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Gas diffusion electrodes (GDEs) are extensively used for high current density electrochemical CO 2 electrolysis (ECO 2 R), enabled by significantly reducing mass transfer resistance of CO 2 to the catalyst layer. Conventionally, these GDEs are based upon hydrophobic carbon-based gas-diffusion layers (GDLs) that facilitate the gas transport; however, these supports are prone to flood with electrolyte during electrolysis. This potential-induced flooding, known as electrowetting, is related to the inherent conductivity of carbon and limits the activity of ECO 2 R. To investigate the effect of electrical conductivity more carefully, a GDE is constructed based on a Cu mesh with a nonconductive microporous GDL applied to this substrate, the latter composed of a mixture of metal oxide and polytetrafluoroethylene. With alumina as the metal oxide, a stable operation is obtained at -200 mA cm -2 with 70% selectivity for ECO 2 R (with over half toward C 2+ products) without flooding as observed by in situ microscopy. On the contrary, with a Vulcan carbon-based GDL, the initial activity is rapidly lost as severe flooding ensues. It is reasoned that electrowetting is averted by virtue of the nonconductive nature of alumina, providing a new perspective on alternative GDL compositions and their influence on ECO 2 R performance.

Lithium metal is a promising anode candidate to achieve high-energy-density lithium metal batteries (LMBs) due to its ultrahigh theoretical capacity (3860 mA h g -1 ) and low electrochemical potential (-3.04 V vs S.H.E). Unfortunately, the commercialization of lithium metal anodes is hindered by the growth of Li dendrites and the infinite Li volume changes during the cycling process. Herein, we introduce a 3D hierarchical multimetal oxide nanowire framework as a current collector for Li metal anodes. The hierarchical metal oxide layers of CoO and Cu x O provide abundant Li nucleation sites and thus offer uniform Li plating and regulate Li nucleation during the charge/discharge process. As a result, half cells present a prolonging Coulombic efficiency of 97% at 1 mA cm -2 with a capacity of 1 mA h cm -2 for over 300 cycles. A stable cyclability of symmetric cells is demonstrated under 1 mA cm -2 with a capacity of 1 mA h cm -2 for 1500 h. Full cells paired with an LFP cathode show a stable capacity of 131.5 mA h g -1 with a capacity retention of 92% for 200 cycles. These results will shed insights into the design of 3D Cu current collectors for high-performance composite Li metal anodes.

To complement or outperform lithium-ion batteries with liquid electrolyte as energy storage devices, a high-energy as well as high-power anode material must be used in solid-state batteries. An overlooked class of anode materials is the one of conversion/alloy active materials (e.g., SnO 2 , which is already extensively studied in liquid electrolyte-based batteries). Conversion/alloy active materials offer high specific capacities and often also fast lithium-ion diffusion and reaction kinetics, which are required for high C-rates and application in high-energy and high-power devices such as battery electric vehicles. To date, there are only very few reports on conversion/alloy active materials─namely, SnO 2 ─as anode material in sulfide-based solid-state batteries, with a relatively complex electrode design. Otherwise, conversion-alloy active materials are used as a seed layer or interlayer for a homogeneous Li deposition or to mitigate the formation and growth of the SEI, respectively. Within this work, four different conversion/alloy active materials─SnO 2 , Sn 0.9 Fe 0.1 O 2 , ZnO, and Zn 0.9 Fe 0.1 O─are synthesized and incorporated as negative active materials ("anodes") in composite electrodes into SSBs with Li 6 PS 5 Cl as solid electrolyte. The structure and the microstructure of the as-synthesized active materials and composite electrodes are investigated by XRD, SEM, and FIB-SEM. All active materials are evaluated based on their C-rate performance and long-term cyclability by galvanostatic cycling under a constant pressure of 40 MPa. Furthermore, light is shed on the degradation processes that take place at the interface between the active material and solid electrolyte. It is evidenced that the decomposition of Li 6 PS 5 Cl to LiCl, Li 2 S, and Li 3 P at the anode is amplified by Fe substitution. Lastly, a 2D sheet electrode is designed and cycled to tackle the interfacial degradation processes. This approach leads to an improved C-rate performance (factor of 3) as well as long-term cyclability (factor of 2.3).

To achieve more stable and efficient metal halide perovskite devices, optimization of charge transport materials and their interfaces with perovskites is crucial. ZnO on paper would make an ideal electron transport layer in perovskite devices. This metal oxide has a large bandgap, making it transparent to visible light; it can be easily n-type doped, has a decent electron mobility, and is thought to be chemically relatively inert. However, in combination with perovskites, ZnO has turned out to be a source of instability, rapidly degrading the performance of devices. In this work, we provide a comprehensive experimental and computational study of the interaction between the most common organic perovskite precursors and the surface of ZnO, with the aim of understanding the observed instability. Using X-ray photoelectron spectroscopy, we find a complete degradation of the precursors in contact with ZnO and the formation of volatile species as well as new surface bonds. Our computational work reveals that different pristine and defected surface terminations of ZnO facilitate the decomposition of the perovskite precursor molecules, mainly through deprotonation, making the deposition of the latter on those surfaces impossible without the use of passivation.

High-rate aqueous hybrid supercapacitors (AHSCs) have attracted relevant scientific significance owing to their expected energy density, supercapacitor-level power density, and battery-level energy density. In this work, a bimetallic nanostructured material with chromium-incorporated cobalt oxide (CCO, i.e., CoCr 2 O 4 ) was prepared via a hydrothermal method to form a stable cubic obelisk structure. Compared with CCO materials prepared using traditional methods, CCO displayed a nanowire structure (50 nm diameter), suggesting an enhanced specific surface area and a large number of active sites for chemical reactions. The electrode possessed a high specific capacitance (2951 F g -1 ) at a current density of 1 A g -1 , minimum R ct (0.135 Ω), and the highest capacitance retention (98.7%), making it an ideal electrode material for AHSCs. Ex situ analysis based on X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed a favorable stability of CCO after 10,000 cycles without any phase changes being detected. GGA and GGA + U methods employed in density functional theory (DFT) also highlighted the enhanced metallic properties of CCO originating from the synergistic effect of semiconducting Cr 2 O 3 and Co 3 O 4 materials.

Although recent dramatic advances in power conversion efficiencies (PCEs) have resulted in values over 19%, the poor photostability of organic photovoltaics (OPVs) has been a serious bottleneck to their commercialization. The photocatalytic effect, which is caused by incident ultraviolet-A (UV-A, 320-400 nm) light in the most commonly used zinc oxide (ZnO X ) electron transport layer (ETL), significantly deteriorates the photostability of OPVs. In this work, we develop a new and facile method to enhance the photostability of nonfullerene acceptor-based OPVs by introducing UV-A-insensitive titanium suboxide (TiO X ) ETL. Through an in-depth analysis of mass information at the interface between the ETL and photoactive layer, we confirm that the UV-A-insensitive TiO X suppresses the photocatalytic effect. The resulting device employing the TiO X ETL shows excellent photostability, obtaining 80% of the initial PCE for up to 200 h under 1 sun illumination, which is 10 times longer than that of the conventional ZnO X system (19 h).

