Query: Preparation of porous Co3O4 and its response to ethanol with low energy consumption

Candidate papers:

abstract: Co3O4 is a promising p type semiconductor for ethanol detection. In this work, ethanol detection sensors were fabricated with nanostructured Co3O4, which exhibited higher selectivity and lower operating temperature. The Co3O4 was synthesised using ZIF 67 as a sacrificial precursor. The T400 Co3O4 that was obtained by calcining ZIF 67 at 400 degC showed the best sensing performance. Its response to 100 ppm ethanol vapor was 221.99 at a low optimal operating temperature (200 degC) Moreover, T400 Co3O4 achieved a low detection limit (1 ppm) remarkable repeatability, and higher selectivity compared to ammonia, carbon monoxide, acetone, hydrogen, methane, methanol, and nitrogen dioxide. The enhanced sensing performance was mainly attributed to three factors: (1) the adsorption/desorption of active adsorbed oxygen molecules (e.g. O and O2 and abundant oxygen vacancies, which increased the number of active sites; (2) the catalytic activity of Co3+ which greatly increased the reaction route and decreased the activation energy; and (3) the effective diffusion of gas molecules, which increased the effect of collisions between gas molecules and the material surface. This work provides an effective means to fabricate sensitive ethanol gas sensors with low energy consumption.
author_names: Xiao Hang Zhang

Yaohua Xu

Hao Liu

Wenru Zhao

Anjie Ming

Fengwei Wei
title: Preparation of porous Co3O4 and its response to ethanol with low energy consumption
year: 2020

abstract: In this paper, Co3O4 ZnO nanomaterials with Co3O4 doping mass fractions of 0% 2.13% 4.13% and 6.13% were prepared by sol gel method. In order to explain and confirm the influence of the incorporation of Co3O4 on the surface morphology and gas sensitivity of ZnO at a relatively low gas concentration, additional studies such as XRD, XPS, SEM, EDS and UV vis spectroscopy were performed. And its photoelectric response to 100 ppm acetone at near room temperature and visible light irradiation was studied. Due to the formation of P N heterojunctions, the Co3O4 ZnO heterostructural nanoparticles has a highe response to low concentrations of acetone gas than undoped ZnO nanoparticles even at operating temperatures as low as 30oC. The addition of Co3O4 improves the sensitivity and selectivity of ZnO thick films. The sensitivity of the 4.13wt% Co3O4 ZnO sample to 100 ppm acetone at a working temperature of 30oC was 24.36. The light excitation effect was significantly enhanced. Under visible light irradiation, the sensitivity can reach 37.21. In addition, the Co3O4 ZnO P N heterojunction model was combined with visible light excitation theory to further explore the mechanism of gas sensing reaction.
author_names: Nan Han

Guofeng Pan

Jie Zheng

Ru Wang

Yudong Wang
title: Co3O4 ZnO P N Heterostructure Nanomaterials Film and its Enhanced Photoelectric Response to Visible Lights at Near Room Temperature
year: 2019

abstract: Developing cheap and stable electrocatalysts is considered the key factor to achieve the large scale application of fuel cells. In this paper, three dimensional (3D) porous Co doped vanadium nitride (VN) nanosheet assembled microflowers are prepared with a facile solvothermal approach followed by nitridation at 500 degC in NH3. It is found that the microflower morphology and the Co doping both significantly enhance the oxygen reduction reaction (ORR) performance of the materials. Because the unique 3D porous structure provides higher specific surface area and more active sites as well as enriching the d electrons of V via doping, Co also improves the intrinsic activity of VN. Our optimal V0.95Co0.05N microflowers achieve a half wave potential for the ORR of up to 0.80 V in 0.1 M KOH solution, which is almost comparable to that of commercial 20% Pt/C. More importantly, the catalysts show superior durability with little current decline (less than 12% during chronoamperometric evaluation for over 25 000 s. These features make the V0.95Co0.05N microflowers attractive for fuel cell applications.
author_names: Haibo Tang

Jun-ming Luo

Xin Long Tian

Yuanyuan Dong

Jianhai Li

Mingrui Liu

Li-na Liu

Huiyu Song

Shijun Liao
title: Template Free Preparation of 3D Porous Co Doped VN Nanosheet Assembled Microflowers with Enhanced Oxygen Reduction Activity.
venue: ACS applied materials interfaces
year: 2018

