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Photoelectrochemical Biosensor Based on Co3O4 Nanoenzyme Coupled with PbS Quantum Dots for Hydrogen Peroxide Detection
摘要： A novel kind of hydrogen peroxide (H2O2) photoelectrochemical (PEC) sensor was constructed based on Co3O4 and PbS nanomaterials modified indium tin oxide (ITO) photoelectrode. The Co3O4 nanoparticles, as mimic enzyme of catalase (CAT), can catalyze H2O2 to generate oxygen (O2) in suit. Then the electron acceptor of O2 enhances the cathodic photocurrent of the photoelectrode. The PEC sensor exhibited high sensitivity because of the formation of p-p type heterostructure between PbS and Co3O4 semiconductors. The photocurrent enhancement can be used to detect concentration of H2O2. The calibration plot was linear in the range from 5 to 250 μM and the detection limit was estimated to be 1.2 μM. The results demonstrated the possibility of nanozyme application in PEC biosensors and the substitution of Co3O4 nanozyme for the natural enzyme.
关键词： hydrogen peroxide,PbS,nanozyme,photoelectrochemical biosensor,Co3O4
更新于2025-11-19 16:56:42
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Operando XAS and NAP-XPS investigation of CO oxidation on meso- and nanoscale CoO catalysts
摘要： In contrast to Co3O4, CoO has been much less studied for CO oxidation. Herein, the phase changes of commercial mesoscopic CoO (particle size ?1 μm) and nanosized CoO (20–50 nm particle size), the latter prepared by vacuum reduction of commercial Co3O4, were examined by operando X-ray absorption (XAS) and near-ambient pressure X-ray photoemission (NAP-XPS) spectroscopy during CO oxidation, as well as ex situ by transmission electron microscopy and di?raction (TEM/SAED). Commercial mesoscopic CoO exhibited CO oxidation activity at ?200 °C, but even up to 530 °C in pure O2 no substantial (bulk) oxidation was observed by operando XAS, likely due to the large grains and bulk nature of CoO. After pre-oxidation at 400 C, electron di?raction detected thin surface layers of Co3O4. This increased activity but the activity of nanosized Co3O4 of equal surface area was still not reached. For nanosized CoO (surface layers on vacuum-reduced Co3O4), operando NAP-XPS/XAS, acquired during CO oxidation, revealed oxidation of CoO to Co3O4 above 150 °C, yielding the activity of nanosized Co3O4. Evidently, the nanoscale CoO shell on a Co3O4 core with small grains more easily and more completely transformed to Co3O4 than mesoscopic (bulk) CoO with large grains. Our study demonstrates how ?exible and dynamic surfaces of cobalt oxide materials adjust to various reaction environments, which also depends on grain size and morphology (bulk vs. thin layers), illustrating the importance of operando techniques to determine active catalyst phases under reaction conditions.
关键词： CO oxidation,CoO,Co3O4,NAP-XPS,XAS,TEM,Operando
更新于2025-09-23 15:23:52
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Core-shell structure of ZnO/Co3O4 composites derived from bimetallic-organic frameworks with superior sensing performance for ethanol gas
摘要： In recent years, metal-organic frameworks (MOFs), especially zeolite-imidazole frameworks (ZIFs), have been attracting widespread attention as templates for the synthesis of sensing materials. Limited researches, however, have been carried out to utilize bimetallic ZIFs in gas sensing, as the existing studies mostly involve mono-metallic ZIFs. Here in, the core-shell structure of ZnO and Co3O4 composite (CS-ZnO/Co3O4) was synthesized via chemical etched to Co/Zn based zeolitic imidazolate framework (Co/Zn-ZIF) with subsequent annealing. The morphology, composition and surface characteristics of the as-obtained samples were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Moreover, the gas sensing measurements were implemented under various atmospheres. The response of CS-ZnO/Co3O4 sensor to 100 ppm ethanol at 200 °C achieves 38.87, which is 2.8 times that of single-shell ZnO/Co3O4 (SS-ZnO/Co3O4). The improved response is mainly attributed to the core-shell structure, which offers larger surface area, more active sites for gas diffusion and the formation of p-n heterojunction between ZnO and Co3O4.
关键词： Bimetallic-organic framework,Core-shell structure,ZnO/Co3O4,Ethanol gas sensor
更新于2025-09-23 15:23:52
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Preparation and properties of Co3O4-doped TiO2 nanotube array electrodes
摘要： Co3O4-doped TiO2 nanotube array electrodes were prepared by anodizing the Co–Ti alloys with different Co contents. Morphologies, elemental compositions, crystal structures, and electrochemical properties of the samples were characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical workstation. The effects of Co content, annealing temperature and testing electrolyte on the electrochemical properties of the electrodes were studied. Results show that the areal capacitance values of TiO2 nanotube arrays were obviously improved by doping with Co3O4. The electrochemical properties of Co3O4-doped TiO2 nanotube array electrodes were best when the Co content in the alloys was 9%; the annealing temperature was 100 °C and the testing electrolyte was 0.5 M Na2SO4. The Co3O4-doped TiO2 nanotube array electrodes prepared under the optimal conditions had a high areal capacitance value of 937.9 μF cm?2 when the scan rate was 10 mV s?1 and the electrodes exhibited good rate and superior cycling performance.
