Conversion Of Oxygen Research Articles

Photo-induced fluorescence discoloration and photo-responsive room temperature phosphorescence carbon dot-based composites with excellent reversibility and water resistance

Photo-stimulation responsive room temperature phosphorescence (RTP) carbon dots (CDs) have potential applications in advanced dynamic information encryption and anti-counterfeiting. However, the development of photo-responsive long-wavelength RTP CD materials with excellent reversibility and water resistance, as well as CD materials with both photo-induced fluorescence discoloration and photo-responsive reversible RTP properties, remains a challenge. Here, pyrene, which has a large conjugated structure, and 4-(1,2,2-triphenylvinyl)benzaldehyde, which has a tetraphenylethylene structure, were selected as the main raw materials to synthesize two CDs. Then, by introducing a PMMA matrix, reversible photo-responsive long-wavelength red RTP emission with a lifetime of 257 ms from a CD-based composite is realized for the first time, and the combination of photo-induced fluorescence discoloration and photo-responsive reversible yellow RTP with a lifetime of 287 ms is realized. Importantly, photo-responsive reversible RTP has excellent water resistance. The fluorescence discoloration was caused by photocyclization under long-term UV irradiation due to the presence of the tetraphenylethylene structure. The rigid environment provided by the PMMA matrix and the hydrogen bonds formed between the PMMA and CDs promote the generation of RTP. The photo-responsiveness of RTP is caused by the conversion of molecular oxygen (3O2) to singlet oxygen (1O2) under continuous UV irradiation. It is filled with 3O2 again after being placed in air to inactivate the RTP, thus achieving reversible RTP behavior. Owing to their excellent photo-responsive properties and water resistance, these materials have the potential to achieve repeatable dynamic information encryption and multilevel pattern anti-counterfeiting while also broadening the range of applications in water environments.

Efficient elimination of organic contaminants via a non-radical pathway involving activation of sulfite by synergistic adsorption-catalysis bifunctional chitosan-modified MOF derivative

Usually, Metal-based sulfite activation systems follow a radical generation pathway but are rare in non-radical pathways. Singlet oxygen (1O2) generation-targeted catalyst was synthesized by introducing non-redox metal oxides ZnO into chitosan-modified cobalt-zinc bimetallic oxides (CZ1.0C) via template method. Compared with Co3O4, the catalyst CZ1.0C coupled to the sulfite system (CZ1.0C/SO32-) maintained good adaptability in a common water background and a wide pH range (7–11). In addition, the CZ1.0C/SO32- system showed high efficiency in the degradation of Congo red (kobs = 0.190 min−1) and 100 % sulfite utilization. EPR, probe experiments, and DFT calculations proved the dominant role of 1O2, with a concentration three orders of magnitude higher than that of radicals. The controlled generation of non-radicals was achieved owing to the doping of ZnO and the conversion of lattice oxygen and oxygen vacancies. The catalytic oxidation intermediate HSO5- has also been demonstrated in the system, which achieves non-radical pathway oxidation through electron-mediated interactions. This article aims to develop a new “waste control by waste” strategy, which combines high selective adsorption and catalysis to achieve sulfur resource recovery and water pollutants elimination.

Atomically Dispersed Iron‐Copper Dual‐Metal Sites Synergistically Boost Carbonylation of Methane

AbstractThe direct liquid‐phase oxidative carbonylation of methane, utilizing abundant natural gas, offers a mild and straightforward alternative. However, most catalysts proposed for this process suffer from low acetic acid yields due to few active sites and rapid C1 oxygenate generation, impeding their industrial feasibility. Herein, we report a highly efficient 0.1Cu/Fe‐HZSM‐5‐TF (TF denotes template‐free synthesis) catalyst featuring exclusively mononuclear Fe and Cu anchored in the ZSM‐5 channels. Under optimized conditions, the catalyst achieved an unprecedented acetic acid yield of 40.5 mmol gcat−1 h−1 at 50 °C, tripling the previous records of 12.0 mmol gcat−1 h−1. Comprehensive characterization, isotope‐labeled experiments and density functional theory (DFT) calculations reveal that the homogeneous mononuclear Fe sites are responsible for the activation and oxidation of methane, while the neighboring Cu sites play a key role in retarding the oxidation process, promoting C−C coupling for effective acetic acid synthesis. Furthermore, the methyl‐group carbon in acetic acid originates solely from methane, while its carbonyl‐group carbon is derived exclusively from CO, rather than the conversion of other C1 oxygenates. The proposed bimetallic catalyst design not only overcomes the limitations of current catalysts but also generalizes the oxidative carbonylation of other alkanes, demonstrating promising advancements in sustainable chemical synthesis.

