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Abstract Bimetallic (zinc-iron) oxide with a pillar-like morphology is decorated over graphene films. The electrosprayed composite demonstrates good electrochemical performance as an anode material for lithium-ion batteries. Scanning and transmission electron microscopy images confirm the effective decoration of graphene sheets with bimetallic Zn-Fe oxide particles. The composite shows a high capacity of 1601 mAh⋅g−1 at 100 mA·g−1 owing to its unique layer-particle morphology. The anode material exhibits excellent capacity retention of 77% (∼1235 mAh⋅g−1 at 100 mA·g−1) after 100 cycles, due to buffering of volumetric strain in the metal oxide by flexible conductive graphene sheets. Zinc forms an alloy with the lithium ions, and the graphene sheets prevent particle agglomeration, keeping transport distances within particles small. Thus, synthesizing a composite of graphene with Zn-Fe oxides via electrospray deposition is a promising method for preparing high-performance anode materials for lithium-ion batteries. Highlights • G/ZnFe 2 O 4 as an anode for LIB, it exhibits 1235 mAh·g-1 after 100 cycles. • The excellent electrochemical performance, high capacity and cycling stability were achieved. • Graphene decorated nanostructured ZnFe 2 O 4 attributed to numerous active sites and interspaces. • Facile electro-spraying of active material straightaway on stainless steel spacer. [ABSTRACT FROM AUTHOR]

Abstract Electrosprayed BiVO 4 adopts a nanopillar structure formed by diffusion-limited aggregation, which maximizes the surface area of the nanopillars. However, increasing the interfacial area between an electrode and the electrolyte through nanostructuring enhances the overall interfacial activity for solar water splitting. For this purpose, the pH of the precursor solution used for electrospraying BiVO 4 was altered by adding ammonium hydroxide, thereby inducing a drastic change in the morphology of BiVO 4. The previously demonstrated nanopillar morphology of electrosprayed BiVO 4 was transformed into a nanofern structure that increased the photocurrent density of BiVO 4 from 0.82 to 1.23 mA·cm−2 at 1.2 V vs. Ag/AgCl. The produced films were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and electrochemical impedance spectroscopy. Highlights • BiVO 4 nanopillar morphology were tuned to nanoferns with a facile one-pot method. • Nanoferns showed the fast photoresponse due to enhanced photoelectrochemical sites. • The photocurrent density of BiVO 4 nanoferns reached to 1.23 mA·cm−2 at 1.2 V vs Ag/AgCl. • The structural and morphological properties of BiVO 4 nanoferns were characterized. [ABSTRACT FROM AUTHOR]

Abstract This manuscript reports the preparation, characterization, and testing of stable high-capacity lithium-ion battery anodes based on graphitic carbon nitride (g-CN) nanosheets hosting ZnFe 2 O 4 nanoparticles (ZFCN). The ZFCN is prepared by a one-pot thermal process, then supersonic cold spraying is used to rapidly deposit films with a lamellar morphology that allows enhanced capacity retention by preventing particle agglomeration. The presence of g-CN nanosheets minimizes degradation of ZnFe 2 O 4 by providing a buffering space during the lithiation/delithiation process. The ZFCN composite anodes exhibit first reversible capacities of 1550 mAh·g−1 at 50 mA·g−1 and up to 934 mAh·g−1 at 1000 mA·g−1 after 20 cycles. The superior electrochemical performance and capacity retention (88% after 160 cycles at 100 mA·g−1 relative to the first reversible capacity) are attributed to highly reversible alloying/conversion mechanisms. The combination of high performance and stability with the use of low-cost earth-abundant elements and scalable processing approaches gives this ZFCN composite immense potential for use as a stable high-performance anode material for lithium-ion batteries. • ZnFe 2 O 4 /g-C 3 N 4 films were fabricated as LIB anode via rapid supersonic spraying. • Lamellar morphology prevented particle agglomeration ensuing enhanced capacity retention. • High capacity retention of 93% is observed at 100 mA·g-1 after 70th cycle. • The ZFCN composite shows high capacity of 934 mAh·g-1 at 1000 mA·g-1 current rate. [ABSTRACT FROM AUTHOR]