关键词： Co–Ti alloys,Electrochemical properties,Co3O4,Anodization,TiO2 nanotube arrays
更新于2025-09-23 15:22:29
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Production of Methanol from Aqueous CO <sub/>2</sub> by Using Co <sub/>3</sub> O <sub/>4</sub> Nanostructures as Photocatalysts
摘要： In this work, we report for the first time the photocatalytic activity of Co3O4 nanostructures for the reduction of aqueous CO2 to methanol (MeOH). This could be considered a simple example of artificial photosynthesis. The photocatalysis experiments were developed under simulated solar light of 100 mW/cm2 and without using any sacrificial agent. To carry out this study, nanostructured mixed valence cobalt oxide (Co3O4) powders, with porous nanoparticle aggregates of different morphologies, have been prepared by two synthesis methods. The characterization of structural (PXRD, XPS, SEM, and TEM) and optical (UV-vis-NIR, Raman, and FT-IR) properties, magnetization curves, and surface area (BET) was accomplished.
关键词： Co3O4,photocatalysis,artificial photosynthesis,CO2 reduction,nanostructures,methanol
更新于2025-09-23 15:22:29
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Atomic-thick TiO <sub/>2</sub> (B) nanosheets decorated with ultrafine Co <sub/>3</sub> O <sub/>4</sub> nanocrystals as a highly efficient catalyst for lithium-oxygen battery
摘要： Development of high efficient catalysts based on transition metal oxides (TMOs) is desirable, and remains a big challenge for lithium-oxygen (Li-O2) batteries. In the present work, atomic-thick TiO2(B) nanosheets decorated with ultrafine Co3O4 nanocrystals (Co3O4-TiO2(B)) was synthesized and utilized as cathode catalyst in Li-O2 batteries by designing a hybrid and inducing oxygen vacancies. The XPS characterization results suggested that the introduction of Co3O4 nanocrystals could induce numerous oxygen vacancies in the TiO2(B) nanosheets through Co doping in the hybrid catalyst. The subsequent electrochemical experiments indicated that the Li-O2 batteries with the prepared hybrid catalysts showed high specific capacity (11000 mAhg-1), and good cycling stability (200 cycles at a limited capacity of 1000mAhg-1) with low polarization (above 2.7V for discharge medium voltage and below 4.0V for charge medium voltage within 80 cycles). Furthermore, a possible working mechanism was proposed for a better understanding of the high performance of Co3O4-TiO2(B) catalysts for the Li-O2 batteries. This work also provided some new insights into designing efficient catalysts through interface engineering between 2D (two dimentional) TMOs and 0D (zero dimentional) TMOs for Li-O2 batteries or other catalysis related fields.
关键词： film-like Li2O2,oxygen vacancies,TiO2(B) nanosheets,Co3O4 nanocrystals,Li-O2 battery
更新于2025-09-23 15:21:21
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[IEEE 2019 International Energy and Sustainability Conference (IESC) - Farmingdale, NY, USA (2019.10.17-2019.10.18)] 2019 International Energy and Sustainability Conference (IESC) - Metal oxide-based heterojunction thin films for solar cell applications
摘要： The interest and development in a fully green future towards sustainable technology and environmental preservation has spurred exponentially for the past few years. The adoption in clean energy is underway with solar photovoltaic (PV) technology leading the race. To keep PV sector competitive with current conventionally generated electricity, an alternative economic PV module using cheap materials with low-cost deposition method is needed. Among the candidate, metal oxides (MO) semiconductors are great potential materials to achieve this goal due to its massive availability, non-toxicity, chemically stable, and can be deposited using low-cost techniques at ambient condition. In this report, the p-n junction solar cell was fabricated using layer by layer deposition of n-type and p-type metal oxide semiconductors. Co3O4 and CuO were used as absorbing layers and ZnO as a window layer in contact with each other using simple spin coating deposition method. Photocurrent density (JSC), photo voltage (VOC) and the crystallinity of materials were investigated to characterize their optoelectronic properties. It is observed that Co3O4 shows larger crystallite size compared to CuO at 26.66 nm and 24.86 nm, respectively. Samples consisting of Co3O4 and CuO p-n junction solar cell exhibits high absorbance in the visible spectral region of 350 nm to 750 nm. J-V measurement of FTO/ZnO/Co3O4/In heterojunction films exhibits short-circuit current density of 0.391 mA/cm-1 and open-circuit voltage of 0.476 V under the illumination of AM1.5 solar simulation (100mW/cm2). Meanwhile, FTO/ZnO/CuO/In shows short-circuit current density of 0.429 mA/cm-1 and open-circuit voltage of 0.048 V. Thus, it shows that green materials without any environmental issue has high potential in solar cells application.
