Tuning A-Site Cation Deficiency in Pr0.5La0.5BaCo2O5+ δ Perovskite to Realize Large-Scale Hydrogen Evolution at 2000 mA cm-2.

Industrial-level hydrogen production from the water electrolysis requires reducing the overpotential (η) as much as possible at high current density, which is closely related to intrinsic activity of the electrocatalysts. Herein, A-site cation deficiency engineering is proposed to screen high-performance catalysts, demonstrating effective Pr0.5- xLa0.5BaCo2O5+ δ (P0.5- xLBC) perovskites toward alkaline hydrogen evolution reaction (HER). Among all perovskite compositions, Pr0.4La0.5BaCo2O5+ δ (P0.4LBC) exhibits superior HER performance along with unique operating stability at large current densities (J = 500-2000 mA cm-2 geo). The overpotential of ≈636 mV is achieved in P0.4LBC at 2000 mA cm-2 geo, which outperforms commercial Pt/C benchmark (≈974 mV). Furthermore, the Tafel slope of P0.4LBC (34.1 mV dec-1) is close to that of Pt/C (35.6 mV dec-1), reflecting fast HER kinetics on the P0.4LBC catalyst. Combined with experimental and theoretical results, such catalytic activity may benefit from enhanced electrical conductivity, enlarged Co-O covalency, and decreased desorption energy of H* species. This results highlight effective A-site cation-deficient strategy for promoting electrochemical properties of perovskites, highlighting potential water electrolysis at ampere-level current density.

CuCo2O4 nanoneedle arrays growth on carbon cloth as a non-enzymatic electrochemical sensor with low detection limit ketoprofen recognition.

An electrochemical sensor for detecting ketoprofen was constructed by in-situ grown copper cobaltate (CuCo2O4) nanoneedle arrays on a carbon cloth (CC) substrate. The resulting porous nanoneedle arrays not only expose numerous electrochemically active sites but also significantly enhance the electrochemical apparent active area and current transmission efficiency. By leveraging its electrochemical properties, the sensor achieves an impressive detection limit for ketoprofen of 0.7 pM, with a linear range spanning from 2 pM ~ 2 µM. Furthermore, the sensor exhibits remarkable reproducibility, anti-interference capabilities, and stability. Notably, the developed sensor also performed ketoprofen detection on real samples (including drug formulations and wastewater) and demonstrated excellent recognition ability. These exceptional performances can be attributed to the direct growth of CuCo2O4 nanoneedle arrays on the CC substrate, which facilitates a robust electrical connection, provides abundant electrocatalytic active sites, and expands the apparent active area. Consequently, these improvements contribute to the efficient trace detection capabilities of the ketoprofen sensor.

Willow catkin template synthesis of NiS@NSC hollow tubes for highly sensitive dual-function electrochemical detection of acetaminophen and Cu2.

Public health and environmental well-being have become increasingly threatened by the contamination of pharmaceuticals and heavy metal ions. This study focuses on addressing this critical issue by developing a novel electrochemical sensor for the dual-functional detection of acetaminophen (AP) and Cu2+. Utilizing willow catkins as a biomass template, a hollow tubular NiS@NSC composite was prepared by simple nickel salt impregnation combined with calcination and sulfurization. A highly sensitive dual-functional electrochemical sensor was thus constructed that can detect both acetaminophen (AP) and Cu2+. By examining its electrochemical properties, the sensor achieves an impressive detection limit of 1.33 pM for AP, with a linear range of 4.00 pM ~ 0.15 mM. The sensor can also detect Cu2+, with a detection limit of 1.04 µM, and a linear range of 3.13 µM ~ 0.66 mM. The sensor also exhibits strong resistance to interference, and good repeatability and stability. In addition, the sensor has demonstrated good performance in actual sample analysis, including the detection of AP in serum and Cu2+ in wastewater. This excellent electrochemical sensing performance is mainly attributed to the synergistic effect of its unique tubular structure and highly conductive N, S co-doped carbon. This results in the sensor exhibiting minimal charge transfer resistance, an extensive electrochemically active surface area, and a high density of active sites.

One-pot synthesis and hydrogen peroxide electrochemical sensing of 3D TiO2/MnO2 nanorods assembled microspheres.

