O2 Adsorption Research Articles

Fine-Tuning the d-Band Center Position of Zinc to Increase the Anti-Tumor Activity of Single-Atom Nanozymes.

The exceptional biocompatibility of Zn-based single-atom nanozymes (SAzymes) has led to extensive research in their application for disease diagnosis and treatment. However, the fully occupied 3d10 electron configuration has seriously hampered the enzymatic-like activity of Zn-based SAzymes. Herein, a B-doped Zn-based SAzymes is fabricated by carbonizing zeolite-like Zn-based boron imidazolate framework at different temperatures (Zn-SAs@BNCx, x = 800, 900, 1000, and 1100°C). The formed B─N bond yielded a local electric field, which changes the position of the d-band center and improved the oxidation state of Zn by facilitating the electron transfer from Zn to N to B. These changes enhanced the adsorption and activation of H2O2 and O2 by Zn-SAs@BNC1000, increasing the nanozymes' multi-enzyme catalytic activity. B doping led to 24.81-, 32.37-, and 13.98-fold increase in the peroxidase-, oxidase- and catalase-like, respectively, catalytic efficiency (Kcat/Km) of Zn-SAs@BNC1000 when compared with no B doping. In addition, Zn-SAs@BNC1000 showed excellent ability to kill tumor cells both in vitro and in vivo. This study demonstrates that the modulation of the electron configuration of Zn is an effective strategy to develop efficient anti-tumor approaches by boosting the enzymatic activity of Zn-based SAzymes.

Study on the variability of oxygen adsorption behavior in coal gangue based on pore size structure

To investigate the adsorption and migration behavior of oxygen in coal gangue with different pore sizes, this study characterizes the multiscale morphology of coal gangue pores and fractures using SEM NMR, and low-temperature N2 (77 K) adsorption methods. As well, the study simulates the adsorption and diffusion behavior of O2 within the pore structures of coal gangue based on GCMC and MD methods. The study examines the oxygen adsorption characteristics across different pore sizes and analyzes the mass transfer mechanisms during oxygen diffusion. Results indicate that the pores in coal gangue are predominantly micropores within the 1–10 nm range. As pore size increases, the absolute adsorption amount of oxygen increases while the isosteric heat of adsorption decreases. The isosteric heat of adsorption in coal gangue models with different pore sizes is less than 42 kJ/mol, indicating the physical adsorption of oxygen within the pores. Oxygen shows adsorption layering perpendicular to the coal gangue surface, with adsorption density distribution differences decreasing and adsorption capacity weakening as pore size increases. The O2 adsorption isotherms in coal gangue follow Langmuir adsorption principles, with oxygen saturation adsorption decreasing as absolute adsorption increases. The confinement effect of coal gangue on oxygen weakens as pore size increases, and the impact of increasing pore size on oxygen diffusion is stronger than adsorption. These findings are significant for understanding the microscopic adsorption and diffusion behavior of O2 in coal gangue pores and fractures and are crucial for accurately preventing and managing spontaneous combustion in coal gangue piles.

Fabrication of boron modified bi-functional air diffusion electrode for ciprofloxacin degradation: In-situ H2O2 generation and self-activation

In order to improve H2O2 in-situ generation in electrochemical system, a boron (B) modified air diffusion electrode (B@ADE) was fabricated in the present study. Carbon black (CB) doped by B was deposited on ADE surface as catalytic layer. Performance of B@ADE with different B/C mass ratios has been investigated and 0.3 was identified as the optimal one·H2O2 yield can be achieved 204.85 mg L-1 within 45 min at 0.3-B@ADE, which was 1.51 times for that of ADE. Meanwhile, H2O2 self-activation on B@ADE surface was observed and effects of different operating parameters on •OH formation have been analyzed. XPS analyzation demonstrated that BC2O, BC2O and C=O/O-C=O were related to H2O2 generation. DFT calculation revealed that BCO2 was benefit for O2 adsorption, while BC2O promoted *OOH desorption with lower free energy barriers for H2O2 and •OH generation. Quenching experiments for ciprofloxacin (CIP) demonstrated that •OH, O2•- and 1O2 were co-existed in the system with their contribution quantified. Four possible degradation pathways were proposed through active sites identification by DFT calculation and intermediates detection by HPLC-MS/MS. Bio-toxicity analyzation results showed that the toxicity of most intermediates was lowered than CIP. These results proved that electrochemical oxidation system with B@ADE enhanced in-situ H2O2 generation and self-activation, with great potential for practical application.

