Atmospheric Pressure Plasma Jet Processing Research Articles

The Conversion of Li2SnO3 Li-Ion Hybrid Supercapacitors from Pastes Containing LiCl-SnCl2 Liquid Precursors Using an Atmospheric-Pressure Plasma Jet

We fabricate lithium tin-based oxide Li2SnO3 on carbon cloth from a gel-state precursor containing LiCl and SnCl2·2H2O using a nitrogen atmospheric-pressure plasma jet (APPJ). APPJ treatment provides both a high-temperature environment for the conversion of precursor into Li2SnO3 and nitrogen plasma reactive species for electrode surface modification. Here, the best electrochemical performance for the Li2SnO3 Li-ion hybrid supercapacitors (Li–HSCs) is achieved with 480 s of APPJ processing. The areal capacity of the 480 s APPJ-processed Li2SnO3 Li–HSCs reached 46.113 mC/cm2. The results indicate that APPJ is an effective tool for the rapid conversion processing of Li2SnO3 electrodes for Li–HSCs.

Ultrafast Fabrication of H2SO4, LiCl, and Li2SO4 Gel Electrolyte Supercapacitors with Reduced Graphene Oxide (rGO)-LiMnOx Electrodes Processed Using Atmospheric-Pressure Plasma Jet.

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.

LiMn2O4 Li-ion hybrid supercapacitors processed by nitrogen atmospheric-pressure plasma jet

LiCl–Mn(NO3)2·4H2O pastes were screen-printed on a carbon cloth substrate and furnace-calcined to convert them into LiMn2O4. The LiMn2O4 electrode was then post-processed using a nitrogen atmospheric-pressure plasma jet (APPJ). APPJ processing created oxygen vacancy defects on the electrode surface. Electrochemical tests of the Li-ion hybrid supercapacitors (Li–HSCs) were performed by cyclic voltammetry (CV) and galvanostatic charging/discharging (GCD) in 1-M Li2SO4 aqueous solution. The results indicate that proper APPJ treatment optimizes the Li–HSCs performance, whereas excessive APPJ treatment may cause material damage. After 3-min APPJ treatment at 620 °C, the Li–HSCs exhibited a maximum areal capacitance of 87.96 mF/cm2 with capacitance retention of 124.8% after a 1000-cycle CV test.

Comparison between atmospheric-pressure-plasma-jet-processed and furnace-calcined rGO-MnOx nanocomposite electrodes for gel-electrolyte supercapacitors

Reduced graphene oxide (rGO)-Mn(NO3)2·4H2O pastes were screen-printed on a carbon cloth substrate and then calcined using a nitrogen atmospheric-pressure-plasma-jet (APPJ) and/or tube furnace to convert it into rGO-MnOx. The rGO-MnOx electrodes were then used in a PVA/H2SO4 gel-electrolyte supercapacitor (SC). The SCs were characterized by cycle voltammetry (CV) and galvanostatic charging/discharging (GCD). The results reveal better performance of the APPJ-processed SCs in comparison with furnace-processed ones under the same processing temperature, possibly owing to the synergetic effect of heat and reactive nitrogen plasma species. The rGO-MnOx SC is also superior to the rGO-SnOx SC reported in our previous study processed under similar APPJ processing. The rGO-MnOx SC processed by APPJ at 620 °C for 8 min exhibits the best areal capacitance of 57.01 mF/cm2 as evaluated by GCD with a capacitance retention rate of 84.41% after a 10,000-cycle CV test.

Reactive plasma oxygen-modified and nitrogen-doped soft carbon as a potential anode material for lithium-ion batteries using a tornado-type atmospheric pressure plasma jet

In this study, a tornado-type atmospheric pressure plasma jet (APPJ) system was used to modify soft carbon (SC) as an anode material for lithium-ion batteries (LIBs). We used both argon plasma–derived reactive oxygen species and reactive nitrogen species to activate SC electrodes in an ambient environment using in-situ hydrophilic surface modification and nitrogen-doping technology. After the APPJ modification, the contact angle of the electrode was substantially reduced from 113° to less than 10° because of the formation of oxygen-containing functional groups on the SC surface. The hydrophilic nature of the plasma-modified electrode facilitated the penetration of liquid electrolyte. In addition, during the APPJ process, nitrogen atoms were simultaneously doped into the SC to increase its conductivity, reversible capacity, and rate capability. According to electrochemical measurements, the SC-40 electrode (40 cycles of plasma treatment) exhibited a reversible charge and discharge capacity of 293 and 259 mAh/g, respectively, with a Coulombic efficiency of 88.63 % at 0.1C. At 10 C, the reversible capacity of the SC-40 electrode achieved 111 mAh/g, which was 252% greater than that of the pristine SC electrode (approximately 44 mAh/g). Plasma-induced surface hydrophilicity and nitrogen-incorporated soft carbon as an anode material for LIBs using a tornado-type APPJ technique represents a unique and promising technique.