abstract: This article is the first demonstration of a molybdenum disulfide (MoS2)/tricobalt tetraoxide (Co3O4) nanocomposite film sensor toward NH3 detection. The MoS2/Co3O4 film sensor was fabricated on a substrate with interdigital electrodes via layer by layer self assembly route. The surface morphology, nanostructure, and elemental composition of the MoS2/Co3O4 samples were examined by scanning electron microscopy, transmission electron microscopy, X ray diffraction, energy dispersive spectrometry, and X ray photoelectron spectroscopy. The characterization results confirmed its successful preparation and rationality. The NH3 sensing properties of the sensor for ultra low concentration detection were investigated at room temperature. The experimental results revealed that high sensitivity, good repeatability, stability, and selectivity and fast response/recovery characteristics were achieved by the sensor toward NH3. Moreover, the MoS2/Co3O4 nanocomposite film sensor exhibited significant enhancement in ammonia sensing properties in comparison with the MoS2 and Co3O4 counterparts. The underlying sensing mechanisms of the MoS2/Co3O4 nanocomposite toward ammonia were ascribed to the layered nanostructure, synergistic effect, and heterojunction created at the interface of n type MoS2 and p type Co3O4. The synthesized MoS2/Co3O4 nanocomposite proved to be an excellent candidate for constructing high performance ammonia sensor for various applications.
author_names: Dongzhi Zhang

Chuanxing Jiang

Peigang Li

Yan'e Sun
title: Layer by Layer Self assembly of Co3O4 Nanorod Decorated MoS2 Nanosheet Based Nanocomposite toward High Performance Ammonia Detection.
venue: ACS applied materials interfaces
year: 2017

abstract: Two dimensional materials often show a range of intriguing electronic, catalytic, and optical properties that differ greatly from conventional nanoparticles. Herein, we demonstrate the large scale preparation of sub 3 nm atomic layers Co3O4 nanofilms with a nonsurfactant and substrate free hydrothermal method. This successful preparation of ultrathin nanofilms highlighted the reconstruction of cobalt ammonia complexes and synergistic effect of free ammonia and nitrate on film growth control. Subsequent performance tests uncovered that these sub 3 nm atomic layer Co3O4 nanofilms exhibited an ultrahigh specific capacitance of 1400 F/g in the first galvanostatic charge/discharge test. The specific capacitance of Co3O4 nanofilms only slightly decayed less than 3% after 1500 cycling tests. With some parameter adjustments, similar Co(OH)2 nanofilms with a thickness of 3.70 0.10 nm were also prepared. The Co(OH)2 nanofilms possessed maximum specific capacitance of 1076 F/g and peak performance attenuation of about 2% after a cycle stability test.
author_names: Chao Feng

Jinfeng Zhang

Yu He

Cheng Zhong

Wenbin Hu

Lei Liu

Yida Deng
title: Sub 3 nm Co3O4 nanofilms with enhanced supercapacitor properties.
venue: ACS nano
year: 2015

abstract: Efficient bifunctional catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable due to their wide applications in fuel cells and rechargeable metal air batteries. However, the development of nonprecious metal catalysts with comparable activities to noble metals is still challenging. Here we report a one step wet chemical synthesis of Ni /Mn promoted mesoporous cobalt oxides through an inverse micelle process. Various characterization techniques including powder X ray diffraction (PXRD) N2 sorption, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirm the successful incorporation of Ni and Mn leading to the formation of Co Ni(Mn) O solid solutions with retained mesoporosity. Among these catalysts, cobalt oxide with 5% Ni doping demonstrates promising activities for both ORR and OER, with an overpotential of 399 mV for ORR (at 3 mA/cm(2) and 381 mV (at 10 mA/cm(2) for OER. Furthermore, it shows better durability than precious metals featuring little activity decay throughout 24 h continuous operation. Analyses of cyclic voltammetry (CV) X ray photoelectron spectroscopy (XPS) Raman, and O2 temperature programmed desorption (O2 TPD) reveal that redox activity of Co(3+ to Co(4+ is crucial for OER performance, while the population of surface oxygen vacancies and surface area determine ORR activities. The comprehensive investigation of the intrinsic active sites for ORR and OER by correlating different physicochemical properties to the electrochemical activities is believed to provide important insight toward the rational design of high performance electrocatalysts for ORR and OER reactions.
author_names: Wenqiao Song

Zheng Ren

Sheng-Yu Chen

Yongtao Meng

Sourav Biswas

Partha Nandi

Heather A Elsen

Pu-Xian Gao

Steven L Suib
title: Ni and Mn Promoted Mesoporous Co3O4: A Stable Bifunctional Catalyst with Surface Structure Dependent Activity for Oxygen Reduction Reaction and Oxygen Evolution Reaction.
venue: ACS applied materials interfaces
year: 2016

abstract: The photocatalytic activity of TiO2 nanotubes can be improved through the construction of a Z scheme composite, where photogenerated electrons from TiO2 recombine with the photogenerated holes in a coupled semiconductor. This arrangement allows for improved oxidation due to the residual holes of TiO2 and better chemical reduction due to the greater availability of the photogenerated electrons of the coupled semiconductor. Efficient Z scheme porous g C3N4/TiO2 nanotube (PCN/TNTs) composites were developed here using a solid sublimation and transition approach, with Al O links added by an impregnation method to increase interfacial linkages between the PCN and TNTs. The best results for photocatalytic CO2 conversion were obtained using 0.7PCN/0.4Al/TNTs, as shown by production of 54.9 0.70 mg L 1 h 1 of acetic acid, 42.7 0.54 mg L 1 h 1 of formic acid, and 45.4 0.55 mg L 1 h 1 of methanol, which were about 3.8, 4.3, and 4.2 times that produced with bare TNTs. Photocatalytic 2,4 dichlorophenol decompos.
author_names: Jing Wu