Experimental and DFT studies of mercury adsorption and oxidation on CuCo2O4(110) surface

Elemental mercury (Hg0) is a typical toxic pollutant in flue gas from coal-fired power plants. The specific role of oxygen transfer on Hg0 oxidation over CuCo2O4 oxygen carrier and the involved reaction mechanisms were systematically studied by experimental and theoretical methods. In this study, the CuCo2O4 oxygen carrier with spinel-structure was prepared with salt-assisted combustion method. To reduce the grain size and increase the specific surface area of the oxygen carrier, the optimal KCl: CuCo2O4 ratio of 1:1 was obtained. Oxygen uncoupling ability of CuCo2O4 oxygen carrier was very strong, and the oxygen-releasing performance was slightly decreased after ten cyclic processes. Simulation based on density functional theory (DFT) shows that CuCo2O4 has relative low oxygen vacancy formation energy and oxygen transport energy barrier, and the oxygen vacancy is the preferred O2 adsorption site. Hg0 removal experiments show that CuCo2O4 has a strong ability to remove Hg0. The proportion of Hg2+ increases with the temperature, and the proportion of HgP decreases accordingly. Simulation shows that the 3-Co site on the surface of the CuCo2O4 oxygen carrier is the optimum Hg0 adsorption site. CuCo2O4 is found as a strong oxygen-releasing oxygen carrier, which can effectively promote the oxidation of Hg0.

Oxidation behavior of Fe-Ni Invar alloy under high pressure: A ReaxFF molecular dynamics study

The Fe-Ni Invar alloy is often employed under extreme conditions such as high temperatures, high pressures, and corrosive environments, making it susceptible to oxidation and subsequent failure. Hence, a thorough understanding of its oxidation behavior is crucial. We performed ReaxFF-based molecular dynamics (MD) simulations to study the oxidation behaviour of Fe-Ni Invar alloy at the atomic scale under extreme conditions. The initial stage of oxidation involves the preferential adsorption and dissociation of O2, demonstrating its surface-site selectivity. The initial oxidation kinetics follows a logarithmic law, and the whole oxidation process results in dominant low-coordinated clusters configurations in the oxide film. Simultaneously, Fe atoms tend to donate more electrons to O atoms than Ni atoms. Moreover, the O2 consumption rate were found to increase with pressure and amorphous oxides formed more readily under high pressure. Our results indicate that adjusting the pressure may enhance the oxidation resistance of the Fe-Ni alloy, which is significant for the design and application of alloys in extreme conditions.

Synergetic effect of Fe decorated MnO2 nanocatalyst application in propane and benzyl alcohol oxidation

In heterogeneous catalysis, one of the key challenges is to develop inexpensive and abundant materials. Herein, spherically shaped α–Fe2O3 nanoparticles decorated over MnO2 nanorods surface (Fe/MnO2NRs) was synthesized via hydrothermal followed by co–precipitation methods. Experimental results indicated that the inclusion of Fe in MnO2NRs promotes a strong interaction that increases the reducibility of Mn4+ to Mn3+ and surface adsorbed oxygen (Oads.), which in turn increases the activation of surface oxygen on MnO2NRs. The 10 wt% Fe–loaded catalyst (10Fe/MnO2NRs) exhibited the highest catalytic activity. It was observed that oxidizing 10 % (T10), 50 % (T50), and 90 % (T90) of propane required temperatures of 140 °C, 180 °C, and 220 °C, respectively. This catalyst showed stability in H2O atmospheres and apparent activation energy as low as 52.54 kJ mol−1. In addition, the vapour phase oxidation of benzyl alcohol (BnOH) over different Fe–loaded MnO2NRs catalysts is investigated. The rate of BnOH oxidation over 10Fe/MnO2NRs catalyst is 1.71 times greater than bare MnO2NRs at 240 °C. The increased oxygen vacancies can improve the oxidation activity of propane and BnOH by facilitating the adsorption and activation of O2 to produce reactive oxygen species. This work offers a novel approach to increase manganese oxides surface oxygen activity, which can be used to create efficient catalysts for the low–temperature decomposition of volatile organic compounds (VOCs) and other organic functional group transformations via oxidation reaction.

