SnO2 Surface Research Articles

Atomically dispersed low-cost transition metals catalyze efficient hydrogen evolution on two-dimensional SnO nanosheets

Two-dimensional (2D) electrocatalyst plays an important role in hydrogen production via water splitting. In this work, the first-principles calculation was used to investigate the hydrogen evolution reaction (HER) performance of transition metal (TM) single atom catalysts (SACs) on 2D SnO nanosheets. Among the TM considered (TM = V, Cr, Mn, Fe, Co, Ni, Cu and Pt), V, Fe, Co, Ni, Cu and Pt can effectively improve the catalytic activity of SnO. More importantly, the low-cost Co can exhibit promising HER performance with the Gibbs free energy as low as ~0.015 eV, which is competitive with the precious catalyst Pt. The theoretical exchange current densities of Co SACs can reach ~10−16 A/site. The exciting HER activity is mainly facilitated through the d-d hybridization between the TM and Sn atoms on the SnO surface, which introduces new electron states near the Fermi level. Our work highlights the complexity and diversity of the effect of TM SACs on SnO nanosheets and implies their potential applications as efficient HER electrocatalysts.

Adsorption of gas molecules on Co-doped SnO2 (110): First-principles investigation

First-principles calculations based on density functional theory were employed to study the adsorption of gas molecules (CH4, CO, H2O) on various SnO2 (110) surfaces. We found that CO and CH4 molecules are weakly adsorbed on intrinsic SnO2 (110) surfaces, and intrinsic SnO2 is sensitive only to the H2O molecule. Compared with the gas molecules adsorbed on the intrinsic SnO2 surfaces, the significantly increased adsorption energy indicates that there is an improvement in the gas sensitivity properties of Co-doped SnO2 (Co/SnO2) and oxygen vacancy modified Co-doped SnO2 (Co/VO/SnO2) to CO, CH4, and H2O gas. The CO adsorbed on the Co/VO/SnO2 surface has the strongest adsorption energy (−1.402 eV). We also studied the optical properties of the Co/SnO2 and Co/VO/SnO2 surfaces influenced by the three gas molecules. We found that the three gas molecules cause an enhancement of the adsorption peaks of Co/SnO2 configuration in the visible light range. Our study benefits research on the potential application of SnO2 sensor materials.

Flotation of cassiterite using alkyl hydroxamates with different carbon chain lengths: A theoretical and experimental study

The effects of five alkyl hydroxamates (hexyl hydroxamate (C6), octyl hydroxamate (C8), decyl hydroxamate (C10), dodecyl hydroxamate (C12) and tetra-decyl hydroxamate (C14)) with different carbon chain lengths on the flotation behaviour of cassiterite have been studied by using theoretical and experimental methods. Microflotation tests results showed that increasing the carbon chain length improved the collecting abilities of hydroxamates for cassiterite under acidic to weak alkaline conditions. Adsorption measurements suggested that the adsorption amount of hydroxamic species on the cassiterite surface increased along with carbon chain length. Density functional theory (DFT) calculation results indicated that alkyl hydroxamates with a longer carbon chain have lower electronic stabilities and larger dipole moments. In the absence of H2O molecules, hydroxamates with longer carbon chains easily absorbed on the SnO2 surface by chelating 6-membered rings.H2O molecules could spontaneously adsorb on the SnO2 surface. Hydroxamates adsorbed on the hydroxylated SnO2 surface via hydrogen bonding interaction. X-ray photoelectron spectroscopy (XPS) analysis revealed that hydroxamates adsorbed on cassiterite through physical interaction, thereby suggesting that the computational simulation results are reliable.