Nanorods assembled 3D microspheres of TiO2/MnO2 were prepared via a simple one-pot hydrothermal approach. The resultant composite material exhibited remarkable electrocatalytic activity for hydrogen peroxide (H2O2) in comparison to each single component. The electrochemical sensor constructed with TiO2/MnO2 exhibited a linear relationship within the range 0.0001-5.6 mmol·L-1 for H2O2. The limit of detection (LOD) and sensitivity for H2O2 were 0.03 µmol·L-1 (S/N = 3) and 316.6 µA (mmol·L-1)-1 cm-2. Moreover, this sensor can be employed to detect trace amount of H2O2 in serum and urine samples successfully, supporting an insight and strategy for a more sensitive electrochemical sensor.

Bimetallic MOFs-derived coral-like Ag-Mo2C/C interwoven nanorods for amperometric detection of hydrogen peroxide.

Coral-like Ag-Mo2C/C-I and blocky Ag-Mo2C/C-II composites were obtained from one-step in situ calcination of [Ag(HL)3(Mo8O26)]n·nH2O [L: N-(pyridin-3-ylmethyl) pyridine-2-amine] under N2/H2 and N2 atmospheres, respectively. The coral-like morphology of Ag-Mo2C/C-I is composed of interwoven nanorods embedded with small particles, and the nano-aggregate of Ag-Mo2C/C-II is formed by cross-linkage of irregular nanoparticles. The above composites are decorated on glassy carbon electrode (GCE) drop by drop to generate two enzyme-free electrochemical sensors (Ag-Mo2C/C/GCE) for amperometric detection of H2O2. In particular, the coral-like Ag-Mo2C/C-I/GCE sensor possesses rapid response (1.2 s), high sensitivity (466.2 µA·mM-1·cm-2), and low detection limit (25 nM) towards trace H2O2 and has wide linear range (0.08 µM~4.67 mM) and good stability. All these sensing performances are superior to Ag-Mo2C/C-II/GCE, indicating that the calcining atmosphere has an important influence on microstructure and electrochemical properties. The excellent electrochemical H2O2 sensing performance of Ag-Mo2C/C-I/GCE sensor is mainly attributed to the synergism of unique microstructure, platinum-like electron structure of Mo2C, strong interaction between Mo and Ag, as well as the increased active sites and conductivity caused by co-doped Ag and carbon. Furthermore, this sensor has been successfully applied to the detection of H2O2 in human serum sample, contact lens solution, and commercial disinfector, demonstrating the potential in related fields of environment and biology. Graphical abstract.

Ionic liquid([C12mim][PF6])-assisted synthesis of TiO2 /Ti2O (PO4)2 nanosheets and the chemoresistive gas sensing of trimethylamine.

The architecture of PO43- modified 2D TiO2 nanosheets was constructed by ionic liquids (ILs)-assisted hydrothermal method. The nanosheet structure can be regulated by the addition of different amount of ionic liquid. Using the composite nanosheets  a chemoresistive gas sensor was prepared for trimethylamine (TMA) detection. Most reported TMA sensors need to be operated at a relatively high operating temperature, but in this paper, the as-synthesized PO43--modified 2D TiO2/Ti2O(PO4)2 nanosheet sensor has high response (S = 87.46), short response time (14.6 s), and good reproducibility to 100 ppm TMA gas, when the temperature is 170 °C. In contrast to the single-phase TiO2 sensor, the gas-sensing property of the composite one is obviously enhanced. Moreover, its response shows excellent linear relationship with TMA concentration from 0.2 to 500 ppm, and a detection limit of 0.2 ppm. The TMA detection mechanism was investigated by analyzing the changes of the surface adsorption oxygen content by XPS and gaseous products using gas chromatography after the sensor was in contact with TMA.

Synthesis of ZnO@poly-o-methoxyaniline nanosheet composite for enhanced NH3-sensing performance at room temperature.

Poly-o-methoxyaniline (POMA) and zinc oxide (ZnO) composites were prepared via in situ polymerization and characterized by thermogravimetry thermal analysis, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and N2 sorption measurement. The composites show different morphology when the ratio of POMA and ZnO varies. At a ratio of 2:2, the composite shows thinner nanosheet structure with smooth surface and exhibits best response to NH3 at room temperature. The ZnO@POMA nanosheet sensor shows good selectivity and a wide response range (linear ranges from 0.05-1 pmm and 10-100 ppm of NH3). The lowest detection limit reaches 0.05 ppm. The sensor exhibits good reversibility. Based on the testing results of ultraviolet diffuse reflection spectroscopy and Kelvin probe technique, the adsorption and desorption of NH3 molecules on the sensing material and the formation of p-n heterostructure between ZnO and POMA and their synergistic effects are further explained. More importantly, the sensor possessed excellent moisture resistance. The overall test results of ZnO@POMA show that the sensor has good practical applicability for detecting trace NH3 at room temperature. Graphical abstract.

