Nanoporous SnO2 Research Articles

Electrochemical characterization of nanoporous SnO2 formed by anodization on cold spray tin coating for supercapacitor application

In the present study, tin oxide film with regular nano-channels was formed on the surface of cold sprayed tin coating by the anodizing process. The microstructure of the samples was investigated by field-emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results show that annealing the samples with the assistance of water leads to the formation of crystalline particles on the inner surface of the nanotubes by the dissolution-precipitation mechanism. The electrochemical performance of the nanoporous tin oxide film was evaluated as an electrode by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). Being employed as the supercapacitor electrode materials, the electrode revealed a specific capacitance of 0.0176F/cm2 at a current density of 0.1 mA/cm2. The appropriate capacitive properties were due to the morphology and SnO2 active materials grown on the inside wall of the nanoporous structure, resulting in the enhancement of the active surface area. The investigation of the effect of the preferred orientation on the capacitance of the produced films shows that (020) and (031) have a very positive effect on the capacitive properties of the samples. Also, (110) and (011) preferred orientation has caused a sharp decrease in capacity.

Selective photoactive gas detection of CO and HCHO using highly porous SnO2 and SnO2@TiO2 heterostructure

Herein, a controlled porous structure for photoactive gas sensors was fabricated using the gas-flow thermal evaporation and atomic layer deposition method. To control the porosity of the SnO2 matrix, Ar was introduced to the chamber to adjust the pressure from 0.1 to 1 Torr during thermal evaporation. Furthermore, nanoscale TiO2 layers were conformally deposited on the surface of porous SnO2 by atomic layer deposition as a selective active layer for HCHO. As a result, the sensor deposited at a pressure of 0.2 Torr showed high sensitivity and a relatively fast response than other deposition pressures owing to the optimized porosity and better electron transport. The nanoporous structure of SnO2 showed a high response rate of 56.7% when exposed to CO with a concentration of 50 ppm and a low detection limit of 1 ppm. The introduction of a TiO2 layer on the nanoporous SnO2 allowed selective response to HCHO with a response rate of 20% at 10 ppm when the oxidation level of the target gas was well aligned with the state of reactive oxygen of materials under UV irradiation. Furthermore, the sensing capabilities of the SnO2 and SnO2@TiO2 heterostructures, such as the response rate and response time, were assessed at different deposition pressures. Our results clearly show that the matching of energy levels between the redox energy of the target gas and the conduction band of the materials plays an important role in selectively detecting the target gas in photoactive gas sensors; therefore, we propose a rational design rule to enhance the selectivity for various target gases.

Three-dimensional nanoporous SnO2/CdS heterojunction for high-performance photoelectrochemical water splitting

The porous structure is one of the effective structures to improve the photoelectrochemical (PEC) performance due to its high surface area to volume ratio. In this study, a porous carbon black (CB) film was prepared by a simple and inexpensive flame method, which was used as a template to grow three-dimensional (3D) nanoporous SnO2 through the atomic layer deposition (ALD) method, followed by CdS thin film coating. The photocurrent density of the optimized 3D nanoporous SnO2/CdS heterojunction (11.56 mA/cm2, 1.23 V vs. RHE) shows 9.7 times higher than that of planar SnO2/CdS film (1.20 mA/cm2, 1.23 V vs. RHE), meanwhile, the photocurrent stability was also 2.2 times improved. The maximum incident photon-to-current conversion efficiency (IPCE) and applied bias photo-to-current efficiency (ABPE) values of 35% (around 490 nm at 0 V vs. RHE) and 1.85% (at 0.90 V vs. RHE) were observed for the nanoporous SnO2/CdS. Furthermore, the surface charge separation and bulk charge transfer efficiencies have been achieved by 45.4% and 98.8% (1.23 V vs. RHE). As a whole, the results indicated that the 3D nanoporous SnO2/CdS heterojunction has been demonstrated as an efficient strategy that has been realized to show high performance in PEC water splitting.

Near-complete charge separation in tailored BiVO4-based heterostructure photoanodes toward artificial leaf

As an artificial leaf, a tandem device for zero-bias solar water splitting is a capable solution for practical hydrogen production. Despite a promise, poor charge transport of BiVO4 hampers photoelectrochemical performances under front-side illumination, which is a hindrance to the tandem system. Herein, we design a new photoanode comprising nanoporous BiVO4 and SnO2 nanorods focused on the charge separation via structural and interfacial engineering. BiVO4/SnO2 photoanode exhibits not only remarkable charge separation efficiency of 97% but also, by loading NiFe as a co-catalyst for water oxidation, high photocurrent density of 5.61 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under front-side 1 sun illumination. Consequently, a tandem cell comprising NiFe/BiVO4/SnO2 photoanode and perovskite/Si tandem solar cell generates an operating photocurrent density of 5.90 mA cm−2 with a solar-to-hydrogen conversion efficiency of 7.3% in zero-bias. This work would be a significant step to develop spontaneous solar hydrogen production.