关键词： CuO,Co3O4,Sol-Gel,Solar Cell,Spin Coating,Heterojunction
更新于2025-09-23 15:21:01
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High-performing self-driven ultraviolet photodetector by TiO2/Co3O4 photovoltaics
摘要： Ultraviolet (UV) may provide the essential to maintain the human body and metabolism, however, excessive exposure to UV light is absolutely harmful. We may take advantage of the strong UV energy for energy conversion devices. A stable, simple and scalable heterojunction (TiO2/Co3O4) thin film was developed for UV-absorbing and visible-blind photovoltaic. Effective hole transport layer (HTL, NiO) insertion established photovoltaics, having a power conversion efficiency of 15.8%. The heterojunction exhibits the improved carrier lifetime from 1.94 ms to 9 ms, resulting in the enhancement of both photovoltage and photocurrent from 0.17 V to 0.78 V and from 0.54 mA cm-2 to 13.5 mA cm-2, respectively. The TiO2/Co3O4 device exhibits a photoresponse to a UV light intensity of 60 μW cm-2 in the presence of sunlight and works stable for over a year. The results indicate metal oxide heterojunction (TiO2/Co3O4) photovoltaic device could be useful for monitoring UV radiation exposure and cost-effective self-powered UV optoelectronics. The functional utilization of metal oxide layers would provide strong benefits for photoelectric devices, such as photodetectors and transparent solar cells.
关键词： Metal oxide,Visible-blind UV photodetector,TiO2/Co3O4 photovoltaics,Long-term stability
更新于2025-09-23 15:19:57
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Synthesis and Characterization of Spinel Cobaltite (Co3O4) Thin Films for Function as Hole Transport Materials in Organometallic Halide Perovskite Solar Cells
摘要： Conventional inorganic p-type conductive oxides, e.g. NiO, CuOX, and CuCrOX, can serve as low-cost and efficient hole transport materials for wide bandgap organolead halide perovskites [e.g. MAPbI3], but low bandgap Sn-rich organometallic perovskites fail for (FASnI3)0.6(MAPbI3)0.4], where MA = (CH3NH3) and FA = (HC(NH2)2). In this work, we explore spinel Co3O4 based p-type conductive oxides as hole transport materials in organometallic halide MAPbI3 and (FASnI3)0.6(MAPbI3)0.4 perovskite solar cells. We examine the structural, crystalline, optical, electrical, photoelectrochemical, and surface chemistry properties of spin coated Co3O4 films without and with lithium doping. We find that lithium doping improves hole mobilities as well as film optical transparency and causes a lithium enriched overlayer (e.g. LiCoO2) forming at Co3O4 film surface. As a result, lithium doping can maximise the hole transport properties of Co3O4 in our inverted planar perovskite solar cells, achieving about 14% and 7% light-to-electricity power conversion efficiencies (PCEs) for perovskite halides MAPbI3 and (FASnI3)0.6(MAPbI3)0.4, respectively. This work underscores that cobaltite spinels hold promise in application as working HTLs for all kinds of organometallic halide perovskites.
关键词： cobaltite spinels,hole transport materials,doping,Co3O4,perovskite solar cells
更新于2025-09-23 15:19:57
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Boosted Reactivity of Low-Cost Solar Cells over a CuO/Co <sub/>3</sub> O <sub/>4</sub> Interfacial Structure Integrated with Graphene Oxide
摘要： Developing cost-effective and environment-friendly counter electrodes (CEs) with high performance is central for the commercial application of dye-sensitized solar cells (DSSCs). In this work, the porous interfacial CuO/Co3O4@GO (CCO@GO) hybrid was fabricated by encapsulating the self-assembled CuO/Co3O4 nanosphere in graphene oxide (GO) and acted as a CE for the first time. Further measurements verified that the optimized CCO@GO hybrid not only provided a higher specific surface area (86.7 m2?g?1) with more exposed catalytic sites, but also significantly enhanced the power conversion efficiency (PCE = 8.34%) of DSSC, which was higher than that of the Co3O4-based CE (2.66%) and commercial Pt CE (7.85%). The results indicate that the interfacial CuO/Co3O4@GO hybrid synergistically accelerates the diffusion of I3?/I? redox couple and transmission of electrons, thus promoting the reaction kinetics. This work provides a remarkable way for exploring economical high-performance Pt-free CEs for DSSCs, as well as contributes to the further development for other energy-related fields.
关键词： DSSCs,interfacial structure,transition metal oxides,CuO/Co3O4@GO,counter electrode
更新于2025-09-23 15:19:57