Impact of Pd nanoparticle loading method on SnO2 surface for natural gas detection in humid atmosphere

Impact of Pd nanoparticle loading method on SnO2 surface for natural gas detection in humid atmosphere

Au@SnO2 and SnO2@Au Hollow Spheres for Gas Sensor Applications: Selectivity Control

Introduction Metal oxide semiconductor (MOS) based gas sensors have attracted growing attention due to their excellent gas sensing characteristics, reasonable price, and facile integration. However, MOS based gas sensors show similar gas responses to a number of gases, which means that selective detection to the gases remains challenging. It has been frequently reported that the selectivity of MOS gas sensors can be controlled by doping or loading noble metal catalysts. In this research, we suggest that not only the type but also the location of catalysts in the nanostructure may cause a change in gas selectivity. We fabricated Au@SnO2 and SnO2@Au sensors and measured their sensing characteristics. : SnO2 hollow nanospheres whose inner part or outer part of shell are decorated with 0.3 at% Au. Method 0.15 g of sulfonated polysrtrene (SPS) beads were dispersed in 30 mL ethanol, and 0.075 g of poly-vinylpyrrolidone (PVP, MW = 40,000) was dissolved in 30 mL distilled water. Two solutions were mixed and homogenized by magnetic stirring. 30 mL of SnSO4, (95%) aqueous solution (0.07 M) were added drop by drop to the mixed solution. The solution was stirred at room temperature for 12 h, and subsequently washed and centrifuged five times with distilled water and ethanol. Finally, the precursor powders (SPS@Sn) were converted into SnO2 hollow spheres via a heat treatment at 550 °C for 2 h in air (2 °C min-1).0.0021 g of HAuCl4∙3H2O (99.999%) was dissolved in 30 mL ethanol containing 0.15 g of SPS. After magnetic stirring at room temperature for 2 h, 10 mL of NaBH4 (99.99%) aqueous solution (0.0026 M) was injected drop by drop into Au contained SPS suspension and stirred at 60 °C for 2 h. After washing and centrifuging five times with distilled water and ethanol, the suspensions were dried at 70 °C for 6 h to obtain SPS@Au. To confine the Au nanoparticles inside SnO2 hollow shell, SPS@Au were coated with Sn precursor in the same way as the synthesis of SPS@Sn.To load the Au nanoparticles outside the SnO2 hollow shell, Au was loaded on the as-prepared SPS@Sn, followed by SPS@Sn@Au. Loading Au on the surface of SnO2 was followed the previous way of preparing SPS@Au. The ratio between Au, and Sn ([Au] / [Sn]) were fixed to 0.3 at%. Results and Conclusions The pure SnO2 sensor exhibited the highest response to ethanol and the responses to other analyte gases (HCHO, p-xylene, toluene, benzene, and CO) were low at all sensing temperatures (300 – 375 oC). Both Au-out-SnO2 and Au-in-SnO2 showed significantly enhanced responses to all the analyte gases. However, they showed completely different gas selectivity depending on the location of Au catalysts. The Au-out-SnO2 sensor showed the highest gas response to 5 ppm ethanol over the entire range of sensing temperatures and this sensing characteristics are similar to those of pure SnO2 sensor although the maximum gas response levels were different from each other. In contrast, the Au-in-SnO2 sensor showed the highest response to p-xylene at 300 - 350 oC. Moreover, the responses to toluene and benzene were higher than those of ethanol at 350 and 375 oC. High response to xylene and relatively high responses to less reactive benzene and toluene can be attributed to the reforming of aromatic compounds into more reactive species for gas sensing. The catalyst-loaded micro reactor is a good model system to understand the gas sensing mechanism and provide a promising platform to detect the aromatic indoor pollutants in a highly sensitive and selective manner.

Gas Sensing Properties Comparison between SnO2 and Highly Antimony-Doped SnO2 materials