Preparation and mechanism of honeycomb-like nanoporous SnO2 by anodization

Preparation and mechanism of honeycomb-like nanoporous SnO2 by anodization

Interface strengthening and fracture characteristics of the Ag-based contact materials reinforced with nanoporous SnO2(Cu, CuO) phases

The novel Ag-based contact materials reinforced with nanoporous SnO2 were successfully prepared by chemical corrosion combining with powder metallurgy method. The Cu and CuO particles were respectively loaded in the nanoporous SnO2 reinforcements through simply changing corrosion process. The results showed that the stress concentrations in the prepared Ag-SnO2 materials tended to occur inside the porous SnO2 phase rather than interfaces, which inhibited the initiation of cracks. The loading of CuO was beneficial for improving interfacial strength without loss of electrical conductivity. The porous SnO2 reinforcements could shield the crack tip, increasing the fracture toughness of the Ag-SnO2 materials.

Fabrication of a SnO2-Based Hydroelectric Cell for Green Energy Production.

The generation of electricity by dissociating water into H3O+ and OH– ions through a hydroelectric cell (HEC) without liberating any toxic waste has achieved a groundbreaking feat. Nanoporous magnesium-doped SnO2 and cobalt-doped SnO2 materials have been prepared via a novel sol–gel method. The X-ray diffraction patterns of Mg-doped SnO2 and Co-doped SnO2 completely match with those of pure SnO2, which confirms the interstitial substitution of Mg and Co in the pristine SnO2. The results shown by Brunauer–Emmett–Teller theory curves illustrate the surface area of Mg-doped SnO2 and Co-doped SnO2 to be 46.22 and 46.81 m2/g, respectively, with their pore radii being ∼3 nm. The synthesized nanoparticles were pressed into square pellets of area 4.08 cm2. A zinc electrode was pasted on one side of each pellet and silver was painted on the other side to develop the HECs. The fabricated HECs of Mg-doped SnO2 and Co-doped SnO2 with 4.08 cm2 area deliver short-circuit current, open-circuit voltage, and off-load output power of 41.69 mA, 0.787 V, and 32.81 mW and 77.52 mA, 0.454 V, and 35.19 mW, respectively. Cyclic voltammetry of both materials exhibited cathodic and anodic peaks in relation to the redox reactions taking place at Zn and silver electrodes. Nyquist curves of both HECs in the wet state confirm the ionic diffusion of split H3O+ and OH– ions as compared to the dry state. An off-load output power of 35.19 mW delivered by the HEC of Co-doped SnO2 with 4.08 cm2 area is quite promising and has great potential to replace other green energy sources.

Nanoporous network SnO2 constructed with ultra-small nanoparticles for methane gas sensor

Monitoring the concentration of methane (CH4) can effectively protect the environment from the damage of methane emission. The high sensing performances of methane gas sensor still remain a considerable challenge. Herein, to solve problems mentioned above, nanoporous network SnO2 (NN-SnO2) construct with ultra-small nanoparticles, which exhibits excellent gas-sensing performances for methane, are successfully synthesized via a weak acid glucose-assisted hydrothermal synthesis. The NN-SnO2 displays three particular particle morphologies: roundness, oval and polygon, with an average particle size of ~ 9 nm. When evaluated as a sensing material for methane, the NN-SnO2 sensor exhibits ultra-high response (Ra/Rg = 9.80), fast response/recovery times (τres/τrecov= 1 s/3 s) toward 3000 ppm methane at a operating temperature of 420 °C, which are far superior to the vast majority methane semiconducting sensors, and more importantly, it has barely been reported that the sensor based on NN-SnO2 presented such excellent gas-sensing performances for methane. The outstanding response of the NN-SnO2 for methane gas is derived from the unique mesopores nature and small particles sizes of the as-synthesized NN-SnO2, and the charge transfer between the surface of SnO2 nanoparticles and methane gas molecules.

Progress toward a novel methane gas sensor based on SnO2 nanorods-nanoporous graphene hybrid

In this study, SnO2 nanorods (SnO2 NRs) and SnO2 nanorods–nanoporous graphene hybrids, SnO2 NRs-NPG, with two different weight ratios (0.05 and 0.1) of nanoporous graphene to tin salt have been prepared as sensing materials. These materials were synthesized via a facile hydrothermal method and print screened on alumina substrates for low-temperature methane (CH4) gas sensors. The structure and morphology of the fabricated sensing materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). The results showed that in the case of SnO2 NRs-NPG hybrids, the porous graphene sheets are decorated with SnO2 nanorods. The gas response of the prepared hybrid samples to 1000 ppm methane gas was investigated at 100–200 °C. The nanohybrid with 0.05 wt ratios of nanoporous graphene to tin salt showed significant sensor response of 24.9–51% to 1000–10000 ppm methane at a relatively low operating temperature of 150 °C which is about 600% higher than that of pure SnO2 nanorods. The substantial enhancement in the gas detection of SnO2 NRs-NPG nanohybrid, compared to the pristine SnO2, can be attributed to its larger specific surface area, the presence of nanoporous graphene as a good conductor and interactions between nanoporous graphene and SnO2 nanorods.

