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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.

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.

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.

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.

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 .

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.

Electrochemical water oxidation reaction (WOR) to hydrogen peroxide (H 2 O 2 ) via a 2e − pathway provides a sustainable H 2 O 2 synthetic route, but is challenged by the traditional 4e − counterpart of oxygen evolution. Here we report a CO 2 /carbonate mediation approach to steering the WOR pathway from 4e − to 2e − . Using fluorine-doped tin oxide electrode in carbonate solutions, we achieved high H 2 O 2 selectivity of up to 87%, and delivered unprecedented H 2 O 2 partial currents of up to 1.3 A cm −2 , which represents orders of magnitude improvement compared to literature. Molecular dynamics simulations, coupled with electron paramagnetic resonance and isotope labeling experiments, suggested that carbonate mediates the WOR pathway to H 2 O 2 through the formation of carbonate radical and percarbonate intermediates. The high selectivity, industrial-relevant activity, and good durability open up practical opportunities for delocalized H 2 O 2 production. Electrochemical H 2 O oxidation to H 2 O 2 is challenged by the competitive O 2 evolution reaction. Here, the authors report a CO 2 /carbonate mediation approach to steering the H 2 O oxidation pathway from O 2 evolution to H 2 O 2 generation.

To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeO x @Ge-PH photoanode shows a photocurrent density of 4.6 mA cm −2 at 1.23 V RHE with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9 mA cm −2 in NiFeO x @Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design. Germanium (Ge) has potential as a dopant suitable for the hematite-based photoelectrochemical water splitting system. Here, the authors report the fabrication of Ge doped porous hematite and demonstrate an efficient tandem system of Ge doped porous hematite and the perovskite solar cell.

Tin and its compounds hold promise for the development of high-capacity anode materials that could replace graphitic carbon used in current lithium-ion batteries. However, the introduced porosity in current electrode designs to buffer the volume changes of active materials during cycling does not afford high volumetric performance. Here, we show a strategy leveraging a sulfur sacrificial agent for controlled utility of void space in a tin oxide/graphene composite anode. In a typical synthesis using the capillary drying of graphene hydrogels, sulfur is employed with hard tin oxide nanoparticles inside the contraction hydrogels. The resultant graphene-caged tin oxide delivers an ultrahigh volumetric capacity of 2123 mAh cm –3 together with good cycling stability. Our results suggest not only a conversion-type composite anode that allows for good electrochemical characteristics, but also a general synthetic means to engineering the packing density of graphene nanosheets for high energy storage capabilities in small volumes. The excessive porous space in carbon anodes for lithium-ion batteries has to be utilized for high volumetric performance. Here the authors show an adaptable sulfur template strategy to yield graphene-caged noncarbon materials with a precisely controlled amount of void, enabling ultrahigh volumetric lithium storage.

Metal oxide nanostructures have recently gained high attention due to advances in their synthesis, particularly hydrothermal techniques, which allow precise control over their morphology, composition, and crystallinity, as well as integration into devices. Zinc-tin oxide (ZTO) nanostructures, in particular, are notable for their sustainability and multifunctional applications, including catalysis, electronics, sensors, and energy harvesting. Their ternary oxide nature supports a broad range of functionalities. The use of seed layers during synthesis has proven to be beneficial, particularly for binary systems such as ZnO, as it not only impacts the growth of nanostructures but is also advantageous for applications requiring nanostructures supported on substrates, such as in photocatalysis and sensor technologies. This work investigates the effect of various seed layers (e.g., Cu, stainless steel, Cr, Ni) on the hydrothermal synthesis of ZTO nanostructures. Compared to seed layer free methods under similar conditions, the presence of seed layers significantly influenced the resulting structures. The study produced diverse morphologies, including ZnSnO₃ nanowires and Zn₂SnO₄ nanoparticles, octahedrons, and nanowires. Findings suggest a relationship between the seed layer’s phase and the resulting nanostructure phase. Furthermore, shorter synthesis durations favored discrete nanostructures, while longer durations facilitated the formation of thin films with nanostructured surfaces. These observations underscore the dual role of seed layers in influencing both the structural phase and growth kinetics of ZTO nanostructures.