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The United States emerged from World War II with generally good relations with the countries of Latin America and with the traditional Good Neighbor policy still largely intact. But it wasn’t too long before various overarching strategic and ideological priorities began to undermine those good relations as the Cold War came to exert its grip on U.S. policy formation and implementation. In The Truman Administration and Bolivia, Glenn Dorn tells the story of how the Truman administration allowed its strategic concerns for cheap and ready access to a crucial mineral resource, tin, to take precedence over further developing a positive relationship with Bolivia. This ultimately led to the economic conflict that provided a major impetus for the resistance that culminated in the Revolution of 1952—the most important revolutionary event in Latin America since the Mexican Revolution of 1910. The emergence of another revolutionary movement in Bolivia early in the millennium under Evo Morales makes this study of its Cold War predecessor an illuminating and timely exploration of the recurrent tensions between U.S. efforts to establish and dominate a liberal capitalist world order and the counterefforts of Latin American countries like Bolivia to forge their own destinies in the shadow of the “colossus of the north.”

Even though the mesoporous-type perovskite solar cell (PSC) is known for high efficiency, its planar-type counterpart exhibits lower efficiency and hysteretic response. Herein, we report success in suppressing hysteresis and record efficiency for planar-type devices using EDTA-complexed tin oxide (SnO 2 ) electron-transport layer. The Fermi level of EDTA-complexed SnO 2 is better matched with the conduction band of perovskite, leading to high open-circuit voltage. Its electron mobility is about three times larger than that of the SnO 2 . The record power conversion efficiency of planar-type PSCs with EDTA-complexed SnO 2 increases to 21.60% (certified at 21.52% by Newport) with negligible hysteresis. Meanwhile, the low-temperature processed EDTA-complexed SnO 2 enables 18.28% efficiency for a flexible device. Moreover, the unsealed PSCs with EDTA-complexed SnO 2 degrade only by 8% exposed in an ambient atmosphere after 2880 h, and only by 14% after 120 h under irradiation at 100 mW cm −2 . The development of high efficiency planar-type perovskite solar cell has been lagging behind the mesoporous-type counterpart. Here Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability.

Perovskite solar cells (PSCs) have reached an impressive efficiency over 23%. One of its promising characteristics is the low-cost solution printability, especially for flexible solar cells. However, printing large area uniform electron transport layers on rough and soft plastic substrates without hysteresis is still a great challenge. Herein, we demonstrate slot-die printed high quality tin oxide films for high efficiency flexible PSCs. The inherent hysteresis induced by the tin oxide layer is suppressed using a universal potassium interfacial passivation strategy regardless of fabricating methods. Results show that the potassium cations, not the anions, facilitate the growth of perovskite grains, passivate the interface, and contribute to the enhanced efficiency and stability. The small size flexible PSCs achieve a high efficiency of 17.18% and large size (5 × 6 cm 2 ) flexible modules obtain an efficiency over 15%. This passivation strategy has shown great promise for pursuing high performance large area flexible PSCs. Uniformity and hysteresis are long lasting problems for flexible perovskite solar modules. Here Bu et al. develop a universal potassium passivation strategy to improve the quality of slot-die printed tin oxide electron transport layers and demonstrate highly efficient and hysteresis-free flexible devices.

The electrosynthesis of formate from CO 2 can mitigate environmental issues while providing an economically valuable product. Although stannic oxide is a good catalytic material for formate production, a metallic phase is formed under high reduction overpotentials, reducing its activity. Here, using a fluorine-doped tin oxide catalyst, a high Faradaic efficiency for formate (95% at 100 mA cm −2 ) and a maximum partial current density of 330 mA cm −2 (at 400 mA cm −2 ) is achieved for the electroreduction of CO 2 . Furthermore, the formate selectivity (≈90%) is nearly constant over 7 days of operation at a current density of 100 mA cm −2 . In-situ/operando spectroscopies reveal that the fluorine dopant plays a critical role in maintaining the high oxidation state of Sn, leading to enhanced durability at high current densities. First-principle calculation also suggests that the fluorine-doped tin oxide surface could provide a thermodynamically stable environment to form HCOO* intermediate than tin oxide surface. These findings suggest a simple and efficient approach for designing active and durable electrocatalysts for the electrosynthesis of formate from CO 2 . Though stannic oxides can catalyze CO 2 electroreduction to formate, the stability of these catalysts has been limited. Here, the authors demonstrate stable fluorine-doped SnO2 materials toward formate production at current densities of >300 mA/cm 2 .

