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NiFe2O4 material is grown on carbon paper (CP) with the hydrothermal method for use as electrocatalysts in an alkaline electrolyzer. NiFe2O4 material is used as the anode and cathode catalysts (named NiFe(+)/NiFe(−) hereafter). The results are compared with those obtained using CP/NiFe as the anode and CP/Ru as the cathode (named NiFe)(+)/Ru(−) hereafter). During cell operation with NiFe(+)/Ru(−), the current density reaches 500 mA/cm2 at a cell voltage of 1.79 V, with a specific energy consumption of 4.9 kWh/m3 and an energy efficiency of 66.2%. In comparison, for NiFe(+)/NiFe(−), the current density reaches 500 mA/cm2 at a cell voltage of 2.23 V, with a specific energy consumption of 5.7 kWh/m3 and an energy efficiency of 56.6%. The Faradaic efficiency is 96–99%. With the current density fixed at 400 mA/cm2, after performing a test for 150 h, the cell voltage with NiFe(+)/Ru(−) increases by 0.167 V, whereas that with NiFe(+)/NiFe(−) decreases by only 0.010 V. Good, long-term stability is demonstrated.

Pastes containing reduced graphene oxide (rGO) and LiCl-Mn(NO3)2·4H2O are screen-printed on a carbon cloth substrate and then calcined using a nitrogen atmospheric-pressure plasma jet (APPJ) for conversion into rGO-LiMnOx nanocomposites. The APPJ processing time is within 300 s. RGO-LiMnOx on carbon cloth is used to sandwich H2SO4, LiCl, or Li2SO4 gel electrolytes to form hybrid supercapacitors (HSCs). The areal capacitance, energy density, and cycling stability of the HSCs are evaluated using electrochemical measurement. The HSC utilizing the Li2SO4 gel electrolyte exhibits enhanced electrode–electrolyte interface reactions and increased effective surface area due to its high pseudocapacitance (PC) ratio and lithium ion migration rate. As a result, it demonstrates the highest areal capacitance and energy density. The coupling of charges generated by embedded lithium ions with the electric double-layer capacitance (EDLC) further contributed to the significant overall capacitance enhancement. Conversely, the HSC with the H2SO4 gel electrolyte exhibits better cycling stability. Our findings shed light on the interplay between gel electrolytes and electrode materials, offering insights into the design and optimization of high-performance HSCs.

This study discussed the effect of oxygen impurity in the inlet gas of a nitrogen atmospheric pressure plasma jet (APPJ). A numerical model that takes into account the fluid dynamics, heat transfer, mass transfer, diffusion, and chemical reactions was developed to simulate the nitrogen APPJ. Further, a DC nitrogen APPJ experiment was performed to verify the plasma temperature characteristics on the treated surface. The plasma temperature decreased with an increase in the oxygen impurity. Moreover, the oxygen impurity influenced the related excited and neutral species. Specifically, with added oxygen impurity, N-related species decreased whereas O- and NOx-related species increased. Because the excited state species constitutes the most important reactant in APPJ treatment, this study could serve as a reference for the adjustment of a nitrogen APPJ.

We use screen printing to deposit LiCl + Ni(NO _3 ) _2 ·6H _2 O pastes on a flexible carbon cloth substrate and then calcine it using a nitrogen atmospheric-pressure-plasma jet (APPJ). Through the high-temperature treatment by APPJ, pastes can be rapidly converted into Li-Ni oxides (LNOs). The LNOs on carbon cloth are then used as the electrodes of flexible gel-electrolyte Li-ion hybrid supercapacitors (Li-ion HSCs). The best areal capacity of 21.076 mC cm ^−2 , as measured by cyclic voltammetry, is achieved by APPJ treatment at 620 °C for 480 s. To demonstrate the flexibility of the Li-ion HSCs, the Li-ion HSCs were bent at different curvatures to measure its performance. After bending test, the capacity remains >93% under bending with a curvature of up to 2 cm ^−1 .

RuCo/acid-treated nickel foam (ANF) has been reported to be an excellent electrocatalyst for the hydrogen evolution reaction (HER). In this study, we perform plasma treatment with Ar, Ar/H _2 (95:5), and Ar/O _2 (95:5) as working gases for surface modification to explore the effect on HER performance. The developed electrocatalysts are tested in an alkaline solution (1 M KOH); the results show that Ar/H _2 (95:5) plasma treatment significantly improves the electrocatalytic activity of RuCo/ANF, achieving an overpotential of 98 mV at a current density of 10 mA cm ^−2 . Electrochemical impedance spectroscopy and cyclic voltammetry analyses shSow a large reduction in the charge transfer impedance and a significant increase in the electric double-layer capacitance. This study provides a facile strategy to activate RuCo to improve HER performance.