IntroductionGas sensors are widely applied to monitor the combustible and harmful gases which can be detrimental to safety, health and environmental protection. SnO2, a wide gap semiconductor, is one of the most promising gas sensor material because of high chemical stability and low fabrication cost[1].While due to the drawbacks of SnO2 working as gas sensing material, such as low selectivity and high working temperature, doping by noble or transition metals is a particularly efficient way to improve its sensing properties[2]. SnO2 doped by antimony (SnO2/Sb) is a typical n-type oxide material, which has high electrical conductivity and thermal stability.Materials and MethodThe impacts of Sb doping (10 wt.% doping content) on morphology, nanostructure of commercial SnO2 were investigated by scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. The samples were added into a composed solution mixed with glycol ether as wetting agent and an acrylic resin, and then screen printed onto alumina substrates, where Au was applied as interdigitated electrodes on front-side, and the back-side was equipped with a heater to provide with working temperature. In the last, the screen-printed films were treated at 180 ˝C in a muffle oven for 12 h in air to obtain the thermal stabilization[3]. The response values (R) were obtained by the equation (1), hence Ra is the resistance while exposed to the dry air, and Rg is the resistance while exposed to target gas, which were measured by home-made gas sensing system. The samples under different temperatures were named as SnO2-x and SnO2/Sb-x (x=300°C, 350°C, 400°C and 450°C). The gas sensing properties dependence of samples on different temperatures under acetone gas condition was clarified, and the relationship between doping and selectivity of samples under different target gases at 350°C were demonstrated. The results about high antimony doping content at different working temperatures and target gas situations were investigated in this work. Results and Conclusions The SEM reveled that antimony doping SnO2 contributed to harshen the surface of SnO2, which is beneficial to increase the specific surface area and the adsorption efficiency to target gases, as shown in Fig. 1.[4]. XRD characterization shows that no other phases such as SnO and Sn3O4 were detected, which means the high purity of the SnO2[5]. Meanwhile, Sb doping did not change the tetragonal structure of SnO2, but it distinctly affected the preferred (110), (101) and (211) orientation growth, which can be detected in Fig.2. Furthermore, the gas sensing properties between pure SnO2 and SnO2/Sb were compared at different working temperatures and under different target gases environment. The measurement results in Fig.3 (a) and (b) demonstrated that the response of SnO2 and SnO2/Sb reached highest value at 350°C. While SnO2 and SnO2/Sb showed abnormal trend at 450°C that is conducive to oxygen atoms insertion into the crystal structure[6]. Specifically, SnO2/Sb showed p-type shape response at 450°C, maybe it is because antimony doping decreased the grain size of SnO2 so that the whole grains were fully depleted. In the beginning of reaction with target gas, the concentration of O2 on the surface of SnO2/Sb decreased and the conductance increased. Whilst, when the depletion zone was smaller than the grain size, the conductance decreased a lot. When stopping injection of target gases, the trend processed reversely [6]. Otherwise, this p-type shape response of SnO2/Sb can only be observed under acetone environment at 450°C, which can be used to distinguish acetone among other gases. From Fig.4 (a) and (b), it can be found that Sb doping facilitated SnO2 the highest response to acetone among H2S, ethylene, ethanol, and CO environments, which means antimony doping can improve the selectivity of SnO2.

SnO2/SnSe2 Heterostructures for NO2 and H2 Sensing

SnO2/SnSe2 Heterostructures for NO2 and H2 Sensing

Oxygen vacancy-based Tb-doped SnO2 nanotubes as an ultra-sensitive sensor for ethanol detection

In this work, different concentrations of terbium (Tb) doped SnO2 nanotubes (NTs) were synthesized via simple uniaxial electros-pinning and high-temperature calcination. The mapping results show that Tb elements are uniformly distributed on SnO2 NTs. X-ray photoelectron spectroscopy (XPS) was used to characterize the changes of oxygen ion species of pristine SnO2 and 7 mol% Tb-doped SnO2. In terms of gas sensitive performance, the sensor prepared by this method has low operating temperature, excellent selectivity and ultra-high sensitivity. Notably, compared with other obtained SnO2 samples, the 7 mol% NTs presented the best sensing performance, and the response to 100 ppm ethanol reached 53.6 at 200 °C. Combined with the study of gas sensitivity, it can be confirmed that doping Tb increases the number of active sites (such as oxygen vacancies (VO)) on the surface of SnO2, thus enhancing the gas sensitivity and electrical responsiveness of SnO2. Hence, the research in this work will be helpful to the development of new high performance gas sensors based on dopant metal oxide semiconductor.