Yujie Feng

Bruce E Logan

Changchao Dai

Xiaoyu Han

Da Li

Jia Liu
title: Preparation of Al O Linked Porous g C3N4/TiO2 Nanotube Z Scheme Composites for Efficient Photocatalytic CO2 Conversion and 2,4 Dichlorophenol Decomposition and Mechanism
venue: ACS Sustainable Chemistry Engineering
year: 2019

abstract: The article describes synthesis and sensing properties of SnO2 Co3O4 spheres composed of aggregated nanoparticles. Co3O4 was doped with pristine SnO2, and the resulting nanocomposite spheres were incorporated into a silicon adhesive. This material is shown to enable impedimetric sensing of relative humidity (RH) The impedance of the material decreases by 80% at a 1.0 kHz working frequency and by a factor of 2500 at 100 Hz. Capacitance increases by 70% at 1.0 kHz frequency and by a factor of 1509 at 100 Hz. The sensor works in the 10 90% RH range at temperatures from 10 to 80 degC. SnO2 Co3O4 based humidity sensor exhibited high sensitivity which makes it suitable material for the utilization in humidity meter.
author_names: Alaud Din

Khasan S Karimov

Kalsoom Akhtar

M Imran Khan

Muhammad Tariq Saeed Chani

Murad Ali Khan

Abdullah M Asiri

Sher Bahadar Khan
title: Impedimetric humidity sensor based on the use of SnO2 Co3O4 spheres
venue: Journal of Materials Science: Materials in Electronics
year: 2016

abstract: The one dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co3O4 CuO nanofibers (NFs) in the ratio Co:Cu 1/4 (Co3O4 CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co3O4 CuO NFs but also single mesoporous Co3O4 NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface enhanced Raman scattering (SERS) study and the UV vis NRI diffuse reflectance spectra (DRS) The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co3O4 nanofibers framework (Co3O4 CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co3O4 CuO NFs is due to the internal charge transfer between Co2+ to Co3+ and Cu2+ proved by UV vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co3O4 also prevents the electron hole recombination and enhances the photocatalytic activity in composite Co3O4 CuO NFs. The photocurrent density, Mott Schottky (MS) and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co3O4 CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co3O4 NFs and CuO NFs) The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic activity of composite Co3O4 CuO NFs is attributed to the formation of mesoporosity and interconnected NPs within NFs framework, quantum confinement, extended light absorption property, internal charge transfer, and effective photogenerated charge separations.
author_names: Tamer Uyar
title: Morphological Control of Mesoporosity and Nanoparticles within Co3O4 CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance.
venue: ACS applied materials interfaces
year: 2017

abstract: Co(3)O(4) nanoparticles (NPs) with an average diameter of about 20 nm were synthesized by using MOFs as a template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the as prepared Co(3)O(4) NPs. Fourier transform infrared spectroscopy (FT IR) and X ray diffraction (XRD) were used to confirm the structure of the Co(3)O(4) NPs. Then the Co(3)O(4) NPs were modified on a glassy carbon electrode (GCE) to obtain a non enzymatic glucose and H(2)O(2) sensor. The NPs show electrocatalytic activity toward oxidation of glucose and H(2)O(2) in alkaline medium. For glucose detection, the developed sensor shows a short response time (less than 6 s) a high sensitivity of 520.7 mA mM( 1) cm( 2) a detection limit of 0.13 mM (S/N 3) and good selectivity. The high concentration of NaCl does not poison the electrode. Its application for the detection of glucose in a human blood serum sample shows good agreement with the results obtained from the hospital. Furthermore, the proposed sensor was used for the detection of H(2)O(2) The results indicate that the detection limit and sensitivity for H(2)O(2) are 0.81 mM and 107.4 mA mM( 1) cm( 2) respectively. Determination of H(2)O(2) concentration in a disinfectant sample by the proposed biosensor also showed satisfactory result. The high sensitivity and low detection limit can be attributed to the excellent electrocatalytic performance of the as prepared Co(3)O(4) NPs. These results demonstrate that the as prepared Co(3)O(4) NPs have great potential applications in the development of sensors for enzyme free detection of glucose and H(2)O(2)
author_names: Chuantao Hou

Qin Xu

Lina Yin

Xiaoya Hu
title: Metal organic framework templated synthesis of Co3O4 nanoparticles for direct glucose and H2O2 detection.
venue: The Analyst
year: 2012