A helium (He) dielectric barrier discharge plasma jet (DBD jet) was used for the first time for treating graphite foil as the current collector of a paper-based fluidic aluminum-air battery. The main purpose was to improve the distribution of the catalyst layer through modification and functionalization of the graphite foil surface. The plasma functionalized the graphite foil surface to enhance the wettability where the more hydroxyl could be observed from XPS results. The 30 s-He DBD jet treatment on the graphite foil significantly improved the battery performance. The best current density of 85.6 mA/cm2 and power density of 40.98 mW/cm2 were achieved. The energy density was also improved to 720 Wh/kg.

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Tyrosinase, chitosan, and reduced graphene oxide (rGO) are sequentially used to modify a screen-printed carbon electrode (SPCE) for the detection of dopamine (DA), without interference from uric acid (UA) or ascorbic acid (AA). The use of tyrosinase significantly improves the detection’s specificity. Cyclic voltammetry (CV) measurements demonstrate the high sensitivity and selectivity of the proposed electrochemical sensors, with detection limits of 22 nM and broad linear ranges of 0.4⁻8 μM and 40⁻500 μM. The fabricated tyrosinase/chitosan/rGO/SPCE electrodes achieve satisfactory results when applied to human urine samples, thereby demonstrating their feasibility for analyzing DA in physiological samples.

We vary the substrate temperature by adjusting the nitrogen flow rate and jet-substrate distance during nitrogen atmospheric-pressure plasma jet (APPJ) processing of screen-printed reduced graphene oxides (rGOs) on carbon cloth. The APPJ-processed rGOs on carbon cloth are then used as electrodes for supercapacitors. Increasing the nitrogen flow rate could reduce the gas temperature and enhance the reactivity of the reactive plasma species. Typically, lowering the temperature slows down the chemical reaction; however, increased reactivity of the reactive plasma species at the same jet-substrate distance could compensate the temperature effect. A nitrogen APPJ could improve the wettability of the screen-printed rGOs on carbon cloth. We found that 20-s APPJ treatment increases the areal capacitance from 6.2 mF cm ^−2 (without APPJ treatment) to 22.4 mF cm ^−2 (700 °C, 30 slm), as evaluated by galvanostatic charging/discharging (GCD) measurements under a constant current of 0.25 mA. Further, 20-s nitrogen APPJ processing at temperatures of ∼600 °C–700 °C could obtain the best areal capacitance value. The capacitance value of the fabricated flexible rGO supercapacitor remains at similar level after 1000-cycle mechanical bending test with a bending radius of 5 mm.

We characterize the time evolution (≤120 s) of atmospheric-pressure plasma jet (APPJ)-synthesized Pt-SnOx catalysts. A mixture precursor solution consisting of chloroplatinic acid and tin(II) chloride is spin-coated on fluorine-doped tin oxide (FTO) glass substrates, following which APPJ is used for converting the spin-coated precursors. X-ray photoelectron spectroscopy (XPS) indicates the conversion of a large portion of metallic Pt and a small portion of metallic Sn (most Sn is in oxidation states) from the precursors with 120 s APPJ processing. The dye-sensitized solar cell (DSSC) efficiency with APPJ-synthesized Pt-SnOx CEs is improved greatly with only 5 s of APPJ processing. Electrochemical impedance spectroscopy (EIS) and Tafel experiments confirm the catalytic activities of Pt-SnOx catalysts. The DSSC performance can be improved with a short APPJ processing time, suggesting that a DC-pulse nitrogen APPJ can be an efficient tool for rapidly synthesizing catalytic Pt-SnOx counter electrodes (CEs) for DSSCs.

A photoactivated gas detector operated at room temperature was microfabricated using a simple hydrothermal method. We report that the photoactivated gas detector can detect toluene using a UV illumination of 2 μW/cm2. By ultraviolet (UV) illumination, gas detectors sense toluene at room temperature without heating. A significant enhancement of detector sensitivity is achieved because of the high surface-area-to-volume ratio of the morphology of the coral-like ZnO nanorods arrays (NRAs) and the increased number of photo-induced oxygen ions under UV illumination. The corresponding sensitivity (ΔR/R0) of the detector based on coral-like ZnO NRAs is enhanced by approximately 1022% compared to that of thin-film detectors. The proposed detector greatly extends the dynamic range of detection of metal-oxide-based detectors for gas sensing applications. We report the first-ever detection of toluene with a novel coral-like NRAs gas detector at room temperature. A sensing mechanism model is also proposed to explain the sensing responses of gas detectors based on coral-like ZnO NRAs.