Coating electrode materials with metal oxide thin films can improve the performance of electrocatalysts and charge storage materials. Atomic layer deposition (ALD) enables the deposition of conformal, uniform films on a wide range of electrodes; however, an even film depends on the availability of nucleation sites directly on the electrode surface. Here, we show that the electrochemical oxidation of glassy carbon electrodes prior to the deposition of alumina thin films by ALD leads to more uniform electrochemically passivating films. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) demonstrate that film uniformity increases with the increasing potential of preoxidation until 2.50 V versus Ag/AgCl, at which point the films are fully passivating and appear continuous by SEM. Further increasing the potential of preoxidation leads to uniform but less consistently passivating alumina films. These findings show that electrochemical preoxidation is a rapid and readily tunable strategy for controlling oxygenic nucleation sites and therefore the growth of thin metal oxide films on glassy carbon electrodes.

The widespread adoption of wearable, movable, and implantable smart devices has sparked the evolution of flexible, miniaturized power supplies. High-resolution inkjet printing of flexible microsupercapacitor (μSC) electrodes is a fast, inexpensive, and waste-free alternative manufacturing technology. In this work, a 2D birnessite-type manganese dioxide (δ-MnO 2 ) water-based ink is used to print 10-25 layers of δ-MnO 2 symmetrically on a preprinted interdigitated cell consisting of 10 layers of electrochemically exfoliated graphene (EEG). The cell with 10 printed layers of δ-MnO 2 achieved the highest specific capacitance, energy density, and power density of 0.44 mF cm -2 , 0.045 μW h cm -2 , and 0.0012 mW cm -2 , respectively. Since inkjet-printing technology supports μSC manufacturing with parallel/series connectivity, four cells were used to study and improve the potential window and capacitance that can be used to construct μSC arrays as power banks. This work provides the first approach for designing an inkjet-printed interdigitated hybrid cell based on δ-MnO 2 @EEG that could be a versatile candidate for the large-scale production of flexible and printable electronic devices for energy storage.

Solution-processed metal-oxide thin-film transistors (TFTs) with different metal compositions are investigated for ex situ and in situ radiation hardness experiments against ionizing radiation exposure. The synergetic combination of structural plasticity of Zn, defect tolerance of Sn, and high electron mobility of In identifies amorphous zinc-indium-tin oxide (Zn-In-Sn-O or ZITO) as an optimal radiation-resistant channel layer of TFTs. The ZITO with an elemental blending ratio of 4:1:1 for Zn/In/Sn exhibits superior ex situ radiation resistance compared to In-Ga-Zn-O, Ga-Sn-O, Ga-In-Sn-O, and Ga-Sn-Zn-O. Based on the in situ irradiation results, where a negative threshold voltage shifts and a mobility increase as well as both off current and leakage current increase are observed, three factors are proposed for the degradation mechanisms: (i) increase of channel conductivity, (ii) interface-trapped and dielectric-trapped charge buildup, and (iii) trap-assisted tunneling in the dielectric. Finally, in situ radiation-hard oxide-based TFTs are demonstrated by employing a radiation-resistant ZITO channel, a thin dielectric (50 nm SiO 2 ), and a passivation layer (PCBM for ambient exposure), which exhibit excellent stability with an electron mobility of ∼10 cm 2 /V s and aΔ V th of <3 V under real-time (15 kGy/h) gamma-ray irradiation in an ambient atmosphere.

Low-power metal oxide (MOX)-based gas sensors are widely applied in edge devices. To reduce power consumption, nanostructured MOX-based sensors that detect gas at low temperatures have been reported. However, the fabrication process of these sensors is difficult for mass production, and these sensors are lack uniformity and reliability. On the other hand, MOX film-based gas sensors have been commercialized but operate at high temperatures and exhibit low sensitivity. Herein, commercially advantageous highly sensitive, film-based indium oxide sensors operating at low temperatures are reported. Ar and O 2 gases are simultaneously injected during the sputtering process to form a hydroxy-rich-surface In 2 O 3 film. Conventional indium oxide (In 2 O 3 ) films (A0) and hydroxy-rich indium oxide films (A1) are compared using several analytical techniques. A1 exhibits a work function of 4.92 eV, larger than that of A0 (4.42 eV). A1 exhibits a Debye length 3.7 times longer than that of A0. A1 is advantageous for gas sensing when using field effect transistors (FETs) and resistors as transducers. Because of the hydroxy groups present on the surface of A1, A1 can react with NO 2 gas at a lower temperature (∼100 °C) than A0 (180 °C). Operando diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) shows that NO 2 gas is adsorbed to A1 as nitrite (NO 2 - ) at 100 °C and nitrite and nitrate (NO 3 - ) at 200 °C. After NO 2 is adsorbed as nitrate, the sensitivity of the A1 sensor decreases and its low-temperature operability is compromised. On the other hand, when NO 2 is adsorbed only as nitrite, the performance of the sensor is maintained. The reliable hydroxy-rich FET-type gas sensor shows the best performance compared to that of the existing film-based NO 2 gas sensors, with a 2460% response to 500 ppb NO 2 gas at a power consumption of 1.03 mW.

A facile and versatile strategy was developed to produce highly ordered porous metal oxide structures via block copolymer (BCP) lithography. Phase separation of poly(2-vinylpyridine)- b -polystyrene (P2VP- b -PS) was induced by solvent vapor annealing in a nonselective solvent environment to fabricate cylindrical arrays. In this work, we thoroughly analyzed the effects of the film thickness, solvent annealing time, and temperature on the ordering of a P2VP-majority system for the first time, resulting in "inverse" structures. Reflectometry, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy were used to characterize the formation of the highly ordered BCP morphology and the subsequently produced metal oxide film. At 40 min solvent annealing time, hexagonally close packed structures were produced with cylinder diameters ∼40 nm. Subsequently, the BCP films were infiltrated with different metal cations. Metal ions (Cr, Fe, Ni, and Ga) selectively infiltrated the P2VP domain, while the PS did not retain any detectable amount of metal precursor. This gave rise to a metal oxide porous structure after a UV/ozone (UVO) treatment. The results showed that the metal oxide structures demonstrated high fidelity compared to the BCP template and cylindrical domains presented a similar size to the previous PS structure. Moreover, XPS analyses revealed the complete elimination of the BCP template and confirmed the presence of the metal oxides. These metal oxides were used as hard masks for pattern transfer via dry etching as a further application. Silicon nanopores were fabricated mimicking the BCP template and demonstrated a pore depth of ∼50 nm. Ultimately, this strategy can be applied to create different inorganic nanostructures for a diverse range of applications, for example, solar cells, diodes, and integrated circuits. Furthermore, by optimizing the etching parameters, deeper structures can be obtained via ICP/RIE processes, leading to many potential applications.