Abstract Highly flexible, binder-free, scalable, and high-capacity lithium ion battery anodes were fabricated by ball-milling SnO 2 and ZnO 2 particles to form Zn 2 SnO 4 /SnO 2 ternary oxide particles that were supersonically sprayed over a large area of a flexible copper foil without using any binders. The addition of rGO promoted uniform distribution of the particles and enhanced the overall performance of the composite anodes, which showed excellent long-term stability and a reversible capacity of 1316 mAh·g−1 at a specific current of 100 mA g−1 after 100 cycles. The supersonic deposition promoted inter-particle cohesion as well as adhesion of the coating materials onto the flexible substrate. Without added binder, the potential adverse effects of using binders on the electrical properties of the anodes were eliminated. The morphology and composition of the samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The low-cost and scalable synthesis and deposition methods used here may offer a pathway for achieving commercially viable high-capacity anodes for various flexible electronic devices. Highlights • SnO 2 and ZnO 2 were ball-milled to form Zn 2 SnO 4 /SnO 2 ternary oxide particles. • Reduced graphite oxide (rGO) promoted uniform distribution of the particles. • The uniform distribution enhanced the overall electrode performance. • Supersonic deposition promoted interparticle cohesion & particle−substrate adhesion. [ABSTRACT FROM AUTHOR]

A binder-free nanocomposite consisting of ZnO nanoparticles (NPs) grown directly on graphene sheets by electrospraying was fabricated for use as an electrode material in supercapacitors. The optimal concentrations of graphene and ZnO NPs were determined from the capacitive characteristics of the composite. Scanning electron microscopy confirmed that the ZnO NPs grew in a uniformly distributed manner on the graphene sheets and that they exhibited negligible agglomeration. Further, X-ray diffraction analysis confirmed that ZnO growth was preferentially oriented along (100) plane in the ZnO/graphene composite. A symmetric supercapacitor fabricated using this composite exhibited an energy density of 67 mWh·cm −3 and power density of 6000 mW·cm −3 . The composite also showed good long-term cycling performance, retaining 90% of its capacitance after 1000 galvanostatic charge/discharge cycles. [ABSTRACT FROM AUTHOR]

We demonstrate the fabrication of core-shell SnO x /carbon nanofiber (CNF) composite mats via single-nozzle one-step electrospinning for use as flexible freestanding electrodes in supercapacitors. The freestanding and flexible nature of the composites is essential for their use in lightweight, portable, and foldable electronic devices and eliminates the need for a separate current collector. We fully characterized the structural and morphological properties of the SnO x /CNF mats and optimized the SnO x to CNF precursor ratio. The optimized SnO x /CNF-based symmetric supercapacitor exhibited a capacitance of 289 F·g −1 at a scan rate of 10 mV·s −1 . Moreover, it retained more than 88% of its initial capacitance after 5000 cycles, highlighting the long-term stability of supercapacitors based on these SnO x /CNF mats. [ABSTRACT FROM AUTHOR]

Titania (TiO 2 ) nanoparticles were uniformly distributed on and are well attached to reduced graphene oxide (rGO) by supersonic cold spraying. The process facilitated rapid production of lithium ion battery (LIB) anodes. Integration of TiO 2 with rGO not only enhanced the conductivity of the anode, but also prevented agglomeration of the titania nanoparticles, which facilitated uniform distribution of the nanoparticles and thus consistently reduced the electron diffusion length. Integration of rGO with TiO 2 widened the characteristic voltage range of the resulting rGO-TiO 2 composite (0.01–3 V) relative to that of pure TiO 2 , which enhanced the capacity during the lithiation process. Therefore, the LIB cell exhibited superior performance with long cycle durations even under high current rate. The optimal weight ratio of rGO to TiO 2 was found to be 1:1, which produced a retention capacity of 203 mA h g −1 at N = 300 cycle under a current rate of 1 C = 336 mA g −1 . Rapid production of rGO/TiO 2 nanocomposites via supersonic cold spraying may facilitate commercialization of high-quality LIB cells. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) decorated with tin oxide (SnO 2) is deposited on a fabric via supersonic spraying to produce wearable supercapacitor textiles. rGO improves the electrical conductivity of textiles, while SnO 2 provides energy storage capabilities. The synergetic effect of the combination of rGO and SnO 2 on the overall electrochemical performance of the supercapacitor was studied by varying the SnO 2 concentration. The intermixed rGO flakes and SnO 2 nanoparticles enhanced the charge transport within the composite electrode, ultimately improving the overall electrochemical performance. The porous structure of the fabric enables sufficient electrolyte diffusion into the deposited rGO and SnO 2 , to promote the interfacial activity between the active electrode and electrolyte. The optimal sample exhibited the highest specific capacitance of 1008 mF⋅cm−2 at a current loading of 1.5 mA⋅cm−2, with a capacitance retention of 93% after 10,000 cycles. Stretching and relaxing cyclic tests up to N = 1100 demonstrate the mechanical durability of the wearable supercapacitor. These promising results confirm that supersonic spraying is suitable for producing energy storage devices on wearable fabrics. Image 1 • Wearable supercapacitors comprising reduced graphene oxide and tin oxide were fabricated. • The intermixed rGO flakes and SnO 2 nanoparticles enhanced the charge transport. • The optimal sample exhibited the highest specific capacitance of 1008 mF cm−2 at a current loading of 1.5 mA cm−2. • The capacitance retention of 93% after 10,000 cycles was obtained. • Bending cycles up to N = 1100 demonstrated the mechanical durability of the wearable supercapacitor. [ABSTRACT FROM AUTHOR]

