@article{he_shan_wang_pan_qu_wang_gao_2019, title={Mordant inspired wet-spinning of graphene fibers for high performance flexible supercapacitors}, volume={7}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta12337c}, abstractNote={Al3+ coagulated wet-spun graphene fibers show a large surface area and high electrical conductivity, resulting in large capacitance.}, number={12}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={He, Nanfei and Shan, Weitao and Wang, Julia and Pan, Qin and Qu, Jiangang and Wang, Guofeng and Gao, Wei}, year={2019}, month={Mar}, pages={6869–6876} }
 @article{pan_tong_he_liu_shim_pourdeyhimi_gao_2018, title={Electrospun Mat of Poly(vinyl alcohol)/Graphene Oxide for Superior Electrolyte Performance}, volume={10}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.7b14498}, abstractNote={Here, we describe an electrospun mat of poly(vinyl alcohol) (PVA) and graphene oxide (GO) as a novel solid-state electrolyte matrix, which offers better performance retention upon drying after infiltrated with aqueous electrolyte. The PVA-GO mat overcomes the major issue of conventional PVA-based electrolytes, which is the ionic conductivity decay upon drying. After exposure to 45 ± 5% relative humidity at 25 °C for 1 month, its conductivity decay is limited to 38.4%, whereas that of pure PVA mat is as high as 84.0%. This mainly attributes to the hygroscopic nature of GO and the unique nanofiber structure within the mat. Monolithic supercapacitors have been derived directly on the mat via a well-developed laser scribing process. The as-prepared supercapacitor offers an areal capacitance of 9.9 mF cm-2 at 40 mV s-1 even after 1 month of aging under ambient conditions, with a high device-based volumetric energy density of 0.13 mWh cm-3 and a power density of 2.48 W cm-3, demonstrating great promises as a more stable power supply for wearable electronics.}, number={9}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Pan, Qin and Tong, Ningjun and He, Nanfei and Liu, Yixin and Shim, Eunkyoung and Pourdeyhimi, Behnam and Gao, Wei}, year={2018}, month={Mar}, pages={7927–7934} }
 @article{he_pan_liu_gao_2017, title={Graphene-Fiber-Based Supercapacitors Favor N-Methyl-2-pyrrolidone/Ethyl Acetate as the Spinning Solvent/Coagulant Combination}, volume={9}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.7b05982}, abstractNote={One-dimensional flexible fiber supercapacitors (FSCs) have attracted great interest as promising energy-storage units that can be seamlessly incorporated into textiles via weaving, knitting, or braiding. The major challenges in this field are to develop tougher and more efficient FSCs with a relatively easy and scalable process. Here, we demonstrate a wet-spinning process to produce graphene oxide (GO) fibers from GO dispersions in N-methyl-2-pyrrolidone (NMP), with ethyl acetate as the coagulant. Upon chemical reduction of GO, the resulting NMP-based reduced GO (rGO) fibers (rGO@NMP-Fs) are twice as high in the surface area and toughness but comparable in tensile strength and conductivity as that of the water-based rGO fibers (rGO@H2O-Fs). When assembled into parallel FSCs, rGO@NMP-F-based supercapacitors (rGO@NMP-FSCs) offered a specific capacitance of 196.7 F cm-3 (147.5 mF cm-2), five times higher than that of rGO@H2O-F-based supercapacitors (rGO@H2O-FSCs) and also higher than most existing wet-spun rGO-FSCs, as well as those FSCs built with metal wires, graphene/carbon nanotube (CNT) fibers, or even pseudocapacitive materials. In addition, our rGO@NMP-FSCs can provide good bending and cycling stability. The energy density of our rGO@NMP-FSCs reaches ca. 6.8 mWh cm-3, comparable to that of a Li thin-film battery (4 V/500 μAh).}, number={29}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={He, Nanfei and Pan, Qin and Liu, Yixin and Gao, Wei}, year={2017}, month={Jul}, pages={24568–24576} }
 @article{pan_shim_pourdeyhimi_gao_2017, title={Highly Conductive Polypropylene-Graphene Nonwoven Composite via Interface Engineering}, volume={33}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.7b01508}, abstractNote={Here we report a highly conductive polypropylene-graphene nonwoven composite via direct coating of melt blown polypropylene (PP) nonwoven fabrics with graphene oxide (GO) dispersions in N,N-dimethylformamide (DMF), followed by the chemical reduction of GO with hydroiodic acid (HI). GO as an amphiphilic macromolecule can be dispersed in DMF homogeneously at a concentration of 5 mg/mL, which has much lower surface tension (37.5 mN/m) than that of GO in water (72.9 mN/m, at 5 mg/mL). The hydrophobic PP nonwoven has a surface energy of 30.1 mN/m, close to the surface tension of GO in DMF. Therefore, the PP nonwoven can be easily wetted by the GO/DMF dispersion without any pretreatment. Soaking PP nonwoven in a GO/DMF