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Thermodynamically favorable selective electrooxidation reactions coupled with hydrogen evolution reaction (HER) is a promising strategy for simultaneous production of value-added chemicals and hydrogen. In this work, a binder-free gold nanoflowers electrode based on carbon paper is prepared and used as anode catalyst, which results in good charge transfer, high stability and superior catalytic activity for electrooxidation of glycerol. We develop an integrated system of glycerol electrooxidation with HER, and the effect of potential on the distribution of anodic electrooxidation products and cathodic hydrogen production are investigated. At 1.0 V, the overall reaction reaches 10 mA cm−2 and the selectivity of glyceric acid (GLA) reaches 97.2%. At 1.2 V, hydrogen production reaches the highest value of 960 μmol L−1 and the anode product consists of a mixture of glyceric acid, glycolic acid (GA) and formic acid (FA). At 1.3 V, the selectivity of FA reaches 87.3%. Operando technique in situ infrared spectroscopy is used to monitor the immediate evolution and study the pathway of controlled glycerol electrooxidation. This work demonstrates carbon paper is a promising substrate material of binder-free electrode applied in thermodynamically favorable electrocatalytic reactions boosting hydrogen evolution. [Display omitted] • A binder-free electrode based on carbon paper is developed. • Hydrogen production is increased by 24 times with the addition of glycerol. • The selectivity of glyceric acid on carbon paper supported gold nanoflowers is 97.2%. • In situ FTIR reveals the pathway for electrooxidation of glycerol. [ABSTRACT FROM AUTHOR]

Persulfate is a potential oxidant in direct liquid fuel cells (DLFCs), and the commercial carbon paper (CP) can directly serve as the cathode due to strong oxidizability of persulfate. However, the poor catalytic activity and low specific surface area of CP limit the electrode performance. Herein, a defect-enriched, pyridine-N-dominated and self-standing carbon paper electrode with abundant carbon nanosheets is successfully prepared by hydrothermal treatment combined with in-situ electrochemical exfoliation. Benefitting from the integrated structure, plentiful defects and high-content pyridine-N dopants of the prepared electrode result in the superior electrocatalytic activity and long-term stability in persulfate reduction reaction. Remarkably, a membraneless DLFC with the prepared electrode as cathode and persulfate as the oxidant acquires prominent cell performance and extremely high open circuit voltage of 2.13 V. The maximum power density of the DLFC achieves 241.0 mW cm−2, far higher than those of the previously reported similar membraneless DLFCs. A three-dimensional computational model for the DLFC is developed, which is help to reveal the importance of improving the reaction kinetics and electrical conductivity for the cathode with persulfate as oxidant. A facile approach for in-situ preparation of highly N-doped CP electrode is provided to yield outstanding cell performance for low-cost DLFCs. [Display omitted] • A facile way to introduce high-content nitrogen on carbon paper is proposed. • Massive defective sites, carbon nanosheets and pyridine-N dopants are introduced. • N doping enhances charge transfer and electrocatalytic activity of the electrode. • Effects of hydrothermal duration and precursor concentration are discussed. • The N-doped cathode yields the outstanding cell performance for low-cost DLFC. [ABSTRACT FROM AUTHOR]

Stimuli-responsive phosphorescence materials with dynamic color-changing properties are highly promising for advanced information security. Herein, we demonstrate a novel strategy that effectively induces tunable dynamic phosphorescence color from carbon dots (CDs) on papers via surface ionization engineering for multimode encryption and information storage. Alkali-induced phenolic hydroxyl ionization on CDs can boost intersystem crossing rates, while surface-ionized groups with negative charges significantly passivate the surface defects and reduce non-radiative transitions, which can activate surface state-related blue phosphorescence emission. Combined with the carbon core state-related yellow-green phosphorescence, excitation/time-dependent phosphorescence color-changing from yellow-green to blue are realized from alkali (Na 2 CO 3) treated CDs on paper. Furthermore, benefiting from the transition from NaHCO 3 to Na 2 CO 3 under thermal treatment, dynamic color-changing phosphorescence can also be activated by thermally stimulating NaHCO 3 -treated CDs on paper. Finally, multi-stimuli (alkali or thermal) and multi-modal dynamic phosphorescent colors from a single CDs system are realized for the first time. Based on these unique features, multimode encryption and smart 3D codes with anti-counterfeiting and monitoring functions for medicine during transport or storage are demonstrated by combining an inkjet printing technique using CD inks. Multistimuli and excitation-dependent dynamic phosphorescence colors from a single CD system were realized for the first time for dynamic multimode encryption. Dynamic phosphorescence colors can be modulated from the dual phosphorescent centers of CDs in the surface triplet state and the carbon core-related triplet state, where the surface triplet state can be activated by external stimuli (alkali or thermal). [Display omitted] • A new surface ionization-activated RTP from CDs surface state strategy is proposed. • Multistimuli- and excitation/time-dependent RTP color variations from single CDs system are realized for the first time. • Smart 3D codes with monitoring function for medicine are developed for the first time. [ABSTRACT FROM AUTHOR]