Despite the rapid progress in perovskite solar cells, their commercialization is still hindered by issues regarding long-term stability, which can be strongly affected by metal oxide-based charge extraction layers next to the perovskite material. With MoO 3 being one of the most successful hole transport layers in organic photovoltaics, the disastrous results of its combination with perovskite films came as a surprise but was soon attributed to severe chemical instability at the MoO 3 /perovskite interface. To discover the atomistic origin of this instability, we combine density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) measurements to investigate the interaction of MoO 3 with the perovskite precursors MAI, MABr, FAI, and FABr. From DFT calculations we suggest a scenario that is based upon oxygen vacancies playing a key role in interface degradation reactions. Not only do these vacancies promote decomposition reactions of perovskite precursors, but they also constitute the reaction centers for redox reactions leading to oxidation of the halides and reduction of Mo. Specifically iodides are proposed to be reactive, while bromides do not significantly affect the oxide. XPS measurements reveal a severe reduction of Mo and a loss of the halide species when the oxide is interfaced with I-containing precursors, which is consistent with the proposed scenario. In line with the latter, experimentally observed effects are much less pronounced in case of Br-containing precursors. We further find that the reactivity of the MoO 3 substrate can be moderated by reducing the number of oxygen vacancies through a UV/ozone treatment, though it cannot be fully eliminated.

Graphite is the most popular anode material for lithium-ion batteries (LIBs) owing to its high reversibility and stable cycling performance. With the rapid growth of the global electric vehicle (EV) market, it has become necessary to improve the quick-charge performance of graphite to reduce the charging time of LIBs. Therefore, from a structural viewpoint, it is crucial to control interfacial reactions and stabilize the surface of graphite to improve the sluggish interfacial kinetics. Herein, we propose a facile approach for integrating functional metal oxides on the surface of natural graphite (NG) via a surface-coating technique in combination with a facile-crystallization process. The functionality of the metal oxides, i.e., MoO 2 and Fe 3 O 4 , on the surface of NG was thoroughly investigated based on various structural and electrochemical analyses. The results demonstrate that the metal oxides play critical roles in stabilizing the surface of NG and facilitating faster Li + migration at the interface between NG and the electrolyte during cycling. In particular, the full cell configured with the c-Fe 3 O 4 -NG anode shows remarkably improved charging behavior (3 C charging-1 C discharging) without any significant loss of reversible capacity during 300 cycles. This study has conclusively established that tailoring the surface of NG with functional metal oxides would be a utilitarian way to improve the charging capability of NG. We are confident that the study results would provide utilitarian insights into the development of advanced LIBs for successful implementation in EV applications in the future.

Fabrication and processing approaches that facilitate the ease of patterning and the integration of nanomaterials into sensor platforms are of significant utility and interest. In this work, we report the use of laser-induced thermal voxels (LITV) to fabricate microscale, planar gas sensors directly from solutions of metal salts. LITV offers a facile platform to directly integrate nanocrystalline metal oxide and mixed metal oxide materials onto heating platforms, with access to a wide variety of compositions and morphologies including many transition metals and noble metals. The unique patterning and synthesis flexibility of LITV enable the fabrication of chemically and spatially tailorable microscale sensing devices. We investigate the sensing performance of a representative set of n-type and p-type LITV-deposited metal oxides and their mixtures (CuO, NiO, CuO/ZnO, and Fe 2 O 3 /Pt) in response to reducing and oxidizing gases (H 2 S, NO 2 , NH 3 , ethanol, and acetone). These materials show a broad range of sensitivities and notably a strong response of NiO to ethanol and acetone (407 and 301% R / R 0 at 250 °C, respectively), along with a 5- to 20-fold sensitivity enhancement for CuO/ZnO to all gases measured over pure CuO, highlighting the opportunities of LITV for the creation of mixed-material microscale sensors.

The polyhedra unit structure (MO x ) in an amorphous metal oxide network has more freedom and flexibility than the same unit structure in a crystalline phase. Consequently, a mild external stimulus (e.g., instant photonic and acoustic energy) could affect and change this network parameter, thereby enhancing and modulating the electrical properties. However, it is difficult to tune these atomic parameters solely while maintaining the metal oxide's initial global amorphous phase and thereby preventing mechanical instability at the film-substrate interface (i.e., cracking or distortion). Here, we report local disordering in an amorphous network of a solution-processable indium tin oxide (ITO) film, where the disordering is triggered by mild-light irradiation (<0.1 mJ/cm 2 ). Through a combination of systematic characterizations of the global structural and chemical compositional changes in conjunction with extended X-ray absorption fine structure analyses, we revealed the distortion of the atomic structure in the amorphous network of the ITO film led to the formation of additional structural oxygen vacancies. Our findings enabled us to fabricate mechanical-instability-free, perfect amorphous-phase ITO thin films on plastic substrates, where the sheet resistance substantially decreased to ∼ 2 × 10 3 Ω/□. Furthermore, this sheet resistance did not vary when the film and substrate were bent to a radius of 2 mm and could operate at low temperatures. This work can pave the novel way to fabricate high-quality flexible transparent electrodes suitable for rapid, cost-effective, and patternable processing on plastic substrates, and the domain can be extended to flexible electronics.

In 2017, we reported a dye-sensitized, photoelectrolysis cell consisting of fluorine-doped tin oxide (FTO)-coated glass covered by SnO 2 nanoparticles coated with N , N '-bis(phosphonomethyl)-3,4,9,10-perylenediimide (PMPDI) dye and then a photoelectrochemically deposited CoO x water oxidation catalyst (WOCatalyst), FTO/nano-SnO 2 /PMPDI/CoO x . This system employed nanostructured SnO 2 stabilized by a polyethyleneglycol bisphenol A epichlorohydrin (PEG-BAE) copolymer and other C-containing additives based on a literature synthesis to achieve a higher surface area and thus greater PMPDI dye absorption and resultant light collection. Surprisingly, the addition of the well-established WOCatalyst CoO x resulted in a decrease in the photocurrent, an unexpected "anti-catalyst" effect . Two primary questions addressed in the present study are (1) what is the source of this "anti-catalyst" effect? and (2) are the findings of broader interest? Reflection on the synthesis of nano-SnO 2 stabilized by PEG-BAE, and the large, ca. 10:1 ratio of C to Sn in synthesis, led to the hypothesis that even the annealing step at 450 °C in of the FTO/SnO 2 anode precursors was unlikely to remove all the carbon initially present. Indeed, residual carbon impurities are shown to be the culprit in the presently observed "anti-catalyst" effect. The implication and anticipated broader impact of the results of answering the two abovementioned questions are also presented and discussed along with a section entitled "Perspective and Suggestions for the Field Going Forward."

Anchoring groups are usually needed for the attachment of small molecules to metal oxide surfaces such as in water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs). Here, we optimize the surface loading onto titanium dioxide surfaces of the silatrane anchoring group, a triethanolamine-protected trialkoxysilane. This anchoring group is not yet widely used because prior protocols afforded low surface coverage, but it has the advantage of high stability over a wide pH range and at both oxidizing and reducing potentials when bound. A new and improved method for estimating surface coverage is described here and used to determine that loading using previously reported binding protocols is very low. However, we were able to uncover several factors contributing to this low loading, which has allowed us to develop methods to greatly improve surface coverage for a variety of silatranes. Most notably, we were able to increase the loading of a model arylsilatrane by 145% through use of a benzoic acid additive. This is not general acid catalysis because alkylsilatranes are not similarly affected and 4- t -butylbenzoic acid, having a similar p K a to benzoic acid, is not effective. Because the bulky t -butyl group of the latter additive is not expected to pi-stack with our arylsilatrane, we have tentatively assigned this enhancement to aromatic stacking between the aromatic additive and the arylsilatrane.