Sulfur modified N-doped carbocatalysts promote the selectivity for H2S selective oxidation

Sulfur element is widely applied as a non-metallic dopant into carbon framework for the modulation of their chemical activities. An interesting question is whether the intrinsic catalytic performances for the H2S selective oxidation to sulfur can be manipulated by sulfur element introduction into carbocatalysts. In this study, we employ a simple solvent-free method to introduce S atoms into framework of N-doped carbocatalysts, resulting in a notable enhancement of the product S selectivity with negligible loss of H2S selective oxidation. The experimental results show that the as-synthesized N-S-C-2 catalyst exhibits a H2S conversion of 97.5 % and sulfur selectivity of >80 % at a high O2-to-H2S ratio (2.5) under continuous mode (over the dew point temperature of sulfur, c.a. 210 °C), while also demonstrating robust stability (> 100 h), anti-CO2 (up to 50 vol%) and anti-oxidation properties. Kinetic analysis and H2S/O2-TPD-MS results reveal that S introduction attenuates the adsorption and dissociation of H2S and O2 by the N-doped carbon catalyst. Furthermore, density functional theory calculations elucidate that S doping elevates the adsorption energies of H2S and O2 at the pyridinic N site, thereby moderately reducing the adsorption of H2S and O2, consequently preventing the over-oxidation of H2S to SO2 and enhancing S selectivity. The double doping promotion effect of carbon materials reported in this investigation offers an alternative insight for the development of highly selective carbon desulfurization catalysts.

Preparation of CuCo2O4@NFs nanoflower material with abundant VO/VCo: An excellent catalyst for oxidative breakage of the β-O-4 bond of lignin

A hollow nanoflower material CuCo2O4@NFs with abundant oxygen vacancies (VO) and cobalt vacancies (VCo) was prepared by a simple method. The novel material CuCo2O4@NFs showed excellent oxidation activity, cleaving the β-O-4 bond in lignin model compounds. Conversion of the substrate was as high as 99.02%, and the yield of the main product, phenol, reached 49.50%. Structural analysis showed that the petal and cavity form of the material increased its specific surface area, which facilitated its full contact with O2 molecules. Moreover, the VO generated by lattice oxygen detachment during annealing favor the adsorption of O2, and the VCo generated through lattice distortion induced by Cu-metal doping promoted the detachment of oxygen intermediates. The synergy of these two defects improved the rate of the rate-limiting step. Density functional theory calculations revealed that the synergistic effect of VO and VCo narrowed the gap between the Fermi energy levels and the d-band center, thereby enhancing electron mobility. Finally, excellent recyclability of CuCo2O4@NFs was confirmed through cycling experiments. The application of this material provided technical support for the efficient cracking of lignin into high-value-added chemicals and realized the effective utilization of woody biomass resources.

Study on the mechanism of competitive adsorption on the surface of potassium carbonate during direct air capture process

