Nitrogen-doped carbon nanotubes are selective and robust electrocatalysts for CO2 reduction to formate in aqueous media without the use of a metal catalyst. Polyethylenimine (PEI) functions as a ...co-catalyst by significantly reducing catalytic overpotential and increasing current density and efficiency. The co-catalysis appears to help in stabilizing the singly reduced intermediate CO2 •– and concentrating CO2 in the PEI overlayer.
Stretchable supercapacitors have received increasing attention due to their broad applications in developing self‐powered stretchable electronics for wearable electronics, epidermal and implantable ...electronics, and biomedical devices that are capable of sustaining large deformations and conforming to complicated surfaces. In this work, a new type of highly stretchable and reliable supercapacitor is developed based on crumpled vertically aligned carbon nanotube (CNT) forests transferred onto an elastomer substrate with the assistance of a thermal annealing process in atmosphere environment. The crumpled CNT‐forest electrodes demonstrated good electrochemical performance and stability under either uniaxial (300%) or biaxial strains (300% × 300%) for thousands of stretching–relaxing cycles. The resulting supercapacitors can sustain a stretchability of 800% and possess a specific capacitance of 5 mF cm−2 at the scan rate of 50 mV s−1. Furthermore, the crumpled CNT‐forest electrodes can be easily decorated with impregnated metal oxide nanoparticles to improve the specific capacitance and energy density of the supercapacitors. The approach developed in this work offers an alternative strategy for developing novel stretchable energy devices with vertically aligned nanotubes or nanowires for advanced applications in stretchable, flexible, and wearable electronic systems.
Stretchable electrodes based on crumpled carbon nanotube (CNT)‐forests are fabricated by harnessing the mechanical instability of vertically aligned CNT arrays transferred on an elastomer substrate. The all‐solid‐state stretchable supercapacitors assembled by these electrodes and the PVA/KCl gel electrolyte demonstrate superior performance under large strain deformations, offering a new approach and an opportunity for integrating next‐generation self‐powered flexible and stretchable electronics.
Cu2BaSn(S,Se)4 (CBTSSe) has recently gained substantial attention as an alternative absorber material for photovoltaic (PV) and photoelectrochemical (PEC) applications due to the abundance of the ...constituent elements, a large absorption coefficient, tunable band gap ranging from 1.5 to 2 eV, and reduced tendency for antisite disorder relative to Cu2ZnSn(S,Se)4. In this study, as an alternative to more expensive vacuum-based film-deposition processes, we report a low-toxicity solution-based process for the fabrication of high quality CBTSSe absorber layers with micrometer-scale film thickness and grain size. The facile process involves spin-coating an environmentally benign solution of highly soluble, inexpensive, and commercially available precursors, Ba(NO3)2, Cu(CO2CH3)2, and SnI2, followed by sequential sulfurization/selenization annealing. A high-temperature prebaking step under sulfur vapor is needed for each film layer to avoid forming the difficult-to-remove impurity phase, Ba(SO4), when starting from the soluble Ba(NO3)2 reagent. The solution-based CBTSSe films have been employed in a Pt/TiO2/CdS/CBTSSe photocathode structure (e.g., for water splitting), exhibiting an ∼10 mA/cm2 current density at 0 VRHE, comparable to that of vacuum-deposited CBTSSe PEC devices. Our approach for the fabrication of CBTSSe absorbers represents a first step in achieving low-cost and large-scale solution-processed solar devices based on this material.
Cu2BaSnS4–x Se x films consisting of earth-abundant metals have been examined for photocathode application. Films with different Se contents (i.e., Cu2BaSnS4–x Se x with x ≤ 2.4) were synthesized ...using a cosputter system with post-deposition sulfurization/selenization annealing treatments. Each film adopts a trigonal P3 1 crystal structure, with progressively larger lattice constants and with band gaps shifting from 2.0 to 1.6 eV, as more Se substitutes for S in the parent compound Cu2BaSnS4. Given the suitable bandgap and earth-abundant elements, the Cu2BaSnS4–x Se x films were studied as prospective photocathodes for water splitting. Greater than 6 mA/cm2 was obtained under illumination at −0.4 V versus reversible hydrogen electrode for Pt/Cu2BaSnS4–x Se x films with ∼60% Se content (i.e., x = 2.4), whereas a bare Cu2BaSnS4–x Se x (x = 2.4) film yielded ∼3 mA/cm2 at −0.4 V/RHE.
This work investigates the surface chemistry of H2O2 generation on a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode. It is motivated by the need to efficiently disinfect liquid waste in ...resource constrained environments with limited electrical power. X-ray photoelectron spectroscopy was used to identify functional groups on the BD-UNCD electrode surfaces while the electrochemical potentials of generation for these functional groups were determined via cyclic voltammetry, chronocoulometry, and chronoamperometry. A colorimetric technique was employed to determine the concentration and current efficiency of H2O2 produced at different potentials. Results showed that preanodization of an as-grown BD-UNCD electrode can enhance the production of H2O2 in a strong acidic environment (pH 0.5) at reductive potentials. It is proposed that the electrogeneration of functional groups at oxidative potentials during preanodization allows for an increased current density during the successive electrolysis at reductive potentials that correlates to an enhanced production of H2O2. Through potential cycling methods, and by optimizing the applied potentials and duty cycle, the functional groups can be stabilized allowing continuous production of H2O2 more efficiently compared to static potential methods.
The Cu2BaSnS4–x Se x (CBTSSe) system has attracted remarkable attention as an emerging chalcogenide semiconductor with desirable electronic and optical properties for solar energy conversion ...applications. The current study combines sputtered band gap-tailored CBTSSe films with TiO2/CdS protective overlayers to significantly improve photoelectrochemical (PEC) properties as well as device stability in aqueous solutions under AM 1.5G simulated sunlight. The Pt/TiO2/CdS/CBTSSe(x ≈ 3) photocathode exhibits relatively high photocurrent (∼12.08 mA/cm2 at 0 V/RHE, i.e., the highest value reported for CBTSSe-based PEC devices) and stable hydrogen evolution for more than 10 h. The applied TiO2/CdS layers protect the underlying CBTSSe and create desirable band alignment for efficient charge extraction at the heterointerfaces. The present results highlight the opportunities that CBTSSe materials provide as efficient and stable photocathodes for water electrolysis.
Graphenated carbon nanotubes (g-CNTs) were investigated as the electrode support in MnO2 composite cathodes for aqueous asymmetric supercapacitors. The electrode performance could be tuned by ...optimizing the density of graphene foliates on the g-CNTs, which enabled geometric/morphologic control over the MnO2 electrodeposits. The synergy and optimization of the g-CNT hybrid structure led to a high specific capacitance (640 F/g) at high MnO2 specific loading (2.3 mg/cm2), thus creating a unique pathway toward improved practical performance.
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