One step synthesis of PANI/Fe2O3 nanocomposites and flexible film for enhanced NH3 sensing performance at room temperature.

Novel sea cucumber-shaped polyaniline/ferric oxide (PANI/Fe2O3) nanocomposites were synthesized using a simple and efficient one step hydrothermal process, and the nanocomposites were further assembled onto a polyethylene terephthalate (PET) flexible substrate. Through the monitoring of the resistance of the PANI/Fe2O3 nanocomposites thick films and PANI/Fe2O3-PET flexible sensors, the responses of the sensors to various 100 ppm gases including methanol, triethylamine, aniline and another five gases were obtained. It was found that two kinds of sensors exhibit a high selectivity towards NH3. The PANI/Fe2O3 nanocomposites-based sensor has a good response and a low detection limit (0.3 ppm) at room temperature (20 ± 5 °C). It also shows a good linearity relationship in a certain concentration of NH3. After assembling into the PANI/Fe2O3-PET flexible film sensor, the response of the sensor is significantly increased to 6.12 for 100 ppm NH3, the detection limit is as low as 0.5 ppm, and the sensor shows good stability and linearity, which is more conducive to the application of such a material in wearable gas sensors.

Ladder chain Cd-based polymer as a highly effective adsorbent for removal of Congo red.

Developing of high effective and fast-rate adsorbent materials has been recently attracted intensive attentions all over the world due to organic dye polluted water treatment. However, few studies have been reported on the ultrahigh-capacity and fast-rate removal of Congo red. In this work, a new stable Cd-based coordination polymer exhibits excellent adsorption performance towards Congo Red. This ladder chain [Cd4(H2L)4(H2O)8(NDS)]n·3n(NDS) (I) (H2L = N1,N2-bis(pyridin-3-ylmethyl) ethane-1,2-diamine, 1,5-H2NDS = 1,5-naphthalene disulfonic acid) has been successfully synthesized by the hydrothermal reaction. At room temperature, the experimental adsorption capacity of coordination polymer (I) towards Congo red can reach up to 16,880 mg g-1 in 20 min (pH = 2.0-3.2), and its higher capacity and faster rate are all better than those in reported inorganic and metal-organic frameworks absorbents. The adsorption process is spontaneous and endothermic reaction, and fits well with the second-order kinetics, Langmuir and Scatchard isotherm adsorption models. The excellent adsorption performance of (I) towards Congo red is related to the strong electrostatic, various hydrogen bonding and π-π stacking interactions under acidic conditions.

A hollow urchin-like α-MnO2 as an electrochemical sensor for hydrogen peroxide and dopamine with high selectivity and sensitivity.

A hollow urchin-like α-MnO2 material has been synthesized by a hydrothermal method starting from MnSO4·H2O and (NH4)2S2O8, and by using silver(I) as the catalyst. It has a hollow morphology with diameters of 5-6 µm and consists of densely aligned nanowires, with a 30-40 nm width and a 1.5 µm length. The diameter of the cavities and the thickness of the shell are about 1.2 µm and 300 nm, respectively. The material was placed on a glassy carbon electrode (GCE), and electrochemical experiments showed the respective sensor to possess good stability and reproducibility. The modified GCE displays response to both hydrogen peroxide (H2O2) and dopamine (DA) at working potentials of -0.40 V and +0.4 V, respectively (both versus SCE). H2O2 can be detected with an 80 nM detection limit, and DA with a 12 nM detection limit (at S/N = 3). Graphical abstract Schematic presentation of synthesis of a hollow urchin-like α-MnO2, which taking MnSO4.H2O and (NH4)2S2O8 as raw materials and was further used to construct an electrocatalytic sensor for hydrogen peroxide and dopamine with low detection limit, desirable selectivity and sensitivity.

Co3O4/carbon hollow nanospheres for resistive monitoring of gaseous hydrogen sulfide and for nonenzymatic amperometric sensing of dissolved hydrogen peroxide.

