Abundant Oxygen Vacancies Research Articles

Enhanced photocatalytic degradation by higher exposure of {110} facet and surface oxygen vacancies of BiOBr through cobalt doping strategy

Transition metal cobalt doped BiOBr (Co-BOB) was successfully synthesized by using hydrothermal method. The optimized Co-BOB achieved a remarkable rhodamine B degradation rate of 97 % in 30 min under visible light irradiation when initial concentration was 80 mg·L−1. Satisfactory removal efficiency was also observed under ambient sunlight irradiation and various water conditions. The cobalt doping strategy induced abundant surface oxygen vacancies formation (43.22 %) and resulted in an increasing exposure of {110} facets. The photosensitization and photocatalytic activities of Co-BOB significantly enhanced comparing with that of pure BiOBr. The synergy of Co doping and oxygen vacancies also induced the formation of a new band structure in Co-BOB. The synergistic effect promoted the efficient separation of photogenerated electrons and holes. By combining with density functional theory calculation, the RhB photocatalytic degradation mechanism by Co-BOB was proposed.

Enhancing Photocatalytic CO2 Conversion through Oxygen-Vacancy-Mediated Topological Phase Transition.

Weak adsorption of gas reactants and strong binding of intermediates present a significant challenge for most transition metal oxides, particularly in the realm of CO2 photoreduction. Herein, we demonstrate that the adsorption can be fine-tuned by phase engineering of oxide catalysts. An oxygen vacancy mediated topological phase transition in Ni-Co oxide nanowires, supported on a hierarchical graphene aerogel (GA), is observed from a spinel phase to a rock-salt phase. Such in situ phase transition empowers the Ni-Co oxide catalyst with a strong internal electric field and the attainment of abundant oxygen vacancies. Among a series of catalysts, the in situ transformed spinel/rock-salt heterojunction supported on GA stands out for an exceptional photocatalytic CO2 reduction activity and selectivity, yielding an impressive CO production rate of 12.5 mmol g-1 h-1 and high selectivity of 96.5 %. This remarkable performance is a result of the robust interfacial coupling between two topological phases that optimizes the electronic structures through directional charge transfer across interfaces. The phase transition process induces more Co2+ in octahedral site, which can effectively enhance the Co-O covalency. This synergistic effect balances the surface activation of CO2 molecules and desorption of reaction intermediates, thereby lowering the energetic barrier of the rate-limiting step.

General and Scalable Synthesis of Mesoporous 2D MZrO2 (M = Co, Mn, Ni, Cu, Fe) Nanocatalysts by Amorphous-to-Crystalline Transformation.

In modern heterogeneous catalysis, it remains highly challenging to create stable, low-cost, mesoporous 2D photo-/electro-catalysts that carry atomically dispersed active sites. In this work, a general shape-preserving amorphous-to-crystalline transformation (ACT) strategy is developed to dope various transition metal (TM) heteroatoms in ZrO2, which enabled the scalable synthesis of TMs/oxide with a mesoporous 2D structure and rich defects. During the ACT process, the amorphous MZrO2 nanoparticles (M = Fe, Ni, Cu, Co, Mn) are deposited within a confined space created by the NaCl template, and they transform to crystalline 2D ACT-MZrO2 nanosheets in a shape-preserving manner. The interconnected crystalline ACT-MZrO2 nanoparticles thus inherit the same structure as the original MZrO2 precursor. Owing to its rich active sites on the surface and abundant oxygen vacancies (OVs), ACT-CoZrO2 gives superior performance in catalyzing the CO2-to-syngas conversion as demonstrated by experiments and theoretical calculations. The ACT chemistry opens a general route for the scalable synthesis of advanced catalysts with precise microstructure by reconciliating the control of crystalline morphologies and the dispersion of heteroatoms.

