Since their invention in the 1950s, composite carbon electrodes have been employed in a wide variety of applications, ranging from batteries and fuel cells to chemical sensors, because they are easy to make and pattern at millimeter scales. Despite their widespread use, traditional carbon composite electrodes have substandard electrochemistry relative to metallic and glassy carbon electrodes. As a result, there is a critical need for new composite carbon electrodes that are highly electrochemically active, have universal and easy fabrication into complex geometries, are highly conductive, and are low cost. Herein, a new solvent-based method is presented for making low-cost composite graphite electrodes containing a thermoplastic binder. The electrodes, which are termed thermoplastic electrodes (TPEs), are easy to fabricate and pattern, give excellent electrochemical performance, and have high conductivity (700 S m). The thermoplastic binder enables the electrodes to be hot embossed, molded, templated, and/or cut with a CO laser into a variety of intricate patterns. Crucially, these electrodes show a marked improvement in peak current, peak separation, and resistance to charge transfer over traditional carbon electrodes. The impact of electrode composition, surface treatment (sanding, polishing, plasma treatment), and graphite source were found to significantly impact fabrication, patterning, conductivity, and electrochemical performance. Under optimized conditions, electrodes generated responses similar to more expensive and difficult to fabricate graphene and highly oriented pyrolytic graphite electrodes. The TPE electrode system reported here provides a new approach for fabricating high performance carbon electrodes with utility in applications ranging from sensing to batteries.

Understanding light-matter interactions in transition-metal dichalcogenides (TMDs) is critical for optoelectronic device applications. Several studies have shown that high intensity light irradiation can tune the optical and physical properties of pristine TMDs. The enhancement in optoelectronic properties has been attributed to a so-called laser annealing effect that heals chalcogen vacancies. However, it is unknown whether laser annealing improves functional properties such as photocatalytic activity. Here, we show that high intensity supra band gap illumination improves the photoelectrochemical activity of MoSe 2 nanosheets for iodide oxidation in indium doped tin oxide/MoSe 2 /I − , I 3 − /Pt liquid junction solar cells. Ensemble-level photoelectrochemical measurements show that, on average, illuminating MoSe 2 thin films with 1 W/cm 2 532 nm excitation increases the photoelectrochemical current by 142% and shifts the photocurrent response to more favorable (negative) potentials. Scanning photoelectrochemical microscopy measurements reveal that pristine bilayer (2L)-MoSe 2 , trilayer (3L)-MoSe 2 , and multilayer-thick nanosheets are initially inactive for iodide oxidation. The light treatment activates 2L-MoSe 2 and 3L-MoSe 2 materials, and the activation process initiates at the edge sites. The photocurrent enhancement is more significant for 2L-MoSe 2 than for 1L-MoSe 2 . Multilayer-thick MoSe 2 remains inactive for iodide oxidation even after the laser treatment. Our microscopy measurements reveal that the laser-induced enhancement effect depends critically on MoSe 2 layer thickness. X-ray photoelectron spectroscopy measurements further show that the laser treatment oxidizes Mo(IV) species that are initially associated with Se vacancies. Ambient oxygen fills the Se vacancies and removes trap states, thereby increasing the overall photogenerated carrier collection efficiency. To the best of our knowledge, this work represents the first report on using laser to enhance the photoelectrocatalytic properties of few-layer-thick TMDs. The simple and rapid laser annealing procedure is a promising strategy to tune the reactivity of TMD-based photoelectrochemical cells for electricity and chemical fuel production.

Nitrite coordination to heme cofactors is a key step in the anaerobic production of the signaling molecule nitric oxide (NO). An ambidentate ligand, nitrite has the potential to coordinate via the N- (nitro) or O- (nitrito) atoms in a manner that can direct its reactivity. Distinguishing nitro vs nitrito coordination, along with the influence of the surrounding protein, is therefore of particular interest. In this study, we probed Fe(III) heme-nitrite coordination in Alcaligenes xylosoxidans cytochrome c′ (AXCP), an NO carrier that excludes anions in its native state but that readily binds nitrite (Kd ∼ 0.5 mM) following a distal Leu16 → Gly mutation to remove distal steric constraints. Room-temperature resonance Raman spectra (407 nm excitation) identify ν(Fe–NO2), δ(ONO), and νs(NO2) nitrite ligand vibrations in solution. Illumination with 351 nm UV light results in photoconversion to {FeNO}6 and {FeNO}7 states, enabling FTIR measurements to distinguish νs(NO2) and νas(NO2) vibrations from differential spectra. Density functional theory calculations highlight the connections between heme environment, nitrite coordination mode, and vibrational properties and confirm that nitrite binds to L16G AXCP exclusively through the N atom. Efforts to obtain the nitrite complex crystal structure were hampered by photochemistry in the X-ray beam. Although low dose crystal structures could be modeled with a mixed nitrite (nitro)/H2O distal population, their photosensitivity and partial occupancy underscores the value of the vibrational approach. Overall, this study sheds light on steric determinants of hemenitrite binding and provides vibrational benchmarks for future studies of heme protein nitrite reactions.

Nanostructured heaters based on laser-induced graphene (LIG) are promising for heat generation and temperature control in a variety of applications due to their high efficiency as well as a fast, facile, and highly scalable fabrication process. While recent studies have shown that LIG can be written on a wide range of precursors, the reports on LIG-based heaters are mainly limited to polyimide film substrates. Here, we develop and characterize nanostructured heaters by direct writing of laser-induced graphene on nonuniform and structurally porous aramid woven fabric. The synthesis and writing of graphene on aramid fabric is conducted using a 10.6 μm CO 2 laser. The quality of laser-induced graphene and electrical properties of the heater fabric is tuned by controlling the lasing process parameters. Produced heaters exhibit good electrothermal efficiency with steady-state temperatures up to 170 °C when subjected to an input power density of 1.5 W cm −2 . In addition, the permeable texture of LIG−aramid fabric heaters allows for easy impregnation with thermosetting resins. We demonstrate the encapsulation of fabric heaters with two different types of thermosetting resins to develop both flexible and stiff composites. A flexible heater is produced by the impregnation of LIG− aramid fabric by silicone rubber. While the flexible composite heater exhibits inferior electrothermal performance compared to neat LIG−aramid fabric, it shows consistent electrothermal performance under various electrical and mechanical loading conditions. A multifunctional fiber-reinforced composite panel with integrated de-icing functionality is also manufactured using one ply of LIG− aramid fabric heater as part of the composite layup. The results of de-icing experiments show excellent de-icing capability, where a 5 mm thick piece of ice is completely melted away within 2 min using an input power of 12.8 W.

Nanoparticle electrodes are attractive for electrochemical energy storage applications because their nanoscale dimensions decrease ion transport distances and generally increase ion insertion/extraction efficiency. However, nanoparticles vary in size, shape, defect density, and surface composition, which warrants their investigation at the single-nanoparticle level. Here we demonstrate a nondestructive high-throughput electro-optical imaging approach to quantitatively measure electrochemical ion insertion reactions at the single-nanoparticle level. Electro-optical measurements relate the optical density change of a nanoparticle to redox changes of elements in the particle under working electrochemical conditions. We benchmarked this technique by studying Li-ion insertion in hexagonal tungsten oxide (h-WO 3 ) nanorods during chronoamperometry and cyclic voltammetry. Interestingly, the optically detected current response revealed underlying processes that are hidden in the conventional electrochemical current measurements. This imaging technique may be applied to 13 nm particles and a wide range of electrochemical systems such as electrochromic smart windows, batteries, solid oxide fuel cells, and sensors.