Atmospheric pressure plasma jet fabricating of porous silver electrocatalyst as a promising approach to the creation of cathode layers of low temperature solid oxide fuel cells

Abstract Silver (Ag) electrocatalysts as cathode layers for low-temperature solid oxide fuel cells (LT-SOFCs) are prepared using an atmospheric pressure plasma jet (APPJ). The material characteristics of APPJ-coated silver are observed by an X-ray diffractometer and a field-emission scanning electron microscope. The porous cathode films, composed of Ag nanoparticles coated on YSZ electrolytes are observed. The porous Ni anodic layer is also prepared via an APPJ process on the other side of the YSZ. The values of area specific resistance and conductivities of Ag|YSZ are linearly increased with increasing operating temperatures. High conductivities of 139.6 and 143.2 S/cm are obtained at 550 and 600 °C, respectively. The exchange current and power density at 600 °C are 497.9 mA/cm2 and 108.4 mW/cm2, respectively. The AC impedance shows the two oxygen pathways, surface and bulk, of Ag electrocatalysts as reflected by the responses at low and high frequencies, respectively. Furthermore, LT-SOFCs which consist of cathode|electrolyte|anode are fabricated by APPJ technology in a fast-coating process.

Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure Plasma Jet Processing

Titanium dioxide (TiO2) has been widely used as a catalyst material in different applications such as photocatalysis, solar cells, supercapacitor, and hydrogen production, due to its better chemical stability, high redox potential, wide band gap, and eco-friendly nature. In this work TiO2 thin films have been deposited onto both glass and silicon substrates by the atmospheric pressure plasma jet (APPJ) technique. The structure and morphological properties of TiO2 thin films are studied using different characterization techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and field emission scanning electron microscopy. XRD study reveals the bronze-phase of TiO2. The XPS study shows the presence of Ti, O, C, and N elements. The FE-SEM study shows the substrate surface is well covered with a nearly round shaped grain of different size. The optical study shows that all the deposited TiO2 thin films exhibit strong absorption in the ultraviolet region. The oleic acid photocatalytic decomposition study demonstrates that the water contact angle decreased from 80.22 to 27.20° under ultraviolet illumination using a TiO2 photocatalyst.

Flexible rGO-SnO2 supercapacitors converted from pastes containing SnCl2 liquid precursor using atmospheric-pressure plasma jet

Reduced graphene oxide (rGO)-SnO2 nanocomposites are fabricated on carbon cloth from screen-printed pastes containing rGO nanoflakes and SnCl2 liquid precursor by using a nitrogen atmospheric-pressure plasma jet (APPJ). RGO-SnO2-coated carbon cloth is then used as the electrode of gel-electrolyte supercapacitors (SCs). Experiments conducted with various APPJ processing times suggest that the optimal APPJ processing time is 300 s. Cyclic voltammetry (CV) measurements indicate that 300-s APPJ processing results in the best areal capacitance of 97.53 mF/cm2. The capacitance retention rate is ~85% after a 10,000-cycle CV test. Further, capacitance increases by 11% after a 1000-cycle bending test under a bending radius of 7.5 mm, possibly owing to the better electrolyte/electrode contact and decrease in the charge transport resistance after mechanical bending. This study also characterized APPJ-processed rGO-SnO2 nanocomposites by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, Raman spectroscopy, and water contact angle measurements.

Flexible reduced graphene oxide supercapacitors processed using atmospheric-pressure plasma jet under various temperatures adjusted by flow rate and jet-substrate distance

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.

Tuning ZnO nanorods photoluminescence through atmospheric plasma treatments

Room temperature atmospheric plasma treatments are widely used to activate and control chemical functionalities at surfaces. Here, we investigated the effect of atmospheric pressure plasma jet (APPJ) treatments in reducing atmosphere (Ar/1‰ H2 mixture) on the photoluminescence (PL) properties of single crystal ZnO nanorods (NRs) grown through hydrothermal synthesis on fluorine-doped tin oxide glass substrates. The results were compared with a standard annealing process in air at 300 °C. Steady-state photoluminescence showed strong suppression of the defect emission in ZnO NRs for both plasma and thermal treatments. On the other side, the APPJ process induced an increase in PL quantum efficiency (QE), while the annealing does not show any improvement. The QE in the plasma treated samples was mainly determined by the near band-edge emission, which increased 5–6 fold compared to the as-prepared samples. This behavior suggests that the quenching of the defect emission is related to the substitution of hydrogen probably in zinc vacancies (VZn), while the enhancement of UV emission is due to doping originated by interstitial hydrogen (Hi), which diffuses out during annealing. Our results demonstrate that atmospheric pressure plasma can induce a similar hydrogen doping as ordinarily used vacuum processes and highlight that the APPJ treatments are not limited to the surfaces but can lead to subsurface modifications. APPJ processes at room temperature and under ambient air conditions are stable, convenient, and efficient methods, compared to thermal treatments to improve the optical and surface properties of ZnO NRs, and remarkably increase the efficiency of UV emission.