Molecular Engineering of Methylated Sulfone‐Based Covalent Organic Frameworks for Back‐Reaction Inhibited Photocatalytic Overall Water Splitting

AbstractSolar‐to‐hydrogen (H2) and oxygen (O2) conversion via photocatalytic overall water splitting (OWS) holds great promise for a sustainable fuel economy, but has been challenged by the backward O2 reduction reaction (ORR) with favored proton‐coupled electron transfer (PCET) dynamics. Here, we report that molecular engineering by methylation inhibits the backward ORR of molecular photocatalysts and enables efficient OWS process. As demonstrated by a benchmark sulfone‐based covalent organic framework (COF) photocatalyst, the precise methylation of its O2 adsorption sites effectively blocks electron transfer and increases the barrier for hydrogen intermediate desorption that cooperatively obstructs the PCET process of ORR. Methylation also repels electrons to the neighboring photocatalytic sulfone group that promotes the forward H2 evolution. The resultant DS‐COF achieves an impressive inhibition of about 70 % of the backward reaction and a three‐fold enhancement of the OWS performance with a H2 evolution rate of 124.7 μmol h−1 g−1, ranking among the highest reported for organic‐based photocatalysts. This work provides insights for engineering photocatalysts at the molecular level for efficient solar‐to‐fuel conversion.

Molecular Engineering of Methylated Sulfone-Based Covalent Organic Frameworks for Back-Reaction Inhibited Photocatalytic Overall Water Splitting.

Solar-to-hydrogen (H2) and oxygen (O2) conversion via photocatalytic overall water splitting (OWS) holds great promise for a sustainable fuel economy, but has been challenged by the backward O2 reduction reaction (ORR) with favored proton-coupled electron transfer (PCET) dynamics. Here, we report that molecular engineering by methylation inhibits the backward ORR of molecular photocatalysts and enables efficient OWS process. As demonstrated by a benchmark sulfone-based covalent organic framework (COF) photocatalyst, the precise methylation of its O2 adsorption sites effectively blocks electron transfer and increases the barrier for hydrogen intermediate desorption that cooperatively obstructs the PCET process of ORR. Methylation also repels electrons to the neighboring photocatalytic sulfone group that promotes the forward H2 evolution. The resultant DS-COF achieves an impressive inhibition of about 70 % of the backward reaction and a three-fold enhancement of the OWS performance with a H2 evolution rate of 124.7 μmol h-1 g-1, ranking among the highest reported for organic-based photocatalysts. This work provides insights for engineering photocatalysts at the molecular level for efficient solar-to-fuel conversion.

H2S and NIR light-driven nanomotors induce disulfidptosis for targeted anticancer therapy by enhancing disruption of tumor metabolic symbiosis

Disulfidptosis, a novel mechanism of programmed cell death through the disruption of tumor metabolic symbiosis (TMS), has showed tremendous potential in cancer therapy. However, the efficacy of disulfidptosis is limited by poor permeability of drugs in solid tumors. Herein, hydrogen sulfide (H2S) and near-infrared (NIR) light-driven nanomotors (denoted as HGPP) have been constructed to efficiently penetrate tumors and induce disulfidptosis. HGPP demonstrate glutathione (GSH)-responsive release of H2S, which combined with NIR light-induced photothermal effect drive HGPP movement to facilitate deep tumor penetration. The released H2S induces tumor acidosis and disrupts TMS, where disulfide accumulation following cell starvation leads to disulfidptosis. In addition, HGPP induce hepatoma specific cellular uptake and catalyze the conversion of glucose and oxygen to produce hydrogen peroxide (H2O2), leading to glucose starvation. Overall, this study has developed a multifunctional Janus nanomotor that provides a novel strategy for disulfidptosis-based solid tumor therapy.