Herein, we present the facile growth of beehive-like NiFe 2 O 4 nanosheets over Ni nanocones for shorter electron transport distances in supercapacitor electrodes. The electrodeposited ultrathin nanosheets provide excellent electrode–electrolyte interfacial areas, thereby enabling superior electrochemical performances. Notably, the deposition duration is tuned to achieve abundant energy storage sites and controlled cavities for adequate electrolytic ion diffusion. The synergy of these advantageous cavities and active sites of beehive-like NiFe 2 O 4 nanosheets yields excellent stability with a capacitance retention of 95.3% after 10, 000 charging and discharging cycles of the nanosheet-based supercapacitor electrodes. At a high galvanostatic current rate of 5 A g−1, the capacitance was 483 F g−1. The optimal two-dimensional ultrathin NiFe 2 O 4 beehive nanostructure exhibits immense potential for high-energy-storage supercapacitor electrodes, paired with the required pseudocapacitive characteristics. • Facile growth of uniform beehive-like NiFe 2 O 4 nanosheets using electrodeposition. • Ultrathin beehive-like nanosheets with cavities show high electrochemical stability. • One-step synthesized NiFe 2 O 4 showed 95.3% capacitance retention after 10, 000 cycles. • High energy density of 40.3 Wh·kg−1 and power density of 5 kW kg−1 were achieved. [ABSTRACT FROM AUTHOR]

To prepare high-performance ZnO/C nanocomposite anode materials, dodecahedral ZIF-8 was first deposited on exfoliated reduced graphene oxide (rGO) by precipitation from methanol. The ZIF-8 was carbonized by annealing in argon to produce ZnO/C that retained the structure of the ZIF-8 template. ZIF-8-derived ZnO/C and ZnO/C/rGO were deposited over Cu substrates using low-cost, scalable supersonic cold spraying to facilitate the rapid production of Li-ion battery anodes. The synergy of the ZIF-8-derived dodecahedral nano-ZnO/C framework with rGO significantly enhanced conductivity, reduced aggregation, and shortened Li-ion transfer pathways. Electrochemical impedance spectroscopy showed enhanced Li-ion diffusion. The rGO/ZnO/C framework demonstrated a specific capacity of 1325 mAh·g−1 at a specific current of 100 mA·g−1. At a higher current of 2.5 A·g−1, the anode delivered a capacity of 525 mAh·g−1. The composite also showed a highly stable reversible capacity of 1063 mAh·g−1 after 300 cycles. The outstanding electrochemical performance of the rGO/ZnO/C sample was facilitated by the three-dimensional morphology of the exfoliated rGO and ZIF-8-derived dodecahedral porous ZnO/C structure. A quantitative comparison of specific capacity and capacity retention shows that the electrochemical performance of these rGO/ZnO/C composites exceeds that of previously-reported anodes based on ZnO, carbon, and/or rGO. • Dodecahedral ZIF-8 was deposited on exfoliated rGO by precipitation from methanol. • ZIF-8 derived ZnO/C and ZnO/C/rGO composites were produced by supersonic cold spraying. • The composite provided enhanced conductivity, reduced aggregation, and shortened Li-ion transfer pathways. • The composite showed 81% capacity retention after 300 cycles. [ABSTRACT FROM AUTHOR]

We demonstrate the supersonic cold-spray deposition of a Zn 2 SnO 4 /SnO 2 /carbon nanotube (CNT) composite as an exceptionally high-performance photoanode for photoelectrochemical water splitting. We optimized the photoanode thickness (number of deposition passes) and composition to achieve a maximum photocurrent density of 17.2 mA cm−2 at 1.78 V vs. reversible hydrogen electrode, with no additional catalysts or additives. The morphology of the deposited films, as characterized by scanning and transmission electron microscopy, comprises CNTs intermingled with Zn 2 SnO 4 and SnO 2 nanoparticles. The high electron concentration and charge transfer rate achieved by adding CNTs are demonstrated through Mott–Schottky and Nyquist analyses of electrochemical impedance spectroscopy (EIS) data. While we find no prior reports of Zn 2 SnO 4 /SnO 2 /CNT nanocomposites for water splitting, we demonstrate that this combination of ball-milled Zn 2 SnO 4 /SnO 2 nanoparticles mixed with CNTs is a promising candidate for high-performance solar water splitting with dramatically enhanced performance compared to previously-reported ZnO- and SnO-based photoanodes. • Supersonically-sprayed Zn 2 SnO 4 /SnO 2 /CNT photoanodes were fabricated for solar water splitting. • A maximum photocurrent density of 17.2 mA cm−2 at 1.78 V vs. RHE was recorded. • The PCD stabilized at a value above 6.5 mA cm−2 at a fixed voltage and remained constant. [ABSTRACT FROM AUTHOR]