dispersion leads to uniform coatings of GO on PP-fiber surfaces. After chemical reduction of GO to graphene, the resulting PP/graphene nonwoven composite offers an electrical conductivity of 35.6 S m-1 at graphene loading of 5.2 wt %, the highest among the existing conductive PP systems reported, indicating that surface tension of coating baths has significant impact on the coating uniformity and affinity. The conductivity of our PP/graphene nonwoven is also stable against stirring washing test. In addition, here we demonstrate a monolithic supercapacitor derived from the PP-GO nonwoven composite by using a direct laser-patterning process. The resulted sandwich supercapacitor shows a high areal capacitance of 4.18 mF/cm2 in PVA-H2SO4 gel electrolyte. The resulting highly conductive or capacitive PP/graphene nonwoven carries great promise to be used as electronic textiles.}, number={30}, journal={LANGMUIR}, author={Pan, Qin and Shim, Eunkyoung and Pourdeyhimi, Behnam and Gao, Wei}, year={2017}, month={Aug}, pages={7452–7458} }
 @article{pan_shim_pourdeyhimi_gao_2017, title={Nylon-Graphene Composite Nonwovens as Monolithic Conductive or Capacitive Fabrics}, volume={9}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.7b00471}, abstractNote={Here we describe a nylon-graphene nonwoven (NGN) composite, prepared via melt-blowing of nylon-6 into nonwoven fabrics and infiltrate those with graphene oxide (GO) in aqueous dispersions, which were further chemically reduced into graphene to offer electrical conductivity. The correlation between the conductivity and the graphene loading is described by the percolation scaling law σ = (p - pc)t, with an exponent t of 1.2 and a critical concentration pc of 0.005 wt %, the lowest among all the nylon composites reported. Monolithic supercapacitors have been further developed on the nylon-GO nonwoven composites (NGO), via a programed CO2-laser patterning process. The nylon nonwoven works as an efficient matrix, providing high capacity to GO and ensuring enough electrode materials generated via the subsequent laser patterning processes. Our best monolithic supercapacitors exhibited an areal capacitance of 10.37 mF cm-2 in PVA-H2SO4 electrolyte, much higher than the 1-3 mF cm-2 reported for typical microsupercapacitors. Moreover, our supercapacitors were able to retain a capacitance density of 5.07 mF cm-2 at an ultrahigh scan rate (1 V s-1), probably due to the facilitated ion migration within the highly porous nonwoven framework. This is the first report of highly functional nylon-6 nonwovens, fabricated via industrially scalable pathways into low-cost conductive polymer matrices and disposable energy storage systems.}, number={9}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Pan, Qin and Shim, Eunkyoung and Pourdeyhimi, Behnam and Gao, Wei}, year={2017}, month={Mar}, pages={8308–8316} }
 @article{he_yildiz_pan_zhu_zhang_bradford_gao_2017, title={Pyrolytic-carbon coating in carbon nanotube foams for better performance in supercapacitors}, volume={343}, ISSN={["1873-2755"]}, url={https://publons.com/publon/19584407/}, DOI={10.1016/j.jpowsour.2017.01.091}, abstractNote={Nowadays, the wide-spread adoption of supercapacitors has been hindered by their inferior energy density to that of batteries. Here we report the use of our pyrolytic-carbon-coated carbon nanotube foams as lightweight, compressible, porous, and highly conductive current collectors in supercapacitors, which are infiltrated with chemically-reduced graphene oxide and later compressed via mechanical and capillary forces to generate the active electrodes. The pyrolytic carbon coatings, introduced by chemical vapor infiltration, wrap around the CNT junctions and increase the surface roughness. When active materials are infiltrated, the pyrolytic-carbon coatings help prevent the π-stacking, enlarge the accessible surface area, and increase the electrical conductivity of the scaffold. Our best-performing device offers 48% and 57% higher gravimetric energy and power density, 14% and 23% higher volumetric energy and power density, respectively, and two times higher knee frequency, than the device with commercial current collectors, while the “true-performance metrics” are strictly followed in our measurements. We have further clarified the solution resistance, charge transfer resistance/capacitance, double-layer capacitance, and Warburg resistance in our system via comprehensive impedance analysis, which will shed light on the design and optimization of similar systems.}, journal={JOURNAL OF POWER SOURCES}, publisher={Elsevier BV}, author={He, Nanfei and Yildiz, Ozkan and Pan, Qin and Zhu, Jiadeng and Zhang, Xiangwu and Bradford, Philip D. and Gao, Wei}, year={2017}, month={Mar}, pages={492–501} }