Enhanced and Sustainable Removal of Indoor Formaldehyde by Naturally Porous Bamboo Activated Carbon Supported with MnOx: Synergistic Effect of Adsorption and Oxidation

Novel bamboo activated carbon (BAC) catalysts decorated with manganese oxides (MnOx) were prepared with varying MnOx contents through a facile one-step redox reaction. Due to the physical anchoring effect of the natural macropore structure for catalyst active components, homogeneous MnOx nanoparticles (NPs), and high specific surface area over catalyst surface, the BAC@MnOx-N (N = 1, 2, 3, 4, 5) catalyst shows encouraging adsorption and catalytic oxidation for indoor formaldehyde (HCHO) removal at room temperature. Dynamic adsorption and catalytic activity experiments were conducted. The higher Smicro (733 m2/g) and Vmicro/Vt (82.6%) of the BAC@MnOx-4 catalyst could facilitate its excellent saturated and breakthrough adsorption capacity (5.24 ± 0.42 mg/g, 2.43 ± 0.22 mg/g). The best performer against 2 ppm HCHO is BAC@MnOx-4 catalyst, exhibiting a maximum HCHO removal efficiency of 97% for 17 h without any deactivation as RH = 0, which is higher than those of other MnOx-based catalysts. The average oxidation state and in situ DRIFTS analysis reveal that abundant oxygen vacancies on the BAC@MnOx-4 catalyst could be identified as surface-active sites of decomposing HCHO into the intermediate species (dioxymethylene and formate). This study provides a potential approach to deposit MnOx nanoparticles onto the BAC surface, and this hybrid BAC@MnOx material is promising for indoor HCHO removal at room temperature.

Oxygen‐Vacancy‐Engineered W18O49−x Nanobrush with a Suitable Band Structure for Highly Efficient Sonodynamic Therapy

AbstractWith the rapid development of external minimally invasive or noninvasive therapeutic modalities, ultrasound‐based sonodynamic therapy (SDT) is a new alternative for treating deep tumors. However, inadequate sonosensitizer efficiency and poor biosecurity limit clinical applications. In this study, we prepared an oxygen‐vacancy‐engineered W18O49−x nanobrush with a band gap of 2.79 eV for highly efficient SDT using a simple solvothermal method. The suitable band structures of the W18O49−x nanobrush endows it with the potential to simultaneously produce singlet oxygen (1O2), superoxide anions (⋅O2−), and hydroxyl radicals (⋅OH) under ultrasound irradiation. Additionally, abundant oxygen vacancies that serve as further charge traps that inhibit electron‐hole recombination are incidentally introduced through one‐step thermal reduction. Collectively, the in vitro and in vivo results demonstrate that the oxygen‐vacancy‐engineered W18O49−x nanobrush delivers highly efficient reactive oxygen species (ROS) for SDT in a very biosafe manner. Overall, this study provides a new avenue for discovering and designing inorganic nanosonosensitizers with enhanced therapeutic efficiencies for use in SDT.

Oxygen-Vacancy-Engineered W18 O49-x Nanobrush with a Suitable Band Structure for Highly Efficient Sonodynamic Therapy.

With the rapid development of external minimally invasive or noninvasive therapeutic modalities, ultrasound-based sonodynamic therapy (SDT) is a new alternative for treating deep tumors. However, inadequate sonosensitizer efficiency and poor biosecurity limit clinical applications. In this study, we prepared an oxygen-vacancy-engineered W18 O49-x nanobrush with a band gap of 2.79 eV for highly efficient SDT using a simple solvothermal method. The suitable band structures of the W18 O49-x nanobrush endows it with the potential to simultaneously produce singlet oxygen (1 O2 ), superoxide anions (⋅O2 - ), and hydroxyl radicals (⋅OH) under ultrasound irradiation. Additionally, abundant oxygen vacancies that serve as further charge traps that inhibit electron-hole recombination are incidentally introduced through one-step thermal reduction. Collectively, the in vitro and in vivo results demonstrate that the oxygen-vacancy-engineered W18 O49-x nanobrush delivers highly efficient reactive oxygen species (ROS) for SDT in a very biosafe manner. Overall, this study provides a new avenue for discovering and designing inorganic nanosonosensitizers with enhanced therapeutic efficiencies for use in SDT.