Facile mass production of nanoporous SnO2 nanosheets as anode materials for high performance lithium-ion batteries

Facile one-step ultrasonic-assisted chemical precipitation strategy has been developed for the mass production of SnO2 nanomaterials with different morphologies. As anode material for lithium-ion batteries, the nanoporous SnO2 nanosheets exhibited an extremely high initial specific capacity of 2231mAh/g in comparison with 1242mAh/g of the SnO2 microcrystals and 1244mAh/g of the nanoporous SnO2 nanoflowers. Meanwhile the nanoporous SnO2 nanosheet electrode displayed a specific capacity of 688mAh/g after 60 cycles at 0.2 A/g current density and an extraordinary capacity retention of 224mAh/g at a current density of 8A/g (approximately 10 C) owing to a huge increase of Li+ diffusion coefficient.

Anodic nanoporous SnO2 grown on Cu foils as superior binder-free Na-ion battery anodes

We present a convenient, low-cost strategy to fabricate one-dimensional, vertically oriented nanoporous assembly of SnO2 upon a Cu substrate as a potentially promising anode system for Na-ion batteries application. The major novelty of the fabrication stage resides in anodizing a Sn/Cu bilayer film that is created by a facile cold-rolling procedure amenable to large-scale production. The open, nanoporous morphology of SnO2 facilitates the diffusion of electrolytes to access the SnO2 surface. The high porosity of the SnO2 phase also provides large void space to effectively accommodate the volume expansion/contraction during sodiation/desodiation. As a result, the 1-D nanoporous SnO2 thus assembled on the Cu substrate can be directly used as an effective electrode system for Na-ion storage–without the need for additives, delivering a remarkable capacity of 326 mA h g−1 over 200 cycles at a current rate of 0.2 C.

Regulable switching from p- to n-type behavior of ordered nanoporous Pt-SnO2 thin films with enhanced room temperature toluene sensing performance

In this work, a nanoporous SnO2 sensing film is fabricated in situ on a sensing device using a block polymer template and is applied as a chemiresistive gas sensor. The ordered film is capable of detecting 10 ppm toluene at room temperature and shows good stability.

Low-working-temperature, fast-response-speed NO2 sensor with nanoporous-SnO2/polyaniline double-layered film

A SnO2/polyaniline (PANI) double-layered film sensor for NO2 detection was fabricated using nanoporous SnO2 and PANI layers. The double layered film sensor has high selectivity and high response to NO2 gas even with low concentration. Furthermore, the double layered film sensor also has a low optimum working temperature (140°C) and high stability over a long working time period. The response and recovery time of sensor S5P500 is as short as about 17s and 25s to 37ppm NO2 at 140°C, respectively. The experiment results show that the porous characteristics of nanoporous SnO2 and the thickness of PANI have effect on the sensor response of double layered film sensors. The improved sensing properties mainly attributes to the formation of depletion layer at the p–n junction interface in SnO2/PANI double layered film sensor, which makes great resistivity difference in air and NO2 gas. Thus, the combination of n-type SnO2 thick film and p-type PANI thick film provides an effective strategy to design high property gas sensors.

Carbon-Free Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions.

A nanoporous Ag-embedded SnO2 thin film was fabricated by anodic treatment of electrodeposited Ag-Sn alloy layers. The ordered nanoporous structure formed by anodization played a key role in enhancing the electrocatalytic performance of the Ag-embedded SnO2 layer in several ways: (1) the roughness factor of the thin film is greatly increased from 23 in the compact layer to 145 in the nanoporous layer, creating additional active sites that are involved in oxygen electrochemical reactions; (2) a trace amount of Ag (∼1.7 at %, corresponding to a Ag loading of ∼3.8 μg cm(-2)) embedded in the self-organized SnO2 nanoporous matrix avoids the agglomeration of nanoparticles, which is a common problem leading to the electrocatalyst deactivation; (3) the fabricated nanoporous thin film is active without additional additives or porous carbon that is usually necessary to support and stabilize the electrocatalyst. More importantly, the Ag-embedded SnO2 nanoporous thin film shows outstanding bifunctional oxygen electrochemical performance (oxygen reduction and evolution reactions) that is considered a promising candidate for use in metal-air batteries. The present technique has a wide range of applications for the preparation of other carbon-free electrocatalytic nanoporous films that could be useful for renewable energy production and storage applications.