Synthesis and theoretical calculations of N-doped ZnCo2O4 anode for lithium-ion anode via gradient pressure-induced processes and theoretical calculations

The aim of this study is to improve the electrochemical performance of ZnCo2O4 (ZCO) anode by two-steps nitrogen doping processes, including hydrothermal reaction process and atmospheric pressure plasma jet process (APPJ). Via the higher-pressure hydrothermal method, nitrogen was doped in the ZCO spinel lattice, while subsequently “atmospheric-pressure” APPJ mainly activated and modified the electrode surface binding with the dangling bond. The uniformity, chemical composition, and crystal structure of ZCO and N-ZCO were examined by electron probe microanalyzer (EPMA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). First principle calculation based on density functional theory (DFT) results clearly reveal that N-doping could significantly narrow band gap and enhance the electronic transfer towards ZCO framework. Nitrogen doping effectively improves electrochemical performance with superior capacity (1025 mAh⋅g−1) and stability with 63% cycling retention after 100 cycles at a current density of 1C. This study provides a rapid and inexpensive nitrogen doping processes to efficiently promote the ZCO electrochemical performance for anode materials.

Dual RGD-immobilized poly(L-lactic acid) by atmospheric pressure plasma jet for bone tissue engineering.

Surface treatment on PLA substrates by atmospheric pressure plasma jet (APPJ) for polymerization of dual RGD-peptides were investigated. Peptide-modified surfaces have been highlighted as the most promising approach to improve the integration of implants into surrounding bones. By varying the RF power, PLA substrates treated by APPJ process have a tendency to form a hydrophobic surface. The effects on the proliferation and differentiation of MG63 cells were evaluated and osteocalcin (OCN) expression was analyzed using RT-PCR. The water contact angle of the W/APPJ process PLA was approximately 54% of that of the W/O APPJ process PLA substrates. W/APPJ process significantly increased cell proliferation, improved the functionality of the material without using a complicated procedure. We believe that pretreatment using the APPJ processes and dual RGD grafting can be more appropriate than traditional surface modification methods, with more potential for application to bone materials.

Time Evolution Characterization of Atmospheric-Pressure Plasma Jet (APPJ)-Synthesized Pt-SnOx Catalysts

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.

Nitrogen DC-pulse atmospheric-pressure-plasma jet (APPJ)-processed reduced graphene oxide (rGO)‑carbon black (CB) nanocomposite electrodes for supercapacitor applications

This study compares supercapacitors with reduced graphene oxide (rGO)‑carbon black (CB) and CB nanocomposite coated carbon cloth electrodes. We use a nitrogen DC-pulse atmospheric pressure plasma jet (APPJ) to process the electrodes. The APPJ processing time is <40 s. Nitrogen APPJ burns off organic binders to create nanoporous structures. Replacing part of the CB with rGO nano-flakes can increase the overall surface area to improve the supercapacitive performance. Specifically, by replacing 50 wt% of CBs with rGOs, the specific (areal) capacitance can be improved from 91.84 F·g−1 (19.74 mF/cm2) to 162.68 F·g−1 (29.16 mF/cm2), respectively, with 20 s APPJ processing time, as evaluated by cyclic voltammetry under a potential scan rate of 2 mV·s−1. The nitrogen DC-pulse APPJ is demonstrated to be an ultrafast and highly economical tool for efficiently processing nanocomposite electrodes of supercapacitors.

The enhanced abrasion resistance of an anti-fingerprint coating on chrome-plated brass substrate by integrating sputtering and atmospheric pressure plasma jet technologies

We demonstrate the procedure of fabricating an anti-fingerprint coating on plated-Cr/brass substrates by the combination of two processes: (1) Sputtering and (2) Atmospheric pressure plasma jet (APPJ). APPJ surface treatment on sputtered-SiOx glue layer on plated-Cr/brass substrate is conducted to improve its surface property to be hydrophilic for chemical bonding with an anti-fingerprint agent (AF-C01). The results show that the surface energy of original substrate are evolving from 44.2 mN/m to 60.8 mN/m and 76.9 mN/m for the sputtered-SiOx film and APPJ-treated SiOx film, respectively. Subsequently, the spin-coating process using a commercialnt (AF-C01 agent for the prepared sample is implemented. The hydrophobicity of anti-fingerprint characteristics for all of the samples with a quite low surface energy around 10.5 mN/m are obtained. For practical evaluation of abrasion behavior, a good abrasion resistance of AF/APPJ-treated SiOx/plated-Cr/brass sample under 1000 g-steel wood loading is evidently obtained from the slow variation of water contact angle value. The results demonstrate that the feasibility of integrating APPJ process on the sputtered-SiOx film for improving the surface properties of chrome-plated brass substrate is practically achieved.

