Carbothermal Reduction-Assisted Synthesis of a Carbon-Supported Highly Dispersed PtSn Nanoalloy for the Oxygen Reduction Reaction

Exploring high-performance and low-platinum-based electrocatalysts to accelerate the oxygen reduction reaction (ORR) at the air cathode of zinc-air batteries remains crucial. Herein, by combining electroless deposition and carbothermal reduction, a nitrogen-doped carbon-supported highly dispersed PtSn alloy nanocatalyst (PtSn/NC) was prepared for a high-efficiency ORR process. Electrochemical measurements show that PtSn/NC exhibits excellent electrocatalytic ORR activity with a half-wave potential of 0.850 V versus reversible hydrogen electrode (RHE), which is higher than that of commercial Pt/C (0.815 V). The PtSn/NC-based (20 μgPt cm-2) rechargeable Zn-air battery exhibited astonishing performance with a maximum power density of up to 150.1 mW cm-2, as well as excellent rate performance and charge/discharge stability. Physical characterization reveals that carbothermal reduction could compel the transformation of Sn oxide into metallic Sn, which then alloys with the deposited Pt atoms to form the PtSn nanoalloy, in which electrons are transferred from Sn atoms to neighboring Pt atoms, thereby improving the ability of Pt-based active sites to catalyze the ORR process in PtSn/NC by optimizing the unoccupied d-band of Pt atoms. This work provides a reliable and innovative route for the rational design of highly dispersed Pt-based alloy ORR electrocatalysts.

Antiferroelectric Heterostructures Memristors with Unique Resistive Switching Mechanisms and Properties

A novel antiferroelectric material, PbSnO3 (PSO), was introduced into a resistive random access memory (RRAM) to reveal its resistive switching (RS) properties. It exhibits outstanding electrical performance with a large memory window (>104), narrow switching voltage distribution (±2 V), and low power consumption. Using high-resolution transmission electron microscopy, we observed the antiferroelectric properties and remanent polarization of the PSO thin films. The in-plane shear strains in the monoclinic PSO layer are attributed to oxygen octahedral tilts, resulting in misfit dislocations and grain boundaries at the PSO/SRO interface. Furthermore, the incoherent grain boundaries between the orthorhombic and monoclinic phases are assumed to be the primary paths of Ag+ filaments. Therefore, the RS behavior is primarily dominated by antiferroelectric polarization and defect mechanisms for the PSO structures. The RS behavior of antiferroelectric heterostructures controlled by switching spontaneous polarization and strain, defects, and surface chemistry reactions can facilitate the development of new antiferroelectric device systems.

Real-Time Tunable Gas Sensing Platform Based on SnO2 Nanoparticles Activated by Blue Micro-Light-Emitting Diodes

Micro-light-emitting diodes (μLEDs) have gained significant interest as an activation source for gas sensors owing to their advantages, including room temperature operation and low power consumption. However, despite these benefits, challenges still exist such as a limited range of detectable gases and slow response. In this study, we present a blue μLED-integrated light-activated gas sensor array based on SnO2 nanoparticles (NPs) that exhibit excellent sensitivity, tunable selectivity, and rapid detection with micro-watt level power consumption. The optimal power for μLED is observed at the highest gas response, supported by finite-difference time-domain simulation. Additionally, we first report the visible light-activated selective detection of reducing gases using noble metal-decorated SnO2 NPs. The noble metals induce catalytic interaction with reducing gases, clearly distinguishing NH3, H2, and C2H5OH. Real-time gas monitoring based on a fully hardware-implemented light-activated sensing array was demonstrated, opening up new avenues for advancements in light-activated electronic nose technologies.

Chemical bath deposition of SnO2films on PEN/ITO substrates for efficient flexible perovskite solar cells

Flexible perovskite solar cells (f-PSCs) have achieved significant success. However, high-quality tin dioxide (SnO2) electron transport layers (ETLs) fabricated via chemical bath deposition (CBD) have not been achieved on flexible PEN/ITO substrates. This limitation is primarily due to the corrosion of the poor-quality ITO layer by the strongly acidic CBD solution. Here, we analyzed the reasons for the poor corrosion resistance of ITO films on PEN substrate from multiple perspectives, such as element composition, microstructure, and crystallinity. Then, we proposed a modified CBD method for SnO2films suitable for flexible PEN/ITO substrates. We employed SnCl2·2H2O as the tin source and regulated the pH of the CBD solution by NH3·H2O, which effectively avoided the corrosion of the ITO layer by the CBD solution and achieved high-quality SnO2films on the ITO layers. Compared to the commercial SnO2dispersion, the SnO2films prepared by this method have smaller grains and higher transmittance. As a result, we achieved an unprecedented power conversion efficiency (PCE) of 20.71% for f-PSCs fabricated on PEN/ITO substrates with SnO2ETLs by CBD method. This breakthrough facilitates the development of high-performance f-PSCs by a low-cost and large-scale chemical bath deposition of high-quality ETLs on flexible substrates.