Recently, Ni-rich layered cathode materials have become the most common material used for lithium-ion batteries. From a structural viewpoint, it is crucial to stabilize the surface structures of such materials, as they are prone to undesirable side reactions and particle cracking in which intergranular microcracks form at the particle surfaces and then propagate inside. As a simplified engineering technique for obtaining Ni-rich cathode materials with high reversibility and long-term cycling stability, we propose a facile surface coating of piezoelectric LiTaO 3 onto a Ni-rich cathode material to enhance the charge transfer reaction and surface structural integrity. Based on theoretical and experimental investigation, we demonstrate that this surface protection approach is effective at enhancing the reversibility and mechanical strength of Ni-rich cathode materials, leading to a stable cycle performance at up to 150 cycles, even at 60 °C. Furthermore, the piezoelectric characteristics of the surface LiTaO 3 can enhance the rate capability of Ni-rich cathode materials at current densities of up to 2.0C. The results of this study provide a practical insight on the development of Ni-rich cathode materials for practical use in electric vehicle applications.

Due to their various applications, metal oxides are of high interest for fundamental research and commercial usage. Per applications as catalysts or electrochemical devices, the tailored design of metal oxides featuring a high specific surface area and additional functionalities is of the utmost importance for the performance of the resulting materials. We report a new method for preparing free-standing films consisting of hierarchically porous metal oxides (titanium and niobium based) by combining emulsion polymerization and shear-induced monodisperse particle self-assembly in the presence of sol-gel precursors. After thermal treatment, the resulting porous materials can be used as electrodes in Li-ion batteries. The titanium and niobium sol-gel precursors were partially immobilized to the surface of organic core-interlayer particles featuring hydroxyl groups to obtain hybrid organic-inorganic particles through the melt-shear organization process. Free-standing particle-based films, in analogy to elastomeric opal films and colloidal crystals, can be prepared in a convenient one-step preparation process. After thermal treatment, ordered pores are obtained, while the pristine metal oxide precursor shell can be converted to the (mixed) metal oxide matrix. Heat treatment under CO 2 leads to mixed-TiNb oxide/carbon hybrid materials. The highly porous derivative structure enhances electrolyte permeation. When tested as Li-ion battery electrodes, it shows a specific capacity of 335 mAh·g -1 at a rate of 10 mA·g -1 . After 1000 cycles at 250 mA·g -1 , the electrodes still provided a specific capacity of 191 mAh·g -1 .

Conversion/alloy active materials, such as ZnO, are one of the most promising candidates to replace graphite anodes in lithium-ion batteries. Besides a high specific capacity ( q ZnO = 987 mAh g -1 ), ZnO offers a high lithium-ion diffusion and fast reaction kinetics, leading to a high-rate capability, which is required for the intended fast charging of battery electric vehicles. However, lithium-ion storage in ZnO is accompanied by the formation of lithium-rich solid electrolyte interphase (SEI) layers, immense volume expansion, and a large voltage hysteresis. Nonetheless, ZnO is appealing as an anode material for lithium-ion batteries and is investigated intensively. Surprisingly, the conclusions reported on the reaction mechanism are contradictory and the formation and composition of the SEI are addressed in only a few works. In this work, we investigate lithiation, delithiation, and SEI formation with ZnO in ether-based electrolytes for the first time reported in the literature. The combination of operando and ex situ experiments (cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction, coupled gas chromatography and mass spectrometry, differential electrochemical mass spectrometry, and scanning electron microscopy) clarifies the misunderstanding of the reaction mechanism. We evidence that the conversion and alloy reaction take place simultaneously inside the bulk of the electrode. Furthermore, we show that a two-layered SEI is formed on the surface. The SEI is decomposed reversibly upon cycling. In the end, we address the issue of the volume expansion and associated capacity fading by incorporating ZnO into a mesoporous carbon network. This approach reduces the capacity fading and yields cells with a specific capacity of above 500 mAh g -1 after 150 cycles.

Thin SiO x interlayers are often formed naturally during the deposition of transition metal oxides on silicon surfaces due to interfacial reaction. The SiO x layer, often only several atomic layers thick, becomes the interface between the Si and deposited metal oxide and can therefore influence the electrical properties and thermal stability of the deposited stack. This work explores the potential benefits of controlling the properties of the SiO x interlayer by the introduction of pregrown high-quality SiO x which also inhibits the formation of low-quality SiO x from the metal-oxide deposition process. This work demonstrates that a high-quality pregrown SiO x can reduce the interfacial reaction and results in a more stoichiometric MoO x with improved surface passivation and thermal stability linked to its lower D it . Detailed experimental data on carrier selectivity, carrier transport efficiency, annealing stability up to 250 °C, and in-depth material analysis are presented.

The ecofriendly combustion synthesis (ECS) and self-combustion synthesis (ESCS) have been successfully utilized to deposit high- k aluminum oxide (AlO x ) dielectrics at low temperatures and applied for aqueous In 2 O 3 thin-film transistors (TFTs) accordingly. The ECS and ESCS processes facilitate the formation of high-quality dielectrics at lower temperatures compared to conventional methods based on an ethanol precursor, as confirmed by thermal analysis and chemical composition characterization. The aqueous In 2 O 3 TFTs based on ECS and ESCS-AlO x show enhanced electrical characteristics and counterclockwise transfer-curve hysteresis. The memory-like counterclockwise behavior in the transfer curve modulated by the gate bias voltage is comparable to the signal modulation by the neurotransmitters. ECS and ESCS transistors are employed to perform synaptic emulation; various short-term and long-term memory functions are emulated with low operating voltages and high excitatory postsynaptic current levels. High stability and reproducibility are achieved within 240 pulses of long-term synaptic potentiation and depression. The synaptic emulation functions achieved in this work match the demand for artificial neural networks (ANN), and a multilayer perceptron (MLP) is developed using an ECS-AlO x synaptic transistor for image recognition. A superior recognition rate of over 90% is achieved based on ECS-AlO x synaptic transistors, which facilitates the implementation of the metal-oxide synaptic transistor for future neuromorphic computing via an ecofriendly route.

Metal oxide semiconductors doped with additional inorganic cations have insufficient electron mobility for next-generation electronic devices so strategies to realize the semiconductors exhibiting stability and high performance are required. To overcome the limitations of conventional inorganic cation doping to improve the electrical characteristics and stability of metal oxide semiconductors, we propose solution-processed high-performance metal oxide thin-film transistors (TFTs) by incorporating polyaniline (PANI), a conductive polymer, in a metal oxide matrix. The chemical interaction between the metal oxide and PANI demonstrated that the defect sites and crystallinity of the semiconductor layer are controllable. In addition, the change in oxygen-related chemical bonding of PANI-doped indium oxide (InO x ) TFTs induces superior electrical characteristics compared to pristine InO x TFTs, even though trace amounts of PANI are doped in the semiconductor. In particular, the average field-effect mobility remarkably enhanced from 15.02 to 26.58 cm 2 V -1 s -1 , the on/off current ratio improved from 10 8 to 10 9 , and the threshold voltage became close to 0 V actually from -7.9 to -1.4 V.