Design and stabilization of direct autothermal methane steam reformation reactor for producing hydrogen via optimizing oxygen distributed feeding

Direct autothermal methane reforming is an energy-efficient way of hydrogen production. However, significant hot spot is always encountered near the reactor inlet, causing catalyst sinter and even reactor damage. Hence, bed temperature regulation by oxygen distributed feeding was numerically investigated using a one-dimensional heterogeneous model. Simulation results show oxygen feeding along full length of reactor leads to low methane and oxygen conversion despite avoiding hot spot. Elevating feeding temperature solves this problem, but requires extra heat. Shortening feeding length to 1/10 of reactor reduces maximum bed temperature by 100 K; Half oxygen fed into reactor inlet and the other along the length further reduces maximum bed temperature and avoids the transient runaway. Optimization results show that oxygen parabolically and totally fed along the front part of the reactor length shows better performance than that feeding half along reactor length and the other into reactor inlet.

Bimetal Oxides Anchored on Carbon Nanotubes/Nanosheets as High-Efficiency and Durable Bifunctional Oxygen Catalyst for Advanced Zn-Air Battery: Experiments and DFT Calculations.

To meet increasing requirement for innovative energy storage and conversion technology, it is urgent to prepare effective, affordable, and long-term stable oxygen electrocatalysts to replace precious metal-based counterparts. Herein, a two-step pyrolysis strategy is developed for controlled synthesis of Fe2O3 and Mn3O4 anchored on carbon nanotubes/nanosheets (Fe2O3-Mn3O4-CNTs/NSs). The typical catalyst has a high half-wave potential (E1/2 = 0.87V) for oxygen reduction reaction (ORR), accompanied with a smaller overpotential (η10 = 290mV) for oxygen evolution reaction (OER), showing substantial improvement in the ORR and OER performances. As well, density functional theory calculations are performed to illustrate the catalytic mechanism, where the in situ generated Fe2O3 directly correlates to the reduced energy barrier, rather than Mn3O4. The Fe2O3-Mn3O4-CNTs/NSs-based Zn-air battery exhibits a high-power density (153mW cm-2) and satisfyingly long durability (1650 charge/discharge cycles/550h). This work provides a new reference for preparation of highly reversible oxygen conversion catalysts.

Hydrodeoxygenation of C15 furanic precursor over mesoporous NiMo-ZrO2 composite catalysts for the production of sustainable aviation fuel

Sustainable aviation fuel (SAF) is essential for achieving carbon neutrality in the transportation sector. This study elucidates the production of SAF range C9-C15 branched alkanes by hydrodeoxygenation (HDO) of C15 furanic precursor derived from 2-methylfuran and furfural via hydroxyalkylation-alkylation reaction. HDO reaction was performed using high surface area mesoporous NiMo-ZrO2 composite catalysts that exhibited high selectivity to central SAF alkanes (C13-C14). Deoxygenation follows a complex reaction network involving furanic double bond saturation and furan-ring opening reactions in series, followed by the cascade of HDO, dehydroformylation, and C-C bond cleavage. The present investigation enlightens the impact of calcination temperatures and metal (Mo and Ni) contents on structural stability, physicochemical properties, and catalytic performance of NiMo-ZrO2. Both Ni and Mo stabilized the tetragonal ZrO2 phases with improved surface area. The catalytic activity proliferated with rising calcination temperature till 873 K due to the enrichment of Mo-O-Zr acidic species and deteriorated beyond this temperature owing to the generation of crystalline MoO3/Zr(MoO4)2 species. NiMo alloy formation was enhanced, and concurrently, acidity was reduced with increasing Mo content. 30 wt% MoO3-containing catalyst showed the best catalytic activity due to the proper balance between acidity and NiMo alloy. Oxygenate conversion was boosted by increasing NiO addition up to 15 wt% due to the enhanced Ni and NiMo alloy formation and decreased at 20 wt% owing to the evolution of catalytically inactive bulk metal oxide species. Catalytic cracking was prominent at elevated reaction temperatures, with significant amounts of C13 alkane.