A low-temperature (<30 °C) He dielectric-barrier-discharge jet (DBDjet) is applied to treat screen-printed reduced graphene oxide(rGO)/polyaniline (PANI)/chitosan (CS) nanocomposite flexible gel-electrolyte supercapacitors (SCs) with atmospheric-pressure plasma jet (APPJ)-processed carbon cloth current collectors. The APPJ-treated carbon cloth retained it hydrophilicity for more than23 weeks. By contrast, carbon cloth furnace-treated at similar temperatures for 30 s and 30 min retained its hydrophilicity for only6 h and 4 weeks, respectively. Therefore, APPJ treatment benefits the long-term stability of SCs with carbon cloth currentcollectors. Without substantial heating, the reactive plasma species of the He DBDjet can improve the hydrophilicity of screen-printed rGO/PANI/CS nanocomposites, thereby increasing the SC's capacitance value. X-ray photoelectron spectroscopy results reveal increased-COOH and C-N contents after He DBDjet treatment, thus explaining the improved hydrophilicity. Galvano static charging-discharging measurements demonstrate that the capacitance is improved by 181% after two He DBDjet scans. The capacitance value decreases by only 0.2% after a 10000-cycle CV stability test. No apparent degradation is observed after a 1000-cycle mechanical bending test. [ABSTRACT FROM AUTHOR]

A nitrogen DC-pulse atmosphere pressure plasma jet (APPJ) is used to convert ferric nitrate (Fe(NO3)3) and chloroplatinic ac (H2PtCl6) mixed liquid precursor films into PtFe nanocompounds on a fluorine-doped tin oxide (FTO) substrate. Scanning transmi sion electron microscopy indicates nanoparticles distributed on a thin continuous layer on the FTO substrate. The APPJ-synthesize PtFe nanocompounds contain a mixture of crystalline and amorphous phases. X-ray photoelectron spectroscopy shows that mo Pt is in the metallic phase and most Fe, in the oxidized phase. A dye-sensitized solar cell (DSSC) with only 5-s APPJ-processe PtFe counter electrode (CE) shows significantly improved efficiency. This suggests the rapid processing capability of the nitroge DC-pulse APPJ. A PtFe prepared with higher H2PtCl6/Fe(NO3)3 volume ratio shows better catalytic performance, as confirme by cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel experiments. The DSSC with APPJ-processed PtFe C shows comparable efficiency to that of 15-min furnace-calcined Pt CE, suggesting that the APPJ processed PtFe requires less Pt. [ABSTRACT FROM AUTHOR]

We characterize the time evolution (≤120 s) of atmospheric-pressure plasma jet (APPJ)-synthesized Pt-SnOx catalysts. A mixture precursor solution consisting of chloroplatinic acid and tin(II) chloride is spin-coated on fluorine-doped tin oxide (FTO) glass substrates, following which APPJ is used for converting the spin-coated precursors. X-ray photoelectron spectroscopy (XPS) indicates the conversion of a large portion of metallic Pt and a small portion of metallic Sn (most Sn is in oxidation states) from the precursors with 120 s APPJ processing. The dye-sensitized solar cell (DSSC) efficiency with APPJ-synthesized Pt-SnOx CEs is improved greatly with only 5 s of APPJ processing. Electrochemical impedance spectroscopy (EIS) and Tafel experiments confirm the catalytic activities of Pt-SnOx catalysts. The DSSC performance can be improved with a short APPJ processing time, suggesting that a DC-pulse nitrogen APPJ can be an efficient tool for rapidly synthesizing catalytic Pt-SnOx counter electrodes (CEs) for DSSCs. [ABSTRACT FROM AUTHOR]

We performed a comparative study of dye-sensitized solar cells (DSSCs) with screen-printed Pt-decorated reduced graphene oxides (Pt/rGOs) processed by furnace- and atmospheric-pressure-plasma jet (APPJ)-calcination (substrate temperature = 510°C). A nitrogen APPJ interacts vigorously with carbonaceous materials in the pastes to enhance DSSC efficiency with a shorter processing time. However, prolonged APPJ-calcination can damage/oxidize rGOs; therefore, for longer processing times, furnace-calcination in turn achieves better DSSC performance. These results agree well with those of electrochemical impedance spectroscopy (EIS) and Tafel experiments. [ABSTRACT FROM AUTHOR]

This paper reports prototype atmospheric-pressure plasma jet (APPJ)-processed reduced graphene oxide (rGO)-modified carbon electrochemical sensors integrated with 3D-printed microfluidic channels. Dopamine (DA) solutions with various concentrations are used for the model test. The APPJ-calcined rGO coating significantly enhances the electrochemical signal for DA detection by 18 times. X-ray photoelectron spectroscopy (XPS) shows that APPJ-calcined rGO-modified carbon electrodes have more oxygencontaining surface functional groups, leading to the enhanced electrochemical reactivity. The cyclic voltammetry (CV) curves of solutions with various DA concentrations are well-distinguishable in the presence of uric acid (UA) and ascorbic acid (AA) as interfering agents. [ABSTRACT FROM AUTHOR]