Information about the surrounding atmosphere at a real timescale significantly relies on available gas sensors to be efficiently combined into multisensor arrays as electronic olfaction units. However, the array's performance is challenged by the ability to provide orthogonal responses from the employed sensors at a reasonable cost. This issue becomes more demanded when the arrays are designed under an on-chip paradigm to meet a number of emerging calls either in the internet-of-things industry or in situ noninvasive diagnostics of human breath, to name a few, for small-sized low-powered detectors. The recent advances in additive manufacturing provide a solid top-down background to develop such chip-based gas-analytical systems under low-cost technology protocols. Here, we employ hydrolytically active heteroligand complexes of metals as ink components for microplotter patterning a multioxide combinatorial library of chemiresistive type at a single chip equipped with multiple electrodes. To primarily test the performance of such a multisensor array, various semiconducting oxides of the p- and n- conductance origins based on pristine and mixed nanocrystalline MnO x , TiO 2 , ZrO 2 , CeO 2 , ZnO, Cr 2 O 3 , Co 3 O 4 , and SnO 2 thin films, of up to 70 nm thick, have been printed over hundred μm areas and their micronanostructure and fabrication conditions are thoroughly assessed. The developed multioxide library is shown to deliver at a range of operating temperatures, up to 400 °C, highly sensitive and highly selective vector signals to different, but chemically akin, alcohol vapors (methanol, ethanol, isopropanol, and n -butanol) as examples at low ppm concentrations when mixed with air. The suggested approach provides us a promising way to achieve cost-effective and well-performed electronic olfaction devices matured from the diverse chemiresistive responses of the printed nanocrystalline oxides.

High-entropy oxides (HEOs) have attracted increasing interest owing to their unique structures and fascinating physicochemical properties. Spherical mesoporous HEOs further inherit the advantages of spherical mesoporous materials including high surface area and tunable pore size. However, it is still a huge challenge to construct HEOs with uniform spheres and a mesoporous framework. Herein, a wet-chemistry sol-gel strategy is demonstrated for the synthesis of spherical mesoporous HEOs (e.g., Ni-Co-Cr-Fe-Mn oxide) with high specific surface area (42-143 m 2 /g), large pore size (5.5-8.3 nm), unique spherical morphology (∼55 nm), and spinel structure without any impure crystal phase using polyphenol as a polymerizable ligand. The metal/polyphenol-formaldehyde resin colloidal spheres are first synthesized via a sol-gel process. Because of their abundant catechol groups and strong chelating ability with different metal species, polyphenols can not only accommodate five different metal ions in their networks but also be well polymerized by formaldehyde to form colloidal spheres. After calcination, the metal species aggregate together to form HEOs, while the organic resin is fully decomposed to produce mesopores. Because of the open framework with accessible mesopores, they could be used as a peroxymonosulfate catalyst for degradation of organic pollutants and a nanoplatform for efficient detection of DNA. This work demonstrates a straightforward sol-gel strategy for design and synthesis of spherical mesoporous high-entropy materials, which would promote the exploration of new properties of high-entropy materials and extend their application.

Highly efficient redox reaction of active electrode materials is the guarantee for achieving high energy density for energy storage devices. Here, we design a triangle of the electrode material involving the P-N junction between NiO (p-type) and MoO 3 (n-type) and electron trajectory deviation between gold nanoparticles with NiO or MoO 3 . This optimized fundamental triangle structure could facilitate the redox reaction of a metal oxide, and thus the fabricated ternary nanocomposites exhibit excellent electrochemical performance. At a lower current density (0.5 A g -1 ), the mass specific capacitance of a single electrode can reach 943.3 F g -1 , while the NiO/MoO 3 tested under the same conditions only has a specific capacitance of 278.9 F g -1 . The assembled asymmetric device with activated carbon shows a higher capacitance retention rate of 98.7% after long-term cycling under different current densities, and a maximum energy density of 28.9 W h kg -1 (power density of 400.1 W kg -1 ). The crucial prerequisite of this strategy is the lower work function of gold nanoparticles compared with active materials, which significantly reduce the activation energy of NiO/MoO 3 and the formed P-N junction between p-type NiO with n-type MoO 3 in their contact interfaces. This novel design of a triangle structure could be expected to be applied in other materials to develop a kind of energy storage device with excellent electrochemical performance.

Creating new architectures combined with super diverse materials for achieving more excellent performances has attracted great attention recently. Herein, we introduce a novel dual metal (oxide) microsphere reinforced by vertically aligned carbon nanotubes (CNTs) and covered with a titanium oxide metal ion-transfer diffusion layer. The CNTs penetrate the oxide particles and buffer structural volume change while enhancing electrical conductivity. Meanwhile, the external TiO 2 -C shell serves as a transport pathway for mobile metal ions (e.g., Li + ) and acts as a protective layer for the inner oxides by reducing the electrolyte/metal oxide interfacial area and minimizing side reactions. The proposed design is shown to significantly improve the stability and Coulombic efficiency (CE) of metal (oxide) anodes. For example, the as-prepared MnO-CNTs@TiO 2 -C microsphere demonstrates an extremely high capacity of 967 mA h g -1 after 200 cycles, where a CE as high as 99% is maintained. Even at a harsh rate of 5 A g -1 (ca. 5 C), a capacity of 389 mA h g -1 can be maintained for thousands of cycles. The proposed oxide anode design was combined with a nickel-rich cathode to make a full-cell battery that works at high voltage and exhibits impressive stability and life span.

Metal-organic framework (MOF) fibrous composites were synthesized in a variety of methods in attempt to incorporate the highly effective reactivity of MOFs into a more facile and applicable format. Recent advances have demonstrated incorporating a metal oxide nucleation surface or reactive layer promotes conformal, well-adhered MOF growth on substrates. These materials have demonstrated promising reactivity in capturing or degrading chemical warfare agents and simulants. Here, we examine the mechanisms for MOF nucleation from metal oxide thin films to explore why some metal oxide sources are better suited for one synthesis mechanism over another. We isolate metal oxide extent of hydroxylation as an indicative factor as to whether the film serves as a nucleation promoter or may be converted directly to the MOF thin films. MOF-525 growth on Al 2 O 3 , TiO 2 , and ZnO coated fibers is demonstrated to corroborate these findings and used to degrade chemical warfare agent simulant dimethyl-4-nitrophenyl phosphate.

Memristors have shown an extraordinary potential to emulate the plastic and dynamic electrical behaviors of biological synapses and have been already used to construct neuromorphic systems with in-memory computing and unsupervised learning capabilities; moreover, the small size and simple fabrication process of memristors make them ideal candidates for ultradense configurations. So far, the properties of memristive electronic synapses (i.e., potentiation/depression, relaxation, linearity) have been extensively analyzed by several groups. However, the dynamics of electroforming in memristive devices, which defines the position, size, shape, and chemical composition of the conductive nanofilaments across the device, has not been analyzed in depth. By applying ramped voltage stress (RVS), constant voltage stress (CVS), and pulsed voltage stress (PVS), we found that electroforming is highly affected by the biasing methods applied. We also found that the technique used to deposit the oxide, the chemical composition of the adjacent metal electrodes, and the polarity of the electrical stimuli applied have important effects on the dynamics of the electroforming process and in subsequent post-electroforming bipolar resistive switching. This work should be of interest to designers of memristive neuromorphic systems and could open the door for the implementation of new bioinspired functionalities into memristive neuromorphic systems.