A facile and scalable approach to modify electrodes with achieving excellent performance and low-cost is urgently needed for direct liquid fuel cells (DLFCs). A carbon paper (CP) electrode with porous carbon nanosheets is successfully fabricated by electrochemical exfoliation to enhance the charge transfer and increase reaction sites in DLFCs. After in-situ electrochemical exfoliation for 4 min, the carbon fiber surface becomes porous and rough to enlarge specific surface area and produce abundant defects for the electrode, greatly increasing reaction active sites. In addition, massive oxygen functional groups are introduced to significantly improve the reaction kinetics and wettability of the electrode. The exfoliated CP shows superior electrocatalytic activity with minimum overpotential and highest reduction reaction rate, benefitting from the larger specific surface area, abundant defects, and superhydrophilic property. Moreover, the exfoliated CP without catalysts is directly used as the cathode for a membraneless DLFC with sodium persulfate as an oxidant to yield outstanding performance. The peak power density of the DLFC with the exfoliated CP is 188.6 mW cm−2, 93.4% higher than that with the pristine CP. Results show that a feasible way to acquire excellent cell performance and low cost is obtained by electrochemically exfoliated CP electrode for DLFCs. [Display omitted] • An effective method to modify cathode is proposed for low-cost DLFCs. • Carbon fiber surface becomes porous and rough to enlarge specific surface area. • Abundant defects and oxygen functional groups are introduced. • Electrochemical exfoliation enhances charge transfer and increases active sites. • The exfoliated cathode without catalysts yield the outstanding cell performance. [ABSTRACT FROM AUTHOR]

A free-standing cathode without any binder, conductor, and current collector is attractive due to its reduced weight and cost. This study introduces nitrogen-rich and hierarchical porous carbon fibers in the form of a free-standing carbon paper synthesized by NaBH 4 -aided electrospinning and subsequent CO 2 annealing. This modified process leads to a large mesopore volume of 1.007 cm3 g−1 and exposes the nitrogen inside the polymer to the surface of the fiber, resulting in the outstanding surface nitrogen content of 19.38 wt% with abundant pyridinic-N and pyrrolic-N of 16.24 wt% in total surface atoms, while eliminating any further treatment for increasing porosity or coating the polar active sites. The resultant material impregnated by sulfur and filtered by a graphene solution is directly employed as a cathode without any additives. As a result, the capacity is maintained at 696 mAh g−1 up to the 500th cycle at 0.2 C, and 645 mAh g−1 at a high current density of 5.0 C. Even with a high sulfur loading of 6.11 mg cm−2, a remarkable areal capacity of 3.09 mAh cm−2 is recorded after 500 cycles at 0.2 C with the free-standing form preserved. Image 1 • NaBH 4 -added electrospinning and subsequent heat treatment under CO 2 atmosphere. • High meso pore volume of 1.007 cm3 g−1, and surface nitrogen contents of 19.38 wt%. • Employed as a cathode without any additives due to a free-standing paper form. • High sulfur amount of 6.11 mg cm−2, and capacity of 3.09 mAh cm−2 for 500 cycles. [ABSTRACT FROM AUTHOR]