Oxygen vacancy induction strategy to regulate the evolution of valence- and free-electrons for boosting visible photodegradation of tetracycline hydrochloride

The generation, migration and reaction paths of electrons are the key steps for photodegradation of pollutants. However, efficient operation of the above pathways is still challenging. Herein, by strong coordination and slow pyrolysis, we constructed a narrow band Zn-Mn bimetallic photoactive core-shell material (Mn@Zn-N-C, Eg = 3.38 eV) with abundant oxygen vacancies for enhancing the above electronic paths. The photodegradation experiments of tetracycline hydrochloride (TCH) showed that the formation and transfer of vacancy-induced free electrons in the synthesized Mn@Zn-N-C was the key to improve the photocatalytic activity. The DFT calculation results revealed that the photogenerated electrons can transfer along the Mn-O-Zn bridge in Mn@Zn-N-C, and promote the formation of MnIV, which directly capture the free electrons and reset itself to MnII site. In this case, the introduction of Mn would enhance the separation of h+ and e-. The adjacent vacancies and defects then also trapped the above free electrons and hinder the recombination of photogenerated carriers. Simultaneously, the localized valence electron transfer between the above redox pairs (Mn4+/Mn2+ and Zn2+/Zn0) also promoted the long-term stability of the photocatalytic process. In summary, using vacancy induction strategy to regulate the evolution of valence- and free-electrons is a promising method to improve the production-transfer-utilization efficiency of photogenerated carriers.

Effective degradation of quinoline by catalytic ozonation with MnCexOy catalysts: performance and mechanism.

Quinoline inevitably remains in the effluent of coking wastewater treatment plants due to its bio-refractory nature, which might cause unfavorable effects on human and ecological environments. In this study, MnCexOy was consciously synthesized by α-MnO2 doped with Ce3+ (Ce:Mn = 1:10) and employed as the ozonation catalyst for quinoline degradation. After that, the removal efficiency and mechanism of quinoline were systematically analyzed by characterizing the physicochemical properties of MnCexOy, investigating free radicals and monitoring the solution pH. Results indicated that the removal rate of quinoline was greatly improved by the prepared MnCexOy catalyst. Specifically, the removal efficiencies of quinoline could be 93.73, 62.57 and 43.76%, corresponding to MnCexOy, α-MnO2 and single ozonation systems, respectively. The radical scavenging tests demonstrated that •OH and •O2- were the dominant reactive oxygen species in the MnCexOy ozonation system. Meanwhile, the contribution levels of •OH and •O2- to quinoline degradation were about 42 and 35%, respectively. The abundant surface hydroxyl groups and oxygen vacancies of the MnCexOy catalyst were two important factors for decomposing molecular O3 into more •OH and •O2-. This study could provide scientific support for the application of the MnCexOy/O3 system in degrading quinoline in bio-treated coking wastewater.

Facile synthesis of NiCo2O4 nanostructures with abundant surface oxygen vacancies, and reduced content of Co and Ni valence states for the efficient and bifunctional electrochemical and photocatalytic oxidation of methylene blue

