or cryogenic separations. Herein, we investigated the cumulative roles that surface area, pretreatment, and elemental composition have on the oxygen storage properties of a state-of-the-art carrier system, Sr1−xCaxFeO3-δ (x = 0.20, 0.25, 0.30) synthesized using multiple methods. Porous materials synthesized by the Pechini, or citrate, method had their surface area controlled using the synthesis temperature. The high surface area of the Sr0.7Ca0.3FeO3-δ materials is most beneficial at low operating temperatures, such as 350 and 400 °C, as their reduction rates are twice as fast as those obtained with their bulk counterparts. These effects are observed at higher operating temperatures and within a single composition, but temperature tunability using variable Ca2+ substitution in the Sr1−xCaxFeO3-δ overshadows the improvements gained from higher surface areas. Additionally, we establish that pretreatment in N2 at an elevated temperature is necessary to enhance kinetics further. For maximum efficiency, pretreatment at the synthesis temperature is suggested for the Pechini method-synthesized systems, whereas 800 °C is adequate for bulk materials.

Characterization of adsorption sites on IrO2via temperature programmed O2 desorption simulations.

This study presents simulations of temperature-programmed desorption (TPD) profiles using desorption energy data from density functional theory (DFT) calculations. We apply this method to investigate the desorption of oxygen (O2) from IrO2(110) to gain insight into the kinetics of oxygen coupling and desorption, important elementary steps in the oxygen evolution reaction (OER). Initially, we confirm the thermodynamically stable adsorption site for oxygen in the pristine IrO2(110) as IrCUS, even with a high oxygen coverage. We successfully simulate TPD for O2 desorption, achieving good agreement with experimental TPD data for different initial oxygen exposures when including more than one adsorption site. We identify a new adsorption site, related to the formation of steps on IrO2(110)(IrCUS-step-0.5), that is essential for reproducing the experimental TPD. Our findings suggest that the observed TPD peaks are the result of different adsorption sites on the surface, rather than solely a lateral interactions effect. This work provides insight into the behavior of oxygen adsorption on IrO2, with implications for understanding surface reactivity and catalytic processes involving this material.

Flux and fluence effects on the vacuum-UV photodesorption and photoprocessing of CO2 ices.

CO2 is a major component of the icy mantles surrounding dust grains in planet and star formation regions. Understanding its photodesorption is crucial for explaining gas phase abundances in the coldest environments of the interstellar medium irradiated by vacuum-UV (VUV) photons. Photodesorption yields determined experimentally from CO2 samples grown at low temperatures (T = 15 K) have been found to be very sensitive to experimental methods and conditions. Several mechanisms have been suggested for explaining the desorption of CO2, O2 and CO from CO2 ices. In the present study, the cross-sections characterizing the dynamics of photodesorption as a function of photon fluence (determined from released molecules in the gas phase) and of ice composition modification (determined in situ in the solid phase) are compared for the first time for different photon flux conditions (from 7.3 × 1012 photon per s cm-2 to 2.2× 1014 photon per s cm-2) using monochromatic synchrotron radiation in the VUV range (on the DESIRS beamline at SOLEIL). This approach reveals that CO and O2 desorptions are decorrelated from that of CO2. CO and O2 photodesorption yields depend on photon flux conditions and can be linked to surface chemistry. In contrast, the photodesorption yield of CO2 is independent of the photon flux conditions and can be linked to bulk ice chemical modification, consistently with indirect desorption induced by an electronic transition (DIET) process.

Dense r-Ru/FeCoP heterointerfaces induced by a defect-assisted strategy for ultrastable alkaline overall water splitting.

Simplifying the anchoring process of Ru nanoparticles (NPs) and activating their bifunctional activity are challenges in the construction of Ru-based catalysts. In this work, FeCoP nanosheets anchored by Ru NPs (r-Ru/FeCoP) were innovatively synthesized using an oxygen defect-assisted-gas-phase phosphorization strategy. Surprisingly, the η100 values of r-Ru/FeCoP in the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes were 0.8 and 0.58 times those of Pt/C and RuO2, respectively. Notably, the rich Ru NPs as HER active sites on r-Ru/FeCoP enhanced the conductivity of the catalyst and promoted the reaction kinetics for HER, while the metal atoms on the FeCoP nanosheets served as OER active sites to accelerate the desorption of O2. The synergy between the two promoted the improvement of overall water splitting efficiency. Overall, this work provides a new approach for the development of low-cost bifunctional catalysts with high Ru utilization.

Impact of operation parameters and lambda input signal during lambda-dithering of three-way catalysts for low-temperature performance enhancement

A synthetic exhaust gas bench was dynamically operated to investigate the impact of temperature, amplitude, split cycle, mean lambda, gas hourly space velocity, and oxygen storage capacity on average pollutant conversion and product selectivity of three-way catalysts in periodic operation. As temperature and amplitude increase and oxygen storage capacity decreases, the optimal frequency for maximum pollutant conversion increases. This is consistent with faster desorption of CO and O2 from the catalyst, yielding free surface sites. Regarding the formation of secondary products, the optimal frequency for maximum pollutant conversion does not always correspond to minimal N2O and NH3 emissions. The split cycle variation reveals the enhancement of C3H8 and NO conversion after both lean-rich and rich-lean switches and C3H6 and CO conversion after rich-lean switches at the optimal frequency. As periodic operation does not affect existing engine settings or operating conditions, it is a cost-effective control strategy for meeting future emission limits.