Atomically Dispersed Iron-Copper Dual-Metal Sites Synergistically Boost Carbonylation of Methane.

The direct liquid-phase oxidative carbonylation of methane, utilizing abundant natural gas, offers a mild and straightforward alternative. However, most catalysts proposed for this process suffer from low acetic acid yields due to few active sites and rapid C1 oxygenate generation, impeding their industrial feasibility. Herein, we report a highly efficient 0.1Cu/Fe-HZSM-5-TF (TF denotes template-free synthesis) catalyst featuring exclusively mononuclear Fe and Cu anchored in the ZSM-5 channels. Under optimized conditions, the catalyst achieved an unprecedented acetic acid yield of 40.5 mmol gcat -1 h-1 at 50 °C, tripling the previous records of 12.0 mmol gcat -1 h-1. Comprehensive characterization, isotope-labeled experiments and density functional theory (DFT) calculations reveal that the homogeneous mononuclear Fe sites are responsible for the activation and oxidation of methane, while the neighboring Cu sites play a key role in retarding the oxidation process, promoting C-C coupling for effective acetic acid synthesis. Furthermore, the methyl-group carbon in acetic acid originates solely from methane, while its carbonyl-group carbon is derived exclusively from CO, rather than the conversion of other C1 oxygenates. The proposed bimetallic catalyst design not only overcomes the limitations of current catalysts but also generalizes the oxidative carbonylation of other alkanes, demonstrating promising advancements in sustainable chemical synthesis.

Constructing an Interlaced Catalytic Surface via Fluorine-Doped Bimetallic Oxides for Oxygen Electrode Processes in Li-O2 Batteries.

Lithium-oxygen (Li-O2) batteries, renowned for their high theoretical energy density, have garnered significant interest as prime candidates for future electric device development. However, their actual capacity is often unsatisfactory due to the passivation of active sites by solid-phase discharge products. Optimizing the growth and storage of these products is a crucial step in advancing Li-O2 batteries. Here, a fluorine-doped bimetallic cobalt-nickel oxide (CoNiO2- xFx/CC) with an interlaced catalytic surface (ICS) and a corncob-like structure is proposed as an oxygen electrode. Unlike conventional oxide electrodes with a "single adsorption catalytic mechanism," the ICS of CoNiO2- xFx/CC offers a "competitive adsorption catalytic mechanism," where oxygen sites facilitate oxygen conversion while fluorine sites contribute to the growth of Li2O2. This results in a change in Li2O2 morphology from a surface film to toroidal particles, effectively preventingthe burial of active sites. Additionally, the unique open architecture aids in the capture and release of oxygen and the formation of well-contacted Li2O2/electrode interfaces, which benefits the complete decomposition of Li2O2 products. Consequently, the Li-O2 battery with a CoNiO2- xFx/CC cathode demonstrates a high specific capacity of up to 30923 mAh g-1 and a lifespan exceeding 580 cycles, surpassing most reported metal oxide-based cathodes.

Heterostructure catalyst coupled wood-derived carbon and cobalt-iron alloy/oxide for reversible oxygen conversion

As promising energy-storage devices, zinc–air batteries (ZABs) exhibit slow reaction kinetics for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occurring at their electrodes. High-performance bifunctional catalysts must thus be synthesized to accelerate the reversible conversion of oxygen and improve the rate and overall performance of ZABs. Herein, we reported the promising prospects of self-supported composite electrodes composed of wood-derived carbon (WDC) and bimetallic cobalt-iron alloys/oxides (CoFe-CoFe2O4@WDC) as efficient electrocatalysts for alkaline ORR/OER. WDC provided a favorable three-phase interface for heterogeneous reactions owing to its layered porous structure and genetic stability, thereby enabling mass diffusion and improving reaction kinetics. The CoFe2O4 spinel surface was reduced to bimetallic CoFe alloy to form abundant heterostructure interfaces that promote electron transfer. Under alkaline conditions, the optimized composite electrode exhibited a remarkable high half-wave potential of 0.85 V and an exceptionally low overpotential of 1.49 V. It also exhibited stable performance over an impressive 2340 cycles in a ZAB. Theoretical calculations also confirmed that the heterointerface addresses the issue of proton scarcity throughout the reaction and actively facilitates the creation of O–O bonds during the reversible transformation of oxygen. This study introduces a new concept for developing bifunctional and efficient electrocatalysts based on charcoal and encourages the sustainable and high-value use of forest biomass resources.Graphical

Destabilization of Oxidized Lattice Oxygen in Layered Oxide Cathode.