Ultrafast atmospheric-pressure plasma jet (APPJ) processed Pt-decorated reduced graphene oxides (rGOs) were used as counter-electrodes in dye-sensitized solar cells (DSSCs). Pastes containing rGO, ethyl cellulose, terpineol, and chloroplatinic acid were screen-printed and sintered by nitrogen dc-pulse APPJs. Pt nanodots were uniformly distributed on the rGO flakes. When using Pt-decorated rGOs as the counter electrodes of DSSCs, the efficiency of the DSSC first increased and then decreased as the APPJ processing time increased. Nitrogen APPJs can effectively remove organic binders and can reduce chloroplatinic acid to Pt, thereby improving the efficiency of DSSCs. However, over-calcination by APPJ can damage the graphenes and degrade the DSSCs. The addition of Pt mainly improves the fill factor, which thereby increases the efficiency of DSSCs. The optimized APPJ processing time was merely 9 s owing to the vigorous interaction among the rGOs, chloroplatinic acid and nitrogen APPJs. [ABSTRACT FROM AUTHOR]

Rf-sputtered ZnO films, annealed by atmospheric pressure plasma jet (APPJ), are characterized and used for MgZnO/ZnO heterostructures. The highly reactive N2 plasma generated by APPJ allows much shorter treatment time compared with conventional thermal anneals. The APPJ treatment can increase the crystallinity of ZnO films and release the compressive residue stresses, verified by XRD and UV-Vis transmission measurements. In our previous studies, we demonstrate that thermal anneal is the critical step for the formation of two-dimensional electron gases in defective rf-sputtered MgZnO/ZnO heterostructures. This paper reports the experimental results that APPJ treatments can be used for the same purpose with a much shorter processing time. A thirty-second APPJ anneal on ZnO can be used to replace 400 °C × 30 min furnace-anneal to promote the formation of 2DEGs in MgZnO/ZnO heterostructure. The ultra-short processing time is attributed to the synergy of plasma reactivity and temperature of APPJ. [ABSTRACT FROM AUTHOR]

We have fabricated active-matrix organic light emitting diode (AMOLED) test arrays on an optically clear high-temperature flexible plastic substrate at process temperatures as high as 285 °C using amorphous silicon thin-film transistors (a-Si TFTs). The substrate transparency allows for the operation of AMOLED pixels as bottom-emission devices, and the improved stability of the a-Si TFTs processed at higher temperatures significantly improves the reliability of light emission over time. [ABSTRACT FROM AUTHOR]

Nitrogen DC-pulse atmospheric-pressure plasma jet (APPJ) and nitrogen dielectric barrier discharge (DBD) were applied to pre-treat fluorine-doped tin oxide (FTO) glass substrates for perovskite solar cells (PSCs). Nitrogen DC-pulse APPJ treatment (substrate temperature: ~400 °C) for 10 s can effectively increase the wettability, whereas nitrogen DBD treatment (maximum substrate temperature: ~140 °C) achieved limited improvement in wettability even with increased treatment time of 60 s. XPS results indicate that 10 s APPJ, 60 s DBD, and 15 min UV-ozone treatment of FTO glass substrates can decontaminate the surface. A PSC fabricated on APPJ-treated FTO showed the highest power conversion efficiency (PCE) of 14.90%; by contrast, a PSC with nitrogen DBD-treated FTO shows slightly lower PCE of 12.57% which was comparable to that of a PSC on FTO treated by a 15 min UV-ozone process. Both nitrogen DC-pulse APPJ and nitrogen DBD can decontaminate FTO substrates and can be applied for the substrate cleaning step of PSC. [ABSTRACT FROM AUTHOR]

We report on the development of a PDMS-SMA composite whose surface micro wrinkles can be dynamically programmed by an electrical current supplied to the SMA wire. It is advantageous over other techniques for surface topographical modulation, including portability, real-time programmability, no requirement for specific surface chemistry, operability under ambient conditions, and relative ease of control. A simplified mechanical model is also developed to describe the force-deflection balance of the PDMS-SMA composite. The wavelengths and amplitudes of the wrinkles when different currents applied to the SMA are characterized, and the experimental results agree with the theoretical model. The developed composite device can be applied to programmable modulations of surface adhesion, friction, wettability, etc. [ABSTRACT FROM AUTHOR]

The thermoelectric power of a material, typically governed by its band structure and cartier density, can be varied by chemical doping that is often restricted by solubility of the dopant. Materials showing large thermoelectric power are useful for many industrial applications, such as the heat-to-electricity conversion and the thermoelectric cooling device. Here we show a full electric-field tuning of thermoelectric power in a dual-gated bilayer graphene device resulting from the opening of a band gap by applying a perpendicular electric field on bilayer graphene. We uncover a large enhancement in thermoelectric power at a low temperature, which may open up a new possibility in low temperature thermoelectric application using graphene-based device. [ABSTRACT FROM AUTHOR]