Preparation and Characterization of SnO2 / AC as a Novel High Surface Area Nanocatalyst

A new solid nanoparticle sorbent (SnO2 / AC) could serve as high surface area and inexpensive nanocatalyst was prepared. Many properties were characterized by SEM and UV spectroscopy. High surface area, large micro pore volume and total pore volume were found to be 571 m2 g−1, 0.4785 cm3 g−1 and 0.7267 cm3 g−1 respectively even with very high loaded ratio (60 %) of tin dioxide to Activated Carbon (SnO2 / AC). Taguchi factorial design method was used to get the maximum MB dye adsorption on the surface of SnO2 / AC nanoparticle sorbent. Contact time (60 min), initial dye concentration (5 mM) and solution temperature (293 K) were found to be the best conditions for the more effective absorption process.

Spontaneous Enhancement of Power Conversion Efficiency in SnO2-Based Dye-Sensitized Solar Cells

Power conversion efficiency (PCE) of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based dye-sensitized solar cells (DSSCs) is reported to increase slowly over a period of days after their fabrication. Thus far, underlying processes involved in this slowly increasing phenomenon of PCE are not understood. In this article, we investigate the spontaneous enhancement of PCE in SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based DSSCs and the underlying mechanism by using the X-ray diffraction, the X-ray photoelectron spectra (XPS), electrochemical impedance spectrum, and first-principles calculations. The Sn 3d and O 1s binding energy are observed to shift toward low binding energy over time by the XPS measurements, and the ratio of O/Sn on the surface of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> increases from 1.9 to 2.1 implying the adsorption of oxygen atom on the surface of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Our first-principles calculation results confirm that a shift-up in the conduction band minimum of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> owing to its adsorption of oxygen atom. We, therefore, attribute the slowly increasing phenomenon of PCE to oxygen adsorption effect on the surface of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . This article gives a comprehensive understanding of the surface oxidation effect on the PCE enhancement in DSSCs and provides an effective way to fabricate DSSCs based on oxide semiconductors with good performance and long-time stability.

Pyridine Grafted on SnO2 -Loaded Carbon Nanotubes Acting as Cocatalyst for Highly Efficient Electroreduction of CO2.

Sn-based electrocatalysts have shown great potential in the future industrial application of CO2 electroreduction (CO2 ER) to C1 products due to their non-toxicity and low price. However, it is a great challenge to fabricate a Sn-based electrocatalytic system with high performance and stability. Herein, grafted pyridine was innovatively coupled with SnO2 to construct an organic-inorganic composite (SnO2 /Py-CNTO) for highly efficient CO2 ER. The detailed studies showed that pyridine and protonated pyridine coexist on the surface of SnO2 /Py-CNTO, and both play distinctive roles in promoting the selectivity of CO2 ER. Benefiting from the merits, SnO2 /Py-CNTO delivered an excellent faradaic efficiency (FE) of 96 % for CO2 ER at -1.29 VRHE where the HCOOH production with 85 % FE dominated, and good stability for 32 h electrolysis. The theoretical calculations showed that protonated pyridine not only facilitates the CO2 adsorption and HCOOH desorption, but also significantly reduces the limiting potential for the conversion of CO2 to HCOOH.

Detection of the organic solvent vapors by the optical gas sensors based on polyaminoarenes