Atomic layer deposition of SnO2 using hydrogen peroxide improves the efficiency and stability of perovskite solar cells

Low-temperature processed SnO₂ is a promising electron transporting layer in perovskite solar cells (PSCs) due to its optoelectronic advantage. Atomic layer deposition (ALD) is suitable for forming a conformal SnO₂ layer on a high-haze substrate. However, oxygen vacancy formed by the conventional ALD process using H₂O might have a detrimental effect on the efficiency and stability of PSCs. Here, we report on the photovoltaic performance and stability of PSCs based on the ALD-SnO₂ layer with low oxygen vacancies fabricated via H₂O₂. Compared to the ALD-SnO₂ layer formed using H₂O vapors, the ALD-SnO₂ layer prepared via H₂O₂ shows better electron extraction due to a reduced oxygen vacancy associated with the highly oxidizing nature of H₂O₂. As a result, the power conversion efficiency (PCE) is enhanced from 21.42% for H₂O to 22.34% for H₂O₂ mainly due to an enhanced open-circuit voltage. Operational stability is simultaneously improved, where 89.3% of the initial PCE is maintained after 1000 h under an ambient condition for the H₂O₂-derived ALD SnO₂ as compared to the control device maintaining 72.5% of the initial PCE.

Ultraviolet Filtration Passivator for Stable High-Efficiency Perovskite Solar Cells

Although the published values of power conversion efficiency (PCE) have increased continuously in recent years for perovskite solar cells (PSCs), improvements in the stability and performance of PSCs with conventional TiO₂ or SnO₂ electron transport layers (ETLs) remain limited by the presence of nonideal interface defects and low ultraviolet (UV) absorption. In this study, 2-hydroxy-4-methoxy-5-sulfonate-benzophenone (SBP), an inexpensive water-soluble sunscreen raw material, was incorporated into the SnO₂ ETL as a UV filter. It was found that the exposure of perovskite to UV light was significantly reduced, and, more importantly, the carbonyl and sulfonic acid groups in the SBP influenced both the perovskite crystallization process and the passivation of defects in the ETL/perovskite film interface. As a result, the PCE of SBP-based devices was increased to 22.54% from 20.78% of the control sample, with a concomitant decrease in the hysteresis. Moreover, the efficiency of champion devices with SBP decreased by less than 5% after 200 h of continuous UV (1.63 mW/cm², 285 nm) irradiation, while the control group dropped to below 75% of the initial value, thus showing significantly improved stability.

Visible Light Driven Ultrasensitive and Selective NO2 Detection in Tin Oxide Nanoparticles with Sulfur Doping Assisted by l-Cysteine

In the pandemic era, the development of high-performance indoor air quality monitoring sensors has become more critical than ever. NO₂ is one of the most toxic gases in daily life, which induces severe respiratory diseases. Thus, the real-time monitoring of low concentrations of NO₂ is highly required. Herein, a visible light-driven ultrasensitive and selective chemoresistive NO₂ sensor is presented based on sulfur-doped SnO₂ nanoparticles. Sulfur-doped SnO₂ nanoparticles are synthesized by incorporating l-cysteine as a sulfur doping agent, which also increases the surface area. The cationic and anionic doping of sulfur induces the formation of intermediate states in the band gap, highly contributing to the substantial enhancement of gas sensing performance under visible light illumination. Extraordinary gas sensing performances such as the gas response of 418 to 5 ppm of NO₂ and a detection limit of 0.9 ppt are achieved under blue light illumination. Even under red light illumination, sulfur-doped SnO₂ nanoparticles exhibit stable gas sensing. The endurance to humidity and long-term stability of the sensor are outstanding, which amplify the capability as an indoor air quality monitoring sensor. Overall, this study suggests an innovative strategy for developing the next generation of electronic noses.