Due to recent breakthroughs in silicon photonics, sub-band-gap photodetection in silicon (Si) has become vital to the development of next-generation integrated photonic devices for telecommunication systems. In particular, photodetection in Si using complementary metal-oxide semiconductor (CMOS) compatible materials is in high demand for cost-effective integration. Here, we achieve broad-band near-infrared photodetection in Si/metal-oxide Schottky junctions where the photocurrent is generated from interface defects induced by aluminum-doped zinc oxide (AZO) films deposited on a Si substrate. The combination of photoexcited carrier generation from both interface defect states and intrinsic Si bulk defect states contributes to a photoresponse of 1 mA/W at 1325 nm and 0.22 mA/W at 1550 nm with zero-biasing. From a fit to the Fowler equation for photoemission, we quantitatively determine the individual contributions from these effects. Finally, using this analysis, we demonstrate a gold-nanoparticle-coated photodiode that has three distinct photocurrent responses resulting from hot carriers in the gold, interface defects from the AZO, and bulk defects within the Si. The hot carrier response is found to dominate near the band gap of Si, while the interface defects dominate for longer wavelengths.

Defects engineering can broaden the absorption band of wide band gap van der Waals (vdW) materials to the visible or near-IR regime at the expense of material stability and photoresponse speed. Herein, we introduce an atomic intercalation method that brings the wide band gap vdW α-MoO 3 for vis-MIR broadband optoelectronic conversion. We confirm experimentally that intercalation significantly enhances photoabsorption and electrical conductivity buts effects negligible change to the lattice structure as compared with ion intercalation. Charge transfer from the Sn atom to the lattices induces an optoelectrical change. As a result, the Sn-intercalated α-MoO 3 shows room temperature, air stable, broadband photodetection ability from 405 nm to 10 μm, with photoresponsivity better than 9.0 A W -1 in 405-1500 nm, ∼0.4 A W -1 at 3700 nm, and 0.16 A W -1 at 10 μm, response time of ∼0.1 s, and peak D* of 7.3 × 10 7 cm Hz 0.5 W -1 at 520 nm. We further reveal that photothermal effect dominates in our detection range by real-time photothermal-electrical measurement, and the materials show a high temperature coefficient of resistance value of -1.658% K -1 at 300 K. These results provide feasible route for designing broadband absorption materials for photoelectrical, photothermal, or thermal-electrical application.

Praseodymium-doped indium zinc oxide (PrIZO) has been employed as the channel layer of thin-film transistors (TFTs). The TFTs with Pr doping exhibited a remarkable suppression of the light-induced instability. A negligible photo-response and remarkable enhancement in negative gate bias stress under illumination (NBIS) were achieved in the PrIZO-TFTs. Meanwhile, the PrIZO-TFTs showed reasonable characteristics with a high-field-effect mobility of 26.3 cm 2 /V s, SS value of 0.28 V/decade, and I on / I off ratio of 10 8 . X-ray photoelectron spectroscopy, microwave photoconductivity decay, and photoluminescence spectra were employed to analyze the effects of the Pr concentrations on the performance of PrIZO-TFTs. We disclosed that acceptor-like trap states induced by Pr ions might lead to the suppression of photo-induced carrier in conduction band, which is a new strategy for improving illumination stability of amorphous oxide semiconductors. Finally, a prototype of fully transparent AMOLED display was successfully fabricated to demonstrate the potential of Pr-doping TFTs applied in transparent devices.

MoO 3 is widely used in polymer-based organic solar cells as an anode buffer layer because of its high workfunction and formation of a strong dipole at the MoO 3 /polymer interface facilitating charge transfer across the MoO 3 /polymer interface. In the present work, we show that exposure of the MoO 3 /polymer interface to moisture attracts water molecules to the interface via diffusion. Because of their own strong dipole, water molecules counter the dipole at the MoO 3 /polymer interface. As a consequence, the charge transfer across the MoO 3 /polymer will reduce and affect the charge transport across the interface. The outcome of this work thus suggests that it is critical to keep the MoO 3 /polymer interface moisture-free, which requires special precautions in device fabrications. The composition of the MoO 3 /P3HT:PC 61 BM interface is analyzed with X-ray photoelectron spectroscopy and the depth profiling technique, neutral impact collision ion scattering spectroscopy. The results show that the concentration of oxygen increases upon exposure but leaves the oxidation state of Mo unchanged. The valence electron spectroscopy technique shows that the dipole across the MoO 3 /P3HT:PC 61 BM interface decreases even for short-time exposure to atmosphere because of the diffusion of water molecules to the interface. The far-ranging consequences for organic electronic devices are discussed.

In recent years, many solution-processed oxide transistors have been reported with mobility rivaling or exceeding their vacuum-deposited counterparts. Here, we show that water absorption from the environment by solution-processed dielectric materialsexplains this enhanced mobility. By monitoring the water content of Al 2 O 3 , ZrO 2 , and bilayer dielectric materials, we demonstrate how water absorption by the dielectric affects electrical characteristics in solution-processed metal oxide transistors. These effects, including capacitance-frequency dispersion, counterclockwise hysteresis in transfer curves, and high channel mobility, are elucidated by electron transfer between the gate/channel and trap states within the band gap of the dielectric created by the water.

This study introduces a cyclical annealing technique that enhances the reliability of amorphous indium-gallium-zinc-oxide (a-IGZO) via-type structure thin film transistors (TFTs). By utilizing this treatment, negative gate-bias illumination stress (NBIS)-induced instabilities can be effectively alleviated. The cyclical annealing provides several cooling steps, which are exothermic processes that can form stronger ionic bonds. An additional advantage is that the total annealing time is much shorter than when using conventional long-term annealing. With the use of cyclical annealing, the reliability of the a-IGZO can be effectively optimized, and the shorter process time can increase fabrication efficiency.

Interfacial charge transport in optoelectronic devices is dependent on energetic alignment that occurs via a number of physical and chemical mechanisms. Herein, we directly connect device performance with measured thickness-dependent energy-level offsets and interfacial chemistry of 1,2-ethanedithiol-treated lead sulfide (PbS) quantum dots and molybdenum oxide. We show that interfacial energetic alignment results from partial charge transfer, quantified via the chemical ratios of Mo 5+ relative to Mo 6+ . The combined effect mitigates leakage current in both the dark and the light, relative to a metal contact, with an overall improvement in open circuit voltage, fill factor, and short circuit current.

The submicrometer resolution printing of various metal acetylacetonate complex inks including Fe, V, Mn, Co, Ni, Zn, Zr, Mo, and In was enabled by a robust ink formulation scheme which adopted a ternary solvent system where solubility, surface wettability, and drying as well as absorption behavior on a polydimethylsiloxane sheet were optimized. Hydrogen plasma in heated conditions resulted in bombarded, resistive, or conductive state depending on the temperature and the metal species. With a conductivity-bestowed layer of MoO x and a plasma-protecting layer of ZrO x situated on the top of an IGZO layer, a solution-processed TFT exhibiting an average mobility of 0.17 cm 2 /(V s) is demonstrated.