Direct air capture carbon dioxide (DAC) technology has the potential to achieve negative carbon emissions. Alkali metal-based absorbents (the active ingredient is mainly potassium carbonate or sodium carbonate) have a broad application prospect in DAC field. There is a paucity of reports on the competitive adsorption of major components of air on adsorbent surfaces. In this paper, the competitive adsorption behaviors of CO2, H2O, N2, and O2 on the surface of K2CO3 were investigated based on first principles and density functional theory (DFT), the synergic competition mechanism of each gas during adsorption was revealed by analyzing the parameters of adsorption energy, charge transfer, weak interactions and so on. The results showed that the maximum adsorption energy of CO2 by K2CO3 was 0.557 eV, and the relationship between the maximum adsorption energies of the four gases was O2 > H2O > CO2 > N2. The interaction between H2O and CO2 during co-adsorption inhibited their adsorption on the K2CO3 surface, especially weakening the adsorption effect of the surface O atoms on the H2O. Under CO2_N2_O2 gas composition, CO2 chemisorption occurred due to the strong oxidizing property of O2, the charge transfer effect commonly existed in the adsorption process of each gas, which contributed the most to O2 adsorption. The obtained results can further deepen the decarbonization mechanism of alkali metal-based adsorbents.

Cu‐Doped 0D Bi2WO6 Nanoparticles for Efficient Visible‐Light‐Driven Photocatalytic Tetracycline Degradation

AbstractBismuth‐based photocatalysts have been widely employed in the photocatalytic degradation of organic pollutants in wastewater. However, the lack of rational structural design and the slow generation of active free radicals have hindered its efficiency. Here, we stabilized Bi2WO6 nanoparticles by wrapping them with hydroxyl groups, introduced metal Cu doping, and underwent an annealing process to construct Cu‐BiNP nanocatalysts with exposed active sites. Under visible light irradiation, 0.03Cu‐BiNP achieved a 94.5% TC degradation efficiency, which is 15.8 times higher than the rate of bulk BiWO. The 0D structure endows Cu‐BiNP with ample opportunities for O2 adsorption and activation, and Cu atomic doping reduces the bandgap and increases the oxygen vacancy, promoting the generation of active oxygen species. This work demonstrates the rapid charge separation and activation of O2 to generate active oxygen species by 0D bismuth‐based nanocatalysts in photocatalytic oxidation reactions, providing a scalable nanocatalyst platform for TC photocatalytic degradation.

Electrocatalysis of Co/CoxOy nanofilms supported by synchronously nitrogen-doped Ketjenblack carbon towards oxygen reduction reaction

Developing a highly active and stable non-precious metal catalyst for oxygen reduction reaction (ORR) is of great practical significance for advancing fuel cell technology. In this work, a continuous two-step hydrothermal reaction followed by high temperature pyrolysis were employed to achieve in situ N-doping preferentially into Ketjenblack carbon (KB-N) and composite of KB-N and Co/CoxOy nanofilms (Co/CoxOy-NFs) as Co/CoxOy-NFs@KB-N. The N-doped state strongly affects the ORR activity of catalyst. All prepared Co/CoxOy-NFs@KB-N catalysts exhibit observably improved ORR activity compared with the basal KB-N and N-doped Co/CoxOy-NFs, in which the optimal Co/CoxOy-NFs@KB-N catalyst demonstrate the positive Eonset (0.864 V) and E1/2 (0.788 V) vs. RHE, the low Tafel slope (69.27 mV dec−1), implying quick ORR kinetics. And, the Co/CoxOy-NFs@KB-N catalyst exhibits highly electrochemical durability. The KB-N substrate can purify Co valence in CoO component, promote amorphization of CoO crystalline structure and enhance the interaction between Co/CoxOy-NFs and KB-N in Co/CoxOy-NFs@KB-N catalyst. Thus electronic effect, structural effect and synergistic effect can strengthen O2 adsorption, provide enough adsorbed sites and accelerate electron transfer, resulting in prominent ORR performance of Co/CoxOy-NFs@KB-N catalyst.