The important problem to ensure the safety of life is the development of effective methods for monitoring of toxic gases in the atmosphere and industrial premises. To ensure such control, various gas sensors are developed that work on the effects of changes in electrical resistance, optical absorption or radiation in a certain spectral range. Most known gas sensors have high operating temperatures, which creates some difficulties in their operation, so more and more attention is paid to sensors based on conjugated electrically conductive polymers, in particular, polyaminoarenes. In result of absorption of inorganic polar gases such as ammonia, nitrogen oxide, hydrogen chloride and others the significant changes in conductivity, optical absorption and morphology of polyaminoarene films are observed. However influence of organic solvent vapors on the optical spectra of polyaminoarene films for today is poorly studied. In the present work the functional polymer films of polyanisidine (PoA) and polytoluidine (PoTI) are proposed as sensitive elements of optical sensors operating at room temperatures. The sensitive films on the transparent SnO2 surface were prepared by electrodeposition. The influence of vapors of organic solvents (dimethylformamide, tetrahydrofuran, chloroform, nitrobenzene, toluene) on the optical characteristics of PoTi and PoA films was established. The optical absorption spectra investigated PoA film was characterized by two band with maximum near 360–410 nm (π–π* transition) and broad band in the range of 620–950 nm which is a superposition of the second and third bands. Influence of organic vapors causes the changes in films coloration. The maximum of sensitivity to the organic vapors for PoTI films in all cases is observed at λ &gt; 550 nm and extends to near-infra-red area indicating a formation of free charge carriers of polaron type. Nonpolar solvent vapors insignificantly affect the optical properties of polyaminoarene films responсes to spectral changes in the visible and NIR range of spectrum. A highest gas sensitivity of optical signal was observed under influence of dimethylformamide and tetrahydrofuran vapors. The time to establish the steady-state value of the optical response is 30–60 s for PoTi, while for PoA reaches 120–180 s depending on the nature of organic vapors.

Mechanism of bifunctional p-amino benzenesulfonic acid modified interface in perovskite solar cells

• ABSA is firstly used to synergistically modify the interface between SnO 2 and perovskite layer. • The acidic sulfonic acid groups in ABSA connect to the under-coordinated Sn ions. • The alkaline amino groups passivate the defects on surface of perovskite. • The energy band model for SnO 2 nanoparticle and interface is established. • The mechanism of significantly improved PCE is analyzed. The n-type metal oxide SnO 2 exists surface energy band bending due to massive vacancy oxygen. The bending will cause unnecessary electron accumulation and recombination at the interface between electron transport layer (ETL) and perovskite layer. Besides, there exist massive deep-level defects (Pb I , Pb i , I Pb ) for solution-processed polycrystalline perovskite films, which will aggravate the energy band uncoordinated and non-radiative recombination, limiting device efficiency and stability. Herein, amphoteric linking molecule p-amino benzenesulfonic acid (ABSA) is firstly used to synergistically modify the interface between SnO 2 ETL and perovskite layer. The acidic sulfonic acid groups in ABSA modify SnO 2 ETL by inactivating the under-coordinated Sn ions, which reduces the energy band barrier on the surface of SnO 2 film, increasing the conduction and reduces charge recombination. Besides, the alkaline amino groups also passivate the deep-level defects on surface of perovskite to lessen intermediate energy level and non-radiative recombination. The power conversion efficiency (PCE) of perovskite solar cells (PSCs) based on MAPbI 3 is obviously increased from 18.02% to 20.32% after 0.10 mg ml −1 ABSA modification. Simultaneously, the modified devices show better stability due to improved perovskite crystallization and the reduced defects. The energy band model for SnO 2 nanoparticle and interface between perovskite layer and SnO 2 ETL is established to explain the interfacial engineering from a new physical perspective.

Nitrogen-doped graphene quantum dots-modified mesoporous SnO2 hierarchical hollow cubes for low temperature detection of nitrogen dioxide