Excellent Electrocatalytic Hydrogen Evolution Reaction Performances of Partially Graphitized Activated-Carbon Nanobundles Derived from Biomass Human Hair Wastes

Carbonaceous materials play a vital role as an appropriate catalyst for electrocatalytic hydrogen production. Aiming at realizing the highly efficient hydrogen evolution reaction (HER), the partially graphitized activated-carbon nanobundles were synthesized as a high-performance HER electrocatalyst by using biomass human hair ashes through the high-temperature KOH activation at two different temperatures of 600 and 700 °C. Due to the partial graphitization, the 700 °C KOH-activated partially graphitized activated-carbon nanobundles exhibited higher electrical conductivity as well as higher textural porosity than those of the amorphous activated-carbon nanobundles that had been prepared by the KOH activation at 600 °C. As a consequence, the 700 °C-activated partially graphitized activated-carbon nanobundles showed the extraordinarily high HER activity with the very low overpotential (≈16 mV at 10 mA/cm² in 0.5 M H₂SO₄) and the small Tafel slope (≈51 mV/dec). These results suggest that the human hair-derived partially graphitized activated-carbon nanobundles can be effectively utilized as a high-performance HER electrocatalyst in future hydrogen-energy technology.

Silica covered stannic oxide nanoparticles-an easily prepared robust substrate for optical sensors

This paper describes a facile way to prepare a photophysically inert sensor substrate. Stannic oxide encapsulated silica nanoparticles with average diameters between 30 and 70 nm have been prepared by one-pot reverse-phase emulsion methodology. The constituents and core/shell morphology of the nanoparticles were demonstrated by electron microscopic technology, energy-dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. X-ray diffraction was employed to provide additional constitutional and structural information. It has been shown that nanoparticles prepared by this method are optically clear in suspension. After anchoring optical indicators, this nanoparticle can be utilized as a sensor module both in biology and other analytical areas.

Efficient perovskite solar cells via improved carrier management

Metal halide perovskite solar cells (PSCs) are an emerging photovoltaic technology with the potential to disrupt the mature silicon solar cell market. Great improvements in device performance over the past few years, thanks to the development of fabrication protocols^1-3, chemical compositions^4,5 and phase stabilization methods^6-10, have made PSCs one of the most efficient and low-cost solution-processable photovoltaic technologies. However, the light-harvesting performance of these devices is still limited by excessive charge carrier recombination. Despite much effort, the performance of the best-performing PSCs is capped by relatively low fill factors and high open-circuit voltage deficits (the radiative open-circuit voltage limit minus the high open-circuit voltage)¹¹. Improvements in charge carrier management, which is closely tied to the fill factor and the open-circuit voltage, thus provide a path towards increasing the device performance of PSCs, and reaching their theoretical efficiency limit¹². Here we report a holistic approach to improving the performance of PSCs through enhanced charge carrier management. First, we develop an electron transport layer with an ideal film coverage, thickness and composition by tuning the chemical bath deposition of tin dioxide (SnO₂). Second, we decouple the passivation strategy between the bulk and the interface, leading to improved properties, while minimizing the bandgap penalty. In forward bias, our devices exhibit an electroluminescence external quantum efficiency of up to 17.2 per cent and an electroluminescence energy conversion efficiency of up to 21.6 per cent. As solar cells, they achieve a certified power conversion efficiency of 25.2 per cent, corresponding to 80.5 per cent of the thermodynamic limit of its bandgap.

Enhanced Electro-Optical Performance of Inorganic Perovskite/a-InGaZnO Phototransistors Enabled by Sn-Pb Binary Incorporation with a Selective Photonic Deactivation