An abundant, low cost, scale up and ecofriendly method has been designed about the preparation of NiCo2O4 nanostructures and the electrode material was employed for the electrochemical oxidation and photocatalytic degradation of methylene blue (MB) under the irradiation of natural sunlight. The NiCo2O4 nanostructures prepared with and without spoiled bitter gourd juice were characterized with respect to morphology, crystalline quality, and surface chemical composition. The morphology of NiCo2O4 nanostructures was transformed from nanorod to low dimension nanoparticles using bitter gourd juice. The surface of NiCo2O4 nanostructures was enriched with the abundant surface oxygen vacancies and low content of different Co and Ni valence states using 10 mL of bitter gourd juice. The NiCo2O4 nanostructures obtained with the 10 mL of bitter gourd were observed highly electroactive towards the oxidation of MB in the phosphate buffer solution of pH 7.4. The linear working range of electrode material for the electrochemical oxidation of MB was estimated from 0.1 mM to 7 mM and a low limit of detection of 0.002 mM was found. A10 mL of bitter gourd juice assisted NiCo2O4 nanostructures were characterized by excellent selectivity, stability and reproducibility. Moreover, the NiCo2O4 nanostructures synthesized with the use of 10 mL of bitter gourd extract were also found active to degrade the MB in aqueous solution under the illumination of natural sunlight. The percent removal of MB was found almost 100 % for the time period of 210 min using NiCo2O4 nanostructures. The phytochemicals from spoiled bitter gourd juice has shown high potential to enhance the electrochemical and photocatalytic properties of NiCo2O4 nanostructures, thus it could be used for the preparation of new generation of electrode materials for the diverse applications.

Sulfur-doped Co(OH)2 nanosheets with abundant oxygen vacancies for high-performance non-enzymatic glucose sensing

The development of high-performance materials for electrochemical non-enzymatic glucose sensing is crucial for diabetes detection and management. This study presents a facile approach for synthesizing sulfur-doped Co(OH)2 nanosheets with abundant oxygen vacancies, enhancing glucose sensing capabilities. Initially, ultrathin Co(OH)2 nanosheets are synthesized via a dissolution-recrystallization process, facilitated by l-lysine during hydrothermal synthesis. Subsequently, sulfur-doped Co(OH)2 nanosheets with oxygen vacancies (B-S-Co(OH)2) are produced through a two-step modification process using Na2S and NaBH4. The resulting B-S-Co(OH)2 exhibits high specific surface area, numerous oxygen vacancies, and rapid electron transfer, contributing to increased electrochemical activity. Electrochemical measurements, conducted with a glassy carbon rotating disk electrode (RDE), indicate low charge transfer barriers and enhanced redox properties. Consequently, B-S-Co(OH)2 nanosheets demonstrate superior glucose sensing performances, characterized by rapid response, high sensitivity (1.044 mA·mM–1·cm–2), broad linear range (0.01–1.4 mM and 1.6–3.6 mM), low detection limit (2.4 µM), and excellent long-term stability. This study offers an effective method for modifying the electronic structure and charge transfer properties of Co(OH)2 through surface modification, thereby advancing non-enzymatic glucose sensing capabilities.

Enhanced CO2 Photoreduction with Noble Metal‐Modified CeO2‐Synthesis, Mechanisms, and Catalytic Insights: A Minireview

AbstractComposite materials integrating precious metals (Au, Ag, Pd, Pt, Ru, Rh, Ir) with CeO2, a rare earth metal oxide, are increasingly utilized in photocatalytic CO2 reduction. CeO2, notable for its redox characteristics, oxygen storage capacity (OSC), and abundant oxygen vacancies (Ov), emerges as a key player in semiconductor catalyst research. The selection of precious metals and their application techniques are crucial in modifying CeO2′s wide bandgap and enhancing light absorption, thereby influencing the photocatalytic efficiency. Approaches for incorporating precious metals onto CeO2 include single atoms, metal clusters, and nanoparticles. This review provides an in‐depth analysis of the progress in composite photocatalysts comprising precious metals and CeO2 for CO2 reduction. It examines diverse modification strategies, such as particle size adjustment and heterojunction formation. The review concisely elucidates the principles behind converting CO2 into high‐value products (hydrocarbons, C1, C2, and C2+). Lastly, it addresses the challenges and future directions for precious metal‐CeO2 catalysts in photocatalytic CO2 reduction.