An elastic carbon layer on echeveria-inspired SnO2 anode for long-cycle and high-rate lithium ion batteries

The commercialization of Sn-based anodes for lithium ion batteries is still hindered due to the inherent volume change leading to a rapid capacity fading during the electrochemical cycle. Inspired by echeveria, a plant that stores sufficient water in its hierarchical leaves to survive in a drought, we report a breakthrough by designing the hierarchical and nanoporous SnO2 electrode encapsulated with ultrathin carbon layer (∼2nm). As evidently captured by in situ transmission electron microscopy, the conformal carbon coating on the surface of anode may provide an elastic cover that suppresses the cracks due to severe volume change, and increases both electrical and ionic conductivity, allowing the cells to exhibit excellent lithium storage performance with more than 800 cycles even with relatively high-rate of current densities.

Synthesis and Characterization of Nanoporous SnO2 Thin Film

SnO2 is a kind of typical n-type semiconductor material. Due to its excellent performance in conductivity, optics, thermal stability and corrosion resisting, it has been widely applied in fields of gas sensor, solar cell, chemical electrode materials. A novel synthesis route, originated from dealloying of Sn-Zn alloys films in hydrochloric acid (HCl) solution and then thermal treating, has been developed for the preparation of SnO2 films with three-demensional (3D) nanoporous. The influences of the HCl solution concentration and immersion time on crystal structure and morphology have been investigated. Porous structure and fracture surface morphology of the samples were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that the corrosion weight loss of Zn increased with the increasing of immersion time in HCl solution。An average pore diameter of the porous SnO2 films is 50~200nm after heat treatment at 500°C for 2 hours. XRD patterns show that the films are SnO2 with rutile structure.

A Label-Free Impedimetric DNA Sensor Based on a Nanoporous SnO₂ Film: Fabrication and Detection Performance.

Nanoporous SnO2 thin films were elaborated to serve as sensing electrodes for label-free DNA detection using electrochemical impedance spectroscopy (EIS). Films were deposited by an electrodeposition process (EDP). Then the non-Faradic EIS behaviour was thoroughly investigated during some different steps of functionalization up to DNA hybridization. The results have shown a systematic decrease of the impedance upon DNA hybridization. The impedance decrease is attributed to an enhanced penetration of ionic species within the film volume. Besides, the comparison of impedance variations upon DNA hybridization between the liquid and vapour phase processes for organosilane (APTES) grafting on the nanoporous SnO2 films showed that vapour-phase method is more efficient. This is due to the fact that the vapour is more effective than the solution in penetrating the nanopores of the films. As a result, the DNA sensors built from vapour-treated silane layer exhibit a higher sensitivity than those produced from liquid-treated silane, in the range of tested target DNA concentration going to 10 nM. Finally, the impedance and fluorescence response signals strongly depend on the types of target DNA molecules, demonstrating a high selectivity of the process on nanoporous SnO2 films.

Nanoporous gyroid TiO2 and SnO2 by melt infiltration of block copolymer templates

Fabrication of meso-porous metal oxide thin films with high surface area is a crucial requirement for numerous applications, such as catalysis, photovoltaics and electronics. Despite considerable progress in fabrication of three-dimensional metal oxide nanostructures, it is still quite challenging to manufacture highly ordered structures over a large area in a controlled way. The main objective of this study is to demonstrate fabrication of interconnected, crack-free and highly ordered ceramic films using a nano-porous polymer with gyroid morphology as template. Titanium tetraisopropoxide and tin chloride dihydrate are used as precursors for nanostructured TiO2 and SnO2, respectively. Complete precursor infiltration into the template and successful transformation into metal oxides can be achieved by rational tuning of the template chemistry. As a result, thin films of nanostructured metal oxides with gyroid morphology, such as titania and tin dioxide, are created and thoroughly characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive analysis, x-ray diffraction and Brunauer–Emmett–Teller analysis.

Janus gas: reversible redox transition of Sarin enables its selective detection by an ethanol modified nanoporous SnO₂ chemiresistor.

A reversible janus gas redox transition was discovered in the trace Sarin sensing process using an ethanol-aged nanoporous SnO2 micro-chemiresistor, which was reliable to realize the identification of Sarin from other gases and even its simulant. This sensor also endows a rather low detection threshold of 6 ppb to Sarin.

Superior ethanol-sensing behavior based on SnO2 mesocrystals incorporating orthorhombic and tetragonal phases

Nanoporous SnO2 mesocrystal with mixed tetragonal and orthorhombic phases and superior ethanol-sensing performance is synthesized via a facile annealing topotactic transformation from the ionothermal synthesized SnO precursor under ambient-pressure.