Integrating anion-redox capacity with orthodox cation-redox capacity is deemed as a promising solution for high-energy-density battery cathodes surmounting the present technical bottlenecks. However, the evolution of oxidized oxygen species during the electrochemical or chemical process easily jeopardizes the reversibility of oxygen redox and remains poorly understood. Herein, we showcase the gradual conversion of the π-interacting oxygen (localized hole states on O) to the σ-interacting oxygen upon resting at a high voltage for P3-type Na0.6Li0.2Mn0.8O2 with nominally stable ribbon-like superstructure, accompanied by the O-O dimerization and the local structural reorganization. We further pinpoint an abnormal Li+ migration process from the alkali-metal layer to the transition-metal layer for desodiated P3-Na0.6Li0.2Mn0.8O2, thereby leading to a partial reconstruction of the ribbon superstructure. The high-voltage plateau of oxygen-redox cathodes is concluded to be exclusively controlled by the oxygen stabilization mechanism rather than the superstructure ordering. In addition, there exists a kinetic competition between π and σ interaction during the uninterrupted electrochemical process.

Numerical analysis of transport phenomena in a steam reforming reactor with optimal multi-segments catalyst distribution

The contemporary industrial trends pursue alternative energy sources, to substitute fossil fuels. The current direction is induced by concerns regarding exhausting natural resources and the environmental impact of the technologies rising globally. Conventional technologies have a dominant share of the current energy market. The most crucial issue with current technology is the emission of greenhouse gases and their negative impact on climate. One of the possible approaches to limit the issue of emissions is the steam reforming of natural gas, leading to the production of hydrogen. Fuel cells are a robust technology, able to conduct a catalytic conversion of hydrogen and oxygen, for the direct production of electrical energy. Fuel cells are one of the most environment-friendly technologies to this day, as their exhaust gases mostly consist of steam. Currently, almost 50% of the hydrogen produced is acquired via hydrocarbons reforming. The process described in the presented analysis occurs between methane and steam. The presented numerical analysis regards small-scale reactors, which are more suitable when it comes to the processing of distributed or stranded resources for hydrogen production To optimize the small-scale unit’s performance, the macro-patterning strategy is introduced. Steam reforming has a strong endothermic character and tends to produce unfavorable thermal conditions. The process enhancement is acquired by introducing non-catalytic regions to the catalytic insert geometry. The non-catalytic segments are introduced to suppress the reaction locally, decreasing the magnitude of temperature gradients. Unification of the temperature distribution is proven to increase the reforming’s effectiveness. The presented analysis introduces a new approach to the catalytic insert division, to investigate if a complete temperature field unification is possible. The catalytic insert is simultaneously divided along the reactor’s radius and length, resulting in a set of concentric rings, placed along the reactor’s axis. The calculations are conducted using in-house numerical procedure, coupled with a genetic algorithm. The algorithm optimizes the process effectiveness by modification of the segment’s alignment and porosity.

Use of Suspended Particles as a New Approach to Increase the Active Electrode Area in Water Electrolysis Experiments

AbstractThe development of base metal electrodes that can act as active and stable oxygen generating electrodes in water electrolysis systems, especially at low pH levels, remains a challenge. The use of suspensions as electrolytes for water splitting has until recently been limited to photoelectrocatalytic approaches. A high current density (j=30 mA/cm2) for water electrolysis has been achieved at a very low oxygen evolution reaction (OER) potential (E=1.36 V vs. RHE) using a SnO2/H2SO4 suspension–based electrolyte in combination with a steel anode. More importantly, the high charge–to–oxygen conversion rate (Faraday efficiency of 88 % for OER at j=10 mA/cm2 current density). Since cyclic voltammetry (CV) experiments show that oxygen evolution starts at a low, but not exceptionally low, potential, the reason for the low potential in chronoamperometry (CP) tests is an increase in the active electrode area, which has been confirmed by various experiments. For the first time, the addition of a relatively small amount of solids to a clear electrolyte has been shown to significantly reduce the overpotential of the OER in water electrolysis down to the 100 mV region, resulting in a remarkable reduction in anode wear while maintaining a high current density.