We demonstrate fabrication of films of highly textured bismuth oxide (Bi 2 O 3 ) pillars via electrostatic spray deposition and test the performance of these films as photoanodes in photoelectrochemical water splitting. The β-Bi 2 O 3 and α-Bi 2 O 3 phases were identified and distinguished using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The β-Bi 2 O 3 pillars of optimized thickness exhibited a photocurrent density of 0.97 mA⋅cm −2  at 0.5 V vs Ag/AgCl. The tetragonal β-Bi 2 O 3 pillars had enhanced visible light absorbance compared to α-Bi 2 O 3 as well as other metal oxides like ZnO and TiO 2 . Tauc plot analysis of film absorbance showed a decrease in the bandgap of the β-Bi 2 O 3 phase to 2.5 eV. In Na 2 SO 3 electrolyte, a hole scavenger, the onset voltage for the β-Bi 2 O 3 phase was shifted to a more negative value (−0.4 V), which increased photocurrent density. The electron concentration reached its highest value of 9.1 × 10 20  cm −3 for the film with the highest photocurrent density. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) loaded Fe-Fe 3 C composite nanofibers were prepared via a supersonic blowing technique. After high temperature annealing, the resulting electrodes delivered an excellent reversible capacity of 558 mAh·g −1 at a current rate of 1500 mA g −1 at the 200 th cycle. The supersonic blowing facilitated rapid and simultaneous coupling of exfoliated rGO with the solution-blown nanofibers, which is difficult to achieve by electrospinning methods. The performance of the fabricated electrode is remarkably high compared to the previously reported values; thus, these anodes are promising for application in lithium ion batteries. [ABSTRACT FROM AUTHOR]

Highly uniform, mechanically stable, dense, and water-adsorbing MIL-100(Fe) films were fabricated via supersonic spraying, a rapid, high-throughput, and scalable method compatible with roll-to-roll processing. The film surface area (1667 m 2 g −1 ) was comparable to that of the nanoparticles from which it was prepared (2009 m 2 g −1 ), and was higher than previously reported values for MIL-100(Fe) films. The gas and water adsorption abilities of the film were tested by nitrogen physisorption and water adsorption at 30 °C. The supersonically sprayed film was mechanically resistant up to a critical scratching load of 1.84 N, higher than the critical scratchability loads of dip-coated or spin-coated films. In humidity-sensing applications, films that incorporated conductive Ag nanowires were highly responsive to environmental humidity, demonstrating applicability as water vapor sensors. The fabricated films were characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. [ABSTRACT FROM AUTHOR]

The wearable electronics market is growing exponentially and has benefited considerably from a versatile electrospinning technique capable of fabricating freestanding, binder-free fibers. Using this method in the current study, electrospun fibers were produced from a polymer-salt-ZIF-DMF solution. The obtained fibers were annealed to prepare Fe-ZnO/carbon nanofibers (CNFs), which exhibited a wide potential window of 0–1.6 V in an aqueous electrolyte (6 M KOH). Moreover, the composite fibers exhibited a large interfacial area between the electrode and electrolyte and reduced the ion transport distance during operation. Consequently, a high capacitance of 499 mF·cm–2 was attained at a current density of 5 mA·cm–2. Notably, high energy densities of 0.23–0.18 mWh·cm–2 were achieved owing to the excellent synergy between ZIF-7-derived ZnO and Fe-activated CNFs. The energy density of Fe-ZnO/CNF was approximately four times higher than that of ZnO/CNF at a power density of 16 mW·cm–2. Electrochemical stability testing through 10,000 galvanostatic charging–discharging cycles revealed a capacitance retention of ∼95 %. Practical applications and bendability tests of environmentally benign flexible supercapacitors underscored the potential of the freestanding electrodes in fabricating wearable, portable electronic devices. • Fe-ZnO/carbon nanofibers (CNFs) were fabricated using the polymer-salt-ZIF-DMF. • A high capacitance of 500 mF·cm–2 was attained at a current density of 5 mA·cm–2. • The energy density for Fe-ZnO/CNF was 4 times higher than those of ZnO/CNF without iron. • Electrochemical stability was tested via the galvanostatic charging–discharging cycles of 10,000. [ABSTRACT FROM AUTHOR]