Co3O4/carbon hybrid hollow nanospheres (hs-Co3O4/C) with an empty cavity and a thin shell, were synthesized starting from the pectin and cobalt acetate via cross-linking deposition at room temperature and post-calcination. The hierarchical structure is constructed from the interconnected nanoparticles in the residual carbon matrix, and the carbon content can be adjusted by changing the calcination temperature. The gas sensor based on hs-Co3O4/C calcined at 300 °C in air shows high response towards 50 ppm of H2S (S = 95.5) and good selectivity at a low working temperature (92 °C). The detection limit is as low as 0.1 ppm. The non-enzymatic glassy carbon electrode based sensor constructed from the same material exhibits excellent electrocatalytic activity for H2O2 with the sensitivity of 405.8 µA∙mM∙cm-2 at 0.3 V (vs. SCE) in alkaline solution. The chronoamperometric response time is < 3 s and the detection limit (at S/N = 3) is 0.30 µM. The good sensing performances are attributed to the synergetic effect of unique hollow nanostructure and appropriate amount of carbon in the hybrid material. The porous nanostructure can increase the mass transfer efficiency, and the cross-linked nanoparticles with good crystallinity also improve the conductivity of materials. The presence of carbon enhances the charge transfer ability and increases the specific surface, thereby improving the sensor performance. Graphical abstract Schematic illustration of the formation of hollow Co3O4 nanospheres composited with pectin-derived carbon. The material displays excellent selectivity for H2S gas and in non-enzymatic detection of dissolved H2O2.

A Flexible Portable Glucose Sensor Based on Hierarchical Arrays of Au@Cu(OH)2 Nanograss.

Flexible physiological medical devices have gradually spread to the lives of people, especially the elderly. Here, a flexible integrated sensor based on Au nanoparticle modified copper hydroxide nanograss arrays on flexible carbon fiber cloth (Au@Cu(OH)2/CFC) is fabricated by a facile electrochemical method. The sensor possesses ultrahigh sensitivity of 7.35 mA mM-1 cm-2 in the linear concentration range of 0.10 to 3.30 mM and an ultralow detection limit down to 26.97 nM. The fantastic sensing properties can be ascribed to the collective effect of the superior electrochemical catalytic activity of nanograss arrays with dramatically enhanced electrochemically active surface area as well as mass transfer ability when modified with Au and intimate contact between the active material (Au@Cu(OH)2) and current collector (CFC), concurrently supplying good conductivity for electron/ion transport during glucose biosensing. Furthermore, the device also exhibits excellent anti-interference and stability for glucose detection. Owing to the distinguished performances, the novel sensor shows extreme reliability for practical glucose testing in human serum and juice samples. Significantly, these unique properties and the soft structure of silk fabric can provide a promising structure design for a flexible micro-device and a great potential material candidate of electrochemical glucose sensor.

Synergy of Active Sites and Charge Transfer in Branched WO3/W18O49 Heterostructures for Enhanced NO2 Sensing.

Achieving reliable detection of trace levels of NO2 gas is essential for environmental monitoring and protection of human health protection. Herein, a thin-film gas sensor based on branched WO3/W18O49 heterostructures was fabricated. The optimized WO3/W18O49 sensor exhibited outstanding NO2 sensing properties with an ultrahigh response value (1038) and low detection limit (10 ppb) at 50 °C. Such excellent sensing performance could be ascribed to the synergistic effect of accelerated charge transfer and increased active sites, which is confirmed by electrochemical impedance spectroscopy and temperature-programmed desorption characterization. The sensor exhibited an excellent detection ability to NO2 under different air quality conditions. This work provides an effective strategy for constructing WO3/W18O49 heterostructures for developing NO2 gas sensors with an excellent sensing performance.

Well-designed strategy to construct helical silver(I) coordination polymers from flexible unsymmetrical bis(pyridyl) ligands: syntheses, structures, and properties.