Zinc-oxide (ZnO) is widely used as an n-type electron transporting layer (ETL) for quantum dot (QD) light-emitting diode (QLED) because various metal doping can be possible and ZnO nanoparticle can be processed at low temperatures. We report here a Li- and Mg-doped ZnO, MLZO, which is used for ETL of highly efficient and long lifetime QLEDs. Co-doping, Mg and Li, in ZnO increases its band gap and electrical resistivity and thus can enhance charge balance in emission layer (EML). It is found also that the O-H concentration at the oxide surface decreases and exciton decay time of QDs on the metal oxide increases by co-doping in ZnO. The inverted green QLEDs with MLZO ETL exhibits the maximum current efficiency (CE max ) of 69.1 cd/A, power efficiency (PE max ) of 73.8 lm/W, and external quantum efficiency (EQE max ) of 18.4%. This is at least two times higher compared with the efficiencies of the QLEDs with Mg-doped ZnO ETL. The optimum Li and Mg concentrations are found to be 10% each. The deep-red, red, light-blue, and deep-blue QLEDs with MLZO ETLs exhibit the CE max of 6.0, 22.3, 1.9, and 0.5 cd/A, respectively. The MLZO introduced here can be widely used as ETL of highly efficient QLEDs.

The unsatisfactory rate capability and poor cycle stability are two major obstacles for polyoxometalates (POMs) in lithium-ion storage. On the other hand, how to endow POMs with 3D macrostructures for further practice is a challenge. To this end, a facile hydrothermal strategy was practiced to fabricate Co 8 W 12 O 42 (OH) 4 (H 2 O) 8 microcrystals or CoWO 4 aggregates onto the foamed substrate (denoted as CoW-POM and CoW-Salt, respectively). Integrating the extraordinary redox stability and lattice deformability of POMs with the excellent volume accommodation, the as-prepared CoW-POM presents an extraordinary better electrochemical performance (specific capacity, rate capability, and cycle life) than that of CoW-Salt. In detail, the CoW-POM can deliver a reversible capacity of 737.8 mA h g -1 at the current density of 0.1 A g -1 and provide a capacity retention of 90.1% even after 100 cycles. This work not only promotes the application of POMs in energy storage and conversion but also guides an effect methodology to endow POMs with 3D structures.

ZnO nanoparticles (NPs) are widely used as the electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) owing to their suitable electrical properties. However, because of the well-aligned conduction band levels, electrons in QDs can be spontaneously transferred to adjacent ZnO NPs, leading to severe exciton dissociation, which reduces the proportion of radiative recombination and deteriorates the device efficiency. In this work, Al-doped ZnO NPs are thoroughly investigated as a replacement of ZnO for QLEDs. The energy band structures of Al-doped ZnO are modified by adjusting the concentration of Al dopants. With the increasing Al content, the work function and the conduction band edge of ZnO are gradually raised, and thus the charge transfer at the interface of QDs/ETL is effectively suppressed. Consequently, the green QLEDs with 10% Al-doped ZnO NPs exhibit maximum current efficiency and external quantum efficiency of 59.7 cd/A and 14.1%, which are about 1.8-fold higher than 33.3 cd/A and 7.9% of the devices with undoped ZnO NPs. Our work suggests that Al-doped ZnO NPs can serve as a good electron transport/injection material in QLEDs and other optoelectronic devices.

Technical development for thin-film fabrication is essential for emerging metal-oxide (MO) electronics. Although impressive progress has been achieved in fabricating MO thin films, the challenges still remain. Here, we report a versatile and general thermal-induced nanomelting technique for fabricating MO thin films from the fiber networks, briefly called fiber-to-film (FTF) process. The high quality of the FTF-processed MO thin films was confirmed by various investigations. The FTF process is generally applicable to numerous technologically relevant MO thin films, including semiconducting thin films (e.g., In 2 O 3 , InZnO, and InZrZnO), conducting thin films (e.g., InSnO), and insulating thin films (e.g., AlO x ). By optimizing the fabrication process, In 2 O 3 /AlO x thin-film transistors (TFTs) were successfully integrated by fully FTF processes. High-performance TFT was achieved with an average mobility of ∼25 cm 2 /(Vs), an on/off current ratio of ∼10 7 , a threshold voltage of ∼1 V, and a device yield of 100%. As a proof of concept, one-transistor-driven pixel circuit was constructed, which exhibited high controllability over the light-emitting diodes. Logic gates based on fully FTF-processed In 2 O 3 /AlO x TFTs were further realized, which exhibited good dynamic logic responses and voltage amplification by a factor of ∼4. The FTF technique presented here offers great potential in large-area and low-cost manufacturing for flexible oxide electronics.

A self-aligned inkjet printing process has been developed to construct small channel metal oxide (a-IGZO) thin-film transistors (TFTs) with independent bottom gates on transparent glass substrates. Poly(methylsilsesquioxane) was used to pattern hydrophobic banks on the transparent substrate instead of commonly used self-assembled octadecyltrichlorosilane. Photolithographic exposure from backside using bottom-gate electrodes as mask formed hydrophilic channel areas for the TFTs. IGZO ink was selectively deposited by an inkjet printer in the hydrophilic channel region and confined by the hydrophobic bank structure, resulting in the precise deposition of semiconductor layers just above the gate electrodes. Inkjet-printed IGZO TFTs with independent gate electrodes of 10 μm width have been demonstrated, avoiding completely printed channel beyond the broad of the gate electrodes. The TFTs showed on/off ratios of 10 8 , maximum mobility of 3.3 cm 2 V -1 s -1 , negligible hysteresis, and good uniformity. This method is conductive to minimizing the area of printed TFTs so as to the development of high-resolution printing displays.

The electrografting of [Ru(ttt)(tpy-C 6 H 4 -N 2 + , where "ttt" is 4,4',4″-tri-tert-butyl-2,2':6',2″-terpyridine, was investigated on several wide band gap metal oxide surfaces (TiO 3+ , where "ttt" is 4,4',4″-tri-tert-butyl-2,2':6',2″-terpyridine, was investigated on several wide band gap metal oxide surfaces (TiO 2 , SnO 2 , ZrO 2 , ZnO, In 2 O 3 :Sn) and compared to structurally analogous sensitizers that differed only by the anchoring group, i.e., -PO 3 H 2 and -COOH. An optimized procedure for diazonium electrografting to semiconductor metal oxides is presented that allowed surface coverages that ranged between 4.7 × 10 -8 and 10.6 × 10 -8 depending on the nature of the metal oxide. FTIR analysis showed the disappearance of the diazonium stretch at 2266 cm -2 depending on the nature of the metal oxide. FTIR analysis showed the disappearance of the diazonium stretch at 2266 cm -1 after electrografting. XPS analysis revealed a characteristic peak of Ru 3d at 285 eV as well as a peak at 531.6 eV that was attributed to O 1s in Ti-O-C bonds. Photocurrents were measured to assess electron injection efficiency of these modified surfaces. The electrografted sensitizers exhibited excellent stability across a range of pHs spanning from 1 to 14, where classical binding groups such as carboxylic and phosphonic derivatives were hydrolyzed.