Disordered wrinkles inevitably appear in the fluid assembly process of graphene and heavily depress performances of assembled graphene papers. Achieving high plasticity enables the post modulation to rearrange wrinkles by stretching. Here, we obtain an over 100% improved plasticity by intercalating oligomer into graphene oxide (GO) laminates and fabricate strong, stiff and conductive graphene papers (GPs) via post stretching. The intercalated oligomer activates the mobilization of GO sheets and achieves high plasticity of solid GO papers. The improved plasticity allows high stretching ratio and the post-stretched GP features regular orientation (0.95) of graphene sheets and aligned fine wrinkles. The crystalline GPs have a high tensile strength up to 1.3 GPa, Young's modulus of 92.9 GPa and highly electrical conductivity (1.05 × 105 S m−1). The greatly improved plasticity by oligomer extends the processing capability of graphene materials and the strong and conductive GP can be assembled in high performance nanocomposites with excellent electromagnetic interference shielding effectiveness (EMI SE). [Display omitted] • Intercalating oligomer greatly enhances plasticity of graphene oxide laminates for the improved interlayer friction. • The greatly enhanced plasticity enables to efficiently eliminate disordered wrinkles of assembled graphene sheets. • The crystalline graphene paper (GP) exhibits superior mechanical and electrical properties. • The (GP-based) laminated composite shows high tensile strength and electromagnetic interference shielding effectiveness. [ABSTRACT FROM AUTHOR]

For the electro-reduction of CO 2 to syngas, the fabrication of electrodes with excellent and adjustable catalytic performance is a critical step. In this work, Ni particles encapsulated in N-doped carbon nanotubes on carbon paper (Ni@N-CNTs/CP) composites were designed and prepared via an in-situ chemical vapor deposition method. As confirmed by different characterization techniques, the Ni@N-CNTs are successfully synthesized, and the surface of the CP is evenly covered by the Ni@N-CNTs. The effects of Ni content and treating temperature on the textural properties of composites are carefully investigated. The Ni@N-CNTs/CP composites are directly employed as the electrode for electro-reduction of CO 2 , and the action mechanisms of the N species, Ni particles, and N-CNTs structure are explored as well. The electrode exhibits excellent catalytic activity and high stability, reaching a specific current of 10 mA cm−2. The H 2 /CO ratio in the achieved syngas can be tuned in the range of 5/1 to 1/1.5. Image 1 • A in-situ CVD method was employed to fabricate an electrode for electro-reduction of CO 2. • The as-synthesized Ni@N-CNTs evenly cover on the whole surface of CP. • The Ni@N-CNTs/CP electrode exhibits high CO 2 reduction activity and stability. • The ratio of H 2 /CO can be adjusted in the range of 5/1 to 1/1.5. • The action mechanism of different components are detailedly investigated. [ABSTRACT FROM AUTHOR]

MXene-based nanocomposites are highly desirable for electromagnetic interference (EMI) shielding applications. However, it is crucial but challenging to obtain an excellent trade-off between mechanical properties and EMI performances. Herein, inspired by Janus structure, flexible cellulose nanofiber-assisted MXene/silver nanowires (CNF-MXene/AgNWs) papers (CMAPs) are developed by a scalable sequential self-assembly plus a hot-pressing strategy. The ingenious introduction of highly conductive AgNWs into MXene forms a complementary leaf-like nanostructure, synergistically constructing highly effective conductive frameworks. Contributed by the designed Janus architecture, high-performance CNF substrate, and extensive hydrogen-bonding interactions, the resultant Janus CMAPs (J-CMAPs) with a low MXene/AgNWs addition of 30 wt% possess a high electrical conductivity (1066.85 S/cm), excellent mechanical strength (224.04 MPa) and modulus (9.98 GPa), exceptional EMI shielding effectiveness of 43.65 dB, and record-high EMI SE/t of 16788.51 dB cm−1 and SSE/t of 10543.18 dB cm2 g−1 with a reflection-dominant shielding mechanism, successfully achieving an outstanding balance between mechanical properties and EMI shielding performances. More importantly, high frequency structure simulator (HFSS) simulation in the frequency domain is further conducted to intuitively comprehend the attenuation process of electromagnetic waves and shield mechanism, verifying fascinating EMI shielding performances. Besides, the Janus paper also presents desirable Joule heating performances at low input voltage, short response time (<10 s), and superb heating stability and long-term steady reliability. We believe that the J-CMAPs demonstrate the great potential and advantage for advanced EMI shielding and portable thermal management applications. SynopsisIn this paper, inspired by Janus structure, flexible CNF-assisted MXene/AgNWs nanopapers with both excellent mechanical properties and impressive EMI shielding performance are developed. The nanopapers exhibit a high electrical conductivity, superior mechanical properties, impressive EMI shielding effectiveness of 43.65 dB, and record-high EMI SE/t of 16788.51 dB cm−1 and SSE/t of 10543.18 dB cm2 g−1, suggesting the great potential for advanced EMI shielding applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, carbon paper as positive electrode for vanadium redox flow battery was etched by chlorosulfonic acid with assistance of ultrasonication. Carbon layer-exfoliated, wettability-enhanced, SO 3 H-functionalized carbon paper was successfully achieved by facile treatment. The electrochemical kinetics of VO 2+ /VO 2 + redox reaction on carbon paper was significantly improved after the treatment. Carbon paper after ultrasonication-assisted treatment exhibits better electrochemical activity compared with the untreated and only-soaking samples. The cell using treated carbon paper as positive electrode shows larger discharge capacity and higher energy efficiency compared with the pristine cell. The initial discharge capacity of the cell using optimal treated carbon paper reaches 127.7 mA h, 20.8 mA h larger than that of the pristine one at 50 mA cm −2 . Furthermore, the average energy efficiency increases by 5.1% by using the treated electrode. The introduced sulfonic groups as active sites and increased surface area by etching can reduce the electrochemical polarization of VO 2+ /VO 2 + redox reaction. Moreover, the improved wettability of treated carbon paper can accelerate mass transfer of active species. Therefore, the reduced electrochemical polarization and accelerated mass transfer of active species conjointly cause the enhanced electrochemical properties of the treated carbon paper. [ABSTRACT FROM AUTHOR]