Highly catalytic performance for the selective C–H bond oxidation of p-chlorotoluene over Co, Cr co-doped OMS-2 catalyst

Using O2 as an oxidant, developing a non-noble metal catalyst for the selective catalytic C–H bond oxidation of p-chlorotoluene is desirable and challenging. In this work, a series of Co, Cr co-doped OMS-2 (Octahedral Molecular Sieve-2) catalysts were prepared by a conventional refluxing method. It was found that the incorporation of Co and Cr improved the catalytic activity for the selective oxidation of p-chlorotoluene to p-chlorobenzaldehyde. Among these catalysts, CoCr/OMS-2 (Co: Cr = 1: 1, mass ratio), the best catalyst, shows that the conversion and the selectivity of p-chlorobenzaldehyde is 94.8 % and 94.3 %, respectively. The enhanced catalytic activity was due to the larger specific surface area and even dispersion of active components. The characterization results also disclosed that the co-doping of Co and Cr increased the oxygen vacancy and enhanced the ability to activate the surface lattice oxygen. Additionally, density functional theory calculations demonstrated that co-doping of Co and Cr promoted the adsorption of p-chlorotoluene and O2, and decreased the energy barrier of rate-determining step (the conversion of p-chlorobenzyl alcohol to p-chlorobenzaldehyde). Besides, when H2O was added to the reaction system as the second solvent, the activation and dissociation of O2, and the formation of p-chlorobenzaldehyde were facilitated, in agreement with the experimental results. This work demonstrated the promotional effect of Co, Cr co-doped into OMS-2 catalyst and the role of H2O for the selective oxidation of p-chlorotoluene.

Nanoscale Synergy: Unveiling Gas Sensing Paradigms Through First Principles Exploration of Vertical Hexagonal Boron Nitride/Graphene Heterostructures

Modern civilization relies on rapid and accurate gas molecule identification at low concentrations for environmental surveillance, civilian security, healthcare evaluation, and inside atmospheric control. Density functional theory simulations are used to study the adsorption of CH4, CO2, PH3, N2O, NH3, O3, and SO2 gas molecules on a vertical hexagonal boron nitride/graphene heterostructure using the CASTEP code. Negative adsorption energy is only detected for NH3, O3, and SO2 gases. Our adsorption energy measurements show that the heterostructure is sensitive to NH3, O3, and SO2 gas molecules but insensitive to other gas molecules, as shown by the positive results. Further electrical and optical properties are only performed on gas‐adsorbed structures. It is found that the pure heterostructure acts like a semiconductor and has a band gap of 1.742 eV, which changes when gas is absorbed. Each of the structures has high absorption coefficients in the UV region, making them promising candidates for optoelectronic devices. The determination of the adsorbed gas type can be achieved by measuring the peak intensity and peak position of reflection or absorption. Heterostructures exhibit superior sensing capabilities for NH3 compared to other gases because of their enhanced adsorption energy, distinctive electrical band gap, and notable optical characteristics.

First-principles study of O3 molecule adsorption on pristine, N, Ga-doped and -Ga-N- co-doped graphene

The adsorption of O3 molecules (ozone) on graphene, N-doped graphene, Ga-doped graphene, and -Ga-N- co-doped graphene with an emphasis on O3 detection was examined in this work. The physical characteristics of -Ga-N-co-doped graphene are significantly altered upon O3 adsorption, which makes it a suitable choice for O3 detection molecular sensors. The interaction between the O3 molecule and the adsorbent is explained on the basis of their adsorption energy, adsorption distance and charge transfer. It was found that the adsorption of ozone molecules on the -Ga-N- co-doped graphene was more favorable in energy than that on the pristine one, representing the superior sensing performance of -Ga-N- co-doped system. In our work, we estimated the charge transfer between the O3 molecule and doped graphene nanostructures based on Mulliken population analysis. The calculated adsorption energy value shows the ozone molecule more firmly adsorbs on the surface of -Ga-N- co-doped graphene nanostructures (Eads = –1.74 eV) than that of pristine graphene (Eads = –0.41 eV), deriving from a stronger covalent bond between the ozone molecule and the -Ga- N- co-doped graphene nanostructures. Our findings thus suggest that -Ga-N- co-doped graphene could be a highly efficient gas sensor device for O3 detection in the environment.