Enhanced Proximity of Rh1,2-Rhn Ensembles Encaged in UiO-67 Boosting Catalytic Conversion of Syngas to Oxygenates.

Maintaining high conversion under the premise of high oxygenates selectivity in syngas conversion is important but a formidable challenge in Rh catalysis. Monometallic Rh catalysts provide poor oxygenate conversion efficiency, and efforts have been focused on constructing adjacent polymetallic sites; however, the one-pass yields of C2+ oxygenates over the reported Rh-based catalysts were mostly <20 %. In this study, we constructed a monometallic Rh catalyst encapsulated in UiO-67 (Rh/UiO-67) with enhanced proximity to dual-site Rh1,2-Rhn ensembles. Unexpectedly, this catalyst exhibited high efficacy for oxygenate synthesis from syngas, giving a high oxygenate selectivity of 72.0 % with a remarkable CO conversion of 50.4 %, and the one-pass yield of C2+ oxygenates exceeded 25 %. The state-of-the-art characterizations further revealed the spontaneous formation of an ensemble of Rh single atoms/dimers (Rh1,2) in the proximity of ultrasmall Rh clusters (Rhn) confined within the nanocavity of UiO-67, providing adjacent Rh+-Rh0 dual sites dynamically during the reaction that promote the relay of the undissociated CHO species to the CHx species. Thus, our results open a new route for designing highly efficient Rh catalysts for the conversion of syngas to oxygenates by precisely tuning the ensemble and proximity of the dual active sites in a confined space.

Enhanced Proximity of Rh1,2‐Rhn Ensembles Encaged in UiO‐67 Boosting Catalytic Conversion of Syngas to Oxygenates

AbstractMaintaining high conversion under the premise of high oxygenates selectivity in syngas conversion is important but a formidable challenge in Rh catalysis. Monometallic Rh catalysts provide poor oxygenate conversion efficiency, and efforts have been focused on constructing adjacent polymetallic sites; however, the one‐pass yields of C2+ oxygenates over the reported Rh‐based catalysts were mostly &lt;20 %. In this study, we constructed a monometallic Rh catalyst encapsulated in UiO‐67 (Rh/UiO‐67) with enhanced proximity to dual‐site Rh1,2‐Rhn ensembles. Unexpectedly, this catalyst exhibited high efficacy for oxygenate synthesis from syngas, giving a high oxygenate selectivity of 72.0 % with a remarkable CO conversion of 50.4 %, and the one‐pass yield of C2+ oxygenates exceeded 25 %. The state‐of‐the‐art characterizations further revealed the spontaneous formation of an ensemble of Rh single atoms/dimers (Rh1,2) in the proximity of ultrasmall Rh clusters (Rhn) confined within the nanocavity of UiO‐67, providing adjacent Rh+‐Rh0 dual sites dynamically during the reaction that promote the relay of the undissociated CHO species to the CHx species. Thus, our results open a new route for designing highly efficient Rh catalysts for the conversion of syngas to oxygenates by precisely tuning the ensemble and proximity of the dual active sites in a confined space.