Soft wearable electronics are being applied as state-of-the-art self-powered devices based on piezoelectric nanogenerators (PENGs), which provide flexible energy harvesters and sustainable energy generators. We introduce a composite of poly(vinylidene fluoride) (PVDF) and Fe 2 O 3 nanocube fillers coated via supersonic cold spraying to obtain substrate-free and flexible films for PENGs. The hydrothermally synthesized Fe 2 O 3 nanocubes induce shear stress between Fe 2 O 3 and PVDF during supersonic spraying. An optimized sample having 0.77 g Fe 2 O 3 in 1 g PVDF produces a piezopotential of 25.6 V and a short-circuit current of 70 μA. In addition, a maximum power density of 44.4 μW·cm−2 is achieved at a load resistance of 1 MΩ. Tapping and bending tests for 1800 s confirm the consistent generation of piezopotentials of 25.6 V and 1.5 V, respectively. The developed Fe 2 O 3 /PVDF PENG can power several light-emitting diodes, thus showing promise as a device for sustainable power supply. • Fe 2 O 3 nanocubes were synthesized by hydrothermal method. • The strain inflicted between Fe 2 O 3 nanocubes and PVDF increased the β-phase amount. • The optimized sample produced a piezopotential of 25 V and a short-circuit current of 70 μA. • The maximum power density was found to be 44.4 μW·cm−2 using the optimal sample. [ABSTRACT FROM AUTHOR]

We demonstrate a promising Fe 2 O 3 /ZnO/TiO 2 photoanode for photoelectrochemical water splitting. Passivation of the Fe 2 O 3 surface with thin layers of ZnO and TiO 2 enhances the water splitting photocurrent density of Fe 2 O 3. The increased photoelectrochemical activity of the hematite-based structure with heterojunctions, compared to that of bare Fe 2 O 3 , results from improved charge separation during water oxidation. The multilayered Fe 2 O 3 film exhibits a seven-fold improvement in photocurrent density (to 4.25 mA cm−2) compared with bare Fe 2 O 3 , due to suppression of electron–hole recombination. The transient photocurrent density and impedance were evaluated to assess the effect of the passivation layer thickness and achieve a high photocurrent at low potential (0.7 V vs. Ag/AgCl) through improved light harvesting of the Fe 2 O 3 film with an ultrathin ZnO/TiO 2 overlayer. Image 1 • Photocurrent density is 7 times higher due to TiO 2 protection layer for Fe 2 O 3 than pristine Fe 2 O 3. • Excellent photoelectrochemical performance due to high electron-hole separation. • Large-scale production of an efficient water splitting photoanodes by supersonic cold spray. [ABSTRACT FROM AUTHOR]

We present electrospray-deposited nanotextured Mo-doped BiVO 4 pillars with improved photoelectrochemical water splitting performance. The three-dimensional nanotextured Mo-BiVO 4 pillars exhibit large interstitial spaces, which result in a high photocurrent. The doping of Mo at the optimal concentration (0.15%) results in a two-fold increase in the photocurrent density (PCD) (1.78 mA·cm −2 at 1.2 V versus Ag/AgCl) over that of pristine BiVO 4 . We attribute this increase in the PCD to increases in recombination time and in donor (electron) concentration owing to the doping with hexavalent Mo, as confirmed by Bode phase and Mott-Schottky analyses, respectively. [ABSTRACT FROM AUTHOR]

We demonstrate electrospun ternary Fe 2 O 3 -SnO x -carbon nanofiber (CNF) composites as high-performance, flexible, and freestanding anodes for Li ion batteries (LIBs). In the ternary composites, the CNF matrix accommodates volume changes of Fe and Sn during lithiation and delithiation, while also providing short Li ion diffusion pathways, which ultimately enhances the capacity of the LIB. The concentrations of Fe and Sn were varied to find the optimal composition. Higher Sn content increased capacity at slow discharge rates, but decreased capacity at higher discharge rates. Increasing Fe to Sn ratio improved performance at high discharge rates. The Fe 2 O 3 -SnO x -CNF composite fabricated at a Fe:Sn weight ratio of 3:1 exhibited a reversible capacity value of 756 mAh·g −1 after 55 cycles. The materials and methods demonstrated here are unique in producing a flexible, free-standing mat with high gravimetric capacity using a simple and scalable production process. [ABSTRACT FROM AUTHOR]