Main-group element-boosted oxygen electrocatalysis of Cu-N-C sites for zinc-air battery with cycling over 5000 h

Developing highly active and durable air cathode catalysts is crucial yet challenging for rechargeable zinc-air batteries. Herein, a size-adjustable, flexible, and self-standing carbon membrane catalyst encapsulating adjacent Cu/Na dual-atom sites is prepared using a solution blow spinning technique combined with a pyrolysis strategy. The intrinsic activity of the Cu-N4 site is boosted by the neighboring Na-containing functional group, which enhances O2 adsorption and optimizes the rate-determining step of O2 activation (*O2 → *OOH) during the oxygen reduction reaction process. Meanwhile, the Cu-N4 sites are encapsulated within carbon nanofibers and anchored by the carbon matrix to form a C2-Cu-N4 configuration, thereby reinforcing the stability of the Cu centers. Moreover, the introduction of Na-containing functional groups on the carbon atoms significantly reduces the positive charge on their outer shell C atoms, rendering the carbon skeletons less susceptible to corrosion by oxygen species and further preventing the dissolution of Cu centers. Under these multi-type regulations, the zinc-air battery with Cu/Na-carbon membrane catalyst as the air cathode demonstrates long-term discharge/charge cycle stability of over 5000 h. This considerable stability improvement represents a critical step towards developing Cu-N4 active sites modified with the neighboring main-group metal-containing functional groups to overcome the durability barriers of zinc-air batteries for future practical applications.

Reaxff MD Analysis of Substrate Material Properties into Oxide Films during Thermal Oxidation Process of Group IV Semiconductor Materials

Oxide films used in semiconductor devices have attracted much attention because they can protect substrate surfaces from impurities and suppress current loss. In recent years, there have been growing expectations for oxide film formation on Ge substrate materials, which have a uniquely high hole mobility among group IV semiconductor materials. We have investigated an efficient oxide film formation method using reactive molecular dynamics (ReaxFF MD) simulation. We focused on dissociation, the initial step of oxidation, and confirmed how easily dissociation occurs. To search for conditions that promote dissociation, we checked the dangling bound density and adsorption angle on the substrate surface. The wider space between dimers on the Ge substrate may result in a shallower O2 adsorption angle. This increases the dissociation rate because each of the two O2 atoms is more likely to bond to the substrate.

Platinum-induced nanolization and electron-deficient gold in platinum@gold cocatalyst for efficient photocatalytic hydrogen peroxide production

Simultaneous optimization of the number and intensity of oxygen (O2) adsorption on gold (Au) cocatalyst is highly required to greatly improve their interfacial hydrogen peroxide (H2O2)-production activity. However, it is a great challenge to realize the above effective modulation of Au by traditional photodeposition route. In this study, a platinum (Pt)-induced selective photodeposition method was designed to simultaneously regulate the particle size and electronic structure of Au cocatalyst for boosting the photocatalytic H2O2-production activity of bismuth vanadate (BiVO4) via the selective deposition of Pt@Au core–shell cocatalyst. The photocatalytic results indicate that the as-prepared BiVO4/Pt0.1@Au photocatalyst achieves a considerable H2O2-production activity with a rate of 2752.13 μmol L−1 (AQE = 13.76 %), which is obviously higher than that of BiVO4/Pt (137.63 μmol L−1) and BiVO4/Au (475.33 μmol L−1). It was found that the introduction of Pt successfully induced the formation of Au nanoparticles for enhancing the number of O2 adsorption. Meanwhile, the spontaneous transfer of free electrons of Au to Pt induces the generation of electron-deficient Auδ+ sites, which spontaneously enhances the O2-adsorption intensity for facilitating the 2-electron oxygen reduction reaction (ORR), resulting in efficient H2O2 production. The present strategy may be useful for more comprehensively regulating the intensity and number of O2 adsorption on cocatalysts to facilitate artificial photosynthesis.