In this Article, self-assembly of AgX (X = NO3(-) and ClO4(-)) salts and four flexible unsymmetrical bis(pyridyl) ligands, namely, N-(pyridin-2-ylmethyl)pyridin-3-amine (L1), N-(pyridin-3-ylmethyl)pyridin-2-amine (L2), N-(pyridin-4-ylmethyl)pyridin-2-amine (L3), and N-(pyridin-4-ylmethyl)pyridin-3-amine (L4), results in the formation of eight helical silver(I) coordination polymers, [Ag(L)(NO3)]n [L = L1 (1), L2 (2), L3 (3), L4 (4)] and [Ag(L)(ClO4)]n [L = L1 (5), L2 (6), L3 (7), L4 (8)], which have been characterized by elemental analysis, IR, TG, PL, and powder and single-crystal X-ray diffraction. The alternating one-dimensional (1-D) left- and right-handed helical chains are included in achiral complexes 1-3 and 5-8. By contrast, the ligand L4 only alternately bridges Ag(I) cation to form the 1-D right-handed helical chain in complex 4. The pitches of these helical chains locate in the range 5.694(5)-17.016(6) Å. Meanwhile, the present four unsymmetrical bis(pyridyl) ligands in the eight complexes present diverse cis-trans and trans-trans conformation and facilitate the construction of helical structures. Moreover, the solid-state luminescent emission intensities of the perchlorate-containing complexes are stronger than those of nitrate-containing complexes at room temperature.

Promotion of the Efficient Electrocatalytic Production of H2O2 by N,O- Co-Doped Porous Carbon.

H2O2 generation via an electrochemical two-electron oxygen reduction (2e- ORR) is a potential candidate to replace the industrial anthraquinone process. In this study, porous carbon catalysts co-doped by nitrogen and oxygen are successfully synthesized by the pyrolysis and oxidation of a ZIF-67 precursor. The catalyst exhibits a selectivity of ~83.1% for 2e- ORR, with the electron-transferring number approaching 2.33, and generation rate of 2909.79 mmol g-1 h-1 at 0.36 V (vs. RHE) in KOH solution (0.1 M). The results prove that graphitic N and -COOH functional groups act as the catalytic centers for this reaction, and the two functional groups work together to greatly enhance the performance of 2e- ORR. In addition, the introduction of the -COOH functional group increases the hydrophilicity and the zeta potential of the carbon materials, which also promotes the 2e- ORR. The study provides a new understanding of the production of H2O2 by electrocatalytic oxygen reduction with MOF-derived carbon catalysts.

Selective detection of trace carbon monoxide at room temperature based on CuO nanosheets exposed to (111) crystal facets.

In recent years, carbon monoxide (CO) intoxication incidents occur frequently, and the sensitive detection of CO is particularly significant. At present, most reported carbon monoxide (CO) sensors meet the disadvantage of high working temperature. It is always a challenge to realize the sensitive detection of carbon monoxide at room temperature. In this study, CuO nanosheets exposed more (111) active crystal facets and oxygen vacancy defects were synthesized by a simple and environmentally friendly one-step hydrothermal method. The sensor has good comprehensive gas sensing performance, compared with other sensors that can detect CO at room temperature. The response value to 100 ppm CO at room temperature is as high as 39.6. In addition, it also has excellent selectivity, low detection limit (100 ppb), good reproducibility, moisture resistance and long-term stability (60 days). This excellent gas sensing performance is attributed to the special structural characteristics of 2D materials and the synergistic effect of more active crystal facets exposed on the crystal surface and oxygen vacancy defects. Therefore, it is expected to become a promising sensitive material for rapid and accurate detection of trace CO gas under low energy consumption, reduce the risk of poisoning, and then effectively protect human life safety.

Rapid detection of H2S gas driven by the catalysis of flower-like α-Bi2Mo3O12 and its visual performance: A combined experimental and theoretical study.

Metal oxide semiconductor (MOSs) are attractive materials for the development of H2S gas sensors. However, detecting H2S with short response and recovery times while also lowering the limit of detection to sub-ppb levels remains a significant challenge. We therefore developed flower-like α-Bi2Mo3O12 microspheres for H2S gas detection that provide fast response and recovery times (3 and 22 s, respectively, for 100 ppm H2S), while also reducing the limit of detection to 1 ppb. The sensor performs well in terms of sensitivity, reproducibility, long-term stability, including humidity stability. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that H2S dissociates readily on the reduced α-Bi2Mo3O12 surface and that Mo plays a catalytic role, accelerating the rate of H2S decomposition and enabling a fast response. Moreover, test strips containing α-Bi2Mo3O12 were also prepared, which enabled the naked eye detection of ppm-level H2S gas at room temperature; a light-yellow to orange to brown color change occurs when exposed to H2S, due to its conversion into stable sulfides. This work expands the application of α-Bi2Mo3O12 to H2S gas sensing, and provides a strategy for the use of MOSs as sensor materials for the detection of other gases.