Abstract The exploration of nitrogen dioxide (NO2) gas sensor with high response, fast response and recovery speed, and low working temperature is still an urgent challenge. In this work, a novel SnO2 hierarchical hollow cube composed of ultrathin mesoporous nanosheets was successfully prepared via a simple sulfidation-oxidation method, and nitrogen-doped graphene quantum dots (N-GQDs) were evenly modified on the surface of SnO2. The prepared N-GQDs modified SnO2 (NG/Snx) shows an improved response, and the optimal sample (NG/Sn1.5) response (Rg/Ra = 417) toward 1 ppm NO2 is approximately 2.2 times that of pure SnO2 at 130 °C. Moreover, the NG/Sn1.5 sensing material exhibits fast response and recovery speed, good selectivity, repeatability, and long-term stability. More attractively, the NG/Sn1.5 sensor has outstanding detection ability (Rg/Ra = 25.3) for low concentration NO2 (100 ppb). The significantly improved NO2 sensing performance of NG/Sn1.5 sensing material is mainly attributed to the zero-dimensional/three-dimensional (0D/3D) heterostructure construction and N doping, which increases the space charge modulation depth and NO2 adsorption active sites of the composite material. In addition, the mesoporous hierarchical cubic structure is beneficial to the improvement of NO2 sensing performance due to its stable gas diffusion channels, large specific surface area, and abundant nanoscale grain boundaries. The results obtained herein may provide new ideas for the preparation of high performance NO2 sensors at low temperatures.

Functional Behavior of the Primary Cortical Neuronal Cells on the Large Surface of TiO₂ and SnO₂ Based Biosensing Device.

In this study, we report the fabrication of poly-L-lysine (PLL) coated large surface TiO2 and SnO2 based biosensing devices to analyze the influence of the functional behaviour of primary cortical neuronal cells. Through frequency-dependent impedance study, we observed an increase in the impedance values initially most likely due to cell adhesion, proliferation and differentiation processes leading to an increase in both the single-cell mass as well as overall cellular mass; however, it got decreased eventually with the progression of various other cellular functions including neural activity, synapse formation and neuron-neuron communication. Typically, formation and regulation of the neuronal junction i.e., synapses noticeably affected the functional behaviour of the fabricated biosensing device by increasing the neuronal communication and thereby improving the flow of current by altering the thin film resistance and capacitance. Further, the neuro-electrical phenomenon is validated by fitting the experimental impedance data to an equivalent electrical circuit model. A significant shift in the Nyquist plot was also observed visually, which indicates that this alternation is primarily due to change in characteristic behaviour of the fabricated biosensing device. Hence, we anticipate that the fabricated PLL coated large surface TiO2 and SnO2 based biosensing device can serve as a promising tool to monitor the influence of the functional behaviour of neuronal cells.

Chlorine-passivation of ozone-treated SnO2 thin films: Occurrence of oxygen vacancies to manipulate conducting states and bipolarities in resistive switching

Highly conductive SnO2 thin films are of interest in transparent conducting electrodes for displays and n-type transport layer for perovskite solar cells. We fabricated SnO2 thin films by spin coating with ozone exposure. This process compensates for the oxygen vacancy states of the films. A local current–voltage measurement by conductive atomic force microscopy revealed the conducting characteristics of the films. Under different ambient conditions, the films exhibited an exotic cycling bipolarity in their resistive switching phenomena, which is likely dependent on the distinct formation of the oxygen vacancies. After application of a chlorine-based surface coating, the SnO2 surface showed an identical bipolar resistive switching. In particular, the chlorine-passivation was simple and robust to control oxygen vacancies and conducting states, which yields a low power operation below 1–2 V and a huge difference between low- and high-resistant states of a 108–1010 order of magnitude. Ozone-treated and chlorine-passivated oxide beyond SnO2 will provide guidance for optoelectronic device improvement.

Room temperature gas sensing mechanism of SnO2 towards chloroform: Comparing first principles calculations with sensing experiments

Herein, room temperature sensing of chloroform (CHCl3) gas using SnO2 nanostructured thin films synthesized via a single-step aerosol chemical vapor deposition (ACVD) process is demonstrated. The sensing mechanism is investigated by means of dispersion-corrected density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations of chloroform’s adsorption on the (110) facet of rutile SnO2. Theoretical calculations demonstrate that direct adsorption of chloroform on the stoichiometric and the oxygen defective SnO2 surface is thermodynamically favorable. Upon adsorption, chloroform molecules donate charge to the surface inducing a drop in the surface resistance, thus promoting a sensing response. Calculated adsorption energies are in the range of (0.7–1.0 eV) per chloroform molecule, which is noticeably larger than the previously calculated adsorption energies on graphene and graphene oxide (0.2–0.4 eV), suggesting a stronger binding on metal-oxides compared to carbon-based materials. Long-range dispersive interactions are found to account for>50% of the calculated adsorption energies. AIMD simulations in the canonical ensemble at room temperature show that chloroform molecules minimally interact with the ionosorbed oxygen species (O2-) suggesting that the room temperature sensing mechanism is mainly attributed to the direct binding of chloroform molecules on the sensor surface.