The selection of an appropriate substrate is an important initial step for many studies of electrochemically active materials. In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation. Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide). We determine the inert potential window for each substrate/electrolyte combination and make recommendations about which materials may be most suitable for application under different experimental conditions. Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.

Thermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m –1  K –1 at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material. SnSe has a very high thermoelectric figure of merit ZT, but uncommonly polycrystalline samples have higher lattice thermal conductivity than single crystals. Here, by controlling Sn reagent purity and removing SnO x impurities, a lower thermal conductivity is achieved, enabling ZT of 3.1 at 783 K.

Nanotechnology has become the most promising area of research with its momentous application in all fields of science. In recent years, tin oxide has received tremendous attention due to its fascinating properties, which have been improved with the synthesis of this material in the nanometer range. Numerous physical and chemical methods are being used these days to produce tin oxide nanoparticles. However, these methods are expensive, require high energy, and also utilize various toxic chemicals during the synthesis. The increased concerns related to human health and environmental impact have led to the development of a cost-effective and environmentally benign process for its production. Recently, tin oxide nanoparticles have been successfully synthesized by green methods using different biological entities such as plant extract, bacteria, and natural biomolecules. However, industrial-scale production using green synthesis approaches remains a challenge due to the complexity of the biological substrates that poses a difficulty to the elucidations of the reactions and mechanism of formations that occur during the synthesis. Hence, the present review summarizes the different sources of biological entities and methodologies used for the green synthesis of tin oxide nanoparticles and the impact on their properties. This work also describes the advances in the understanding of the mechanism of formation reported in the literature and the different analytical techniques used for characterizing these nanoparticles.

A cost-effective, facile hydrothermal approach was made for the synthesis of SnO2/graphene (Gr) nano-composites. XRD diffraction spectra clearly confirmed the presence of tetragonal crystal system of SnO2 which was maintaining its structure in both pure and composite materials' matrix. The stretching and bending vibrations of the functional groups were analyzed using FTIR analysis. FESEM images illustrated the surface morphology and the texture of the synthesized sample. HRTEM images confirmed the deposition of SnO2 nanoparticles over the surface of graphene nano-sheets. Raman Spectroscopic analysis was carried out to confirm the in-plane blending of SnO2 and graphene inside the composite matrix. The photocatalytic performance of the synthesized sample under UV irradiation using methylene blue dye was observed. Incorporation of grapheme into the SnO2 sample had increased the photocatalytic activity compared with the pure SnO2 sample. The electrochemical property of the synthesized sample was evaluated.

This study utilized a postdeposition sulfurization method to produce thin films of the Cu2SnSnS4 (CZTS) absorber layer. Initially, metal precursors were deposited onto a tin oxide-coated substrate through thermal evaporation. Subsequently, sulfurization occurred in a mixed environment of sulfur vapor and argon gas. The sulfurization temperature was set at 500°C for a duration of 30 min. During the sulfurization process, the facile evaporation of tin compounds could lead to a deviation in the atomic ratio within the absorber layer and potentially result in the attachment of secondary phases to the surface of the absorber layer. Therefore, this study employed a multilayered metal precursor structure (with a constant total thickness for each metal and nonmetal sulfides as precursors) for sulfurization. This method effectively suppressed the formation of secondary phases, including ZnS within the absorber layer and SnS2 on the surface. From the quantification results, the ratio of ZnS to CZTS signal intensity decreased from 0.52 to 0, while the ratio of SnS2 to CZTS signal intensity dropped from 1.2 to 0. Additionally, the efficiency increased to 2.79%. In summary, this research introduced a novel preparation method to enhance the quality of CZTS films. The modification to a multilayered metal precursor structure reduced the evaporation of tin compounds, consequently minimizing the generation of secondary phases.

Nucleation and growth of hydrogen nanobubbles are key initial steps in electrochemical water splitting. These processes remain largely unexplored due to a lack of proper tools to probe the nanobubble’s interfacial structure with sufficient spatial and temporal resolution. We report the use of superresolution microscopy to image transient formation and growth of single hydrogen nanobubbles at the electrode/solution interface during electrocatalytic water splitting. We found hydrogen nanobubbles can be generated even at very early stages in water electrolysis, i.e., ∼500 mV before reaching its thermodynamic reduction potential. The ability to image single nanobubbles on an electrode enabled us to observe in real time the process of hydrogen spillover from ultrathin gold nanocatalysts supported on indium–tin oxide.