Non-enzymatic nitrite amperometric sensor fabricated with near-spherical ZnO nanomaterial.

A unique near-spherical ZnO nanostructure was synthesized by using mixed solvents composed of polyethylene glycol-400 (PEG-400) and water at the volume ratio of 12:1 via the solvo-thermal method, and it possessed an ideal morphology with higher uniformity, better dispersion and small particle size. Such ZnO was employed to modify glass carbon electrode (GCE) for the construction of electrochemical sensor, i.e. near-spherical ZnO/GCE, whose nitrite sensing performance was evaluated by Chronoamperometry (CA) and Linear Sweep Voltammetry (LSV). In order to emphasis the superior sensing property and extensive suitability for different electrochemical detection techniques, the excellent but not the same nitrite detection performance obtained from CA and LSV was individually given in detail. This sensor based on CA showed broad linearity range of 0.6 µM-0.22 mM and 0.46 mM-5.5 mM, improved sensitivity of 0.785 µA µM-1 cm-2 accompanied with low LOD of 0.39 µM. With regard to LSV, wide linearity response of 1.9 µM-0.8 mM and 1.08 mM-5.9 mM, high sensitivity of 0.646 µA µM-1 cm-2 with LOD of 0.89 µM were obtained. Meanwhile, this sensor displayed outstanding repeatability with RSD of 2.96% (n = 4), high reproducibility with low RSD (1.72%-2.35%, n = 4), strong selectivity towards nitrite with the concentration set at one-tenth of the interfering substances, ideal stability with the peak current intensity above 90% of its initial value after storage for one month and acceptable recovery of 1.72-2.35% to actual samples including ham sausage, pickle and tap water. The near-spherical ZnO nanomaterial may be a preferred candidate for the fabrication of nitrite electrochemical sensor, which may exhibit a fascinating application in terms of food analysis and environmental monitoring.

Porous Cr2O3 Architecture Assembled by Nano-Sized Cylinders/Ellipsoids for Enhanced Sensing to Trace H2S Gas.

How to achieve high sensing of Cr2O3-based sensors for harmful inorganic gases is still a challenge. To this end, Cr2O3 nanomaterials assembled from different building blocks were simply prepared by chromium salt immersion and air calcination with waste scallion roots as the biomass template. The hierarchical architecture calcined at 600 °C is constructed from nanocylinders and nanoellipsoids (named as Cr2O3-600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr2O3-based sensor to realize highly sensitive detection of trace H2S gas. At 170 °C, Cr2O3-600 exhibits a high response of 42.8 to 100 ppm H2S gas, which is 3.45 times larger than that of Cr2O3-500 assembled from nanocylinders. Meanwhile, this sensor has a low detection limit of 1.0 ppb (S = 1.4), good selectivity, stability, and moisture resistance. These results show that the combination of nanosized cylinders/ellipsoids together with exposed (104) facet can effectively improve the sensing performance of the p-type Cr2O3 material. In addition, the Cr2O3-600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.

Controllable construction of ZnFe2O4-based micro-nano heterostructure for the rapid detection and degradation of VOCs.

Micro-nano heterogeneous oxides have received extensive attention due to their distinctive physicochemical properties. However, it is a challenge to prepare the hierarchical multicomponent metal oxide nanomaterials with abundant heterogeneous interfaces in a controllable way. In this work, the effective construction of the heterogeneous structure of the material is achieved by regulating the ratio of metal salts under thermal solvent condition. Three-dimensional spheres (ZnFe2O4) constructed by zero-dimensional ultra-small nanoparticles, in particular three-dimensional hollow sea urchin spheres (ZnO/ZnFe2O4) constructed by one-dimensional nanorods and three-dimensional hydrangeas (α-Fe2O3/ZnFe2O4) assembled by two-dimensional nanosheets were obtained. The two composite materials contain a large number of heterojunctions, which enhances the sensitivity of material to volatile organic compounds gas. Among them, the α-Fe2O3/ZnFe2O4 composite shows the best sensing performance for VOCs. For example, its response to 100 ppm acetone reaches 142 at 170 °C with the response time shortened to 3 s and the detection limit falling to 10 ppb. Meanwhile, the composite material presents a degradation rate of more than 90% for VOCs at a flow rate of 20 mL/min at 170 °C. In addition, the sensing and sensitivity mechanism of the composite material are studied in detail by combining GC-MS, XPS with UV diffuse reflectance tests.