Highly selective production of light aromatics from co-catalytic fast pyrolysis of pre-deoxygenated biomass and hydrogen-rich polyethylene using a dual-catalyst system

Co-catalytic fast pyrolysis of torrefaction deoxygenated pine wood (PW) and high-density polyethylene (HDPE) in dual-catalyst (metal oxidize and zeolite) system is an effective technology to produce renewable bio-aromatics. In this work, the torrefaction deoxygenation pretreatment (TDP) was carried out to remove oxygen element from PW prior to catalytic fast pyrolysis (CFP). 56.90 % oxygen could be removed at TDP temperature of 300 °C, releasing in the oxygen carrier of CO2, CO, H2O, alcohols, acids, phenols, etc. Then, the synergistic effect between the metal oxide and the HZSM-5 in dual-catalyst system was also investigated. Among these metal oxides (Al2O3, MgO, CaO, ZnO, and Fe2O3) and hierarchical HZSM-5, the dual-catalyst of CaO and hierarchical HZSM-5 (treated by 0.2 M NaOH) was the optimal combination. The layout mode between feedstock and dual catalyst was also optimized. The highest yield of aromatics was produced in layout Mode 8, where the CaO was mixed with torrefied PW, but the hierarchical HZSM-5 and HDPE were laid in separated layers. The mixing of CaO and torrefied PW promoted the conversion of the macromolecular oxygenates into micromolecular oxygenates. Then, these small-molecular oxygenates could enter the hierarchical channel of HZSM-5, being converted into aromatics by undergoing the Diels-Alder reaction.

Fe, N‐Inducing Interfacial Electron Redistribution in NiCo Spinel on Biomass‐Derived Carbon for Bi‐functional Oxygen Conversion

AbstractHerein, an interfacial electron redistribution is proposed to boost the activity of carbon‐supported spinel NiCo2O4 catalyst toward oxygen conversion via Fe, N‐doping strategy. Fe‐doping into octahedron induces a redistribution of electrons between Co and Ni atoms on NiCo1.8Fe0.2O4@N‐carbon. The increased electron density of Co promotes the coordination of water to Co sites and further dissociation. The generation of proton from water improves the overall activity for the oxygen reduction reaction (ORR). The increased electron density of Ni facilitates the generation of oxygen vacancies. The Ni−VO−Fe structure accelerates the deprotonation of *OOH to improve the activity toward oxygen evolution reaction (OER). N‐doping modulates the electron density of carbon to form active sites for the adsorption and protonation of oxygen species. Fir wood‐derived carbon endows catalyst with an integral structure to enable outstanding electrocatalytic performance. The NiCo1.8Fe0.2O4@N‐carbon express high half‐wave potential up to 0.86 V in ORR and low overpotential of 270 mV at 10 mA cm−2 in OER. The zinc‐air batteries (ZABs) assembled with the as‐prepared catalyst achieve long‐term cycle stability (over 2000 cycles) with peak power density (180 mWcm−2). Fe, N‐doping strategy drives the catalysis of biomass‐derived carbon‐based catalysts to the highest level for the oxygen conversion in ZABs.

Experimental and mechanistic studies on the thermo-electric synergistic catalytic oxidation of acetone over MnO2/TiO2-Ni foam catalyst

Volatile organic compounds (VOCs) cause serious environmental and human health risks and must be efficiently removed. In this work, a metal-structured catalyst of Ni foam loaded Mn/Ti oxides was used for the oxidation of acetone, a typical VOC compound. The catalyst was in-situ joule heated when applying an electric current and produced the thermo-electric synergistic oxidation (TEO) effect. Compared with conventional thermal oxidation (CTO), the oxidation rate of acetone significantly increased by 124.19 % and the energy consumption of per unit complete oxidation rate was reduced by 66.67 % in TEO reaction with a 12 A electric current at 200 °C. The efficiency gradually improved (from 16.12 % to 36.14 %) and the energy consumption of per unit complete oxidation rate decreased (from 2.85 W/% to 0.95 W/%) with the increase of electric current. Besides, the thermal (including the catalyst thermal effect and reaction gas thermal effect) and electric effects in TEO reaction were analyzed by the statistical analysis method. With the temperature increasing from 200 °C to 400 °C, the proportion of electric effect slightly decreased while that of reaction gas thermal effect increased from 5.2 % to 18.1 %. It proved that the TEO method has the advantage of improving low-temperature catalytic activity. Furthermore, the mechanism of electric effect was investigated, in which it enhances the conversion of lattice oxygen in TiO2 to surface-adsorbed oxygen species and promotes the oxidation of Mn oxides, sequentially improving the oxidation of acetone.