Plasma activation is increasingly used to tailor the electronic properties of carbon materials by surface functionalization, especially with various oxygen groups. However, the actual application of these materials may be some time after the modification was performed, and what is more, in a different environment, e.g. in an aqueous solution. The presented research addresses the problem of instability of plasma-induced changes of graphene paper material where the desired surface property – work function – was verified just after plasma treatment and after bringing the plasma-treated surface to a stable state. In this study, we optimised plasma treatment for the maximum work function changes, and then we determined the speciation of the resulting oxygen groups before and after immersion of the plasma-treated samples in water. We found that the plasma-modified graphene paper's functionalization degree and electronic properties highly depend on the post-plasmatic reactions in water, which increase the concentration of surface oxygen groups. The observed reactivity is rationalized in terms of plasma-emitted irradiation in the ultraviolet range resulting in an enhanced delocalized radical species generation. These radicals react upon contact with water and increase the number of oxygen functional groups. [Display omitted] [ABSTRACT FROM AUTHOR]

Laser-induced graphene from paper (paper-LIG) was applied in non-enzymatic electrochemical sensing of uric acid (UA) in human urine. Paper-LIG was formed by CO 2 laser modification of paper into a 3D graphene arrangement. Kinetic analysis of paper-LIG electrodes returned effective heterogeneous electron transfer standard rate constants of 1.4 × 10−3 cm s−1 and 7.8 × 10−4 cm s−1 for [Ru(NH 3) 6 ]2+/3+ and [Fe(CN) 6 ]4−/3− redox probes, respectively. These electrodes were able to detect and quantify uric acid in PBS within the 10–300 μM range at pH between 5.6 and 7.4. At pH 7.4, a linear response (R2 = 0.999) from 10 to 250 μM was achieved, with a limit of detection of 3.97 μM and a sensitivity of 0.363 μA cm−2 μM−1. Paper-LIG electrodes denoted adequate selectivity in synthetic urine as well as in ascorbic acid (AA) and dopamine (DA)-containing electrolytes. Determination of urinary UA content in human samples returned a concentration of c.a. 1.8–1.9 mM, within the range for healthy individuals. Recoveries of samples spiked with 50 and 100 μM UA were 100.6% and 95.4%, respectively, with satisfactory reproducibility and stability. These cheap, lightweight, flexible, and eco-friendly paper-LIG biosensors for non-enzymatic quantification of UA in human urine pave the way to widespread application in the detection of other important biomarkers. [Display omitted] • "Green" graphene electrodes by CO 2 laser irradiation of paper ("paper-LIG"). • Uric acid (UA) quantification at clinically relevant concentrations and pH (5.6–7.4). • Limit of detection of 3.97 μM and a sensitivity of 0.363 μA cm−2 μM−1 (pH = 7.4). • Adequate selectivity in synthetic urine, as well as in ascorbic acid and dopamine-containing electrolytes. • Recoveries of 100.6% and 95.4% for human urine samples spiked with 50 and 100 μM UA. [ABSTRACT FROM AUTHOR]