Enhancing Photocatalytic CO2 Conversion through Oxygen‐Vacancy‐Mediated Topological Phase Transition

Weak adsorption of gas reactants and strong binding of intermediates present a significant challenge for most transition metal oxides, particularly in the realm of CO2 photoreduction. Herein, we demonstrate that the adsorption can be fine‐tuned by phase engineering of oxide catalysts. An oxygen vacancy mediated topological phase transition in Ni‐Co oxide nanowires, supported on a hierarchical graphene aerogel (GA), is observed from a spinel phase to a rock‐salt phase. Such in‐situ phase transition empowers the Ni‐Co oxide catalyst with a strong internal electric field and the attainment of abundant oxygen vacancies. Among a series of catalysts, the in‐situ transformed spinel/rock‐salt heterojunction supported on GA stands out for an exceptional photocatalytic CO2 reduction activity and selectivity, yielding an impressive CO production rate of 12.5 mmol g‐1h‐1 and high selectivity of 96.5%. This remarkable performance is a result of the robust interfacial coupling between two topological phases that optimizes the electronic structures through directional charge transfer across interfaces. The phase transition process induces more Co2+ in octahedral site, which can effectively enhance the Co‐O covalency. This synergistic effect balances the surface activation of CO2 molecules and desorption of reaction intermediates, thereby lowering the energetic barrier of the rate‐limiting step.

Cationic regulation of specificity and activity of defective MCo2O4 nanozyme (M=Fe, Co, Ni, Cu) for colorimetric detection of caffeic acid

Spinel oxide has great promise in constructing highly active nanozymes due to its tunable crystal structure. However, it still faces the problems of poor specificity and insufficient enzyme activity, which limits its application in the field of analysis. Herein, a series of transition metal spinel oxides were synthesized by cation regulation strategy, and their enzymatic activity and catalytic mechanism were analyzed. Interestingly, FeCo2O4, Co3O4 and NiCo2O4 had oxidase-like activity and peroxidase-like activity, while CuCo2O4 had specific and high oxidase-like activity. Their oxidase-like activities follow the order of FeCo2O4 < Co3O4 < NiCo2O4 < CuCo2O4, which is consistent with their cation radius. The smaller the cation radius of tetrahedral site, the more beneficial it is to increase the oxidase-like activity. The high oxidase-like activity of CuCo2O4 may be attributed to the production of 1O2, •O2− and •OH. EPR results showed the presence of abundant oxygen vacancies in CuCo2O4. Upon the introduction of EDTA, TMB color reaction fades because of oxygen vacancies elimination by EDTA, indicating that oxygen vacancies played an important role in the reaction. Based on the inhibition effect of caffeic acid on the high oxidase-like activity of CuCo2O4, a simple and sensitive caffeic acid colorimetric sensing platform was developed. The linear range for the detection of caffeic acid is 0.02–15 μM, with a detection limit as low as 13 nM. The constructed sensor enables the detection of caffeic acid in caffeic acid tablets and actual water samples, providing a new strategy for the detection of caffeic acid and drug quality control.

High density ultra-small Cu nanoparticles with abundant oxygen vacancies for efficient hydrogen evolution from MeOH/H2O

Efficient release of H2 with negligible CO impurities from sustainable MeOH/H2O has become a promising goal for on-board hydrogen generator. However, hydrogen release kinetics still face challenges. In this work, the Cu/ZnO/CeO2 catalyst with high density ultra-small Cu nanoparticles and abundant oxygen vacancies were prepared for intensifying hydrogen evolution in aqueous phase reforming of methanol (APRM). The optimized 55% Cu/ZnO/CeO2 catalyst (Cu NPs of 3.8 nm, Cu loading of 55.89 wt%, oxygen vacancies of 2.316 × 1015 spins g−1) exhibited an excellent H2 evolution rate of 58.39 μmolgcat−1 s−1 even at low temperature of 210 °C, which was 2.1-fold enhancement than that of commercial Cu/ZnO/Al2O3 catalyst. Characterizations and experiments revealed that ZnO/CeO2 intensified the strong metal-support interaction (SMSI), which anchored the Cu NPs, generated abundant oxygen vacancies and adjusted electronic structure to form Cu0-Cu+-Ov active sites for facilitating the kinetics of APRM.