Scan-Mode Atmospheric-Pressure Plasma Jet Processed Reduced Graphene Oxides for Quasi-Solid-State Gel-Electrolyte Supercapacitors

A scanning atmospheric-pressure plasma jet (APPJ) is essential for high-throughput large-area and roll-to-roll processes. In this study, we evaluate scan-mode APPJ for processing reduced graphene oxides (rGOs) that are used as the electrodes of quasi-solid-state gel-electrolyte supercapacitors. rGO nanoflakes are mixed with ethyl cellulose (EC) and terpineol to form pastes for screen-printing. After screen-printing the pastes on carbon cloth, a DC-pulse nitrogen APPJ is used to process the pastes in the scan mode. The maximal temperature attained is ~550 °C with a thermal influence duration of ~10 s per scan. The pastes are scanned by APPJ for 0, 1, 3 and 5 times. X-ray photoelectron spectroscopy (XPS) indicates the reduction of C-O binding content as the number of scan increases, suggesting the oxidation/decomposition of EC. The areal capacitance increases and then decreases as the number of scan increases; the best achieved areal capacitance is 15.93 mF/cm2 with one APPJ scan, in comparison to 4.38 mF/cm2 without APPJ processing. The capacitance retention rate of the supercapacitor with the best performance is ~93% after a 1000-cycle cyclic voltammetry (CV) test. The optimal number of APPJ scans should enable the proper removal of inactive EC and improved wettability while minimizing the damage caused to rGOs by nitrogen APPJ processing.

Application of atmospheric-pressure plasma jet processed carbon nanotubes to liquid and quasi-solid-state gel electrolyte supercapacitors

We use a dc-pulse nitrogen atmospheric-pressure plasma jet (APPJ) to calcine carbon nanotubes (CNTs) pastes that are screen-printed on carbon cloth. 30-s APPJ treatment can efficiently oxidize and vaporize the organic binders, thereby forming porous structures. As indicated by X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA), the oxygen content decreases after APPJ treatment owing to the oxidation and vaporization of ethyl cellulose, terpineol, and ethanol. Nitrogen doping was introduced to the materials by the nitrogen APPJ. APPJ-calcination improves the wettability of the CNTs printed on carbon cloth, as evidenced by water contact angle measurement. Raman spectroscopy indicates that reactive species of nitrogen APPJ react violently with CNTs in only 30-s APPJ processing time and introduce defects and/or surface functional groups on CNTs. Carbon cloths with calcined CNT layers are used as electrodes for liquid and quasi-solid-state electrolyte supercapacitors. Under a cyclic voltammetry test with a 2mV/s potential scan rate, the specific capacitance is 73.84F/g (areal capacitance=5.89 mF/cm2) with a 2M KCl electrolyte and 66.47F/g (areal capacitance=6.10 mF/cm2) with a H2SO4/polyvinyl alcohol (PVA) gel electrolyte.

Flexible quasi-solid-state SnO2/CNT supercapacitor processed by a dc-pulse nitrogen atmospheric-pressure plasma jet

This study investigates flexible quasi-solid-state SnO2/CNT nanocomposite supercapacitors fabricated using a dc-pulse nitrogen atmospheric-pressure plasma jet (APPJ). The optimal APPJ processing time is merely 15s. Cyclic voltammetry (potential scan rate=2mV/s) shows an areal capacitance of 3.86mF/cm2 when flat and 4.42mF/cm2 under bending (bending radius R=0.55cm), indicating good functionality under flexing. The capacitance retention rate is 98.3% as evaluated after a 1000-cycle cyclic voltammetry test under bending (R=0.55cm), suggesting good operational stability.

Atmospheric-Pressure Plasma Jet Processed Pt-Decorated Reduced Graphene Oxides for Counter-Electrodes of Dye-Sensitized Solar Cells

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.

Development of a scanning nanopipette probe microscope for fine processing using atmospheric pressure plasma jet

We developed a novel technique for fine material processing based on a localized atmospheric-pressure plasma jet (APPJ) using a scanning probe microscope equipped with a nanopipette. Using a nanopipette — a tapered glass capillary with an aperture of sub-micrometer diameter — as a nozzle makes it possible to localize the discharge area of the APPJ for fine surface processing. The nanopipette can also be used as a probe for a scanning probe microscope operated with shear-force feedback control, which is capable of positioning the pipette edge in the vicinity of material surfaces for APPJ processing and imaging of the processed surface. Sub-micrometer holes and line patterns were successfully processed on a photoresist film. It was possible to control the size of the processed patterns by varying the applied pulse voltage and the distance between the pipette and the surface.