Optoelectronic applications using perovskites have emerged as one of the most promising platforms such as phototransistors, photovoltaics, and photodetectors. However, high-performance and reliable perovskite photonic devices are often hindered by the limited spectral ranges of the perovskite system along with the lack of appropriate processing technologies for the implementation of reliable device architectures. Here, we explore a hybrid phototransistor with a heterojunction of a Sn-Pb binary mixed halide perovskite (CsSn_0.6Pb_0.4I_2.6Br_0.4) light absorber and an amorphous-In-Ga-Zn-O (a-IGZO) charge carrying layer. By incorporating Sn-Pb binary components with an all-inorganic base, broadening of light-absorbing spectral ranges with enhanced stability has been achieved, indicating inevitable highly increased conductivity, which triggers a high off-current of the devices. Accordingly, the selectively ultraviolet (UV)-irradiated electrical deactivation (SUED) process is carried out to suppress the high off-current with a reliable device structure. Particularly, it is noted that the selective UV irradiation can facilitate oxidation and distortion of the chemical structure in specific perovskite regions, providing enhanced gate bias modulation of the phototransistor with an increased on/off-current ratio from ∼10³ to ∼10⁶. Finally, the SUED-processed phototransistor exhibits an improvement in the photosensitivity by more than 3 orders of magnitude up to 8.0 × 10⁴ and detects in the spectral range from visible to near-infrared (NIR) light (∼860 nm) with good on/off switching behaviors.

Experimental Evidence of CO2 Photoreduction Activity of SnO2 Nanoparticles

Tin dioxide (SnO₂ ) has intrinsic characteristics that do not favor its photocatalytic activity. However, we evidenced that surface modification can positively influence its performance for CO₂ photoreduction in the gas phase. The hydroxylation of the SnO₂ surface played a role in the CO₂ affinity decreasing its reduction potential. The results showed that a certain selectivity for methane (CH₄ ), carbon monoxide (CO), and ethylene (C₂ H₄ ) is related to different SnO₂ hydrothermal annealing. The best performance was seen for SnO₂ annealed at 150 °C, with a production of 20.4 μmol g^-1 for CH₄ and 16.45 μmol g^-1 for CO, while for SnO₂ at 200 °C the system produced more C₂ H₄ , probably due to a decrease of surface -OH groups.

Role of Synthetic Parameters on the Structural and Optical Properties of N,Sn-Copromoted Nanostructured TiO2: A Combined Ti K-Edge and Sn L2,3-Edges X-ray Absorption Investigation

Sn-modification of TiO2 photocatalysts has been recently proposed as a suitable strategy to improve pollutant degradation as well as hydrogen production. In particular, visible light activity could be promoted by doping with Sn2+ species, which are, however, thermally unstable. Co-promotion with N and Sn has been shown to lead to synergistic effects in terms of visible light activity, but the underlying mechanism has, so far, been poorly understood due to the system complexity. Here, the structural, optical, and electronic properties of N,Sn-copromoted, nanostructured TiO2 from sol-gel synthesis were investigated: the Sn/Ti molar content was varied in the 0-20% range and different post-treatments (calcination and low temperature hydrothermal treatment) were adopted in order to promote the sample crystallinity. Depending on the adopted post-treatment, the optical properties present notable differences, which supports a combined role of Sn dopants and N-induced defects in visible light absorption. X-ray absorption spectroscopy at the Ti K-edge and Sn L2,3-edges shed light onto the electronic properties and structure of both Ti and Sn species, evidencing a marked difference at the Sn L2,3-edges between the samples with 20% and 5% Sn/Ti ratio, showing, in the latter case, the presence of tin in a partially reduced state.

Improved Efficiency of Perovskite Solar Cells Using a Nitrogen-Doped Graphene-Oxide-Treated Tin Oxide Layer

Tin oxide (SnO₂) is widely adopted as an electron transport layer in perovskite solar cells (PeSCs) because it has high electron mobility, excellent charge selective behavior owing to a large band gap of 3.76 eV, and low-temperature processibility. To achieve highly efficient SnO₂-based PeSCs, it is necessary to control the oxygen vacancies in the SnO₂ layer, since the electrical and optical properties vary depending on the oxidation state of Sn. This study demonstrates that the performance of PeSCs may be improved by using nitrogen-doped graphene oxide (NGO) as an oxidizing agent for SnO₂. Since NGO changes the oxidation state of the Sn in SnO₂ from Sn²⁺ to Sn⁴⁺, the oxygen vacancies in SnO₂ can be reduced using NGO. Multiple devices are fabricated, and various techniques are used to assess their performance, including X-ray photoelectron spectroscopy, dark current analysis, and the dependence of the open-circuit voltage on light intensity. Compared with the average power conversion efficiency (PCE) of control devices, PeSCs with SnO₂:NGO composite layers exhibit greater PCEs with less deviation. Therefore, the introduction of NGO in a SnO₂ layer can be regarded as an effective method of controlling the oxidation state of SnO₂ to improve the performance of PeSCs.