Vitamin C-regulated CoAl- layered double hydroxide with oxygen vacancies to efficiently activate peroxydisulfate for sulfamethoxazole removal triggered via reactive oxygen and high-valent cobalt species

In this study, a vitamin C-regulated CoAl-layered double hydroxide with abundant oxygen vacancies was synthesized via a simple hydrothermal process. The resulting CoAl-layered double hydroxide was employed to activate peroxydisulfate for removal of sulfamethoxazole. The effect of the experimental parameters such as pH, catalyst dose and peroxydisulfate concentration on sulfamethoxazole removal was investigated. The current system exhibited excellent catalytic performance for sulfamethoxazole removal in a broad pH range (i.e., pH 3.0–11.0). Under the optimized condition, 94.2% of sulfamethoxazole was degraded within 15 min, accompanied by a 67.6% reduction in chemical oxygen demand. The effective sulfamethoxazole degradation could be attributed to four pathways. Firstly, the ≡ Co2+ in catalyst reacted with peroxydisulfate to generate reactive species, including SO4•−, •OH, O2•− and 1O2, which could degrade sulfamethoxazole. Secondly, the oxygen vacancies could modulate intrinsic electrons, resulted in the surface activation of catalyst and accelerated charge transfer, which was favorable for the degradation of sulfamethoxazole. Thirdly, the presence of vitamin C not only promoted the formation of oxygen vacancies but also expanded the interlayer spacing of layered double hydroxide. A large interlayer spacing facilitated the diffusion of peroxydisulfate and pollutants in the interlayer and improved the utilization efficiency of the active site. Lastly, the high-valent cobalt species exhibited excellent oxidation ability and enhanced the catalyst performance through continuously being employed as an electron acceptor. This study provided a valuable insight for the design and application of Co-based catalysts in peroxydisulfate-based advanced oxidation processes.

High-Surface Area Mesoporous Sc2O3 with Abundant Oxygen Vacancies as New and Advanced Electrocatalyst for Electrochemical Biomass Valorization.

Scandium oxide (Sc2O3) is considered as omnipotent "Industrial Ajinomoto" and holds promise in catalytic applications. However, rarely little attention is paid to its electrochemistry. Here, the first nanocasting design of high-surface area Sc2O3 with abundant oxygen vacancies (mesoporous VO-Sc2O3) for efficient electrochemical biomass valorization is reported. In the case of the electro-oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), quantitative HMF conversion, high yield, and high faradic efficiency of FDCA via the hydroxymethylfurancarboxylic acid pathway are achieved by this advanced electrocatalyst. The beneficial effect of the VO on the electrocatalytic performance of the mesoporous VO-Sc2O3 is revealed by the enhanced adsorption of reactants and the reduced energy barrier in the electrochemical process. The concerted design, in situ and ex situ experimental studies and theoretical calculations shown in this work should shed light on the rational elaboration of advanced electrocatalysts, and contribute to the establishment of a circular carbon economy since the bio-plastic monomer and green hydrogen are efficiently synthesized.

Insight into the extremely different catalytic behaviors of asymmetric and symmetric oxygen vacancies for peroxymonosulfate activation

Oxygen vacancies (OVs) play crucial role in peroxymonosulfate (PMS) activation, however, the corresponding catalytic mechanism is ambiguous. Herein, we constructed abundant interfacial asymmetric oxygen vacancies (As-OVs) in OVs-ZnO/Co3O4 that displayed remarkable different catalytic behavior from the symmetric oxygen vacancies (S-OVs) in OVs-CoOx. Specifically, the As-OVs achieved ultra-fast contaminants degradation (∼ 1 min) through both radical attack and electron-transfer process (ETP), while S-OVs exhibited sluggish kinetics for both pathways. Experimental and theoretical analyses revealed that PMS was easily adsorbed on the As-OVs to form PMS* , then ETP immediately occurred once OVs-ZnO/Co3O4 encountered with electron-rich bisphenol A. When electron-poor benzoic acid replaced bisphenol A, the peroxide bond was quickly broken to produce radicals due to the largely polarized PMS* on the asymmetric sites. Conversely, the S-OVs cannot realize rapid removal of both targets because the symmetric sites weakened ETP. This work provides atomic-level insights to understand the catalytic behaviors of OVs.