Metal-organic frameworks (MOFs) are hybrid inorganic-organic materials that can be used as effective precursors to prepare various functional nanomaterials for energy-related applications. Nevertheless, most MOF-derived metal oxides exhibit low electrical conductivity and mechanical strain. These characteristics limit their electrochemical performance and hamper their practical application. Herein, we report a rational strategy for enhancing the lithium storage performance of MOF-derived metal oxide. The hierarchically porous Co 3 O 4 @NGN is successfully prepared by embedding ZIF-67-derived Co 3 O 4 particles in a nitrogen-doped graphene network (NGN). The high electrical conductivity and porous structure of the NGN accelerates the diffusion of electrolyte ions and buffers stress resulting from the volume changes of Co 3 O 4 . As an anode material, the Co 3 O 4 @NGN shows high capacity (1030 mA h g -1 at 100 mA g -1 ), outstanding rate performance (681 mA h g -1 at 1000 mA g -1 ), and good cycling stability (676 mA h g -1 at 1000 mA g -1 after 400 cycles).

Nanostructured metal oxides with cationic or anionic deficiency find applications in a wide range of technological areas including the energy sector and environment. However, a facile route to prepare such materials in bulk with acceptable reproducibility is still lacking; many synthesis techniques are still only bench-top and cannot be easily scaled-up. Here, we report that the benzyl alcohol (BA)-mediated method is capable of producing a host of nanostructured metal oxides (MO x , where M = Ti, Zn, Ce, Sn, In, Ga, or Fe) with inherent nonstoichiometry. It employs multifunctional BA as a solvent, a reducing agent, and a structure-directing agent. Depending on the oxidation states of metal, elemental or nonstoichiometric oxide forms are obtained. Augmented photoelectrochemical oxidation of water under visible light by some of these nonstoichiometric oxides highlights the versatility of the BA-mediated synthesis protocol.

Inorganic-organic hybrid perovskite solar cells (PSCs) are promising devices for providing future clean energy because of their low cost, ease of fabrication, and high efficiencies, similar to those of silicon solar cells. These materials have been investigated for their potential use in bifacial PSCs, which can absorb light from both sides of the electrodes. Here, we fabricated bifacial PSCs featuring transparent BCP/Ag/MoO 3 rear electrodes, which we formed through low-temperature processing using thermal evaporation methods. We employed a comprehensive optical distribution program to calculate the distributions of the optical field intensities with constant thicknesses of the absorbing layer in the top electrode configuration. The best PSC having a transparent BCP/Ag/MoO 3 electrode achieved PCEs of 13.49% and 9.61% when illuminated from the sides of the indium tin oxide and BCP/Ag/MoO 3 electrodes, respectively. We observed significant power enhancement when operating this PSC using mirror reflectors and bifacial light illumination from both sides of the electrodes.

We have developed highly sensitive, low-power gas sensors through the novel integration method of porous SnO 2 nanotubes (NTs) on a micro-electro-mechanical-systems (MEMS) platform. As a template material, ZnO nanowires (NWs) were directly synthesized on beam-shaped, suspended microheaters through an in situ localized hydrothermal reaction induced by local thermal energy around the Joule-heated area. Also, the liquid-phase deposition process enabled the formation of a porous SnO 2 thin film on the surface of ZnO NWs and simultaneous etching of the ZnO core, eventually to generate porous SnO 2 NTs. Because of the localized synthesis of SnO 2 NTs on the suspended microheater, very low power for the gas sensor operation (<6 mW) has been realized. Moreover, the sensing performance (e.g., sensitivity and response time) of synthesized SnO 2 NTs was dramatically enhanced compared to that of ZnO NWs. In addition, the sensing performance was further improved by forming SnO 2 -ZnO hybrid nanostructures due to the heterojunction effect.

Amorphous zinc tin oxide (ZTO) thin films are accessible by a molecular precursor approach using mononuclear zinc(II) and tin(II) compounds with methoxyiminopropionic acid ligands. Solution processing of two precursor solutions containing a mixture of zinc and tin(II)-methoxyiminopropinato complexes results in the formation of smooth homogeneous thin films, which upon calcination are converted into the desired semiconducting amorphous ZTO thin films. ZTO films integrated within a field-effect transistor (FET) device exhibit an active semiconducting behavior in the temperature range between 250 and 400 °C, giving an increased performance, with mobility values between μ = 0.03 and 5.5 cm 2 /V s, with on/off ratios increasing from 10 5 to 10 8 when going from 250 to 400 °C. Herein, our main emphasis, however, was on an improved understanding of the material transformation pathway from weak to high performance of the semiconductor in a solution-processed FET as a function of the processing temperature. We have correlated this with the chemical composition and defects states within the microstructure of the obtained ZTO thin film via photoelectron spectroscopy (X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy), Auger electron spectroscopy, electron paramagnetic resonance spectroscopy, atomic force microscopy, and photoluminescence investigations. The critical factor observed for the improved performance within this ZTO material could be attributed to a higher tin concentration, wherein the contributions of point defects arising from the tin oxide within the final amorphous ZTO material play the dominant role in governing the transistor performance.

Electrochemical conversion reactions of metal oxides provide a new avenue to build high capacity anodes for sodium-ion batteries. However, the poor rate performance and cyclability of these conversion anodes remain a significant challenge for Na-ion battery applications because most of the conversion anodes suffer from sluggish kinetics and irreversible structural change during cycles. In this paper, we report an Fe 2 O 3 single crystallites/reduced graphene oxide composite (Fe 2 O 3 /rGO), where the Fe 2 O 3 single crystallites with a particle size of ∼300 nm were uniformly anchored on the rGO nanosheets, which provide a highly conductive framework to facilitate electron transport and a flexible matrix to buffer the volume change of the material during cycling. This Fe 2 O 3 /rGO composite anode shows a very high reversible capacity of 610 mAh g -1 at 50 mA g -1 , a high Coulombic efficiency of 71% at the first cycle, and a strong cyclability with 82% capacity retention after 100 cycles, suggesting a potential feasibility for sodium-ion batteries. More significantly, the present work clearly illustrates that an electrochemical conversion anode can be made with high capacity utilization, strong rate capability, and stable cyclability through appropriately tailoring the lattice structure, particle size, and electronic conduction channels for a simple transition-metal oxide, thus offering abundant selections for development of low-cost and high-performance Na-storage electrodes.

We developed a new and simple solvent vapor-assisted thermal annealing (VA) procedure which can reduce grain boundaries in a perovskite film for fabricating highly efficient perovskite solar cells (PSCs). By recycling of solvent molecules evaporated from an as-prepared perovskite film as a VA vapor source, named the pot-roast VA (PR-VA) method, finely controlled and reproducible device fabrication was achieved for formamidinium (FA) and methylammonium (MA) mixed cation-halide perovskite (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 . The mixed perovskite was crystallized on a low-temperature prepared brookite TiO 2 mesoporous scaffold. When exposed to very dilute solvent vapor, small grains in the perovskite film gradually unified into large grains, resulting in grain boundaries which were highly reduced and improvement of photovoltaic performance in PSC. PR-VA-treated large grain perovskite absorbers exhibited stable photocurrent-voltage performance with high fill factor and suppressed hysteresis, achieving the best conversion efficiency of 18.5% for a 5 × 5 mm 2 device and 15.2% for a 1.0 × 1.0 cm 2 device.