Enhanced Vis-NIR light absorption and thickness effect of Mo-modified SnO2 thin films: A first principle calculation study

The thickness effect on ultraviolet, visible and near-infrared (UV–Vis-NIR) light absorption of Mo-modified tin oxide (SnO2) thin films is investigated by the first principle calculation based on the density functional theory. The electronic structures and optical properties of the pristine, defective, Mo-doped and Mon (n = 1, 2, 3, 4) cluster adsorbed SnO2 (110) surfaces with film thickness from 0.594 to 3.273 nm are discussed. The results show that the pristine SnO2 semiconductor thin films can hardly absorb the Vis-NIR light. The absorption peaks in the Vis-NIR light region of the defective SnO2 (110) surface increase with the film thickness. The Vis-NIR light absorption of SnO2 is significantly enhanced by Mo modification. Mon cluster adsorption on SnO2 makes the greatest enhancement in Vis-NIR light absorption. The surface modification of Mo is concluded to be a promising route for SnO2 semiconductor thin film as a photocatalyst under Vis-NIR light irradiation.

Metallic Ag Confined on SnO2 Surface for Soot Combustion: the Influence of Ag Distribution and Dispersion on the Reactivity

AbstractTo unravel the surface confinement effect of SnO2 for Ag, and find an effective way to design practical soot combustion catalysts, an XRD extrapolation method has been adopted for the first time to analyze the distribution and dispersion of metallic Ag on SnO2 surface. Ag addition can generate more surface oxygen vacancies on SnO2, thus forming richer amount of surface O2− and O22− anions. However, the amount of soot reactive oxygen sites is significantly influenced by the distribution of Ag. It is quantified that 1.86 mmol Ag/100 m2 SnO2 surface, which is equal to 5.2 wt% loading, is a threshold value for Ag distribution. Below the threshold, Ag is nearly in amorphous state, and has strong interaction with the SnO2 support, thus producing more soot reactive surface oxygen sites. Furthermore, the redox property of SnO2 lattice oxygen is enhanced by Ag addition. Therefore, metallic Ag in nearly amorphous state plays a critical role for the reaction. Ag crystallites formed on the surface above the threshold have negative influence on the activity. The best Ag/SnO2 catalyst can be fabricated by loading the threshold amount of Ag over SnO2 surface to get the maximum quantity of amorphous Ag species.

Rubidium Fluoride Modified SnO2 for Planar n‐i‐p Perovskite Solar Cells

AbstractRegulating the electron transport layer (ETL) has been an effective way to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs) as well as suppress their hysteresis. Herein, the SnO2 ETL using a cost‐effective modification material rubidium fluoride (RbF) is modified in two methods: 1) adding RbF into SnO2 colloidal dispersion, F and Sn have a strong interaction, confirmed via X‐ray photoelectron spectra and density functional theory results, contributing to the improved electron mobility of SnO2; 2) depositing RbF at the SnO2/perovskite interface, Rb+ cations actively escape into the interstitial sites of the perovskite lattice to inhibit ions migration and reduce non‐radiative recombination, which dedicates to the improved open‐circuit voltage (Voc) for the PSCs with suppressed hysteresis. In addition, double‐sided passivated PSCs, RbF on the SnO2 surface, and p‐methoxyphenethylammonium iodide on the perovskite surface, produces an outstanding PCE of 23.38% with a Voc of 1.213 V, corresponding to an extremely small Voc deficit of 0.347 V.