Boosting N2O Catalytic Decomposition by the Synergistic Effect of Multiple Elements in Cobalt-Based High-Entropy Oxides.

Nitrous oxide (N2O) has a detrimental impact on the greenhouse effect, and its efficient catalytic decomposition at low temperatures remains challenging. Herein, the cobalt-based high-entropy oxide with a spinel-type structure (Co-HEO) is successfully fabricated via a facile coprecipitation method for N2O catalytic decomposition. The obtained Co-HEO catalyst displays more remarkable catalytic performance and higher thermal stability compared with single and binary Co-based oxides, as the temperature of 90% N2O decomposition (T90) is 356 °C. A series of characterization results reveal that the synergistic effect of multiple elements enhances the reducibility and augments oxygen vacancy in the high-entropy system, thus boosting the activity of the Co-HEO catalyst. Moreover, density functional theory (DFT) calculations and the temperature-programmed surface reaction (TPSR) with isotope labeling demonstrate that N2O decomposition on the Co-HEO catalyst follows the Langmuir-Hinshelwood (L-H) mechanism with the promotion of abundant oxygen vacancies. This work provides a fundamental understanding of the synergistic catalytic effect in N2O decomposition and paves the way for the novel environmental catalytic applications of HEO.

Laser assisted oxygen vacancy engineering on Fe doped CoO nanoparticles for oxygen evolution at large current density

Exploring cost-effective non-noble metal-based catalysts with high activity and stability is of great significance for energy conversion and storage involving oxygen evolution reaction (OER). Here, we employed a laser irradiation technique to synthesis Fe doped CoO nanoparticles with ultrafine size (≈ 5.4 nm) and abundant oxygen vacancies (Fe-Ov-CoO). The ultrafine size of Fe-Ov-CoO nanoparticles provides more active sites to be exposed. Fe doping and oxygen vacancy promote the intrinsic activity and electron transfer rates of Fe-Ov-CoO, giving rise to high activity and stability catalyst for OER. Fe-Ov-CoO delivers a large current density of 1000 mA cm−2 at an overpotential of 548 mV, which is much better than commercial RuO2. Moreover, Fe-Ov-CoO presents a remarkable long-term stability with negligible degeneration at a high current density of 500 mA cm−2 for 120 h. This work provides a new route to develop OER electrocatalyst with high activity and stability.

Oxygen-enriched vacancy spinel Mn-Co oxides by deep thermal reduction for enhanced antibiotics degradation efficiency

In this research work, flower-like MnCo2O4.5 was synthesized by introducing a short-chain surfactant as a surface-active agent. This structure was utilized as a precursor, and a gas atmosphere pyrolytic deep reduction strategy was employed to construct a sea urchin-like catalyst (DTR-Vo-MCO) with abundant oxygen vacancies. A series of characterizations were conducted to reveal the catalyst's microstructure and crystal phase composition. DTR-Vo-MCO achieved more than 90% degradation of OTC within 10 min, and the efficiency was 1.5 times that of Vp-MCO. The substantial presence of oxygen defects on the DTR-Vo-MCO surface expedited charge transfer processes, resulting in a remarkable enhancement of PMS activation efficiency. Electron paramagnetic resonance spectroscopy (EPR) and radical quenching experiments indicated that the contributions of radicals to oxytetracycline (OTC) degradation were in the order of 1O2 > SO4•– > O2•– > •OH. 1O2 and SO4•– played dominant roles in OTC degradation. The possible oxytetracycline degradation pathways were proposed based on LC-MS analysis. In summary, this work presents an efficient method for a highly oxygen-deficient catalyst, expanding the application of binary transition metal materials in environmental remediation.