 @article{wang_babaahmadi_he_liu_pan_montazer_gao_2017, title={Wearable supercapacitors on polyethylene terephthalate fabrics with good wash fastness and high flexibility}, volume={367}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2017.09.047}, abstractNote={All solid-state micro-supercapacitors (MSC) have emerged as attractive energy-storage units for portable and wearable electronics. Here, we describe a textile-based solid-state MSC via laser scribing of graphene oxide (GO) coatings on a flexible polyethylene terephthalate (PET) fabric. The laser-scribed graphene oxide layers (LGO) possess three-dimensionally porous structure suitable for electrochemical-double-layer formation. To improve the wash fastness and the flexibility of the as-prepared MSCs, glutaraldehyde (GA) was employed to crosslink the GO layers and PVA-gel electrolyte onto the PET fabric. The resultant all solid-state MSCs exhibited excellent flexibility, high areal specific capacitance (756 μF·cm−2 at 20 mV·s−1), and good rate capability when subject to bending and laundering. Furthermore, the MSC device showed a high power density of about 1.4 W·cm−3 and an energy density of 5.3 × 10−5 Wh·cm−3, and retained 98.3% of its initial capacitance after 1000 cycles at a current density of 0.5 mA·cm−2. This work is the first demonstration of in-plane MSCs on PET fabric surfaces with enhanced durability and flexibility.}, journal={JOURNAL OF POWER SOURCES}, author={Wang, Guixia and Babaahmadi, Vahid and He, Nanfei and Liu, Yixin and Pan, Qin and Montazer, Majid and Gao, Wei}, year={2017}, month={Nov}, pages={34–41} }
 @article{pan_chung_he_jones_gao_2016, title={Accelerated Thermal Decomposition of Graphene Oxide Films in Air via in Situ X-ray Diffraction Analysis}, volume={120}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.6b05031}, abstractNote={Thermal decomposition of graphene oxide (GO) has been extensively investigated in the past decade, but the detailed reaction kinetics remains elusive so far. Here we employ an in situ X-ray diffraction (XRD) analysis to clarify the kinetics of GO decomposition in different atmospheres and sample morphologies. The XRD peak (002), which is the major diffraction peak corresponding to the interlayer distance in GO samples, shifted from 11.5° to 23° along with significant decrease in intensity when samples were heated from 25 to 350 °C. The decomposition in air exhibits a higher reaction rate compared with that in pure nitrogen gases because the O2 molecules in air facilitate the oxidation of carbon atoms, leading to the evolution of CO and CO2. Free-standing films of GO also decompose significantly faster than GO powders, owing to their slower heat dissipation into the environment and higher thermal conductivity within the well-stacked lamella. This study has provided new insights into the reaction kinetics o...}, number={27}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Pan, Qin and Chung, Ching-Chang and He, Nanfei and Jones, Jacob L. and Gao, Wei}, year={2016}, month={Jul}, pages={14984–14990} }
 @article{gao_havas_gupta_pan_he_zhang_wang_wu_2016, title={Is reduced graphene oxide favorable for nonprecious metal oxygen-reduction catalysts?}, volume={102}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2016.02.054}, abstractNote={Reduced graphene oxide (rGO), as a newly emerged carbon material, has attracted great attention concerning its applications for electrocatalysts. Presently, there are mixed opinions regarding the advantages to using rGO as a support for preparing nonprecious metal catalysts for the oxygen reduction reaction (ORR). The primary goal of this work is to determine whether rGO would be favorable for non-precious metal catalysis of oxygen reduction or not. In the case of Fe-free catalysts, when polyaniline (PANI) was used as nitrogen/carbon precursor, the PANI-rGO catalyst is superior to the PANI-Ketjenblack (KJ) carbon black catalyst in terms of ORR activity and H2O2 yield. When comparing the ORR activity of PANI-Fe-rGO to the traditional PANI-Fe-KJ, in more challenging acidic electrolyte, PANI-Fe-rGO performed no better than PANI-Fe-KJ. However, rGO does indeed enhance stability of the Fe–N–C catalyst in acidic media. In addition, in an alkaline electrolyte, ORR activity was significantly improved when using rGO in comparison to the KJ-supported Fe–N–C catalysts. Based on detailed comparisons of structures, morphologies, and reaction kinetics, the traditional KJ support with dominant microporous is able to accommodate more FeNx moieties that are crucial for the ORR in acid. Oppositely, the richness of nitrogen-doped graphene edge sites provided by rGO facilitates the ORR in the alkaline electrolyte.}, journal={CARBON}, author={Gao, Wei and Havas, Dana and Gupta, Shiva and Pan, Qin and He, Nanfei and Zhang, Hanguang and Wang, Hsing-Lin and Wu, Gang}, year={2016}, month={Jun}, pages={346–356} }