Room-temperature rapid oxygen monitoring system in high humidity hydrogen gas environment towards water electrolysis application

Water electrolysis is one of the key processes for carbon-free hydrogen (H2) generation, yet it inherently presents the risk of oxygen (O2) permeation, a significant concern that must be addressed. Contrary to external atmospheric conditions, the environment within a water electrolysis system is characterized exclusively by high-purity H2, little O2, and moisture (H2O). However, there has been limited research on sensors capable of detecting O2 crossover in such a pure H2 atmosphere under high humidity conditions. In this study, we developed an electrolysis O2 monitoring (E-OM) sensor based on a semiconducting metal oxide (SMO) that can operate at a room-temperature with such high humidity through photoactivation with 365 nm LED light. A porous In2O3 nanofilm, prepared by glancing angle deposition (GLAD), was used as the gas sensing material, and copper nanoparticles (Cu NPs) were decorated on the In2O3 surface through electron beam evaporation to accelerate the O2 adsorption. Remarkably, the E-OM sensor showed a humidity-independent response to O2 gas in the H2 atmosphere. Meanwhile, since the response of the E-OM sensor itself was not fast enough for water electrolysis system application, convolutional neural network (CNN)-based signal processing in the time domain was applied. As a result, our E-OM sensor system could predict O2 concentrations from 0 to 2 vol% in an H2 environment with a relative humidity (RH) of 30–90 %, and the detection time was under 5 s. This development could enable safe, rapid, and cost-effective monitoring of O2 crossover in H2 production infrastructure.

New insights into the influence mechanism of carbides on the localized corrosion of N80 carbon steel: Experiments and first-principles study

Carbides significantly influenced the corrosion behavior of N80 carbon steel. The specific types of carbides and their adsorption behavior at the interface with the steel matrix were particularly complex. This study comprehensively evaluated the impact of carbides on the localized corrosion of N80 steel using both computational and experimental techniques. The findings revealed that the predominant carbides in the steel were Fe3C, with a potential difference of approximately 65.3 mV greater than that of the steel matrix, leading to preferential dissolution of the steel matrix. The corrosion film that formed on the steel surface was loose and porous, enriched with Cl-, and insufficient to effectively prevent the penetration of corrosive media. The work function relationship between Fe3C and the steel matrix was Fe < Fe3C, and O exhibited a higher adsorption energy on the Fe surface than on the Fe3C surface. This resulted in a strong galvanic coupling corrosion effect between Fe3C and the steel matrix. Fe3C, acting as the cathodic phase in the galvanic corrosion process, accelerated the adsorption of O2 on the steel surface, which in turn led to significant dissolution of the steel matrix. This process facilitated the nucleation of pits, ultimately resulting in the formation of stable pits on the surface.

Construction of ROS-balancing-engineered heterojunction photoswitch for achieving programmed inflammatory management and tissue regeneration

Early instigation and subsequent attenuation of inflammation are crucial for tissue regeneration, which poses a need for inflammatory regulation in the design of materials. In this work, a novel photocatalytic heterojunction consist of MXene, Zr-based porphyrinic metal–organic framework (named PCN-222), and Pt nanoparticles (termed MX/PCN@Pt HJs) is developed to achieve photo-controlled reactive oxygen species (ROS) generation and clearance. According to density function theory calculations and related experiments, the unique heterojunction formed by MXene and MOFs, abundant O2 adsorption sites of metal oxide clusters, and porous features of MOFs promoted the adsorption of active reactants and accelerated electron transfer, thereby exhibiting excellent photocatalytic performance. Meanwhile, the PCN-222 with superoxide dismutase (SOD) activity and Pt nanoparticles with catalase (CAT) activity endowed the MX/PCN@Pt HJs with SOD/CAT mimetic cascade performance. Through the photo-controlled regulation, the MX/PCN@Pt HJs acted as a photoswitch that flexibly achieved the switch between ROS generation and clearance. Effective production of ROS not only enabled antimicrobial activity but also contributed to a pro-inflammatory state; while the timely ROS scavenging activity effectively prevented the detrimental effects of sustained inflammation. Both in vitro and in vivo evaluations had confirmed the inflammatory modulation and tissue regeneration potency of the MX/PCN@Pt HJs based on the ROS-regulated strategy, which offer a vital understanding of the MOF-based photocatalytic heterojunction for programmed inflammatory regulation.